Low-temperature electrochemical direct methane reforming to produce hydrogen

Abstract

Provided herein is a low-temperature methane steam reformer comprising a proton-exchanged membrane fuel cell comprising an anode and a cathode, wherein hydrogen is produced at the cathode, wherein the fuel cell comprises a metal- membrane-assembly utilizing platinum electrocatalysts. Also provided are methods of producing hydrogen using the low temperature methane reformer, comprising feeding methane to the low temperature methane reformer at a relative humidity (RH) of 60% to 100%; and catalyzing the reaction at temperature of 30°C and 120°C or less and back pressure of 90 kPa and 1000 kPa or less.

Description

LOW-TEMPERATURE ELECTROCHEMICAL DIRECT METHANEREFORMING TO PRODUCE HYDROGENACKNOWLEDGMENT OF GOVERNMENT SUPPORT

[0001] This invention was made with government support under DE-SC0021218 awarded by the Department of Energy. The government has certain rights in the invention.REFERENCE TO RELATED APPLICATIONS

[0002] This application claims benefit to and priority7to US Provisional Application Serial Number 63 / 584683, filed on September 22, 2023 which is hereby incorporated by this reference in its entirety.FIELD

[0003] This invention relates generally to devices and methods of producing hydrogen from methane at low-temperature.BACKGROUND

[0004] Scientists worldwide have been motivated by the promising production of chemicals using widely existing methane (CH4) under mild conditions for both chemical synthesis with low energy consumption and climate remediation. Significant strides have been made to develop a library of catalytic chemistries of transforming CH4 to various products under mild conditions. These efforts have demonstrated the feasibility of oxidation of CH4 under mild conditions to value-added intermediate compounds including but not limited to CHsOH, HCHO, HCOOH, and CH3COOH. The fundamental understanding of these chemical and catalytic transformations of CH4 under mild conditions have been achieved to some extent, although currently neither a catalyst nor a catalytic process can be used for chemical production under mild conditions at a large scale, about two dozen thermal catalytic, photocatalytic, and electrocatalytic reaction systems have been developed and investigated for converting CH4 to different types of oxygenates under mild conditions in terms of a relatively low activation or catalysis temperature (Xiong et al., 2019).

[0005] One important application of methane oxidation is in the steam methane reforming (SMR) reaction, which produces a mixture of gases know n as syngas. Syngas can be further purified to hydrogen, a known efficient and clean energy source. Although other methods of hydrogen production are known and used,including electrolysis of water, oil, coal, biomass gasification, and methane pyrolysis, steam reforming of natural gas accounts for the majority’ of hydrogen production (Liu, Ke; Song, Chunshan; Subramani, Velu, eds. (2009). Hydrogen and Syngas Production and Purification Technologies). However, SMR is a highly endothermic process and requires high temperatures and pressures to activate the H3C-H bond in methane (Y an, et al., 2024). Additionally, systems which use a steam methane reformer (SMR) coupled to a pressure swing adsorption (PSA) device suffer from the disadvantage of not converting all of the methane to hydrogen, and thus a substantial amount of feed energy is converted to heat. This generation of heat makes it impractical for the system to use waste heat from other sources to improve efficiency and also increases CO2 emissions (US20210091398A1).

[0006] Methane activation under mild conditions of promising practical outlook is highly desirable economically as methane still is the main stock source for industrial hydrogen production. Because of its profound economic value and importance in mitigating a potent greenhouse gas, methane activation under mild conditions has long been sought after as a “Holy Grail” in chemistry despite challenges caused by methane’s chemical inertness. As such, achieving methane (CH4) to high-value chemicals conversion with high selectivity and efficiency under mild conditions is considered “a remaining grand challenge in chemistry” and has been repeatedly identified as a major unsolved scientific problem of great significance for catalysis. Yet, decades-long intensive research, including electrochemical (EC) methane activation thanks to its generally mild operational conditions, has seen little progress towards achieving the long-sought-after economical revalorization of methane.

[0007] Therefore, there remains a need for an impactful breakthrough in hydrogen production from methane.SUMMARY

[0008] In accordance with the purpose(s) of this invention, as embodied and broadly described herein, this invention, in one aspect, relates to a low-temperature and low-pressure direct steam continuous electrochemical methane (CH4) electrooxidation (EO) system comprising: (a) a metal electrolyte assembly (MEA) reactor; (b) a sampler; and (c) a mass spectrometer detector; wherein the MEA reactor comprises a single-stack proton-exchanged membrane fuel cell (PEMFC) and a MEAassembly unit assembled together, wherein the proton-exchanged membrane fuel cell comprises two electrodes, an anode and a cathode separated by a membrane, and wherein the proton-exchanged membrane fuel cell uses methane or hydrogen as a fuel source.

[0009] In one embodiment, the membrane is aNafion membrane. In another embodiment, the proton-exchanged membrane fuel cell comprises a metal-membrane- assembly, wherein the metal-membrane-assembly comprises a catalyst that is capable of promoting both hydrogenation and partial oxidation reactions. In other embodiments, the catalyst is one or more electrocatalysts selected from platinum, platinum alloy, palladium, palladium alloy, copper, copper alloy, vanadium, vanadium alloy, nickel or nickel alloy or combinations thereof.

[0010] In another embodiment, the cathode is catalyzed with a platinum, platinum alloy, palladium, or palladium alloy based electrocatalyst and the cathode is oxygen-fed and hy drogen or H2O are produced at the cathode. In another embodiment the anode is catalyzed with a platinum, platinum alloy, palladium, palladium alloy, copper, copper alloy, vanadium, vanadium alloy, nickel or nickel alloy based electrocatalyst and carbon dioxide or CH3OH are produced at the anode.

[0011] In yet another embodiment, a small portion of a FC outlet flows gas into the sampler and the sampler flows gas into a gas chromatographer via a typical split / spiritless inlet through a deactivated fused silica (dFS) tubing. In one embodiment, a high split ratio was used in the inlet to dilute a sample gas and significantly reduce the moisture content, protecting the mass spectrometer detector.

[0012] In one other embodiment, the mass spectrometer detector is an operando electrochemistry-mass spectroscopy detector (OECMS) that simultaneously monitors and observes the production of CO2 via EC-direct steam methane reforming reaction (EC-DSMR).

[0013] In another aspect, the invention relates to a method of generating hydrogen (H2) gas from the electro-oxidation (EO) of methane (CH4) at low temperature and ambient pressure comprising; feeding methane to the anode of the low- temperature methane reforming system described herein at a relative humidity (RH) of 90%; catalyzing the reaction with electrocatalysts at temperature of 80 °C and back pressure of 4 bar; and starting the EC-MRR system with the hydrogen-fed RHE cathode; wherein the hydrogen produced by the reformer is used to self-sustain thehydrogen-fed RHE cathode, wherein the relative humidity may be 60% to 100%; wherein the reaction temperature is between 30 °C and 120 °C, wherein the reaction back pressure is between 90 kPa and 1000 kPa, and wherein the reaction turnover frequency is fast enough at the gas / solid interface to generate sustained electron transfer.

[0014] In one embodiment, carbon dioxide is produced by conversion from methane in an anodic reaction.

[0015] In another embodiment, the low temperature methane reforming system activity' is 10 times higher on Pt / C than PtRu / Cwherein the number of experimental active site percentages are 5% and 1% at 40 °C for Pt / C and PtRu / C, respectively, and wherein the number of experimental active site percentages are 14% and 2% at 80 °C for Pt / C and PtRu / C, respectively. The Pt comer / edge sites are the active sites for the low temperature methane reforming system and the reaction works preferentially with the edge sites. In another embodiment, electrocatalysts Pt / C and PtRu / C exhibit longterm CH4 EO activity, up to 48 hours without a poison-cleaning procedure, recover catalytic performance after holding the cell potential at 1.2 V for 1 min, then at 0.07 V for 1 min, and wherein up to 80% of initial CH4 EO activity of Pt / C or PtRu / C is regained after employing the cleaning procedure.

[0016] In one other aspect, the invention relates to a method of electrocatalytic direct methane to methanol (DMTM) generation at low temperatures and ambient pressure comprising: feeding methane to the anode of the fuel cell as described herein at a relative humidity' (RH) of 100%; catalyzing the reaction with electrocatalysts at temperature of 80 °C and ambient back pressure; wherein the flowrate of CH4 and O2 to anode and cathode respectively is 0.8 L / min, wherein electrocatalyst surfaces PtRu / C and PdAu produce conversion of CH4 to MeOH, wherein the area of MEA is 5 cm2, and wherein the electrocatalyst loadings are 5 mg / cm2for Pt / C, PtRu / C, and AuPd and 50 mg / cm2for CuNi. In one embodiment, the electrocatalysts Pt / C, PtRu / C, AuPd, and CuNi all produce measurable reaction currents.

[0017] In other embodiments, CuNi has an average particle size of 50 nm and dispersion of around 3%. AuPd electrocatalyst has an average particle size of 5 nm. In another embodiment, MeOH production is increased on PtRu electrocatalyst by subjecting PtRu to multiple CV cycling in MeOH-containing electrolyte. In anotherembodiment, sulfide adsorption on Pt enhances CH4 adsorption generated Coads on Pt surface.

[0018] Additional advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.BRIEF DESCRIPTIONS OF THE DRAWINGS

[0019] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate (one) several embodiment(s) of the invention and together with the description, serve to explain the principles of the invention.

[0020] Figure 1A shows a diagram of the continuous EC-MRR by OECMS. experimental setup. The scheme and operando mass signal response of OECMS. The green-shaded area implies the active EC-MRR window. List of elements in the drawing: (1) - operando electrochemistry-mass spectroscopy (OECMS), (2) - anode, (3) - cathode, (4) - MEA Reactor, (5) - Nafion film / membrane, (6) - gas diffusion layer (GDL) interface, (7) - catalyst. (8) - hydrogen production at the cathode, (9) - carbon dioxide production at the anode, (10) - sptit / splitless inlet to GCMS, (1 1) - operando mass spec response, (12) - vacuum, (13) - relative abundance of compounds, (14) - sampler, (15) - methane inlet.

[0021] Figure IB shows the effect of Relative Humidity (RH) on the EC-MRR in our configuration. >60% of RH (dash line) was sufficient for the steam methane conversion to the CO2 (y-axis).

[0022] Figures 1C-1D show the OECMS for CO stripping experiment on Pt / C (a) and PtRu / C (b) anode at 40 °C and 2 bar under Ar flow: bottom for electrochemistry (black) and top for mass spectroscopy (red).Only the 1stCV shows the current peak and m / z=44 CO2 mass signal for COads oxidation.

[0023] Figure IE shows the reaction order of EC-direct steam methane reforming reaction (EC-DSMR) on PtRu / C anode. The calibrated CO2 production rate was plotted against the CH4 partial pressure in the feed at 50 (green), 60 (blue), 70(red), 80 °C (black). The linear relationship implies a first-order reaction of EC- DSMR on the Pt-based catalyst surfaces.

[0024] Figures 2A-2B shows the operando electrochemical mass spectrometry (OECMS) of CVs on Pt / C at 80 °C and 4 bar: electrochemistry CV (bottom) and MS CV (top). For all CVs: 1stscan (21), 2ndscan (22), and 3rdscan, all with CFE-flow. Bottom trace CVs were under Ar flow. The insert figure enlarged the onset of potential-dependent CO2 generation (20). FIG. 2C shows the OECMS of isotopic13CH4pulse-fed at E=0.5V and E=0.3 V on Pt / C at 80 °C and 4 bar: bottom -13CO2 (m / z=45) and top -13CH4 (m / z=17). List of elements in the drawing (16) - cyclic voltammogram, (17)- MS signal, (18) - oxidation peak. (19) - synchronized peak position (dashed line), (20) - CO2 onset insert, (21) - first CV, (22) - second CV.

[0025] Figure 3A show s the OECMS of continuous EC-direct steam methane reforming reaction (EC-DSMR) CO2 production for 600s on Pt / C at 80 °C and 4 bar (top: EC-DSMR current, 24; second from top: m / z=44 CO2 MS signal, 23). The second from bottom (current) and bottom lines (m / z=44 signal, 25) were obtained under Ar flow without CH4 feed for comparison, respectively. Figure 3B shows the OECMS of CVs on Pt / C at 30 °C and 2 bar: bottom - electrochemistry and top - mass spectroscopy (black-under Ar flow'; red-1stCV with CFL-flow; blue-2ndCV with CH4- flow). List of elements in the drawing (23) - EC-MRR CO2 signal at 0.6 V, (24) - current, (25) - no CO2 produced under Ar. Figures 3C-3D show EC-DSMR on PtRu / C anode at 80 °C and 4 bar. (FIG. 3C) OECMS of CVs: bottom: electrochemistry and top: mass spectroscopy (black-under Ar flow'; red- 1stCV with CEL-flow'; blue-2ndCV with CFLi-flow). (FIG. 3D) OECMS of isotopic13CH4 flowing in and out at E=0.5 V: blue for13CO2 (m / z=45) and green for13CH4 (m / z=17).

[0026] Figures 4A-4D show the comparison of EC and MS cyclic voltammograms of the / ow- / emperature EC-DSMR. Cyclic voltammograms (10 mV / s) obtained on the MEA of Pt / C (4 mg / cm2, anode)|PtRu / C (12 mg / cm2, cathode) with CEL (Figure 4A) and the corresponding CO2 mass (m / z=44) CVs obtained simultaneously by in-line gas chromatograph mass spectrometry (GCMS) (Figure 4B). Cyclic voltammograms (10 mV / s) obtained on the MEA of PtRu / C (12 mg / cm2, anode)| Pt / C (4 mg / cm2, cathode) with CEL (Figure 4D) and the corresponding CO2 mass (m / z=44) CVs obtained simultaneously by in-line GCMS (Figure 4C). The celltemperature was 80 °C and back pressure was 300 kPa. All gas feed were humidified at RH of 90%.

[0027] Figures 5A-5D show isotope labeling experiments in which13C-labeled methane13CH4 was used as the anode pulse feed. Figures 5A and 5B are simultaneous MS readings of13CH4 (m / z = 17) and13CO2 (m / z = 45) respectively at the cell potential of 0.5 V. Figures 5C and 5D are the respective MS readings at the cell potential of 0.3 V.

[0028] Figure 6 shows the specific chronoamperometric current associated CO2 on the Pt / C (top) and the PtRu / C (bottom) measured at 0.5 V, 80 °C cell temperature, and 4 bar back pressure. List of elements in the drawing (26) - 26 - Pt / C, (27) - PtRu / C.

[0029] Figures 7A-7B show the lowest measurable activity by OECMS on the PtRu / C electrode (FIGs. 7A-7B) and the Arrhenius plots of EC-DSMR (FIGs. 7C- 7D). In FIG. 7A, the OECMS (upper panel) and EC (lower panel) CVs of EC-DSMR at 30 °C and 2 bars under Ar (black) and CH4 (red) flow. In FIG. 7B, the potentiostatic OECMS responses of pulse-fed13C isotopic labeled13CH4 at 0.65 V on the PtRu / C for13CH4 (m / z=17) and13CO2. The pressure-dependent Arrhenius plots of EC-DSMR on the Pt / C (FIG. 7C) and PtRu / C (FIG. 7D). Figures 7C and 7D show the activation energy plot of EC-DSMR at 2 bar (square markers), 3 bar (triangle markers), and 4 bar (diamond markers) on Pt / C and PtRu / C. Figure 7Eshows the OECMS of CVs at 30 °C for Pt / C (at 100 kPa): bottom for electrochemistry and top for MS.

[0030] Figures 7F-7G are an example of OECMS CO2 calibration at 80 °C and 4 bar on Pt / C Anode. (FIG. 7F) the m / z=44 signal of CO2 (black) corresponded with the flow meter reading of CO2 flow (red) as external calibration. (FIG. 7G) the linear response of CO2 CPS to the CO2 meter flow rate in SCCM. The slope was used to convert the OECMS CO2 CPS values to the CO2 production rate in mL / min.

[0031] Figures 7H-7K show NEAS experiment on Pt / C (a)(c) and PtRu / C (b)(d) anode at 80 °C and 4 bar. OECMS of CVs under Ar flow (a)(b) and under CEL flow (c)(d): bottom: electrochemistry and top: mass spectroscopy (black-blank(Ar flow); red- 1stCV; blue-2ndCV; green-3rdCV). Under Ar flow, only the 1stCV scan has an oxidative current due to the oxidation of Intad. The slight m / z=44 CPS from 2ndand 3rdtraces in (a) could be due to a slight amount of CEL in Ar. Under CEL flow, all 3 CV- 1 -scans demonstrated oxidative currents. However, the 1stscan had a slightly higher current due to the oxidation of Intad, which formed during the Ar purging by CH4.

[0032] Figures 8A shows a developed OECMS method for obtaining the number of experimental active sites (NEAS): cell potential vs. time (first 20 seconds at 0.8 V (28) and remaining time at open circuit potential (OCP) (30)); OECMS signals of m / z=44 (CO2, 29), m / z=16 (CH4, 32), and m / z=40 (Ar, 33). At time=1600s, CH4 flow was switched into Ar flow. Figure 8B shows the temperature-dependent NEAS of EC- DSMR at 4 bar on Pt / C (triangle markers) and PtRu / C (diamond markers). Figure 8C shows the CO2 production rate vs. NEAS from Pt / C (top 5 blue markers) and PtRu / C (bottom 3 green markers). The inset figure expressed the turnover frequency (TOF) in molecules per second per NEAS at 60 °C (left) and 80 °C (right) on both catalysts. List of elements in the drawing (28) - anode set to 0.8 V for 20 s, (29) - sharp increase in intensity for m / z=44, (30) - open circle potential, (31) - no CO2 production after OCP decrease, (32) - methane, (33) - Ar, (34) - m / z=44 peak at ~3200s, (35) - 3CVs, (36) - Pt / C, (37) - PtRu / C, (38) - insert figure, TOF.

[0033] Figures 9A-9F are a depiction of nudged elastic band paths (starting with reactants on the left-hand side) for the plateau, comer (denoted with a “c”), and edge (denoted with an “e”) Pt(lOO) and Pt(l 11) surfaces as indicated. The energy7of the first point in the path has been used to set the overall zero of energy for the path. Figures 9G-9L are a depiction of the same surface features as in Figures 9A-9F with the surface containing a single subsurface Ru atom.

[0034] Figure 10A shows the preliminary7energetic results of the DFT nudged elastic band calculations of C-H dissociation reaction of CH4 on a Pt(lOO) comer site (bottom) vs on a Pt(lOO) terrace site (top). List of elements in the drawing (39) - Pt(lOO) comer, (40) - Pt(lOO) terrace.

