Electrodes, electrochemical cells, and methods of use thereof

Abstract

The invention relates to an electrode, an electrochemical cell comprising the electrode, and a use method and a preparation method thereof. The electrode includes a plurality of metallic silver nanoparticles, wherein the plurality of metallic silver nanoparticles have an average coordination number of 8.9-11.6 and an average tensile strength strain of 0.14-0.81%.

Description

TECHNICAL FIELD

[0001] The present disclosure relates generally to silver-based electrodes for the electrocatalytic reduction of CO2, electrochemical cells comprising the electrodes, and methods of use thereof. BACKGROUND

[0002] It has been found that the electrocatalytic reduction of CO2 has numerous industrial applications, including, for example, the formation of high-value chemicals and feedstocks. Optimizing the selectivity (i.e., Faradaic Efficiency (FE)) of catalysts towards products (such as CO), increasing their productivity (current density), and reducing the overpotential of the reduction reaction have become a priority. However, major issues remain, such as system stability and efficiency, especially in pure H2O systems.

[0003] Accordingly, there is a need for improved electrodes and electrochemical cells to address at least some of the aforementioned challenges. SUMMARY

[0004] In a first aspect, provided herein is an electrode comprising: a plurality of metallic silver nanoparticles, wherein the plurality of metallic silver nanoparticles has an average coordination number of 8.9-11.6 and an average tensile strength strain of 0.14-0.81%.

[0005] In certain embodiments, each of the plurality of metallic silver nanoparticles comprises a plurality of stacking faults and a plurality of grain boundaries.

[0006] In certain embodiments, the plurality of metallic silver nanoparticles has an average diameter of 10-50 nm.

[0007] In certain embodiments, each of the plurality of metallic silver nanoparticles has an average coordination number of 9.2-9.8 and an average tensile strength strain of 0.56-0.81%.

[0008] In certain embodiments, each of the plurality of metallic silver nanoparticles has an average coordination number of about 9.2 and an average tensile strength strain of about 0.81%.

[0009] In certain embodiments, the plurality of metallic silver nanoparticles is prepared by a method comprising: contacting AgNO3, octadecylamine, oleylamine, squalane, and trioctylphosphine, thereby forming the plurality of metallic silver nanoparticles.

[0010] In certain embodiments, the plurality of metallic silver nanoparticles is prepared by a method comprising: contacting AgNO3, octadecylamine, squalane, and an organic solvent at 60-100 °C, thereby forming a silver-based stock solution; contacting the silver-based stock solution, oleylamine, and trioctylphosphine at 100-200 °C, thereby forming the plurality of metallic silver nanoparticles.

[0011] In certain embodiments, the plurality of metallic silver nanoparticles is not annealed at a temperature higher than 250 °C.

[0012] In certain embodiments, the electrode further comprises a base electrode or a substrate, wherein the plurality of metallic silver nanoparticles is disposed on a surface of the base electrode or the substrate.

[0013] In certain embodiments, the substrate comprises a gas permeable metal mesh.

[0014] In another aspect, provided herein is a method of making an electrode described herein, the method comprising: depositing a solution comprising the plurality of metallic silver nanoparticles, a binder, and a solvent on a surface of the substrate, thereby forming a coated substrate; and calcining the coated substrate, thereby forming the electrode.

[0015] In certain embodiments, the solvent comprises an organic solvent.

[0016] In certain embodiments, the solution is deposited by screen printing.

[0017] In certain embodiments, the method further comprises compressing the coated substrate prior to calcining the coated substrate.

[0018] In a second aspect, provided herein is an electrochemical cell comprising: an electrode described herein; a counter electrode; and an electrolyte solution comprising an electrolyte, wherein the electrolyte solution is located between and in contact with the electrode and the counter electrode.

[0019] In certain embodiments, the electrode further comprises a base electrode or a substrate, wherein the plurality of metallic silver nanoparticles is disposed on a surface of the base electrode or the substrate.

[0020] In certain embodiments, the base electrode is selected from a glassy carbon electrode, a graphite electrode, an indium tin oxide (ITO) electrode, a fluorine-doped tin oxide (FTO) electrode, a carbon paper electrode, a carbon fiber electrode, a polycarbonate track-etched (PCTE)-based electrode, and a titanium-based electrode; and the substrate comprises a gas permeable metal mesh.

[0021] In certain embodiments, the electrolyte comprises water and, optionally, a metal hydroxide and a soluble alkali metal electrolyte.

[0022] In certain embodiments, the electrochemical cell further comprises at least one ion exchange membrane disposed between the electrode and the counter electrode.

[0023] In certain embodiments, the electrochemical cell further comprises an anion exchange membrane and a proton exchange membrane, wherein the electrode is in contact with the anion exchange membrane, the anode is in contact with the proton exchange membrane, and the anion exchange membrane and the proton exchange membrane are in contact with each other.

[0024] In certain embodiments, the electrochemical cell further comprises a CO2 inlet and a water inlet, the CO2 inlet is in fluid communication with the electrode, and the water inlet is in fluid communication with the counter electrode.

[0025] In a third aspect, provided herein is a method for reducing carbon dioxide, the method comprising: providing an electrochemical cell described herein; contacting CO2 and the electrode, and contacting water and the counter electrode; and applying an electric current between the electrode and the counter electrode to electrolytically reduce CO2, thereby forming CO.

[0026] In certain embodiments, an electrode can be prepared by using any electrocatalytic CO2 reduction catalyst instead of the metallic silver catalyst to electrolytically reduce CO2, thereby producing a specific target product. For example, in certain embodiments, a metallic copper electrode can be used instead of the metallic silver electrode described above, and water and the counter electrode are contacted, and an electric current is applied between the metallic copper electrode and the counter electrode to electrolytically reduce CO2, thereby forming C2H4. The copper electrode can be prepared by a similar method as described above for preparing the metallic silver electrode, except that silver nitrate is replaced by cuprous chloride.

[0027] In certain embodiments, the electrochemical cell has a CO Faraday efficiency (FE) of 50-99%.

[0028] In certain embodiments, the electrochemical cell has a CO Faraday efficiency (FE) of 90-99%. BRIEF DESCRIPTION OF DRAWINGS

[0029] The above and other objects and features of the present disclosure will become apparent from the following description of the disclosure taken in conjunction with the accompanying drawings, which

[0030] Figure 1 (A) HAADF-STEM image of the stepped surface silver nanoparticles (SS-Ag). (B) Pseudo-color dark-field four-dimensional STEM (4D-STEM) map corresponding to (A). (C) Atomically resolved HAADF-STEM image of SS-Ag showing the stepped facets caused by stacking faults and twin boundaries all along the {111} planes (white dashed lines).

[0031] Figure 2Fine structural characterization of SS-Ag. (AC) Typical SEM (A) and TEM (B and C) images of SS-Ag. (DG) HR-TEM image of SS-Ag. (E) and (G) are selected regions from (D) and (F), respectively.

[0032] Figure 3 Fine structural characterization of SS-Ag. (A and D) Typical HAADF-STEM images of SS-Ag. (B and C) Atomic-resolution HAADF-STEM images of selected regions in (A) and (B), respectively. (EG) Atomic-resolution HAADF-STEM image showing the stepped surface of SS-