[0035] Figures 10B-10D show7calculations on the adsorption step of CH4 + * -> CHi*: (FIG. 10B) energy' plotted against Pt-C distance; (FIG. 10C) the force plotted against Pt-C distance; (FIG. 10D) summary of Pt-C distance and adsorption energy of CH4* on Pt terrace (111) site, edge site, and comer site. The adsorption energies of the adsorption step (CH4 + * -> CH4*) are quite weak on terrace (111), edge, and comer sites. This is probably associated with the small sticking coefficient of CH4 on Pt. However, CH4 can get much closer to the Pt surface on the comer site (3.34 A) compared to that on the terrace site (4.37 A), favoring the following dissociation step.

[0036] Figure 10E is a depiction of the steps in the nudged elastic band path for the decomposition of CH4 to CH3 + H on a Pt(lOO) surface with a ‘"comer’ feature.” The reaction starts with a H atom attaching to a comer Pt atom (panel 1). Next the C atom moves closer to the same Pt atom (panel 2). At the transition state for the reaction, the C-H bond is broken (panel 4). The H atom continues to migrate until it is bound in a bridge configuration between 2 Pt atoms (panels 6 & 7).

[0037] Figure 10F is similar to Figure 10E, but for a Pt( 111) surface with an “edge” feature and a single sub-surface Ru atom. The path involved the approach of CH4 to the edge feature (panels 1 and 2) and the adsorption of the CH4 to an edge Pt atom via a H atom (panel 3). The transition state (panel 4) involves the breaking of the C-H bond. The H atom then migrates to a bridge-bonded position between two Pt atoms (panel 5) and continues to migrate to an atop position on a neighboring Pt atom (panels 6 and 7).

[0038] Figure 11 A is a schematic of a fuel-cell configuration (as also shown in Figure 1) that we have adapted to demonstrate and study the CH4 electro-oxidation (EO) activity of electrocatalysts. Figure 11 B shows stable open circuit potential (OCP) at 80 °C and ambient pressure of the four electrocatalysts, commercial Pt / C, PtRu / C, CuNi, and home-synthesized AuPd, studied with the fuel-cell configuration in Figure 11 A. The MEA (metal electrolyte assembly) of the four electrocatalysts were made in the lab with a hot pressor. The feeds of humidified CH4 at anode and O2 at cathode were controlled by a fuel-cell test station (805e, Scribner fuel cell housing). List of elements in the drawing (41) - MEA, (42) - anode, (43) - cathode.

[0039] Figures 12A-12D show that CH4 electro-oxidation (EO) currents measured at the cell potentials indicated in the figure on (Figure 12A) Pt / C, (Figure 12B) PtRu / C, (Figure 12C) CuNi, and (Figure 12D) PdAu. The current values given were all measured at 3600 seconds. All currents were after subtracting the corresponding background current obtained by replacing CH4 with nitrogen.

[0040] Figures 13A-13C show the long-term CH4 EO current of (FIG. 13 A) PdAu at 0.05V for 2 hours, (Figure 13B) PtRu / C at 0. IV for 6 hours, and (Figure 13C) NiCu at 0.05V for 48 hours. For the PtRu / C, the cell OCP was measured at a 2- hour interval of which the measured values are shown in Figure 13B.

[0041] Figures 14A-14C show The 90-hour long-term stability test of EC- DSMR at 0.6 V on Pt / C and PtRu / C at 80 °C, and 4 bar using the setup shown inFigure 1 A. Figure 14 A shows CO2 production rate on Pt / C (top - with EC cleaning steps: bottom - no EC cleaning steps) and PtRu / C (top - with EC cleaning steps; bottom - no EC cleaning steps). Figures 14C and 14D show the stable formation rate of CO2 (14C) and Faraday efficiency (14D) from the last 24 hours. The color matches those in Figures 14A and 14B.

[0042] Figures 15A-15B show GC-MS measurements of MeOH in (FIG. 15A) standard sample 1 ppm MeOH in water. (FIG. 15B) MeOH in the eluant of PtRu / C, and (FIG. 15C) MeOH in the eluant of PdAu.

[0043] Figure 16 is a schematic illustration of the hypothetic bifunctional R-l through R-3 on a PteRu in which the light sphere represents Pt and the dark sphere represents Ru.

[0044] Figures 17A-17D show the potential (vs. RHE) dependent in situ IR spectra of formic acid oxidation reaction (FAOR) on commercial Pd black in 0.5 M HCOOD + 0.1 M DC1O4 / D2O: (FIG. 17A) FAOR-generated CO2; (FIG. 17B) HCOOD; (FIG. 17C) FAOR-generated HOD; and (FIG. 17D) formate. The appearance of HOD at the very low potential indicates the special ability of Pd to activate the surface water that enables a reaction of DCOO-Pd + H2O-Pd + e" — > HOD +HCOs +2*Pd.

[0045] Figure 18A shows the PXRD pattern of as-synthesized PdAu interconnected nanochains used in Figs. 1 IB, 12D, and 13A. The standard diffraction peaks for Pd (JCPDS NO. 05-0681, red) and Au (JCPDS NO. 04-0784, blue) are also shown as references The positions of peaks suggest the formation of crystalline alloys and their respective linewidths are consistent with the size seen by the TEM (insets).

[0046] Figure 19A shows the time-dependent in situ EC-IR bands of v(C-H) at 2968 cm’1of Cu-CH3 and the CH4 dissociative adsorption generated COads on Cu at 2030 cm’1and on Ni at 1942 cm’1observed at 1.0 V vs. Ag / AgCl (IM) on the NiCu (1 : 1) alloy surface with humidified CH4 (80 °C) flowing through. Figure 19b shows the comparison of the in situ EC-IR bands of gaseous MeOH’s v(C-O) at 1035 cm’1, the - CHs’s symmetric and asymmetric rocking modes at 1013 cm’1and 1059 cm’1of the gas-phase MeOH produced from direct methane to methanol (DMTM) conversion at 1.0 V on the NiCu (green), as-received PtRu / C (red) and act-PtRu / C (blue).

[0047] Figure 20 shows raman spectra of Cu(I)2O and Cu(II)O, adapted from Debbichi, L, J. Phys. Chem. C 2012, 116 (18), 10232-10237.

[0048] Figure 21A denotes a schematic of a fuel-cell like IR cell for in situ EC ATR-SEIRAS. CE=counter electrode, RE=reference electrode, EI=electrolyte inlet, EO=electrolyte outlet, GI=gas inlet, GO=gas outlet, GDL=gas diffusion layer, Ecatal=electrocatalyst. A Nafion membrane divides the upper part and the lower part of the IR cell, enabling humidified CEE to be transported to electrocatalyst deposited on the IR enhancing Au film. The upper part houses the CE and RE in flowing electrolyte, establishing an overall 3-electrode in situ IR cell. Figure 21B shows a photo showing different parts of the cell. Figure 21C shows a photo of the assembled cell that can be mounted to the IR spectrometer for measurements.

[0049] Figure 22A shows the IR bands of stretching vibration, v(C-H), and bending vibration, 5(H-C-H), of CEE (top) and adsorbed Pt-CFE at the gas-solid- interface with humidified CEE (at 80 °C) flowing over a commercial PtRu (1 : 1) black surface. The insets are the DFT (Gaussian) calculated IR spectra that confirm the band assignments. Figure 22B shows the time-dependent in situ EC-IR spectra of v(C-H) and 5(H-C-H) of the adsorbed Pt-CFE at 0.9 V, 1.0 V and 1.1 V on the PtRu (1: 1) black surface under the same expenmental conditions as in Figure 22A.

[0050] Figures 23 A and 23B show unit cells of metal slab model with a PtsRu surface and representative surface species used for DFT calculations.

[0051] Figure 24 shows the possible two-TM-atom (Pt and / or Ru) configurations with an intemuclear separation fixed at the bulk geometry for R-3 used in the model DFT calculations.

[0052] Figure 25 A shows in situ IR spectra of MeOH-generated (M)-COL (L stands for linear bonding atop a surface atom) on as-received (asrec-), activated (act-), deactivated (deact-) PtRu, Pt / C, and Ru / C. respectively. These series of IR spectra help identify CO IR peaks on the PtRu surface. Figure 25B shows the IR spectra of M-COL after the first (left) and tenth (right) step-potential (SP) as the SP value changes from 0.865 V to 1.365 V. Adapted from Chen, et al., Chemical communications 2014, 50. 12963-12965.

[0053] Figure 26 shows a comparison of the IR spectra of MeOH in gaseous (NIST standard) and liquid phase with those taken during the EO of CEE on the un- activated / asreceived and activated PtRu / C surface at 1 V vs Ag / AgCl (IM). The middle spectrum was obtained at 1 V with Ar only. The gas feed was humidified at 80 °C and the spectra were the results of signal average of 30 interferogramms.

[0054] Figure 27A shows sulfide-coverage dependent SEIRAS spectra at 0.0 V (vs. RHE) in CH4-saturated electrolyte. Figure 27B shows total COads coverage normalized by saturated gaseous CO on pure Pt before sulfide adsorption as a function of sulfide coverage.DETAILED DESCRIPTION

[0055] The present invention may be understood more readily by reference to the following detailed description of preferred embodiments of the invention and the Examples included therein and to the Figures and their previous and following description.I. Definitions

[0056] In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings, which form a part hereof, and within which are show n by way of illustration specific embodiments by which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the invention. Electrical, mechanical, logical, and structural changes may be made to the embodiments without departing from the spirit and scope of the present teachings. The following detailed description is therefore not to be taken in a limiting sense, and the scope of the present disclosure is defined by the appended claims and their equivalents.

[0057] The following disclosure discusses the present invention with reference to the examples shown in the accompanying drawings, though does not limit the invention to those examples.

[0058] The use of any and all examples, or exemplary language (e. , “such as”) provided herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential or otherwise critical to the practice of the invention, unless made clear in context.

[0059] As used herein, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Unless indicated otherwise by context, the term “or” is to be understood as an inclusive “or.” Terms such as “first”, “second”, “third”, etc. when used to describe multiple devices or elements, are soused only to convey the relative actions, positioning and / or functions of the separate devices, and do not necessitate either a specific order for such devices or elements, or any specific quantity or ranking of such devices or elements.

[0060] The word “substantially”, as used herein with respect to any property or circumstance, refers to a degree of deviation that is sufficiently small so as to not appreciably detract from the identified property or circumstance. The exact degree of deviation allowable in a given circumstance will depend on the specific context, as would be understood by one having ordinary skill in the art.

[0061] Use of the terms “about” or “approximately” are intended to describe values above and / or below a stated value or range, as would be understood by one having ordinary skill in the art in the respective context. In some instances, this may encompass values in a range of approx. + / - 10%; in other instances there may be encompassed values in a range of approx. + / -5%; in yet other instances values in a range of approx. + / -2% may be encompassed; and in yet further instances, this may encompass values in a range of approx. + / -!%.

[0062] It will be understood that the terms “comprises” and / or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof, unless indicated herein or otherwise clearly contradicted by context.

[0063] Recitations of a value range herein, unless indicated otherwise, serves as a shorthand for referring individually to each separate value falling within the stated range, including the endpoints of the range, each separate value within the range, and all intermediate ranges subsumed by the overall range, with each incorporated into the specification as if individually recited herein.

[0064] Unless indicated otherwise, or clearly contradicted by context, methods described herein can be performed with the individual steps executed in any suitable order, including: the precise order disclosed, without any intermediate steps or with one or more further steps interposed between the disclosed steps; with the disclosed steps performed in an order other than the exact order disclosed; with one or more steps performed simultaneously; and with one or more disclosed steps omitted.

[0065] As used herein, “MRR” or methane reforming reaction and “SMR” or steam methane reforming refer to the conversion of hydrocarbon feedstocks, such as methane, into a synthesis gas product, often a mixture of hydrogen, carbon dioxide, and carbon monoxide gas.

[0066] As used herein, “WGS” or water gas shift refers to a process for the conversion of carbon monoxide and water to carbon dioxide and hydrogen.

[0067] As used herein, "PSA" or pressure swing adsorption refers to a method for separating gases in a mixture of gases.

[0068] As used herein, “PEMFC” or proton exchange membrane fuel cells, also known as a polymer exchange membrane (PEM) fuel cells, are a type of fuel cell built out of membrane electrode assemblies (MEAs), and which use a proton-conducting polymer membrane as the electrolyte.

[0069] As used herein, “EO” or electro-oxidation refers to oxidation of a substance at the anode of an electrochemical cell.

[0070] As used herein, “EC -MRR"’ or electrochemical methane reforming reaction refers to a methane reforming reaction wherein CEE undergoes electrochemical oxidation. Likewise, “LT-ECMRR” refers to the low-temperature electrochemical methane reforming reaction.

[0071] As used herein, “OECMS” or operando electrochemistry-mass spectrometry refers to a method of simultaneous characterization of compounds and reaction at an electrochemical cell (Pang, et al., ACS Energy Lett. 9, 7, 3587-3594, 2021).

[0072] As used herein, “NHE” or normal hydrogen electrode refers to a redox electrode commonly used in electrochemistry as the reference standard for redox potentials. “RHE’’ or reversible hydrogen electrode refers to an electrode that adjusts potential based on the concentration of H+ions in solution.

[0073] As used herein, “GDL” or gas diffusion layer refers to a porous device that facilitates gaseous diffusion through a membrane. When a catalyst is applied, it is known as a gas diffusion electrode (GDE) (What is the Purpose of a Gas Diffusion Layer.

[0074] As used herein, Pt(lOO) refers to a square cry stallographic arrangement of platinum atoms, and Pt( 111) refers to a hexagonal arrangement of platinum atoms, which is more close-packed.

[0075] As used herein, CO stripping refers to the process of oxidizing a layer of carbon monoxide adsorbed to the surface to an electrocatalyst to release it. CO adsorption may lead to catalyst poisoning.

[0076] As used herein, “OCP” or open-circuit potential refers to the potential of a electrode when no current is flowing.

[0077] As used herein, “FE” refers to Faraday Efficiency.

[0078] As used herein, “EC” refers to electrochemistry or electrochemical.

[0079] As used herein, "‘CV” refers to cyclic voltammetry.

[0080] As used herein, “MS’’ refers to mass spectrometry.

[0081] As used herein, “TOF” refers to turnover frequency.

[0082] As used herein, “dFS” refers to deactivated fused silica.

[0083] As used herein, '‘RH” refers to relative humidity.

[0084] As used herein, “NEAS” refers to the number of experimental active sites.

[0085] As used herein, DFT " refers to density functional theory.IL Methane as a feedstock

[0086] Achieving methane (CEL) to high-value chemicals conversion with high selectivity7and efficiency under mild conditions has long been considered as a “holy grail of chemistry’’ (Ravi, et al., Angew. Chem. Int. Ed. 2017, 56 (52), 16464-16483) or “a remaining grand challenge in chemistry”(Nguyen. V. T., Ph.D. Thesis, Colorado School of Mines, 2017; Joglekar, et al., J. Am. Chem. Soc. 2016, 138, 1 16-125). As such, it has been repeatedly identified in the recent DOE-BES reports (Nandenha, et al., Int. J. Electrochem. Sci. 2019, 10819-10834; Boyd, et al., ACS Catal. 2019, 9 (8), 7578-7587; Xu, et al., Catal. Today 2016, 270. 93-100; Snyder, et al., Chem Rev 2017, 118 (5), 2718-2768) as a major unsolved scientific problem of great significance for catalysis. Furthermore, as the fracking-enabled-easier-access-to-cheaper-shale-gas has changed the energy landscape in US and worldwide and it is further projected that it will reach about 60% of the market share in 2040s (Banerjee, et al.. Nature 2015, 518 (7539). 431-434; Grundner, et al., Nat Comms 2015, 6, 1-9), there is a reinvigorated urgency of researching and developing better catalysis for addressing this “holy grail of chemistry". Furthermore, large amount of CPU whose green-house effect is about 20 times more potent than CO2 could be released from CPU permafrost and clathrate stored in the Arctic if the current global wanning trend is not reversed timely.Consequently, CH4 management is also becoming increasingly a pressing environmental issue facing industry, government, and academy altogether on a global scale (Science 2017, 356 (6337), 523-527; Journal of the American Chemical Society / 2000, 722 (17), 4129-4144).

[0087] One method for the management and use of CH4 is its conversion to hydrogen in the methane reforming reaction (MRR). In addition to the benefit of managing methane, hydrogen presents a cleaner alternative to hydrocarbon fuel sources, producing only water when combusted. Its alternative, fossil fuels, such as coal, oil and gas, are composed of hydrocarbons with varying ratios of carbon and hydrogen, and are non-renewably used when combusted, forming carbon dioxide and water. Despite their wide application and high demand, fossil fuels present a number of disadvantages, including the finite reserve, irreversible combustion and contribution to air pollution and global warming. Considering these disadvantages, and the increasing demand for energy, alternative sources of energy are needed.

[0088] Because free hydrogen is not a natural energy’ source, methane (CH4), the major component of natural gas, is often used as the feedstock in high-value fuel productions via methane reforming reaction (MRR). For example, CH4 can generate H2 via steam methane reforming (SMR) (Hydrogen Production: Natural Gas Reforming. Energy.gov; Sweeney, et al., 2023) and water-gas shift (WGS) reaction, liquid methanol via partial oxidation (Luo. et al., 2021; Jin, et al., 2021), and solid carbon via CH4 pyrolysis (Upham, et al., 2017).

[0089] However, due to its strong C-H bond (439 kJ mol'1), CH4 has long been perceived as a highly chemically inert feed, making SMR and WGS a highly energyconsuming process (Y uliati, et al., 2008):

[0090] Specifically, SMR requires high temperatures and pressure up to 1000 °C and 35 bar, respectively (Hydrogen Production: Natural Gas Reforming. Energy website). SMR produces a syngas consists of hydrogen, carbon monoxide, methane and carbon dioxide. Higher quantities of hydrogen are usually produced by further reacting the syngas with steam over a catalyst to promote the water gas shift reaction of carbon monoxide and steam to hy drogen and carbon dioxide. Additionally , the hydrogen must often be purified from any residual carbon monoxide. This will produce a final product hydrogen stream with about 97% purity. The remainingcomposition is methane, nitrogen (N) and argon (Ar). If higher purity hydrogen (>99%) is desired, the hydrogen is further processed through a Pressure Swing Adsorption (PSA). Due to the limits of PSA technology, the typical hydrogen recovery is about 87-90% (Sjardin, M.; et al., Energy 2006, 31, 2523- 2555). Despite the large energy' intake for the SMR process, it is still responsible for 76% of the worldwide H2 demand (Sweeney, et al., 2023). Therefore, researchers have never ceased to find a better and more energy-efficient MRR method. Among others, electrochemical (EC) methods have been explored as promising alternatives, such as widely studied methane electro-oxidation in solid oxide fuel cells (>300 °C) (Wang, et al., Chem. Rev. 113, (2013)).

[0091] The selective EC conversion of CH4has its own uniqueness and advantages for both practical applications and fundamental studies. It represents emerging alternative opportunities to the conventional high-temperature steam reforming and combustion of CH4 (Xie, et al., Journal of Energy Chemistry 2018, 27 (6). 1629-1636; Baltrusaitis. et al.. Catalysis Science & Technology 2014, 4 (8), 2397- 15). This is rooted fundamentally in that since EC reactions are driven by either electrode potential or current, they can most likely take place under mild recti on conditions (for example, at <100 °C and ambient pressure for the direct methane-to- methanol (DMTM) conversion). Moreover, as the potential or current can be precisely controlled, so can be the EC reactions, which is ideal for in situ mechanistic studies.III. Feasibility of EC DMTM Conversion

[0092] The standard potential for the DMTM conversion, CH4+ H2O — > CH3OH + 2FT + 2e", is 0.58 V vs normal hydrogen electrode (at pH = 0, 298 K) (Xie, et al., Journal of Energy Chemistry 2018, 27 (6), 1629-1636), which is in a practically reachable potential region. Indeed, our own data (vide infra)' as well as recent work from others (Xie, et al., Journal of Energy Chemistry 2018, 27 (6), 1629-1636; Nguyen, V. T., Ph.D. Thesis, Colorado School of Mines, 2017; Joglekar, et al., J. Am. Chem. Soc. 2016, 138, 116-125; Nandenha, et al., Int. J. Electrochem. Sci. 2019, 10819-10834; Boyd, et al.. ACS Catal. 2019, 9 (8), 7578-7587) have clearly demonstrated that electrocatalytic DMTM conversion at low temperature and pressure appears to be feasible and promising.

[0093] Inspired more specifically by the chemistries learned from the “Shilov circle” (Shilov, et al., Chemical Reviews 1997, 97 (8), 2879-2932; Shilov, et al.,Coordination Chemistry Reviews 1977, 24 (2), 97-143) and the “Periana catalyst'’ (Hashiguchi, et al.. Accounts of Chemical Research 2012, 45 (6), 885-898.; Periana, et al., Science 1998, 280 (5363), 560-564) in homogenous catalytic DMTM conversions on the one hand and the enzy me (monooxygnese) mimic Fe- and Cu-exchanged zeolites (Xu, et al., Catal Today 2016, 270, 93-100; Snyder, et al., Chem Rev 2017, 118 (5), 2718-2768; Banerjee, et al., Nature 2015, 518 (7539), 431-434; Grundner, et al., Nat Comms 2015, 6, 1-9; Sushkevich, et al.. Science 2017, 356 (6337), 523-527) in heterogenous catalytic DMTM conversions on the other hand, we hypothesize that having right electrophilic / oxidative sites on the surface of electrocatalysts that favor agostic interaction (Labinger, et al., Journal of Organometallic Chemistry 2015, 793, 47-53; Papoian, et al., Journal of the American Chemical Society 2000, 122 (17), 4129- 4144; Broderick, et al., Inorg Chem 1991, 30 (20), 3875-3881) with methane’s saturated C-H bonds is an advantageous condition for an electrocatalyst to be active for electrocatalytic DMTM conversions.

[0094] Mechanistically, it is rather straightforward to hypothesize that an electrocatalytic DMTM conversion on transition metal (TM) surfaces could involve the following bi-functional elemental reaction steps:CH4 + 2TM* -ATM |-Cf 13 + TM2-I l^TM 1-CI 13 + TM2* + H++ e [2] H2O + 2TM* -> TM’ 1-OH + TM’2-H -> TM’ 1-OH + TM’2* + H++ e [3] TM1-CH3 + TM’ l-OH -> CH3OH + TM1* + TM’l* [4] where * is for a free site and TM and TM’ can be the same or different metal elements. However, in terms of having catalytic tunability for basic mechanistic studies, an alloyed bi-metallic surface would be a better choice than a single-metal one as it would be much more difficult if not impossible to optimize the Reaction [2] and [3] (R- 2 and R-3) simultaneously by which to optimize the Reaction [4] (R-4) on a singlemetal than on a bi-metallic surface. Experimentally, we have indeed observed Faraday efficiencies of about 6% and 11% for electrocatalytic DMTM conversion on PtRu and PdAu respectively at 80 °C. Both are much more active than single Pt or Pd metal, suggesting strongly that R-l through R-3 were likely operational.

[0095] Guided by the aforementioned hypotheses, provided herein are detailed comparative mechanistic studies of the electrocatalytic DMTM conversion on PtRu, PdAu, and NiCu electrocatalysts.IV. Homogeneous Catalysis of DMTM Conversion

[0096] Homogeneous catalysis has long been at the forefront of incessant endeavors in devising milder ways for DMTM conversion, from the early days’ doubting its mere feasibility to the current full-throttle and widely pursued investigations aiming at real -world applications (Labinger et al., Journal of Organometallic Chemistry 2015, 793, 47-53; Gunsalus et al.,. Chem Rev 2017, 117 (13), 8521-8573; Ravi et aL. Angew. Chem. Int. Ed. 2017, 56 (52), 16464-16483;Schwarz, Angew. Chem. Int. Ed. 2011, 50 (43), 10096-10115; Labinger, et al., Nature 2002, 417 (6888), 507-514; Zhou, et al., Chem. Soc. Rev. 2011, 40(4), 1875-11;Conley, et al., Journal of Molecular Catalysis A: Chemical 2006, 251 (1-2), 8-23), largely inspired by the discoveries of the ‘"Shilov circle” (Shilov, et al., Chemical Reviews 1997, 97 (8), 2879-2932; Shilov, et al., Coordination Chemistry Reviews 1977, 24 (2), 97-143) and the “Periana catalyst” (Hashiguchi, et al., Accounts of Chemical Research 2012, 45 (6), 885-898; Periana, et al., Science 1998, 280 (5363), 560-564). Notwithstanding that no industrial processes of DMTM conversion under mild conditions have yet been materialized so far. which is a testament of the high degree of difficulty involved, rich molecular-level chemistries have indeed been uncovered that have advanced our fundamental understanding of the processes needed for breakthroughs. What embodied in the Shilov chemistry are highly instructive to the research proposed herein. First, the Shilov chemistry demonstrates that a C-H bond in CH4 can be activated by a mechanism other than the usually expected homolytic C-H bond cleavage that is the major limiting factor in selective alkane oxidation via radical-based mechanism (Labinger, et al., Journal of Organometallic Chemistry 2015, 793, 47-53). In other words, the Shilov chemistry makes DMTM conversion under mild conditions feasible, at least in principle. Second, the formation of a stable metal-CH3intermediate in Shilov chemistry implies strongly that the initial step of the C-H activation is via an agostic interaction between the C-H bonding electron pair and the metal center Pt(II). Such an agostic interaction could also be operational on transition metal surface (Papoian, et al., Journcd of the American Chemical Society 2000, 122 (17), 4129-4144), as hypothesized in Figure 16. Third, the formation of MeOH derivatives, such as CH3OSO3H, as a protective way to prevent MeOH from being further oxidized, is considered indispensable for achieving high DMTMconversion (Ravi et al., Angew. Chem. Int. Ed. 2017, 56 (52), 16464-16483; Ahlquist, el al.. J. Am. Chem. Soc. 2009, 131 (47). 17110-17115).V. Heterogeneous Catalysis of DMTM Conversion

[0097] While silica-supported molybdenum (MoO3) trioxides and vanadium (V2O5) pentoxides dominated early research in heterogeneous catalysis of DMTM conversion. enzyme-(monooxygnese)-mimic Fe- and Cu-exchanged zeolites have been the focus of late (Xu et al., Catal. Today 2016, 270, 93-100; Snyder, et al., Chem Rev 2017, 118 (5), 2718-2768; Banegee, et al., Nature 2015, 518 (7539), 431-434; Grundner, et al., Nat Comms 2015, 6, 1-9; Sushkevich, et al., Science 2017, 356 (6337). 523-527). It is generally believed that, as suggested by the MoOs or V2O5 loading dependent DMTM conversion activity, the terminal M=O sites, not the O-M-O bridge sites, are the active sites for CH4conversion to formaldehyde for the former and DMTM conversion for the latter (Ravi, et al., Angew. Chem. Int. Ed. 2017, 56 (52), 16464-16483). On the other hand, DFT calculations of alkane activation on PdO(lOl), RUO2(110) and IrO2(l 10) (Weaver et al., Chemical Society Reviews 2014, 43 (22), 7536-7547) predict that the C-H bond is readily activated, as observed experimentally (Liang, et al., Science 2017, 356 (6335). 299-303), via forming strong dative bonds to the coordinately-unsaturated-surface metal sites that leads to the formation of rather strongly adsorbed surface alkane a-complex, similar to the agostic bond formed in the homogeneous catalysts discussed above.

[0098] As to Fe- or Cu-exchanged zeolites, the proposed representative mechanisms of DMTM conversion (Snyder, et al., Chem Rev 2017, 118 (5), 2718- 2768). In Fe-BEA (beta polymorph A, disordered framework), N2O is first activated by forming a dative complex with Fe2+center, which is then converted into the electrophilic a-0 (Fe4+=O) reactive intermediate. The a-0 continues to react oxidatively with CH4, producing MeOH and return Fe to its original oxidation state Fe2+(Snyder, et al., Nature 2016, 536. 317). In Cu-ZSM-5, O2 is activated byoxidizing two adjacent Cu(I) and forms the precursor by bridging them. One of the oxygen atoms is then cleaved off reductively, generating a highly electrophilic Cu(II)2O reactive intermediate to react with CH4for DMTM conversion and returning the two participating Cu back to the original Cu(I) (Smeets, et al., Journal of the American Chemical Society 2010, 132 (42). 14736-14738). Although they differ fromthe cases in homogenous catalysis by activating the oxidant instead of the C-H bond, having the right electrophilic metal centers is still the underlying key chemistry for DMTM conversion. Similarly, an empirical correlation between increasing CH4conversion rate and decreasing MeOH selectivity' in DMTM conversion over the solid catalysts was observed if the produced MeOH was not protected (Ravi, et al., Angew. Chem. Int. Ed. 2017, 56 (52), 16464-16483), indicating that the latter continued to react as it is more reactive than CH4under most circumstances. However. experimental data also strongly suggest that using multicomponent catalysts can be an effective way to prevent the produced MeOH from being further oxidized (Ravi, et al., Angew. Chem. Int. Ed. 2017, 56 (52), 16464-16483), which rends strong support to our proposed bimetallic approach.VI. Electrocatalysis of DMTM Conversion

[0099] As alluded above, low-temperature electrocatalytic DMTM conversion represents an emerging alternative to homogeneous and heterogenous approaches, potentially of great promise. But it is indeed somewhat surprising that it hasn’t gained a lot of tractions in both industry and academia despite decades’ on-going research (Tomita, et al., Angewandte Chemie International Edition 2008, 47 (8). 1462-1464; Lee et al.. Journal of Catalysis 2010, 271 (2), 195-200; Caims, et al., Adv.Electrochem.

[0100] Electrochem. Eng., Tobias, C. W., Ed. Wiley -Interscience: New York, 1971: Vol. 8, p 337; Ogura, et al., Nature 1986, 319, 308; Cook et al., J.Eelectrochem. Soc. 1990, 137 (6). 2007-2008; Freese Jr, et al., Langmuir 1991, 7, 13- 15; Hahn, et al., Electrochimica Acta 2001, 46, 3515-3534; Lin, et al.. Solid State Ionics 2005, 176 (23-24), 1827-1835; Lee, et al., Journal of Catalysis 2011, 279 (2), 233-240; Zhang, et al., Chemistry Letter 1997, 26. 363-364; Murray, et al., Nature 1999, 400, 649- 651; Li, et al.. J. Phys. Chem. C 2010, 114 (2), 723-733; Rocha, et al.. Electrochimica Acta 2013, 87, 606-610; Wang, et al., .7. Electrochem. Soc. 2013, 160 (9), H604-H611; Joglekar, et al., J Am Chem Soc 2016, 138 (1), 116-125;Promoppatum, et al., ACS Sustainable Chem. Eng. 2016, 4 (3), 1736-1745; Nandenha, et al.. Journal of Fuel Chemistry and Technology 2018, 46 (9), 1137-1145; Tan, et al., Materials Research Express 2018, 5 (3), 035056; Torabi, et al., ECS Trans 2016, 73, 193-199), that can be traced back to early 1960s (Grubb, et al., Nature 1964, 201, 287- 288). This probably has to do with (1) methane’s very low solubility' in water (~ 23ppm) and equally low sticking coefficient for adsorption on most transition metals (-0.06 on Pt(l 11). Schoofs, et al.. Surf. Set. 1989, 215 (1-2), 1-28) that have rendered measuring its activity difficult if not impossible and (2) a time mismatching between the early interest and the wide availability of in situ EC spectroscopies that are necessary for advancing molecular-level mechanistic understanding of electrocatalytic DMTM conversion, e.g., R-l through R-3 is a hypothetic one, which involves multi-step and complex reactions. The generally perceived challenges in achieving DMTM conversion and overall lack of available EC data on it have led to somewhat pessimistic believe (Baltrusaitis, et al., Catalysis Science & Technology 2014, 4 (8), 2397-15) that few direct CH4EC oxidation processes can lead to stable and isolable partial oxidation products such as MeOH. Yet, some recent studies show the contraries, i.e., DMTM conversion is not only feasible but also tunable to different electrocatalysts (Xie, et al., Journal of Energy Chemistry 2018, 27 (6), 1629-1636; Tomita, et al., Angewandte Chemie International Edition 2008, 47 (8), 1462-1464; Lee, et al., Journal of Catalysis 2010, 271 (2). 195-200; Lee, et al.. Journal of Catalysis 2011, 279 (2), 233-240).

[0101] Notwithstanding the scope and depth of electrocatalysis of DMTM conversion are far behind those of its homogeneous and heterogenous counterparts, the results presented in art (Lee, et al.. Journal of Catalysis 2010, 271 (2), 195-200; Lee. et al., Journal of Catalysis 2011, 279 (2), 233-240; O”Reilly, et al., ACS Cent. Sci. 2017, 3 (11), 1174-1179) highlight somewhat similar underlying chemistry7between them. Hibino et al.’s work that showed that (1) a cathodic DMTM conversion in a fuel cell setting with solid proton conducting membrane had a better performance on a carbon-supported tri-component (Pt-Au-CuO / C) than on a bi-component (Pd-Au / C) electrocatalyst (Lee et al., Journal of Catalysis 2010, 271 (2), 195-200) and (2) a anodic DMTM conversion over some early transition metal oxides had V2O5 as the best electrocatalyst (Lee et al., Journal of Catalysis 2011, 279 (2), 233-240), as were observed in the cases of heterogeneous catalysis discussed above.

[0102] VII. Developing a Novel Fuel-Cell like in situ IR Cell Enabling the Observation of CH4-EO- Produced MeOH

[0103] Realizing that CEL has an intrinsically low solubility in aqueous electrolyte and also low sticking coefficient for adsorption on most transition metals,the inventor designed and successfully made a novel fuel- cell like in situ IR cell that enables humidified CH4 to be transported directly to electrocatalyst surface by which more amount of reaction-produced species can be generated at the surface thereby to im- prove IR signal over noise ratio. The detail of the cell is shown in Fig. 21A-21C.

[0104] Figure 22 presents the results of the first successful in situ IR measurements carried on a commercial PtRu (1 : 1) using the above cell. Figure 22A compares the in situ IR spectra of gaseous CH4 (red) and surface-adsorbed methyl (Pt-CHs). The insets show the Gaussian DFT calculated IR spectra of gaseous CH4 (top) and of Pt-CH ; (bottom). The rather good agreement between the experimentally observed and DFT-calculated IR frequencies strongly suggests that the first C-H activation took place at Pt sites. Figure 20B compares the time-dependent in situ IR measurements at 0.9V, 1.0V and 1.1V (vs. Ag / AgCl (IM) reference electrode) respectively after potential jump from OV. As can be seen, the adsorbed CH3 was already observed at OV (top spectra), suggesting a reaction step CH4 + Pt ® Pt-CHs + H++ e (or Pt-H) taking place, i.e., R-l in Figure 16. At 0.9V, a gradual decrease in the CH3 bands was observed, indicating further oxidation of Pt-CFL. However, no Pt-CH3 was observed at 1.0V and 1. IV, which could be a result of either faster oxidation of Pt-CH or the electrode potential was too high for surface-bound OH to survive for R- 3 to proceed.

[0105] VII. Palladium, platinum, gold, ruthenium, nickel, and copper as transition metal surfaces for methane conversionPtRu offers an excellent platform to unravel the bifunctional nature of the reaction mechanism as expressed in R-l through R-3. This is because alloying Pt with Ru not only makes the Pt next to Ru more electrophilic / oxidative (Kim et al., ChemCatChem 2017, 9 (9), 1683-1690) therefore could be better for R-l than pure Pt (we indeed observed IR peaks of Pt-CH? on a PtRu surface but not on pure Pt) but also is Ru a well-known element for R-2 (Abild- Pedersen, et al., Phys. Rev. Lett. 2007, 99 (1), 016105). This would lead to RuPt-CH3 + PtRu-OH ® H3COH + RuPt* + PtRu* (the prefix subscript indicates a next- nearest-neighboring element) and rationalize the observation that PtRu has a higher EC direct methane-to-methanol (DMTM) conversion than pure Pt. Also, in view of Pt being a better hydrogen-adsorbing element than Ru, an optimal active PtRu surface ensemble for R-l through R-3 could be a hexagonal Pt6Ru with Ru at the center, as illustrated in Figure 15 . On the other hand, the inventor recognizes that PtRu is alsoamong the best electrocatalysts for methanol (MeOH) electro-oxidation (EO), which may impose challenging constrains on the overall selectivity of the reactions toward MeOH, like any catalytic processes for DMTM conversion would face (Labinger, et al., Journal of Molecular Catalysis A: Chemical 2004, 220 (1), 27-35). However, there is evidence that suggests that accelerating mass transport away from the surface may alleviate these constrains (Seidel, et ^.. Langmuir 2010, 26 (5), 3569-3578; Amarson, et al., Phys. Chem. Chem. Phys 2018, 20 (16), 11152-1 1159), in agreement with the inventor’s observation that the MeOH from the DMTM conversion on the PtRu was in the gaseous form (vide infra).

[0106] In addition to the inventor’s observation that a 5-nm PdAu electrocatalyst showed a Faraday efficiency of about 11% for EC DMTM conversion at 80°C, it was also observed previously that the PdAu’s activity in electrocatalytic DMTM conversion depended on the atomic ratio between Pd and Au, with the highest activity observed at Pd:Au = 8:1 (Tomita, et al., Angewandte Chemie International Edition 2008, 47 (8), 1462-1464). However, although Au has a high electroneg- ativity than Pd. experimental XPS and theoretical DFT calculations (Zhu. et al.. Nat Comms 2019, 10 (1), 362-1 1) indicate that neither Pd nor Au becomes more electron deficient after alloying Pd with Au or vice versa. Instead, alloying changes s-d hybridization at the element and local density of states at the Fermi level (Wang, et al., Aip Advances 2018, 8 (6), 065210; Burch, et al., Accounts of chemical research 1982, 15 (1). 24- 31). This suggests that the underlying chemistry for the observed EC DMTM activity on PdAu may be more nuanced than just total electron-deficient. On the other hand, our own investigation of formic acid EO on Pd (see Fig. 16) suggests strongly that pure Pd possesses a strong ability in activating H2O. i.e., R-2. which may underlie the observation that Pd showed the highest activity in electrocatalytic DMTM conversion among the four metals (Au, Pt, Rh, and Pd) studied (Tomita, et al., Angewandte Chemie International Edition 2008, 47 (8), 1462-1464). The inventors therefore hypothesize that the effect of alloying Pd with Au makes the Pd next to Au more active for R-l through modification of s-d hybrid- ization or / and local density of states at the Fermi level. Thus, an optimal active PdAu surface ensemble for R-l through R-3 could be a hexagonal PdeAu with Au at the center, in qualitative agreement with observing the highest activity at Pd: Au = 8: 1 (Tomita, et al., Angewandte Chemie International Edition 2008, 47 (8), 1462-1464).

[0107] Experimental results suggested that methane EO on NiCu surface follow different reaction pathways as compared with on PtRu or PdAu surface. Since Cu has also shown a rich chemistry in C-H activation (Braga, et al., Organometallics 2006, 25 (22), 5292-5300) while Ni can form diverse hydroxides on surface (Ritzert, et al., J. Phys. Chem. C 2016, 120 (48), 27478-27489) and w as investigated for CH4EO (Jafarian. et al.. Electrochemistry Communications 2003, 5 (2), 184-188). NiCu is expected to offer a thought-provoking contrasting system whose comparison will further the fundamental understanding of electrocatalytic DMTM conversion on transition metal surfaces, let alone Cu and Ni are two non-precious, earth abundant metals. Furthermore, it was observed that impregnating the PdAu with CuO could enhance the former’s activ ity in electrocatalytic DMTM conversion (Lee et al., Journal of Catalysis 2010, 271 (2), 195-200) and Cu-containing zeolites showed exceptional activity' in gas-phase, heterogenous DMTM conversion (Snyder, et al., Chem Rev 2017, 118 (5). 2718-2768; Grundner, et al.. Nat Comms 2015, 6. 1-9;Sushkevich, et al., Science 2017, 356 (6337), 523-527).

[0108] Altogether thence, unraveling the diverse chemistries that these three chosen electrocatalytic systems can bring in play in understanding the fundamental chemistries of and by which to optimize electro- catalytic DMTM conversion w ould make timely and compelling intellectual contributions toward dis- covering the “holy grail of chemistry”.

[0109] Disclosed herein is the observation of sustained low-temperature (< 80 °C) EC-CH4 reforming reactions (EC-MRRs) on commercial carbon-supported Pt and PtRu electrocatalysts in a commercial single-stack proton exchange membrane fuel cell (PEMFC). The reaction activity was further confirmed by isotopic labeling using13CH4with a home-built operando electrochemical mass spectrometry (OECMS). The observations disclosed herein substantiate, likely for the first time, the claim made by Grubb and Michalske six decades ago. Moreover, kinetics studies were conducted on various electrocatalysts and it was found that the activation energy for EC-MRR is surprisingly low: 37.8 ± 2. 1 kJ / mol and 42.4 ± 3.7 kJ / mol for Pt / C and PtRu / C electrodes, respectively. The experimental results disclosed herein suggest that EC- MRR is actually not a difficult process to achieve as long as the right active sites are present. LT EC-MRR is not only possible but also surprisingly easy on a gas / solid interface when using gas diffusion electrode layers. Our LT EC-MRR was observedwithout an extensive period of CH4 adsorption / dissociation, making it feasible to study the reaction kinetics directly. The CH4 oxidative activity was even observable at 30°C and 2 bar and was confirmed via the detection of13CCh using13CH4 as the anode feed. Density functional theory based nudged elastic band calculations supporting evidence for such low activation energies and additional insights into the kinetic barriers on certain possible surface active sites. DFT and NEAS studies provided strong evidence in determining the activity behind comer / comer-like surface sites. Our results provide direct evidence that the electro-activation of saturated hydrocarbons is achievable on a gas / solid interface under mild conditions. Additionally, the experimental surface active studies will facilitate in designing of better EC interfaces for LT EC-MRR.VIII. Electrocatalytic methane reforming under mild conditions to generate hydrogen

[0110] In another embodiment, the disclosure provides a low temperature methane reformer, wherein the metal-membrane-assembly comprises an electrocatalyst that is capable of promoting both hydrogenation and partial oxidation reactions.

[0111] Electrochemical (EC) methods have also been explored as promising alternatives for methane reforming, such as widely studied methane electro-oxidation in solid oxide fuel cells (>300 °C) (Wang et al., 2013). These processes present a more sustainable method for the production of oxygenates in mild conditions. The potential ability to control selectivity by adjusting the voltage is an appealing characteristic. Steady efforts have been made in achieving an EC-MRR under room / mild temperatures and near / under ambient pressure (Wang et al., 2021; Grubb, et al., 1964; Sustersic, et al., 1980). Indeed, in a 1964 Letter to Nature, Grubb and Michalske reported an observation of EC oxidation of CEL in a phosphoric acid fuel cell at 150 °C and proclaimed that “previous ideas regarding the inertness of saturated hydrocarbons toward electrochemical oxidation must be drastically revised7’.However, the ensuing studies have largely failed to substantiate Grubb and Michalske’s claim.

[0112] Electrocatalysts for methane oxidation have been primarily based on platinum (Pt) or platinum alloyed with one or more other metals, such as ruthenium (Ru) (Mostaghimi, et al., 2020). Several studies have provided insight into thecharacteristics and mechanism of methane reforming on Pt surfaces, showing that Pt(lOO) can activate methane, that the rate-determining step is the activation of methane, and that Pt interaction at edges are the most likely reactions centers (Ma, et al., 2019; Boyd, et al., 2019; Gurses,et al., 2021).IX. Compact membrane fuel cell reformers

[0113] In one embodiment, the disclosure provides a low-temperature methane reformer comprising a proton-exchanged membrane fuel cell comprising an anode and a cathode, wherein hydrogen is produced at the cathode.

[0114] Methane steam reforming is a widely used method to produce hydrogen at large-scale due to the well-developed methane infrastructures and the favorably high hydrogen to carbon ratio of methane (Brown, L.F.. Int. J. Hydrogen Energy 2001, 26, 381-397). However, the current existing large-size reformer technology operates under high temperature (>800 °C) and high-pressure and is not suitable for small scale hydrogen production.

[0115] Smaller-size reformers use membrane fuel cell technology, which requires compact and low cost reformers (Sjardin. M.; et al., Energy 2006, 31, 2523- 2555). The compact reformers have shown promise for economic small-scale hydrogen production, e.g. at refueling stations, and have the potential of inexpensive CO2 separation. For optimal use. the compact reformers should operate at low temperature (<700 °C) and low-pressure conditions (<3 bar). Thus, the current existing large-size reformer technology operating under high temperature and high- pressure is not suitable for smaller-size reformers for fuel cell applications.X. Proton exchange membrane fuel cells (PEMFCs)

[0116] Proton exchange membrane fuel cells (PEMFCs) are excellent options for applications in small-scale and portable energy conversion, and are known for their high efficiency and potential for more sustainable energy generation. PEMFCs are made up of two electrodes, an anode and a cathode, which are separated by a membrane. The membranes, sold commercially, allow selective passage of protons but not electrons, and block passage of gases (Nandenha, et al.. 2020). Typically. PEMFCs use hydrogen as the fuel source, but methane has recently emerged as an alternative (Nguyen, 2017).

[0117] Proton exchange membranes can conduct protons only in a water-wetted state, and the conductivity of the proton exchange membranes is reduced due to theexcessively low water content, so that the ohmic voltage loss of the cell is increased, and the activity of the interface of a catalytic layer is reduced after the membranes lose water. Additionally, excessive gaseous water dilutes the concentration of the reactant gas, resulting in insufficient reactant gas at the reaction interface (CN112490473B)

[0118] This disclosure provides a low temperature methane reformer, wherein platinum or platinum alloy electrocatalysts are used for the cathode and anode. Platinum and platinum alloys are the most efficient catalysts for speeding up chemical reactions in hydrogen fuel cells. Platinum is the only metal that can withstand the acidic conditions inside such a cell, but it is expensive, and this has limited the broad, large-scale applications of fuel cells.

[0119] In other embodiments , the disclosure provides a low temperature methane reformer, wherein palladium or palladium alloy electrocatalysts are used for the cathode and anode. In other embodiments , the disclosure provides a low temperature methane reformer, wherein nickel, copper, vanadium or the alloys thereof for use as electrocatalysts for the anode.EXAMPLESExample 1: Proton-exchanged membrane fuel cell with cathode was set like a reversible hydrogen electrode (RHE) or normal hydrogen electrode (NHE)

[0120] Materials and Methods

[0121] Reagent Gas Tanks

[0122] Methane Gas: ME 5.0RS (Research Grade, 99.999%), H2 gas tank (5.0UH-T 99.999%), and Ar gas tank (UHP 5.0, 99.999%) were all purchased from Roberts Oxygen Company, Inc. Methane-13C (99 atom %13C) was purchased from Sigma Aldrich (Cat#490229). The CO2 gas tank (99.999%) was purchased from Specialty Gases of America (Lot#0307FA13). The CO gas tank (UHP) was purchased from GT&S, Inc.

[0123] Materials used in making Membrane Electrode Assembly (MEA)

[0124] Pt / C (60 wt%) and PtRu / C (60 wt%) were both purchased from Johnson Matthey Technology Centre. MilliQ water was from a Millipore Direct 8 / 16 model. The sulfuric acid was purchased from Fisher Chemical (CAS#: 7664-93-9). The 30% hydrogen peroxide was purchased from Innovating Science (CAS#: 7722-84-1) The carbon cloth used for the gas diffusion layers was purchased from the FuelCell Store(Cat#: 23070001) and the Nafion film was purchased from Sigma-Aldrich (Cat#: 1003354334). The Nafion solution was purchased from Sigma Aldrich (Cat#: 274704). The isopropanol was purchased from Sigma-Aldrich (CAS#: 67-63-0)

[0125] Fabrication of Membrane Electrode Assembly (MEA)

[0126] The MEA was made from the following composition: 60 wt% Pt / C (4 mg / cm2) | 60 wt% PtRu (12 mg / cm2). The 25 cm2single-stack fuel cell fixture and the MEA assembly unit were commercial products purchased from Scribner. Before assembly, the Nafion film was treated with H2O2 (3 wt%), Milli-Q water, 1 M H2SO4, and Milli-Q water again all at 80 °C for one hour each to obtain conductivity. The “ink’" containing the electrocatalysts was made by dissolving Pt / C and PtRu / C powders in a solvent mixture by adding 1 mL water, 305 gL 5% Nafion solution, and 6 mL isopropanol sequentially. After sonication in an ice-water bath, the ink was then sprayed onto both sides of the Nafion film by using an ultrasonic sprayer system (SONO-TEK, SimCoat), and then sandwiched with tw o carbon clothes of gas diffusion layers (GDL) by a hot press for 5 minutes at 140 °C and 4 MPa. The fuel cell was then assembled following the instructions for the fuel cell fixture from Scribner.

[0127] Instrumental Configuration and Electrochemical Cell Preparation

[0128] All EC experiments w ere performed using a Scribner 850e fuel cell test system with a Scribner 885-HS potentiostat and a Scribner auto back pressure unit. The operando electrochemistry mass spectrometry used a modified GC-MS system for the product sampling (Agilent Technologies, 7890A GC and 5975C MSD). The GC column w as replaced by a 50 m length of deactivated fused silica tubing (Agilent Technologies, Part Number: 19091-60620E). The interface between electrochemistry (Fuel Cell test system) and GC-MS was home-assembled with a 2 m deactivated fused silica tubing (Agilent Technologies, Part Number: Part Number: 160-2200-10) heated by a heating coil (Omega, Item# HTC-060) to transfer the moisture gas to the GC inlet.

[0129] In the Fuel Cell test station, the anode flow was either Ar gas as the blank signal (no EC-DSMR) or CH4 (13CH4) for the EC-DSMR monitoring. The cathode flow was H2 gas under all the test conditions the same as the anode, which created a reference electrode as the solid / gas interface reversible hydrogen electrode (SG-RHE) to the anode. The working electrode clamp was on the anode. The clamps of thereference electrode and counter electrode were on the cathode. All the gases were fed into the cell fixture with 90% relative humidity (RH). Notice that > 60% RH (> 15.2% in mole fraction of total flow gas) proved to be enough to reach the maximum activity of EC-DSMR (Figure IB).

[0130] Evaluation Protocol of Low -temperature Methane Oxidation

[0131] (i). For each MEA in the cell fixture, the following protocol was used in testing for EC-DSMR activity: Elimination of the surface impurities: MEA was cycled between 0.07 V to 1.4 V until stable CVs and OECMS under Ar flow at 80 °C and 4 bar were obtained.

[0132] Activity optimization: Switch to CEU flow at 80 °C and 4 bar and obtain stable CVs (0.07 V to 1.4 V) and OECMS signal of EC-DMSR. To avoid the loss of Ru in Ru-containing catalyst, the high potential was limited to 1.10 V.Set conditions to designed temperatures and pressures: 30 to 80 °C with 10 °C increments and 2 to 4 bar of cell pressure with 0.5 bar increments. The following steps were repeated at each temperature / pressure combination.

[0133] (ii) Under Ar flow, obtain the blank OECMS signals of 3 continuous CVs and current-time (IT) test at constant potential.

[0134] (iii) Repeat (ii) with CEU flow' and obtain the OECMS signals of EC- DSMR.

[0135] (iv) CO2 calibration: An external calibration using a flow meter (Omega, FMA-1 17A) with digital output function was conducted immediately following step (iii) under the same temperature / pressure with no potential applied.

[0136] The CO2 gas was introduced directly into the fuel cell through a separate gas line. The flow rate of CO2 was regulated using a mechanical flow regulator (Cole- Parmer, item#: EW-99673-19), and it ranged from high to low (~20 to ~3 seem, standard cubic centimeters per minute) to mimic the production of CO2 from EC- DSMR. Each flow rate w as held for about 4 minutes, during which the m / z=44 signal in CPS was collected (see an example in Figure 7G). A linear correlation was obtained between the m / z=44 signal and the CO2 SCCM flow rate due to the good linearity of mass detector response (Figure 7B).

[0137] Purging of CO2 by CFU: Once a calibration curve w as made betw een the m / z=44 signal and the CO2 SCCM flow rates, CO2 was purged out by CEU. whilerepeating step iii. This aim to ensure the activity of EC-DSMR was recovered for further experiments.

[0138] Evaluation of number of experimental active sites (NEAS): as illustrated in Figure 8 A, the process began with 20 s at 0.8 V to induce EC-DSMR, followed by 1000 s at open circuit potential (OCP) under CFU flow and 1500 s of OCP under Ar flow. This OCP relaxation process allowed the production of the adsorbed intermediates (Intad) of EC-DSMR on the available active sites. After OCP. 3 CV scans were conducted to oxidize the Intad and OECMS was collected.

[0139] Before proceeding to the next step, 3 CVs (under Ar) with the OECMS were conducted to ensure no EC-DSMR.

[0140] Assessment of the total surface sites via COads stripping: CO gas was introduced directly into fuel cell through a separate gas line. During COads formation, the potential was held constant at the lowest potential of CV. The full adsorption was ensured by the complete suppression of hydrogen adsorption / desorption peaks (Figures 1C-1D). 3 continuous CV scans were conducted to oxidize the COads and OECMS was collected.

[0141] 90-hour long-term stability test: A detailed diagram of the experimental procedure can be found in Figure 14G-14H.

[0142] Results

[0143] The schematic configuration of operando electrochemistry-mass spectrometry (OECMS) is illustrated in Figure 1 A (1). Continuous EC-MRR was carried on the anodic gas diffusion layer (GDL) interface in a single-stack proton- exchanged membrane fuel cell (PEMFC) setting:CH4+ 2H2O - CO2 + 8H++ 8e [5]

[0144] The generated protons were transferred through the proton-exchanged Nafion membrane (5) and reduced to H2 gas on the cathodic gas diffusion layer (GDL) interface:

[0145] The CO2 production in anode (2). as observed by MS, implies a full oxidation of CFU with 8-electron transfer and 4-H2production. A reference of reversible hydrogen electrode (RHE) under the same conditions as the anode (temperature, pressure, and relative humidity (RH)) was created via a constant flow of H2 gas to the cathode (3). The original goal for the anode reaction was to look forevidence of methane partial oxidation to methanol and / or formic acid. Instead, CO2 was observed. Hydrogen is produced at the cathode (8). The detection of CO2 using MS was achieved by a house-made interface, where a small portion of the FC outlet gas (9) flowed into the gas chromatography via a typical split / splittless inlet (10) through a deactivated fused silica (dFS) tubing. A high split ratio was used in the inlet to dilute the sample gas and significantly reduce the moisture content, protecting the MS mass detector. Consequently, only a small portion of the gas was analyzed by the MS25-C. Figure 1 displays a typical operando response between EC and MS (11). After correcting the required travel time of gas from the cell to the MS detector, the “on and off’ m / z=44 (CO2) signal was well synchronized with the reaction current “on and off’ by applied potential and current (shaded area of 11).

[0146] Figure 2 displays the OECMS results of cyclic voltammogram (CV, at 10 mV / s, 16) and the corresponding CO2 MS signal (m / z 44, 17) obtained on the Pt / C anode at 80°C and 4 bar with Ar blanking and CH4 feeding. In this embodiment, the cathode was a hydrogen-fed reversible hydrogen reference electrode (RHE), and both anode and cathode gas feeds were humidified with a RH of 90%. In another embodiment, the cathode was a hydrogen-fed normal hydrogen reference electrode (NHE), and both anode and cathode gas feeds were humidified with a relative humidity (RH) of 100%. No corresponding potential response of CO2 was observed with Ar blanking, but under CH4 feeding, a clear oxidation peak of EC-MRR w as observed (Figure 2, 18). The corresponding OECMS identified the production of CO2 (Figure 2, 17) with the synchronized peak position at 0.58 V of applied cell voltage (19). The onset of CO2 generation identified by m / z=44 was about 0.3 V (20).Example 2: Long adsorption at low potential is unnecessary to achieve sustained current / MS peaks with no delay to cell potential

[0147] Materials and Methods

[0148] Kinetics Data Analysis of EC-DSMR

[0149] A calibration curve was plotted between the m / z=44 signal in CPS and the CO2 meter flow rates in SCCM (Figure 7G). The slope of the calibration curve was then used to convert EC-DSMR signals to the CO2 production rate. Notice that the calibration and EC-DSMR should be under the same temperature / pressure and CH4 flow rate.

[0150] The kinetics study for the estimation of activation energy of EC-DSMR (Figures 7C-7D) were extracted from the OECMS data from protocol step iii at various temperatures (40 °C to 80 °C) and pressures (2 bar to 4 bar) on Pt / C and PtRu / C. The activation energy of EC-DSMR at each pressure was obtained by using the Arrhenius equation (Equation I ). where the natural log of the formation rate of CO2 at a given pressure was plotted against the corresponding temperatures and then fitted to a linear model. The slope of the fitted line was then used to calculate the activation energy. ln(kco2) = ln(A)-^ [Eq. 1]

[0151] Data Analysis of number of experimental active sites (NEAS)

[0152] Analysis of the NEAS was conducted via the ratio taken between the amount of CO2 generated from CEE-generated Intad stripping CV in protocol step (vi) and COads stripping CV in protocol step (viii). Since both stripping were conducted with Ar flow, the ratio of the integrated intensities of the m / z=44 signals in CPS from Intad and COads stripping can be used to represent the ratio of CO2 amount. Assuming one CO2 per active site, this ratio represents the percentage of NEAS for EC-DSMR compared to the CO2 amount generated from a fully COads-covered surface (Figures 7H-7K).

[0153] Results

[0154] Achieving sustained EC CEU oxidation remains challenging at a liquid / solid interface for Pt electrodes where the oxidation of CH4 can only be observed in a two-step method: a very slow dissociation of CH4 at low potential followed by a high-potential oxidation of the intermediates generated from methane- adsorption (Sustersic, et al., 1980; Ma. et al., 2019; Boyd, et al., 2019; Gurses, et al., 2021). However, in low-temperature electrochemical methane reforming reaction (LT-ECMRR) cell configuration, where reactions most likely occurred at the liquid / gas interface, the long adsorption step at low potential appears unnecessary in observing sustained current / MS peaks (Figure 2). Specifically , the 2ndand 3rdEC- MRR CVs overlapped with the 1stCV, achieved by the enhanced mass transport provided by the gas diffusion electrode (GDE), which ensured an adequate supply of CH4 to the electrode surface (Yan, et al., 2024).

[0155] To rule out the possibility' that a trace amount of CO in CH4 might cause the oxidation peak,13C isotopically -labeled methane,13CH4, was used to confirm thatthe CO2 observed in Figure 2A was indeed the product of EC-DSMR. Potentialdependent isotope-labeling tests were conducted (Figure 2B) in which13CH4 was pulse-fed under Ar flow (a method dictated by the cost of13C labeled methane) to the anode at 0.5 V and 0.3 V. Several observations can be made. First, the synchronization between the OECMS readings of13CH4 (m / z=17) and13CO2 (m / z=45) at 0.5 V confirms that the source of the13CCh was the EC-DSMR of13CH4. Second, even though the amount of13CH4 pulse-fed was the same at 0.3 V and 0.5 V, the amount of13CCh production at 0.3 V was much less than that at 0.5 V, consistent with the results presented in Figure 2A that shows the onset potential for CO2 production by EC-DSMR at 0.3 V and the maximum current at 0.58 V. Third, production of13CO2 can be observed even at 0.3 V, suggesting that EC-DSMR can also be operational at low cell potential. Fourth, CPU can be oxidized directly to CO2 on a Pt electrocatalyst under mild conditions (80 °C and 4 bars).

[0156] As alluded to above, literature data indicates that achieving sustained EC CH4 oxidation remains challenging at the liquid / solid interface of Pt electrodes where CH4 activation can only be observed in the two-step method: a very slow dissociative adsorption of CH4 at low potential followed by a high-potential oxidation of the adsorbates generated from methane-adsorption (Boyd, et al., 2019, Sustersic et al., 1980. Ma et al., 2019, Gurses et al., 2021). However, in our PEMFC EC-DSMR, where reactions most likely occurred at the gas / solid interface that may also contain a small amount of water, no long adsorption step is needed for observing sustained methane activation, as evidenced by the current / MS CVs (Figure 2A). Indeed, the 1stCV produced noticeably higher current and amount of CO2 on the left ramp of the peak than the 2ndand 3rdCV, where the latter two overlapped completely. The higher current is caused by the oxidation of the adsorbed species, such as COads, (Sustersic et al., 1980, Gurses et al., 2021, Lucky' et al., 2024, de Souza et al., 2022) generated during the methane purge of the cell (approx. 30 minutes) before taking the EC- DSMR CVs and the corresponding OECMS CVs, similar to the slow methane dissociative adsorption and ensuing adsorbate stripping observed previously at the liquid / solid interface. Clearly, sustained EC-DSMR under mild conditions as reported here, embodied by the 2ndand 3rdCVs in Figure 2A, follows a reaction pathway different from the one represented by the two-step methane activation reported previously in the literature. In other words, they are different reactions with verydifferent reaction kinetics. Specifically, the reactions reported in the literature are the oxidation of methane-adsorption-generated intermediates (the left ramp of our 1stCV). However, in addition to the literature-reported currents, we also observed sustained and direct CH4 oxidative currents that do not originate from the oxidation of the intermediates (2ndand 3rdCV scans). Our observations of the EC-DSMR current were likely associated with the gas / solid interface at the GDL, where a greater mass transport ability was achieved (Yan et al., 2024. Fomaciari et al., 2020).17 18.

[0157] Sustained CO2 formation via EC-DSMR is also evident in Figure 3A, where the CO2 OECMS signal at 0.6 V (the upper black curve) was observed continuously and simultaneously with the EC current (the upper red curve) for 600 s, while no CO2 was produced under Ar flow (lower black curve). Noticeably, the sustained reaction current was observed without an extensive period of methane adsorption and with instantaneous response to the applied cell potential, indicating that the EC-DSMR reaction kinetics (or reaction turnover frequency, TOF) is fast enough at the gas / solid interface to generate sustained electron transfer that can maintain the current. Similar EC-DSMR behaviors, but with an overall much lower activity, were also observed on the commercial carbon-supported PtRu and Pd black electrocatalysts, with the generation of13CCh from isotopic EC-13CH4 oxidation from the former. (Figures 3C-3D).

[0158] Even more surprisingly, as demonstrated in Figure 3B. sustained formation of CO2 is observed by the OECMS at temperatures and pressures as low as 30°C (303 K) and 2 bars (upper panel), suggesting again that methane activation with sufficiently fast reaction kinetics can take place at room temperature. However, the EC-DSMR window, which was 0.55 V to approximately 0.8 V as highlighted by the green-shaded area, was much narrower than that at 80°C and 4 bars (Figure 2A).

[0159] The lowest activity7we observed with CO2 OECMS CV was on PtRu / C at 30°C and 2 bars (the upper red curve in Figure 7A). where a similar EC-DSMR window as in Figure 2A was observed, also with no discernible current. Moreover, the generation of CO2 from EC-DSMR was also confirmed independently on PtRu / C, Figure 7B, by the same13C-labeled / 13CH4 pulsing test as shown in Figure 2B.Example 3: Comparison of catalysts used for the / ow-temperature / / / ethane electrochemical reforming reaction (LT-ECDSMR).

[0160] Results

[0161] Figures 4A-4D compare the cyclic voltammograms of the LT- ECDSMR, CH4 + 2H2O — > CO2 + 4H2, at 80 °C and 300 kPa back pressure on the 25- cm2metal-membrane-assembly consisting of commercial 60 wt% Pt / C (Figure 4A 4 mg / cm2) vs 40 wt% PtRu / C (Figure 4D 12 mg / cm2). The corresponding in-line GCMS detected CO2: Figure 4B for on Pt / C and Figure 2C on PtRu / C. In one embodiment, the cathode was NHE, and both anode and cathode gas feeds were humidified with a RH of 100%. Sustained LT-ECDSMR current was observed on both electrocatalysts at 10 mV / s potential scan rate under very mild condition, i.e., at 80 °C and about 4 atmospheric pressures, with activity' appearing much higher on Pt / C than on PtRu / C. Using isotopically-labeled13CEL confirmed unambiguously that the MS-observed CO2 came directly from the LT-ECDSMR.Example 4: Isotope labeling of methane

[0162] The anodic reaction CEE + 2H2OCO2 + 8H++ 8e was confirmed by isotope labeling experiments as shown in Figures 5A-5D. Isotopically labeled13CH4 was pulse-fed to the anode at 0.5 V and 0.3 V. As can be observed in Figures 5B and 5D, the13CO2MS reading is dependent of the cell potential: the amount of13CO2production is much larger at 0.5 V (Figure 5B) where higher reaction current was observed (Figure 4A) but much smaller at 0.3 V (Figure 5D) where the reaction current was lower. Moreover, the13CO2 MS reading is also synchronous to that of unreacted13CH4 (Figures 5A and 5C), indicating the formation of13CCh was due to LT-ECMRR of13CH4. These two observations confirm unambiguously that13CCh was the product of the anodic reaction CEL + 2H2O CO2 + 8H++ 8e . ruling out the possibility of trace CO in CEL causing the oxidation peak. Additional conclusions can be made from these data, including that the production of13CO2even at 0.3 V suggests that EC-DSMR is achievable at low cell potential and that CEL can be completely oxidized to CO2 on Pt electrocatalyst under mild conditions (80 °C. 4bar).Example 5: Comparison of specific chronoamperometric current associated CO2production measured on Pt and PtRu catalysts

[0163] Results

[0164] Figure 6 compares the specific chronoamperometric current associatedCO2 production measured at 0.5 V, 80 °C and 4 bar back pressure on Pt / C (26) vs PtRu / C (27). The results indicate that the LT-ECDSMR activity was about 10 timeshigher on the Pt / C than on the PtRu / C, even though the evidence indicates that the surface Ru atoms of the latter anode were largely etched away.

[0165] Consistent with the unexpected observations reported above, surprisingly low activation energies (Ea) were observed for both Pt / C and PtRu / C (Figures 7C and 7D, respectively). To convert the reaction current to the CO2 production rate used in the y-axis in the figures, an external CO2 calibration was obtained using a flow meter that converts MS count per second values to standard flow (standard cubic centimeters per minute, SCCM) of CO2 mixed in the CH4 stream under each temperature and pressure (see Figures 7F-7G). Figures 7A and 7B show back-pressure dependent measurements of the activation energy of the LT-ECMRR on the Pt / C and PtRu / C, respectively. The results reveal an Eaaveraged from 2 (square markers), 3 (triangle markers), and 4 bar (diamond markers), to be 37.8 ± 2.1 kJ / mol (-0.39 eV) and 42.4 ± 3.7 kJ / mol (-0.44 eV) for Pt / C and PtRu / C, respectively. The lower Eafor Pt / C was expected, since it gave the higher activity'. It was noted that the onset potential for the LT-ECDSMR was almost the same on both anodes and lower than 0.3 V (vs. NHE). which is only slightly higher than the standard potential (0.17 vs RHE) for CH4 + 2H2O «-> CO2 + 8H+± 8e . This indicates that for the active sites that enabled the observed LT-ECMRR, the reaction is rather counter-intuitively easy.

[0166] Figures 7C and 7D show the classic Arrhenius plots at different cell back pressures for EC-DSMR on Pt / C (FIG. 7C) and PtRu / C (FIG. 7D), respectively. The slopes of the plots enable the determination of reaction activation energies (Ea). These activation energies are largely pressure-independent, giving an average value of 37.8 ± 2.1 kJ / mol (approx. 0.39 eV) and 42.4 ± 3.7 kJ / mol (approx. 0.44 eV) for EC- DSMR on Pt / C and PtRu / C, respectively. The lower Eafor Pt / C is consistent with the higher activity observed (Figure 2A vs. Figures 3C-3D).

[0167] The activation energies of the EC-DSMR under mild conditions measured above are comparable to that (45.2 kJ / mol) obtained from the molecular catalyst of vanadium (V)-oxo dimer at 25 °C and 3 bars of methane pressure (Deng et al., 2020), but much lower than that (108.4 kJ / mol) on Pd2n niin concentrated sulfuric acid electrolyte at 140 °C and 34.5 bars of methane pressure (O’Reilly et al., 2017). of 43.4 kJ / mol was also reported with a non-EC methane conversion on a gold single atom catalyst at 90 °C and 33 bars of methane pressure under light irradiation (Luo, L. et al, 2021). Experimentally, the activation energies obtained herein areconsistent w ith observation of sustained EC-DSMR under mild conditions (Figures 1- 3) and the long-term stability- of the reaction (vide infra). As mentioned previously, although the underlying reason(s) are still largely unclear, the observed fast kinetics of the EC-DSMR may be associated with the gas / solid interface at the GDE, a configuration known to be highly beneficial to EC methane conversion by enhancing mass transport and reducing the diffusion distance, in contrast to the normal liquid / solid interface encountered in electrochemistry (Yan. et al. 2024. Fomaciari. J. C. et / ., 2020).Example 6: Electochemical methane reforming to produce hydrogen under low temperature and atmospheric pressure

[0168] Results

[0169] Figure 8 A and 8B show that even at 30 °C and 2 bar or 100 kPa back pressure, sustained CV CO2 could still be observed with the PtRu / C (at 2 bar) and Pt / C (at 100 kPa) surface, respectively. Although the electrochemical CVs (Figure 8A) do not show observable difference, the MS CVs do reveal that the LT-ECMRR produced CO2 did take place and the amplitude is the same for the 2ndCV. This is consistent with other studies which indicated that CV current w as not observable until a long dissociation step on the liquid / solid interface (Sustersic, et al., 1980; Ma, et al., 2019; Boyd, et al., 2019; Gurses, et al., 2021). This indicates that the Pt / C was still active in LT-ECMRR, even at 30 °C and 100 kPa cell back pressure.Example 7: Number of Active Sites

[0170] Results

[0171] The key to unraveling the unusual LT-ECDSMR activities observed above is identifying the active sites. For this purpose, we designed an experimental procedure to estimate the number of experimental active sites (NEAS) by using OECMS (Figure 9A).

[0172] First, under CH4 flow, the anode was set to 0.8 V for 20 seconds (28, Figure 9A) so that methane could be fully oxidized to CO2, as observed by a sharp increase in the intensity of m / z=44 (29). Second, the potential was switched to open circle potential (OCP, 30), where a 2000-second slow regression to about 0. 1 V was observed. Since the current was forbidden from flowing through the electrode at OCP, the continuous decrease of potential implies a period of electron transfer onto the electrode from surface reactions, which included EC-MRR for OCP > 0.3 V, the onsetpotential of EC-MRR (see 20, insert in Figure 2). This was confirmed by the production of CO2 during the time it took for the OCP to drop to ~0.3 V (~100s to 250s), as shown by the broad peak following the sharp peak in the bottom line. Beyond 0.3 V, no additional CO2 was produced as the OCP continuous to regress toward -0. 1 V. This indicates, as illustrated by the scheme above the OCP curve in Figure 9A (31), that the electrons causing the OCP drop likely originated from methane partial oxidation to intermediate(s). rather than direct complete oxidation to CO2, at the active sites. Assuming that the generated intermediate(s) were stable at the active sites (Intads) and had a one-to-one stoichiometry', a stripping of the Intads to CO2 in a CFU-free environment would enable a determination of the amount of the Intads as well as the active sites. A CEU-free environment was achieved by Ar purge and flow, indicated by the total decrease of methane (m / z=16, lower left line, 32) and the concomitant increase of Ar (m / z=40, lower right line, 33). Under Ar flow, 3 consecutive CV scans were performed. The 1st CV stripped the Intads to CO2, and the last two CVs confirmed no further CO2 production from EC-DSMR. As indicated by the m / z=44 peak (~3200s) (34) that overlapped with the 3 CVs, CO2 was only observed during the 1st CV. Thus, this experiment confirmed that the process of CH4 -> Intads + e- contributed to the OCP drop. Notice that a long period of stable OCP at -0. 1 V was reached after the second stage of OCP drop under CFU flow between 1000 s and 1600 s. suggesting that CEUIntads + e- had been stopped or the active sites had been fully occupied.

[0173] To further understand the NEAS of the Pt electrodes, a CO adsorptionstripping experiment was done to obtain the total number of available surface sites. Comparing the integrated mass intensity of the Intads stripping with that of COads stripping, the NEAS, expressed in percentage to the total surface sites, was plotted as a function of the cell temperature from 40 °C to 80 °C at 4 bar for Pt / C (triangle markers) and PtRu / C (diamond markers) in Figure 9B. The NEAS percentages were - 5% and 1% at 40 °C. -14% and 2% at 80 °C for Pt / C or PtRu / C, respectively. Interestingly, a linear relationship between the NEAS and temperature for both the Pt / C and PtRu / C was observed, though the underlying reason is still unclear. Additionally, an almost linear relationship between the corresponding CO2 rate of EC- MRR and NEAS could also be obtained for both the Pt / C (upper 5 points) and PtRu / C (lower 3 points) (Figure 9C) with a slope of 253.5 pmol / h / m2per unit percent ofNEAS (p value=0.00105), suggesting that the active sites on the Pt / C and PtRu / C may share some common characteristics. Interestingly, as illustrated in the insert figure in Figure 9C, the calculated values of the TOF on the active sites at 60 °C (left) and 80 °C (right) were very similar. This may explain why the lower EC-MRR activity observed on the PtRu / C is likely due to its significantly lower NEAS.

[0174] Although the physicochemical nature of NEAS is largely unknown, the estimated surface fractions still offer useful clues about the possible types of these active sites. For a truncated octahedral-shaped Pt nanoparticle supported on a (111)- plane, a recent sophisticated analysis (Hansen et al., 2017) shows that the surface fractions of comer / edge / terrace Pt atoms are 13% / 37% / 50% for 2-nm and 4% / 28% / 68% for 4-nm Pt nanoparticles, respectively. Considering that the estimated maximum NEAS fractions were ~14% / 2% for Pt / C / PtRu / C, respectively (Figure 9B), and the size range of the electrocatalysts (2 to 4 nm), the active sites would likely be the comer sites or / and certain type of comer-edge ensemble sites according to the in- situ 3D Bragg coherent X-ray diffraction imaging for methane oxidation on Pt nanocrystals (Kim et al.. 2018). This is consistent with the results of DFT calculations (vide infra).Example 8: Density Functional Theory (DFT) Calculations

[0175] Materials and Methods

[0176] Details of Nudged Elastic Band Calculations

[0177] The nudged elastic band (NEB) method was used to determine reaction paths for the reactionCH -> CH3+ H [7]

[0178] on Pt(lOO), Pt(l 11), PtRu(100) and PtRu(l l 1) surfaces. On the PtRu surfaces, a single sub-surface Ru atom was included to mimic the alloy surface. On each surface, three structures were modeled. A plateau (flat surface), a comer (a 2x2 array of Pt atoms on the surface), and an edge (a 2x4 array of Pt atoms on the surface). The NEB calculations used 7 points to describe the reaction path. The path was converged using a threshold of 0. 1 eV / A. Reactant and product geometries were optimized along with intermediate geometries during the NEB calculation. All surfaces were modeled as a 4x4x4 unit cell with a vacuum layer of 25 A above the surface. All calculations w ere carried out using the Quantum Espresso program (Zhang, J. et al., 2021, Giannozzi, et al., 2017). The electronic structure calculationswere performed using the Perdew-Burke-Emzerhof (PBE) density' functional (Perdew et al.. 1996, Perdew et al., 1997). The plane wave basis set for the atoms was of the RRKJUS (ultrasoft) type (Rappe et al., 1991) and was taken from the Quantum Espresso library (Dal Corso et al., 2014). The kinetic energy cutoff for the wavefunction was 40 Ry and a kinetic energy cutoff for the charge density7and potential of 400 Ry was used. Methfessel -Paxton smearing (Methfessel et al., 1989) with a Gaussian spreading parameter of 0.2 Ry.

[0179] Results

[0180] Figure 10 show s the results of preliminary DFT nudged elastic band calculations of C-H dissociation reaction of CEU on a Pt(lOO) comer site (bottom), vs on a Pt(lOO) terrace site. For the Pt(lOO) comer site, the calculations reveal a shallowenergy well before reaching the transition state. Its existence would significantly increase the surface residence time of CEE thus facilitate C-H bond dissociation. However, no such well exists for C-H dissociation on the Pt(lOO) terrace site. Moreover, the activation energy is much lower at the Pt(lOO) comer site (0.47 eV) than that at the Pt(lOO) terrace site (0.51 eV). The former compares extremely well with the experimentally determined values (0.44 eV) on the PtRu / C and (0.39 ev) on Pt / C, Figure 7B. . Also, the dissociation products are more stable at the Pt(lOO) comer site (-0.21 eV) than at the terrace site (-0.072 eV). The above discussed comparison suggests strongly that the Pt comer / edge sites are likely the active sites for the LT- ECMRR.

[0181] Further density7functional theory7(DFT) calculations were used to explore the reaction path and estimate the barrier height for the breaking of the first C-H bond in CH 4 on the Pt(lOO), Pt(l 11). PtRu(100). and PtRu(l 11) surfaces. On each surface, three different surface geometries were modeled: a plateau, a comer, and an edge. All reaction paths were modeled in the gas phase, i.e. no solvent water was modeled. In all cases, the reaction path exhibits similarities. The reactant state involves the CH4 at some distance from the surface feature. The reaction progresses as one of the H atoms on the methane approaches the surface and is adsorbed onto a Pt atom. The adsorbed methane then rotates so that the C atom moves closer to the Pt surface. The C-H bond is then broken and the CH3 and H moieties end up on neighboring Pt atoms. In some cases, the H atom was observed in a bridge bonded configuration between two Pt atoms.

[0182] Calculated values for the forward reaction barriers are presented below.

[0183]

[0184] The results clearly show that a barrier height of approximately 0.4 eV is feasible on the 100 surface, with variation due to the type surface feature (plateau, comer, edge). On the 111 surface the plateau is considerably less reactive (barrier heights approximately double of those on the 100 surface). However, the barrier height for the 11 1 comer feature is much lower at approximately 0.2 eV.

[0185] A rough estimate using the specific chronoamperometric current obtained at 0.5V (vs normal hydrogen electrode - NHE) and 3600 s gives a price of hydrogen production by the LT-ECDSMR at 15 / kg H2. This is comparable to the estimated cost of producing hydrogen by water electrolysis (Pal, A. et al., 2024). A 10-time improvement in its specific activity (a reasonably achievable aspiration) would bring the cost down to $1.5 / kg H2, which is in the current cost range of industrial hydrogen production.Example 9: Stability and Regeneration of the Electrocatalysts

[0186] Materials and Methods

[0187] Data Analysis of long-term stability’ test

[0188] The m / z=44 signal in CPS was converted to the CO2 production rate using the calibration slope under the same conditions. The CO2 rate during the last 2 minutes for each hour was extracted to represent the CO2 production rate during the entire hour. The stability of R / Ro in Figure 14A and 14B was calculated by the ratio between the CO2 rate at the end of each hour and the best rate recorded initially (normally 1stor 2ndhour). The stable CO2 production rate in Figure 14B was the average value of the CO2 production rate collected during the last 2 minutes of each hour across the last 24 hours. The Faraday efficiency (FE) was calculated by the ratio between the moles of CO2 produced during the last 2 minutes of each hour and 1 / 8 of the moles of electron transferred from the recorded corresponding current data. The latter was obtained by average current in A * 120s / 96485C / mol. The FE shown in Figure 14C was the average FE of the last 24-hour FEs during the last 2 minutes.

[0189] Results

[0190] One of the challenges for heterogeneous electrocatalysis is low cell stability’, which can be caused by surface poisoning, reactant crossover, or degradation of the electrocatalyst itself. Various groups have reported the presence of poisoning species of COads on the Pt surface (Ma, et al. 2019; Lucky7, et al., 2024). Long-term stability7studies confirmed the presence of poisoning species that significantly degraded the electrode’s catalytic performance. However, we also observed that introducing an intermittent poison-cleaning procedure largely recovered the catalytic performance, leading to a surprising long-term stability.

[0191] The initial activities on Pt / C and PtRu / C measured during the first 10 minutes at the potential of the current peak (0.6 V) at 80 °C and 4 bar were about 2448 and 269 pmol / h / m2, respectively. The 90-hour long-term stability test of continuous EC-DSMR at 0.6 V on Pt / C (bottom curve in Figure 14A) exhibited a continuous decrease of CO2 production rate, evidencing an ongoing surface poisoning formation. However, the activity could be recovered after about 10-CV scans to a high potential (Figures 14A-14BThe poisoning species were unlikely to be COads because the applied potential of 0.6 V during the long-term stability test would easily oxidize COads to CO2. Additionally, the partially dehydrogenated methane (CHx-* (x=0 or 1 or 2 or 3)) was likely involved in the incomplete electrochemical oxidation of methane.

[0192] Considering that the initial activity could be recovered by multiple CV scans to a high potential, a cleaning procedure was carried out at the end of each hour during the experiment (Figure 14G-14H). First, an intermittent l.OV / lmin to eliminate the poisoning species at the active sites, and second, a O. lV / lmin of surface recovery by reducing the oxides formed during the 1.0 V oxidation. As illustrated by the top triangle line in Figure 14A, when the cleaning procedure was employed, the recovery of the rate of CO2 production during the long-term stability test w as significantly improved: -80% of the initial activity7. The insert in Figure 14A shows a similar trend in the long-term stability of LT-ECDSMR on PtRu / C using the cleaning steps. Without cleaning steps, the CO2 production rate on PtRu / C (bottom) decreased much more slowly than on Pt / C (bottom), consistent with the anti-poisoning effect of PtRu / C (Du, et al., 2009; Zhang, et al., 2021). With cleaning procedures, both catalysts revealed a surprisingly high and stable production rate of CO2 after the 90- hour LT-ECDSMR .

[0193] The stable formation rate of CO2 and the Faraday Efficiency of LT- ECDSMR from the last 24-hour were plotted in Figure 14B and 14C, respectively. In Figure 14B, the stable CO2 production rates were 25.2 ± 0.2 pmol / h / m2and 13 ± 22 pmol / h / m2on Pt / C without EC surface cleaning (bottom) and with cleaning (top), respectively. For PtRu / C, the rates were 13.5 ± 0.5 pmol / h / m2without cleaning (bottom) and 30.6 ± 1.4 pmol / h / m2with cleaning (top). The stable CO2 production rate on Pt / C was about 16.8 times higher than that on PtRu / C using the EC surface cleaning procedure, but only 1.9 times higher when not using the surface cleaning procedure. This demonstrates the importance of the elimination of poisoning species at the active sites in achieving a sustained high CO2 production rate from LT- ECDSMR at the gas / solid interface. Figure 14C displays the stable Faraday Efficiencies (FE). For Pt / C, the FE were 8% and 80% without and with EC surface cleaning, respectively. For PtRu / C, the FE were 30% and 52% without and with EC surface cleaning, respectively. Although the stable CO2 production rate without the EC cleaning procedure on the Pt / C is higher than that on the PtRu / C, the stable Faraday Efficiency on the latter is about 3.8 times higher than the former. With the EC surface cleaning procedure, the FE on both surfaces was improved. Since PtRu / C had a much better anti -poisoning effect (vide supra), the improvement of FE was not significant. However, the FE on the Pt / C with the EC surface cleaning was substantially enhanced about ten times to >80%. This indicates that the removal of the surface poisoning species is crucial in achieving a high electricity efficiency of EC- MRR to CO2 on the Pt / C catalyst.Example 10: Making the activity of CH4 electro-oxidation (EO) measurable at low temperature and ambient pressure

[0194] Results

[0195] In our studies on the electrochemical conversion of methane to methanol, we acknowledged the difficulties of mass transport of methane to the electrode surface. This arises due to the low solubility of methane in aqueous electrolyte, due to strong C-H bonds of CH4 (439 kJ / mol per bond), low pKa (=48). high ionization potential (12.5 eV) and low proton affinity (4.4 eV). As such, it is not surprising that few successful studies of CH4 EO have been reported in a conventional 3-electrode setup. Realizing that a conventional laboratory' 3-electrode setup is highly unlikely to lead us to a better situation after several-month’s frustrating trials, a fuel-cellconfiguration was adapted to demonstrate and study the CH4 EO activity of electrocatalysts, as shown in Figure 11 A (also depicted in Figure 1), for two reasons: (1) feeding 100% humidified CH4 to anode will enable a much higher amount of CH4 to be transported to the electrocatalyst surface than by diffusion in aqueous electrolyte. Moreover, the amount can be easily varied and the type of medium changed. (2) MEA configuration will enable loading a substantially more amount of the electrocatalyst. Both are expected to substantially increase the amount of current generated by CEU EO if the reaction indeed takes place so that it can become measurable; thereby, the CH4 EO activity can be studied.

[0196] Indeed, the four samples tested, commercial carbon-supported Pt (Pt / C, 40% Pt loading, ~3.3 nm, Johnson Matthey), carbon-supported PtRu (PtRu / C, 40% Pt and 20% Ru loading, ~2.5 nm, Johnson Matthey), and NiCu (—40 nm to 100 nm, US Research Nanomaterials, Inc.), and home-synthesized PdAu nanoparticles (Hong, et al., ACS Applied Materials & Interfaces 2014, 6 (12), 9481-9487) (~ 5 nm, see TEM image in Fig. 11B), all exhibited reactivity. Different but stable open-circuit potentials (OCPs) were established and measured after the Nafion membrane was sufficiently- wetted and stable proton conductivity established, as presented in Fig. 11B. Smaller OCP indicates a more oxidized surface. The experimental conditions were as follows: cell temperature was at 80°C, the flow rate of 100% humidified CH4 and O2 to anode and cathode respectively was 0.8 L / min. the area of MEA was 5 cm2, the electrocatalyst loadings were 5mg / cm2for Pt / C, PtRu / C and AuPd and 50mg / cm2 for CuNi respectively, and the back pressure for the feeds was ambient. That stable yet different OCPs could be established for different electrocatalysts under the same experimental conditions indicates different chemistry taking place on the surface of electro-catalysts in terms of CH4 adsorption and EO. The PdAu had the largest OCP, implying a least oxidized surface. Moreover, all four samples produced measurable reaction currents as shown in Figures 12A-12D (current spikes in FIG. 12B, PtRu / C, were caused by short-period flooding of the electrode). All measurements are reproducible.

[0197] Several interesting observations can be made from these data. First, it is interesting that the non-precious metal sample NiCu produced comparable specific current, i.e., activity, against its precious metal counterparts. Assuming that NiCu has an average particle size of 50 nm which gives a dispersion (i.e.. fraction of surfaceatoms in a nanoparticle) of -3%. A nanoparticle (NP) of 3 nm or 5 nm has a dispersion of -39% or 25% respectively. Therefore, the same-surface-area normalized mass activity measured at 3600s (FIGs. 12A-12D) are estimated to be about 68 pA / g at the cell potential of 0. IV for the Pt / C, 1086 pA / g at 0. IV for the PtRu / C, 1384 pA / g at 0.05V for the NiCu, and 216 pA / g at 0.05V for the PdAu, respectively. To our best knowledge, these represents the first observed stable CPU EO activity on a non-preci ous metal surface at low temperature (80 °C) and ambient pressure.

[0198] Second, the PtRu / C showed the highest activity (FIGs. 12A and 13B) among the four samples but also had some large current spikes due to unstable water humidification caused short-period electrode flooding (clipped in the figure for a better presentation of the currents).

[0199] Third, Pt / C deactivated the fastest, likely due to CO poisoning.

[0200] Fourth, the PdAu had the largest OCP (800 mV, Fig. 7B) but medium activity. It also showed a decent stability: the reaction current only decreased by 5 pA from 1 to 2 hours period (Fig. 13A). It is worth noting that it was reported very recently that PVP-stabilized PdAu sol (-4 nm) could catalyze selective CFU oxidation to MeOH with O2 as oxidant and H2O2 as activating agent in aqueous environment under mild conditions (50 °C and 30 bars) (Agarwal. N., et al, Science, 11, eaan6515- 10 (2017)).

[0201] Methane electro-oxidation was also run on the PtRu / C (at a cell potential of 0. 1 V) and on the NiCu (at a cell potential of 0.05V) for 6 and 48 hours respectively. The results are shown in Figures 13B and 13C. For the PtRu / C, the cell OCP was also measured at every 2 hours and the measured values are presented in Figure 13 A. As can be seen, the OCP also decreased gradually as the reaction continued, indicating that the electrocatalyst surface was deactivating, leading to smaller current. Nonetheless, it is rather encouraging to observe some measurable long-term activity' of CH4 EO on three out of four samples (up to 48 hours for the non-precious metal NiCu).Example 11. The PtRu system

[0202] Results

[0203] To assess further the validity of R-l through R-3, preliminary qualitative DFT model calculations were carried out in which the PtRu catalyst system was modeled by metal slabs with a PtsRu surface (the metal unit cell is the same in Fig.23A and 23B) but two different configurations of surface-bound species. Calculations were performed using the Quantum Espresso code (version 6.3). Planewave energycutoffs of 50 Ry and 600 Ry were used for the kinetic energy and charge density / potential cutoffs, respectively. A RRKJUS pseudopotential basis set taken from the Quantum Espresso library- was used for core electrons. The Perdew-Burke- Emzerhof (PBE) functional was used for all calculations. The unit cell consisted of 4 layers of 9 atoms (3x3) plus surface-bound species. The slab geometry was constructed such that the surface was infinite in the xy plane with a separation between slabs of approximately 30 A in the z direction. During optimizations, the bottom two metal layers were fixed at their bulk-optimized positions, while the geometry of the top two metal layers and all surface-bound species were fully optimized. For systems with an odd number of electrons, Methfessel-Paxton smearing was used with e smearing parameter of 0.02 Ry. All structures were optimized within the default convergence parameters. An offset, 4x4x1 Monkhorst-Pack grid was used for integration within the Brillouin zone. As presented in the table below (middle row), the calculations show that the configurations of surface-bound species similar to Fig. 16 have the most favorable energetics among the different surface configurations studied, offering theoretical support to the hypothetic R-l and R-2.

[0204] Qualitative calculations were performed on simple model systems shown in Fig. 24 for R-3. The calculations were performed at the B3LYP / cc-pVDZ level of theory-, with a cc-pVDZ-PP effective core potential basis set used for the metal atoms. Geometries of all intermediate species were optimized and vibrational frequencies were calculated at the stated level of theory. The reaction mechanism involves steps that describe the binding of CFU to the metal surface, the loss of a H atom to O+, rearrangement of OH, the formation of CH3OH, and the departure of CH3OH from the metal surface. The overall reaction is written as:TMi(-OH) + TM2(-CH3) -> TMi + TM2 + CH3OH

[0205] The exothermicity of this reaction was calculated from the energies and free energies (at 298 K) of the species involved in the usual manner. The exothermi cities (i.e. including vibrational effects) are Pt(-OH)Pt(-CH3) = 105.64 kJ / mol, Ru(-OH)Pt(-CH3) = 182.71 kJ / mol, and Pt(-OH)Ru(-CH3) = 127.21 kJ / mol, which suggests that R-3 as represented in Scheme 1c and d would be favored. With these promising results of preliminary model DFT calculations that appear to support the proposed DMTM mechanism of R-l through R-3. we will develop more realistic surface-model systems for detailed DFT and microkinetic calculations under the framework of R-l to R-3 for DMTM conversion that will incorporate the effect of electrode potential and electrolyte into the calculations.

[0206] Our recent revision of the bifunctional mechanism for MeOH EO to CO2 on PtRu47 led us to believe that the best place for R-3, i.e., the step of oxygenation, is at the Ru-Pt boundary with Ru site supplying oxygen-containing species as hypothesized in Fig. 16. The inventors also discovered that the process of catalytic activation of PtRu electrocatalyst by multiple CV cycling or step potential (SP) is to change the surface composition of Pt vs Ru and maximize the Pt-Ru boundaries, as illustrated in Fig. 25 in which the distinguishable IR bands on Ru and Pt were used to quantify the elemental surface fraction changes (Chen et al., Chemical communications 2014, 50. 12963-12965). In fact, by subjecting the PtRu to even mild multiple CV cycling in MeOH-containing electrolyte already led to an substantial increase of MeOH production, as indicated by the data in Fig. 26. More information is needed to better understand whether R-3 is indeed taking place at the Pt-Ru boundaries.

[0207] Concerning studying the agnostic interaction, the inventors hypothesized that an electron-deficient surface would favor such interaction. One way to create electron-deficient surface sites is to deposit element of high electronegativity. Indeed, encouraging preliminary results presented in Fig. 27 show that sulfide adsorption on Pt did enhance substantially the CH4-adsorption generated COads on Pt surface, which could be an indication that sulfide adsorption created electron-deficient Pt sites neighboring to the adsorbed sulfide and by which strengthened the agostic interaction with the saturated C-H bond of methane.Example 12. The PdAu system

[0208] Results

[0209] For the PdAu system, the primay concern is the effect of bulk composition changes and that of impregnated CuO because it was reported that a PdAu of atomic composition Pd:Au = 8: 1 had the highest activity in DMTM conversion as the bulk atomic composition varied and its activity was further enhanced with the impregnated CuO as a promoter, with high selectivity7at 250 °C to 400 °C in a solid-electrolyte fuel cell setting among those electrocatalysts studied (Lee. et al.. Journal of Catalysis 2010, 271 (2), 195-200). The inventor pondered whether the activity enhancement observed at a given Pd:Au ratio had to do with bringing the surface as equally active as possible to R-l and R-2 so to maximize R-3 by changing the s-d hybridization or / and the local density of states at the Fermi level and (2) impregnating PdAu surface might make the surface more electrophilic so to enhance the agostic interaction by which to better activate the C-H bond. These are a few hypothetical questions about the PdAu system that are deeply interesting to study, particularly how can the DMTM conversion observed on PtAu be understood within the framework of R-l through R-3 or used to test the validity of it. These questions can at least partially be probed by in situNMR and IR using CO as a surface molecular probe (Tong, et al., Journal of the American Chemical Society 2002, 124 (3), 468- 473; Tong, et al., J Phys Chem B 1997, 101, 10155-10158; Tong, et al., Journal of the American Chemical Society 1997, 119, 3929-3934).

[0210] One unique feature of a Pd surface that was observed is its ability to activate surface water to generate Pd-OH over a wide electrode potential range, as demonstrated by the in situ IR study of formic acid oxidation reaction (FAOR) on commercial Pd black in 0.5 M HCOOD + 0.1 M DCIO4 / D2O, Fig. 17. The experiments were specifically designed to assess the reaction Pd-HCOO + Pd-DO2Pd + CO2 + HOD. The observations of the FAOR-generated HOD over a wide potential range of - 0.045V to 1.045V vs. RHE as evidenced by Fig. 17C suggests strongly that Pd-OD was available over such a potential range. According to our hypothetic R-l through R-3, this unique feature might underlie that Pd showed the highest activity in electrocatalytic DMTM conversion among the four metals (Au, Pt, Rh, and Pd) studied (Tomi ta, et A.. Angewandle Chemie International Edition 2008, 47 (8), 1462-1464). It is hypothesized that alloying with Au would help enhance the surface’s ability to activate C-H bond. The higher Faraday efficiencyobserved on PdAu vs PtRu may also have to with that the former is not good electrocatalyst for MeOH EO.

[0211] More recently, it was also reported that PVP-stabilized PdAu colloidal sol could also catalyze selective oxidation of CH4to MeOH under mild condition with O2 as oxidant and with H2O2 as activation agent (Agarwal, et al., Science 2017, 11, eaan6515-10), which adds more impetus to study PdAu. The results obtained on a PdAu electrocatalyst (FIGs. 12D, 13A, and 15C) are very encouraging. Altogether, the PdAu appears to be an excellent system to assess the validity7of R-l through R-3.

[0212] Moving forward, we will adapt the same investigative strategy outlined for the PtRu system to study the PdAu as function of Pd:Au atomic ratio and of CuO impregnation for comparative studies. If time permits, we may also look into a PdCu sample that is readily available for comparative studies. Fig. 17 compares PXRD patterns and representative TEM images of PdAu and PdCu electrocatalysts already synthesized in the lab.Example 13. The NiCu system

[0213] Results

[0214] For the NiCu system, it was its different catalytic behavior in EC conversion of CH4as compared to the PtRu and PdAu systems that caught our eyes. That is, CH4EO on it did not generate observable MeOH, neither by GC-MS (Fig. 15) nor by in situ IR (Fig. 19). Fig. 19A presents the time-dependent in situ IR spectra obtained during the DMTM conversion at 1.0 V vs. Ag / Ag / Cl (IM) on the commercial NiCu alloy electrocatalyst. The inventors tentatively assigned the band at 2968 cm'1to -CH3 on the Cu sites, the bands at 2030 cm'1and 1942 cm'1to CH4- adsorption generation COads on the Cu and Ni sites respectively. The negative-going band at 2968 cm'1correlates with the positive-going COads bands, indicating the COads was generated at the expense of consuming -CH3. In other words, -CH3 was the COads’s parent molecular fragment. It is interesting to note that no COads was observed on the PtRu / C during the DMTM conversion, which is a clear indication of different surface chemistry as manifested on the PtRu as compared with that on the NiCu. This is reinforced by the data shown in Fig. 19B where possible IR bands in the spectral range of gaseous MeOH are compared. The clear disappearance of the 1059-cm'1band for CuNi indicates that little if any gaseous MeOH was produced during the CH4EO on it.Although this would agree with the GC-MS measurements in which no MeOH was detected in the eluants on CuNi (Fig. 15), it could also be caused by strong adsorption of the produced MeOH that led to the formation of COads. Fig. 19C compares the pristine CVs ofNiCu (green), as-received PtRu (red) and activated PtRu (blue) obtained with the IR cell. Fig. 21 A.

[0215] As such, the primary concerns are (1) why did it demonstrate such a different chemistry (Figure 19) as compared with that of PtRu and of PdAu and (2) what is the dominant chemistry responsible for it? Particularly, it appears that the NiCu is more reactive than PtRu. It is possible that this is because that the surface ofNiCu is largely been oxidized and oxidized metal cations are usually more electrophilic than a metallic surface site, a key feature of Shilov-like chemistry for DMTM conversion.

[0216] The complete disclosure of all patents, patent applications, and publications, and electronically available material (including, for instance, nucleotide sequence submissions in, e.g., GenBank and RefSeq, and amino acid sequence submissions in, e.g., SwissProt, PIR, PRF, PDB, and translations from annotated coding regions in GenBank and RefSeq) cited herein are incorporated by reference. In the event that any inconsistency exists between the disclosure of the present application and the disclosure(s) of any document incorporated herein by reference, the disclosure of the present application shall govern. The foregoing detailed description and examples have been given for clarity of understanding only. No unnecessary7limitations are to be understood therefrom. The invention is not limited to the exact details shown and described, for variations obvious to one skilled in the art will be included within the invention defined by the claims.References:1. Hydrogen Production: Natural Gas Reforming. US Government Energy website.2. Sweeney, D. M., Alves, V., Sakhai, S., Dinh, S. & Lima, F. V. Techno-economic Analysis and Optimization of Intensified, Large-Scale Hydrogen Production with Membrane Reactors. Ind. Eng. Chem. Res. 62, 19740-19751 (2023).3. Luo, L. et al. Water enables mild oxidation of methane to methanol on gold single-atom catalysts. Nat. Commun. 12, 1218 (2021).4. Jin, Z. et al. Hydrophobic zeolite modification for in situ peroxide formation in methane oxidation to methanol. Science 367, 193-197 (2020).5. Upham, D. C. et al. Catalytic molten metals for the direct conversion of methane to hydrogen and separable carbon. Science 358, 917-921 (2017).6. Yuliati, L. & Yoshida, H. Photocatalytic conversion of methane. Chem. Soc. Rev. 37, 1592-1602 (2008).7. Wang, W., Su, C., Wu, Y., Ran, R. & Shao, Z. Progress in Solid Oxide Fuel Cells with Nickel-Based Anodes Operating on Methane and Related Fuels. Chem. Rev. 113, (2013).8. Wang, Q., Kan, M., Han, Q. & Zheng, G. Electrochemical Methane Conversion. Small Struct. 2, 2100037 (2021).9. Grubb, W. T. & Michalske, C. J. Electrochemical Oxidation of Methane in Phosphoric Acid Fuel Cells at 150°C. Nature 201, 287-288 (1964).10. Sustersic. M. G., O., R. C.. Triaca, W. E. & Arvia, A. J. The Electrosorption of Methane and Its Potentiodynamic Electrooxidation on Platinized Platinum. J. Electrochem. Soc. 127, (1980).11. Baltrusaitis, J., Jansen, I. & Christus, J. D. S. Renewable energy based catalytic CH 4 conversion to fuels. Catal. Sci. Technol. 4, 2397-2411 (2014).Gurses, S. M. & Kronawitter, C. X. Electrochemistry of the Interaction of Methane with Platinum at Room Temperature Investigated through Operando FTIR Spectroscopy and Voltammetry. J. Phys. Chem. C 125, 2944-2955 (2021). Lucky, C., Fuller, L. & Schreier, M. Determining the potential-dependent identity of methane adsorbates at Pt electrodes using EC-MS. Catal. Sci. Amp Technol.14, (2024). Du, B., A. Rabb, S., Zangmeister, C. & Tong, Y. A volcano curve: optimizing methanol electro- oxidation on Pt-decorated Ru nanoparticles. Phys. Chem. Chem. Phys. 11. 8231-8239 (2009). Zhang, J. et al. Engineering the Near-Surface of PtRu3 Nanoparticles to Improve Hydrogen Oxidation Activity in Alkaline Electrolyte. Small 17, 2006698 (2021). Hansen, T. K., Hoj, M., Hansen, B. B., Janssens, T. V. W. & Jensen, A. D. The Effect of Pt Particle Size on the Oxidation of CO, C3H6, and NO Over Pt / A12O3 for Diesel Exhaust Aftertreatment. Top. Catal. 60, 1333-1344 (2017). Kim, D. et al. Active site localization of methane oxidation on Pt nanocrystals. Nat. Commun. 9, 3422 (2018). Sustersic. M. G.. O., R. C.. Triaca. W. E. & Arvia, A. J. The Electrosorption of Methane and Its Potentiodynamic Electrooxidation on Platinized Platinum. J. Electrochem. Soc. 127, (1980). Ma. H. et al. High Catalytic Activity of Pt(lOO) for CH4 Electrochemical Conversion. ACS Catal. 9, (2019). Boyd, M. J. et al. Electro-Oxidation of Methane on Platinum under Ambient Conditions. ACS Catal. 9, 7578-7587 (2019). Yan, L., Jiang, L., Qian, C. & Zhou, S. Electrocatalytic conversion of methane: Recent progress and future prospects. Energy Rev. 3, 100065 (2024).Ravi, M.; Ranocchiari, M.; van Bokhoven, J. A., The Direct Catalytic Oxidation of Methane to Methanol-A Critical Assessment. Angew. Chem. Int. Ed. 2017, 56 (52), 16464-16483. Gunsalus, N. J.; Koppaka, A.; Park, S. H.; Bischof, S. M.; Hashiguchi, B. G.; Periana, R. A., Homogeneous Functionalization of Methane. Chem Rev 2017, 117 (13), 8521-8573. Schwarz, H., Chemi stry with Methane: Concepts Rather than Recipes. Angew. Chem. Int. Ed. 2011, 50 (43), 10096-10115. Opportunities for Catalysis in the 21st Century-A Report from the BES Advisory Committee. Department of Energy: Washington DC, 2002. Nanoscience Research for Energy Needs - Report of the March 2004 National Nanotechnology Initiative Grand Challenge Workshop, 2nd Edition. Washington DC, 2005. Directing Matter and Energy: Five Challenges for Science and the Imagination - A Report from the BES Advisory Committee. National Nanotechnology Coordination Office & Department of Energy: Washington DC, 2007. Basic Research Needs: Catalysis for Energy - Report from the DOE-BES Workshop. Department of Energy: Washington DC, 2007. Quadrennial Technology Review: An Assessment of Energy Technologies and Research Opportunities. Department of Energy: Washington, DC. 2015. Peplow, M., The great gas gold rush. Nature 2017, 550, 26-28. Fletcher, S. E. M.; Schaefer, H., Rising methane: A new climate challenge. Science 2019, 364 (6444), 932-933. Ausfelder, F.; Bazzanella, A.; VanBrackle, H.; Wilde. R.; Beckmann. C.; Mills, R.; Rightor, E.; Tam. C.; Trudeau. N.Botschek, P. Technology Roadmap: Energy and GHG Reductions in the Chemical Industrial via Catalytic Processes;International Energy Agency, International Council of Chemical Associations, DECHEMA: Washington DC, 2013. Monastersky, R., The lee that bums: Can methane hydrates fuel the 21st century? Sci. News 1998, 154, 312-314. Debbichi, L, et al., Vibrational Properties of CuO and Cu4O3 from First- Principles Calculations, and Raman and Infrared Spectroscopy. J. Phys. Chem. C 2012, 116 (18), 10232-10237. Labinger, J. A.; Bercaw, J. E., Mechanistic studies on the Shilov system: A retrospective. Journal of Organometallic Chemistry 2015, 793, 47-53. Shilov, A. E.; Shul'pin. G. B., Activation of C~H Bonds by Metal Complexes. Chemical Reviews 1997, 97 (8), 2879-2932. Shilov, A. E.; Shteinman, A. A., Activation of saturated hydrocarbons by metal complexes in solution. Coordination Chemistry Reviews 1977, 24 (2), 97-143. Hashiguchi, B. G.; Bischof, S. M.; Konnick, M. M.; Periana, R. A., Designing Catalysts for Functionalization of Unactivated C-H Bonds Based on the CH Activation Reaction. Accounts of Chemical Research 2012, 45 (6), 885-898. Periana, R.; Taube, D.; Gamble, S.; Taube, H.; Satoh, T.; Fujii, H., Platinum catalysts for the high-yield oxidation of methane to a methanol derivative. Science 1998, 280 (5363), 560-564. Gunsalus, N. J.; Koppaka, A.; Park, S. H.; Bischof, S. M.; Hashiguchi, B. G.; Periana, R. A., Homogeneous Functionalization of Methane. Chem Rev 2017, 117 (13), 8521-8573. Xie, S.; Lin, S.; Zhang, Q ; Tian, Z.; Wang, Y., Selective electrocatalytic conversion of methane to fuels and chemicals. Journal of Energy Chemistry 2018, 27 (6), 1629-1636.Ravi, M.; Ranocchiari, M.; van Bokhoven, J. A., The Direct Catalytic Oxidation of Methane to Methanol-A Critical Assessment. Angew. Chem. Int. Ed. 2017, 56 (52), 16464-16483. O’Reilly, M. E.; Kim, R. S.; Oh, S.; Surendranath, Y., Catalytic Methane Monofunctionalization by an Electrogenerated Eligh-Valent Pd Intermediate. ACS Cent. Sci. 2017, 3 (11), 1174-1179. Schwarz, H., Chemi stry with Methane: Concepts Rather than Recipes. Angew. Chem. Int. Ed. 2011, 50 (43), 10096- 10115. Baltrusaitis, J.; Jansen, I.; Schuttlefield Christus, J. D., Renewable energy based catalytic CH4 conversion to fuels. Catalysis Science & Technology 2014, 4 (8), 2397-15. Nguyen, V. T. Development of direct-methane proton exchange membrane fuel cells at low and elevated temperatures. Ph. D. Thesis, Colorado School of Mines, 2017. Joglekar, M.; Nguyen, V.; Pylypenko, S.; Ngo, C.; Li, Q.; O’Reilly, M. E.; Gray, T. S.; Hubbard, W. A.; Gunnoe, T. B.; Herring, A. M.; Trewyn, B. G., Organometallic Complexes Anchored to Conductive Carbon for Electrocatalytic Oxidation of Methane at Low Temperature. J. Am. Chem. Soc. 2016. 138, 116- 125. Nandenha, J.; Nagahama, I. H. F.; Yamashita, J. Y.; Fontes, E. H.; Ayoub, J. M. S.; Souza, R. F. B. d.; Fonseca, F. C.; Neto, A. O.. Activation of Methane on PdZn / C Electrocatalysts in an Acidic Electrolyte at Low Temperatures. Int. J. Electrochem. Sci. 2019, 10819-10834. Boyd, M. J.; Latimer, A. A.; Dickens, C. F.; Nielander, A. C.: Hahn, C.; Norskov, J. K.; Higgins, D. C.; Jaramillo, T. F., Electro-Oxidation of Methane on Platinum under Ambient Conditions. ACS Catal. 2019, 9 (8), 7578-7587. Xu. J.; Armstrong, R. D.; Shaw, G.; Dummer, N. F.; Freakley, S. J.; Taylor, S. H.;Hutchings, G. J., Continuous selective oxidation of methane to methanol over Cu-and Fe-modified ZSM-5 catalysts in a flow reactor. Catal. Today 2016, 270, 93- 100. Snyder, B. E. R.; Bols, M. L.; Schoonheydt, R. A.; Seis, B. F.; Solomon, E. I., Iron and Copper Active Sites in Zeolites and Their Correlation to Metalloenzymes. Chem Rev 2017. 118 (5), 2718-2768. Banerjee, R.; Proshlyakov, Y.; Lipscomb, J. D.; Proshlyakov, D. A., Structure of the key species in the enzymatic oxidation of methane to methanol. Nature 2015, 518 (7539). 431-434. Grundner, S.; Markovits, M. A. C.; Li, G.; Tromp, M.; Pidko, E. A.; Hensen, E. J. M.; Jentys, A.; Sanchez- Sanchez, M.; Lercher, J. A., Single-site trinuclear copper oxygen clusters in mordenite for selective conversion of methane to methanol. Nat Comms 2015, 6, 1-9. Sushkevich, V. L.; Palagin, D.; Ranocchiari, M.; van Bokhoven, J. A., Selective anaerobic oxidation of methane enables direct synthesis of methanol. Science 2017. 356 (6337), 523-527. Papoian, G.; Norskov, J. K.; Hoffmann, R., A Comparative Theoretical Study of the Hydrogen, Methyl, and Ethyl Chemisorption on the Pt(l 11) Surface. Journal of the American Chemical Society 2000, 122 (17), 4129-4144. Broderick, W. E.; Kanamori, K.; Willett, R. D.; Legg, J. I., Intramolecular carbonhydrogen bond activation: preparation, structure, and properties of a unique cobalt(III) complex, K[Co(III)(dacoda)(SO3).cntdot.5H2O, containing a weak agostic interaction in aqueous solution. Inorg Chem 1991, 30 (20), 3875-3881. Kim, Y.; Kim, H. W.; Lee, S.; Han, J.; Lee, D ; Kim, J. R.; Kim, T. W.; Kim, C. U.; Jeong, S. Y.; Chae. H. J.; Kim. B. S.; Chang, H.; Kim. W. B.; Choi. S. M.; Kim, H. J., The Role of Ruthenium on Carbon-Supported PtRu Catalysts for Electrocatalytic Glycerol Oxidation under Acidic Conditions. ChemCatChem 2017, 9 (9). 1683-1690.Abild-Pedersen, F.; Greeley, J.; Studt, F.; Rossmeisl, J.; Munter, T.; Moses, P.; Skulason, E.; Bligaard. T.; Norskov. J., Scaling Properties of Adsorption Energies for Hydrogen-Containing Molecules on Transition-Metal Surfaces. Phys. Rev. Lett. 2007, 99 (1), 016105. Labinger. J. A., Selective alkane oxidation: hot and cold approaches to a hot problem. Journal of Molecular Catalysis A: Chemical 2004, 220 (1), 27-35. Seidel, Y. E.; Schneider, A.; Jusys, Z.; Wickman, B.; Kasemo, B.; Behm, R. J., Transport Effects in the Electrooxidation of Methanol Studied on Nanostructured Pt / Glassy Carbon Electrodes. Langmuir 2010. 26 (5), 3569-3578. Amarson, L.; Schmidt, P. S.; Pandey, M.; Bagger, A.; Thygesen, K. S.; Stephens, I. E. L.; Rossmeisl. J., Fundamental limitation of electrocatalytic methane conversion to methanol. Phys. Chem. Chem. Phys 2018, 20 (16), 11152-11159. Tomita, A.; Nakajima, J.; Hibino, T., Direct Oxidation of Methane to Methanol at Low Temperature and Pressure in an Electrochemical Fuel Cell. Angewandte Chemie International Edition 2008, 47 (8), 1462-1464. Zhu, X.; Guo, Q.; Sun, Y.; Chen, S.; Wang, J.-Q.; Wu, M.; Fu, W.; Tang, Y.; Duan, X.; Chen, D.; Wan, Y., Optimising surface d charge of AuPd nanoalloy catalysts for enhanced catalytic activity. Nat Comms 2019, 10 (1), 362-11. Wang, D.; Cui, X.; Xiao, Q.; Hu, Y.; Wang, Z.; Yiu, Y. M.; Sham, T. K„ Electronic behaviour of Au-Pt alloys and the 4f binding energy shift anomaly in Au bimetallics- X-ray spectroscopy studies. Aip Advances 2018, 8 (6), 065210. Burch, R., Importance of electronic ligand effects in metal alloy catalysts. Accounts of chemical research 1982, 15 (1), 24-31. Braga, A. A. C.; Maseras, F.; Urbano, J.; Caballero, A.; Diaz-Requejo, M. M.; Perez, P. J., Mechanism of Alkane C-H Bond Activation by Copper and Silver Homoscorpionate Complexes. Organometallics 2006, 25 (22), 5292-5300.Ritzert, N. L.; Moffat, T. P., Ultramicroelectrode Studies of Self-Terminated Nickel Electrodeposition and Nickel Hydroxide Formation upon Water Reduction. J. Phys. Chem. C 2016, 120 (48), 27478-27489. Jafarian, M.; Mahjani, M. G.; Heli, H.: Gobal, F.; Heydarpoor, M., Electrocatalytic oxidation of methane at nickel hydroxide modified nickel electrode in alkaline solution. Electrochemistry Communications 2003, 5 (2), 184- 188. Lee, B.; Sakamoto. Y.; Hirabayashi, D.; Suzuki. K.; Hibino, T., Direct oxidation of methane to methanol over proton conductor / metal mixed catalysts. Journal of Catalysis 2010, 271 (2), 195-200. Labinger. J. A.; Bercaw, J. E., Understanding and exploiting C-H bond activation. Nature 2002. 417 (6888), 507-514. Zhou, M.; Crabtree, R. H., C-H oxidation by platinum group metal oxo or peroxo species. Chem. Soc. Rev. 2011, 40(4), 1875-11. Conley, B. L.; Tenn III, W. J.; Young, K. J. H.; Ganesh, S. K.; Meier, S. K.; Ziatdinov, V. R.; Mironov, O.; Oxgaard, J.; Gonzales, J.; Goddard III, W. A.; Periana, R. A., Design and study of homogeneous catalysts for the selective, low temperature oxidation of hydrocarbons. Journal of Molecular Catalysis A: Chemical 2006, 251 (1 -2), 8-23. Ahlquist, M.; Nielsen, R. J.; Periana, R. A.; Goddard III, W. A.. Product Protection, the Key to Developing High Performance Methane Selective Oxidation Catalysts. J. Am. Chem. Soc. 2009, 131 (47), 17110-17115. Weaver, J. F.; Hakanoglu, C.; Antony, A.; Asthagiri, A., Alkane activation on crystalline metal oxide surfaces. Chemical Society Reviews 2014, 43 (22), 7536- 7547. Liang, Z.; Li, T.; Kim, M.; Asthagiri, A.; Weaver, J. F., Low-temperature activation of methane on the IrO 2(110) surface. Science 2017, 356 (6335). 299- 303.Snyder. B. E. R.; Vanelderen, P.; Bols, M. L.; Hallaert, S. D.; Bottger, L. H.; Ungur, L.; Pierloot, K.; Schoonheydt, R. A. Seis, B. F.; Solomon, E. I., The active site of low-temperature methane hydroxylation in iron-containing zeolites. Nature 2016, 536, 317. Smeets, P. J.; Hadt, R. G.; Woertink, J. S.; Vanelderen, P.; Schoonheydt, R. A.; Seis, B. F.; Solomon, E. I., Oxygen Precursor to the Reactive Intermediate in Methanol Synthesis by Cu-ZSM-5. Journal of the American Chemical Society 2010, 132 (42), 14736-14738. Caims. E. J., The Anodic Oxidation of Hydrocarbons and the Hydrocarbon Fuel Cell. In Adv. Electrochem. Electrochem. Eng., Tobias, C. W., Ed. Wiley- Interscience: New York, 1971; Vol. 8, p 337. Ogura, K.; Takamagari, K., Direct conversion of methane to methanol, chloromethane and dichloromethane at room temperature. Nature 1986, 319, 308. Cook, R. L.; Sammells, A. F , Ambient-Temperature Methane Activation to Condensed Species Under Cathodic Conditions. J. Eelectrochem. Soc. 1990, 137 (6), 2007-2008. Freese Jr., K. W., Partial Electrochemical Oxidation of Methane under Mild Conditions. Langmuir 1991, 7. 13-15. Hahn, F.; Melendres, C. A., Anodic oxidation of methane at noble metal electrodes: an ‘in situ’ surface enhanced infrared spectroelectrochemical study. Electrochimica Acta 2001. 46, 3515-3534. Lin, Y.; Zhan, Z.; Liu, J.; Barnett, S., Direct operation of solid oxide fuel cells with methane fuel. Solid State Ionics 2005, 176 (23-24), 1827-1835. Lee, B.; Hibino, T., Efficient and selective formation of methanol from methane in a fuel cell-type reactor. Journal of Catalysis 2011, 279 (2), 233-240. Zhang, Q.; Otsuka. K.. Partial Oxidation of Light Alkanes during O2-H2 Cell Reactions at Room Temperature. Chemistry Letter 1997, 26, 363-364.Murray, E. P.; Tsai, T.: Barnet, S. A., A direct-methane fuel cell with a ceriabased anode. Nature 1999, 400, 649-651. Li, Z.; Gao, J.; Xing, X.; Wu, S.; Shuang, S.; Dong, C.; Paau, M. C.; Choi, M. M. F., Synthesis and Characterization of n-Alkylamine-Stabilized Palladium Nanoparticles for Electrochemical Oxidation of Methane. J. Phys. Chem. C 2010, 114 (2), 723-733. Rocha, R. S.; Reis, R. M.; Lanza, M. R. V.; Bertazzoli, R., Electrosynthesis of methanol from methane: The role of V2O5 in the reaction selectivity for methanol of a TiO2 / RuO2 / V2O5 gas diffusion electrode. Electrochimica Acta 2013, 87, 606-610. Wang, Z.; Zeng, X., Bis(trifluoromethylsulfonyl)imide (NTf2)-Based Ionic Liquids for Facile Methane Electro- Oxidation on Pt. J. Electrochem. Soc. 2013, 160 (9), H604-H611. Joglekar, M.; Nguyen, V.; Pylypenko, S.; Ngo, C.; Li. Q.; O’Reilly, M. E.; Gray, T. S.; Hubbard. W. A.; Gunnoe, T. B.; Herring, A. M.; Trewyn. B. G., Organometallic Complexes Anchored to Conductive Carbon for Electrocatalytic Oxidation of Methane at Low Temperature. J Am Chem Soc 2016, 138 (1), 116- 125. Promoppatum, P.; Viswanathan, V., Identifying Material and Device Targets for a Flare Gas Recover}' System Utilizing Electrochemical Conversion of Methane to Methanol. ACS Sustainable Chem. Eng. 2016, 4 (3), 1736-1745. Nandenha, J.; Fontes, E. H.; Piasentin, R. M.; Fonseca, F. C.; Neto, A. O., Direct oxidation of methane at low temperature using Pt / C, Pd / C, Pt / C-ATO and Pd / C- ATO electrocatalysts prepared by sodium borohydride reduction process. Journal of Fuel Chemistry and Technology 2018, 46 (9), 1137-1145. Tan, D.-X.; Wang, Y.-L., Visible-light-assisted SLCs template synthesis of sea anemone-like Pd / PANI nanocomposites with high electrocatalytic activity for methane oxidation in acidic medium. Materials Research Express 2018, 5 (3), 035056.Torabi, A.; Barton, J.; Willman, C.; Ghezel-Ayagh, H.; Li, N.; Poozhikunnath, A.; Marie, R.; Marin, O. A., Developing Low- Intermediate Temperature Fuel Cells for Direct Conversion of Methane to Methanol Fuel. ECS Trans 2016, 73, 193- 199. Grubb, W. T.; Michalske, C. J., Electrochemical oxidation of Methane in Phosphoric Acid Fuel Cells at 150* C. Nature 1964, 201, 287-288. Schoofs, G. R.; Arumainayagam, C. R.; McMaster, M. C.; Madix, R. J., Dissociative chemisorption of methane on Pt(l 11). Surf. Sci. 1989, 215 (1-2), 1- 28. Agarwal, N.; Freakley, S. J.; McVicker, R. U.; Althahban, S. M.; Dimitratos, N.; He, Q.; Morgan, D. J.; Jenkins, R. L.; Willock, D. J.; Taylor, S. H.; Kiely, C. J.; Hutchings, G. J., Aqueous Au-Pd colloids catalyze selective CH4oxidation to CH3OH with 02 under mild conditions. Science 2017, 11, eaan6515-10. Tong; Kim. H. S.; Babu, P. K.; Waszczuk. P.; Wieckowski, A.; Oldfield, E., An NMR Investigation of CO Tolerance in a Pt / Ru Fuel Cell Catalyst. Journal of the American Chemical Society 2002, 124 (3), 468-473. . Tong, Y. Y.; Meriaudeau, P ; Renouprez, A. J.; van der Klink, J. J., Tailoring the Frontier Orbitals at the Surfaces of Platinum Catalysts. J Phys Chem B 1997. 101, 10155-10158. . Tong, Y. Y.; Billy, J.; Renouprez, A. J.; van der Klink, J. J., Correlation between the stretching frequency of carbon monoxide adsorbed and the Fermi level local density of states at surfaces of platinum catalysts. Journal of the American Chemical Society 1997, 119, 3929-3934. . Chen, D. J.; Sun, S. G.; Tong. Y. Y. J., On the chemistry of activation of a commercial carbon-supported PtRu electrocatalyst for the methanol oxidation reaction. Chemical communications 2014, 50, 12963-12965.. Hong, W.; Wang, J.: Wang, E., Facile Synthesis of Highly Active PdAu Nanowire Networks as Self-Supported Electrocatalyst for Ethanol Electrooxidation. ACS Applied Materials & Interfaces 2014, 6 (12), 9481-9487..Xiong, H.; and Zeng, Z. et. al. Adv. Sci. 2023, 10 (5), 2204566; Bao. X. et. al., Chem 2019, 5 (9), 2296-2325. .Fomaciari, J. C. et al. A Perspective on the Electrochemical Oxidation of Methane to Methanol in Membrane Electrode Assemblies. ACS Energy Lett. 5, (2020). . Deng, J. et al. Ambient methane functionalization initiated by electrochemical oxidation of a vanadium (V)-oxo dimer. Nat. Commun. 11, 3686 (2020). .P Giannozzi, O Andreussi, T Brumme, O Bunau, M Buongiomo Nardelli, M Calandra, R Car, C Cavazzoni, D Ceresoli, M Cococcioni, N Colonna, I Camimeo, A Dal Corso, S de Gironcoli, P Delugas, R A DiStasio Jr, A Ferretti, A Floris, G Fratesi, G Fugallo, R Gebauer, U Gerstmann, F Giustino, T Gomi, J Jia, M Kawamura, H-Y Ko, A Kokalj. E Kiifukbenli, M Lazzeri, M Marsili, N Marzari, F Mauri, N L Nguyen, H-V Nguyen, A Otero-de-la-Roza, L Paulatto, S Ponce, D Rocca, R Sabatini, B Santra, M Schlipf, A P Seitsonen, A Smogunov, I Timrov, T Thonhauser, P Umari, N Vast, X Wu and S Baroni, Advanced capabilities for materials modelling with Quantum ESPRESSO. J.Phys.: Condens. Matter 29, 465901 (2017). .P. Perdew, K. Burke, M. Emzerhof, Generalized Gradient Approximation Made Simple. Phys Rev Lett. 77. 3865-3868 (1996). DOI: 10.1103 / PhysRevLett.77.3865. .P. Perdew, K. Burke, M. Emzerhof, Generalized Gradient Approximation Made Simple [Phys. Rev. Lett. 77, 3865 (1996)], Phys. Rev. Lett. 78, 1396-1396 (1997). DOI: 10.1103 / PhysRevLett.78.1396. . A. M. Rappe, K. M. Rabe, E. Kaxiras, and J. D. Joannopoulos, Optimized Pseudopotentials, Phys. Rev. B 41, 1227 (1990); Erratum Phys. Rev. B 44, 13175 (1991).. A. Dal Corso, Pseudopotentials periodic table: From H to Pu, Comp. Mat. Sci. 95. 337 (2014). .M. Methfessel and A. T. Paxton, High-precision sampling for Brillouin-zone integration in metals, Phys. Rev. B 40, 3616 (1989).

Claims

What is claimed is:

1. A low-temperature and low-pressure direct steam continuous electrochemical methane (CH4) electro-oxidation (EO) system comprising:(a) a metal electrolyte assembly (MEA) reactor;(b) a sampler; and(c) a mass spectrometer detector; wherein the MEA reactor comprises a single-stack proton-exchanged membrane fuel cell (PEMFC) and a MEA assembly unit assembled together, wherein the proton-exchanged membrane fuel cell comprises two electrodes, an anode and a cathode separated by a membrane, and wherein the proton-exchanged membrane fuel cell uses methane or hydrogen as a fuel source.

2. The system of claim 1, wherein the membrane is aNafion membrane.

3. The system of claim 1, wherein the proton-exchanged membrane fuel cell comprises a metal-membrane-assembly.

4. The system of claim 3, wherein the metal-membrane-assembly comprises a catalyst that is capable of promoting both hydrogenation and partial oxidation reactions.

5. The system of claim 4, wherein the catalyst is one or more electrocatalysts selected from platinum, platinum alloy, palladium, palladium alloy, copper, copper alloy, vanadium, vanadium alloy, nickel or nickel alloy or combinations thereof.

6. The system of claim 1, wherein the cathode is a hydrogen-fed reversible hydrogen reference electrode (RHE).

7. The system of claim 1, wherein the cathode is catalyzed with a platinum, platinum alloy, palladium, or palladium alloy based electrocatalyst.

8. The system of claim 2, wherein the cathode is oxygen-fed and hydrogen or H2O are produced at the cathode.

9. The system of claim 1, wherein the anode is catalyzed with a platinum, platinum alloy, palladium, palladium alloy, copper, copper alloy, vanadium, vanadium alloy, nickel or nickel alloy based electrocatalyst.

10. The system of claim 1, wherein carbon dioxide or CH3OH are produced at the anode.

11. The system of claim 1, wherein a small portion of a FC outlet flows gas into the sampler and the sampler flows gas into a gas chromatographer via a t pical split / spiritless inlet through a deactivated fused silica (dFS) tubing.

12. The system of claim 11, wherein a high split ratio was used in the inlet to dilute a sample gas and significantly reduce the moisture content, protecting the mass spectrometer detector.

13. The system of claim 1, wherein the mass spectrometer detector is an operando electrochemistry-mass spectroscopy detector (OECMS) that simultaneously monitors and observes the production of CO2 via EC-DSMR.

14. A method of generating hydrogen (H2) gas from the electro-oxidation (EO) of methane (CH4) at low temperature and ambient pressure comprising: feeding methane to the anode of the low temperature methane reforming system of claim 1 at a relative humidity (RH) of 90%; catalyzing the reaction with electrocatalysts at temperature of 80 °C and back pressure of 4 bar; and starting the EC-MRR system with the hydrogen-fed RHE cathode; wherein the hydrogen produced by the reformer is used to self-sustain the hydrogen-fed RHE cathode,wherein the relative humidity may be 60% to 100%; wherein the reaction temperature is between 30 °C and 120 °C, wherein the reaction back pressure is between 90 kPa and 1000 kPa, and wherein the reaction turnover frequency is fast enough at the gas / solid interface to generate sustained electron transfer.

15. The method of claim 14, wherein carbon dioxide is produced by conversion from methane in an anodic reaction.

16. The method of claim 14, wherein the low temperature methane reforming system activity is 10 times higher on Pt / C than PtRu / C wherein the number of experimental active site percentages are 5% and 1% at 40 °C for Pt / C and PtRu / C, respectively, and wherein the number of experimental active site percentages are 14% and 2% at 80 °C for Pt / C and PtRu / C, respectively.

17. The method of claim 16, wherein the Pt comer / edge sites are the active sites for the low temperature methane reforming system and the reaction works preferentially with the edge sites.

18. The method of claim 16 wherein electrocatalysts Pt / C and PtRu / C exhibit longterm CH4 EO activity, up to 48 hours without a poison-cleaning procedure, recover catalytic performance after holding the cell potential at 1.2 V for 1 min, then at 0.07 V for 1 min, and wherein up to 80% of initial CH4 EO activity of Pt / C or PtRu / C is regained after employing the cleaning procedure.

19. A method of electrocatalytic direct methane to methanol (DMTM) generation at low temperatures and ambient pressure comprising: feeding methane to the anode of the fuel cell of claim 1 at a relative humidity (RH) of 100%; catalyzing the reaction with electrocatalysts at temperature of 80 °C and ambient back pressure;wherein the flowrate of CH4 and 02 to anode and cathode respectively is 0.8 L / min, wherein electrocatalyst surfaces PtRu / C and PdAu produce conversion of CH4 to MeOH, wherein the area of MEA is 5 cm2, and wherein the electrocatalyst loadings are 5 mg / cm2 for Pt / C, PtRu / C, and AuPd and 50 mg / cm2 for CuNi.

20. The method of claim 19, wherein electrocatalysts Pt / C, PtRu / C, AuPd, and CuNi all produce measurable reaction currents.

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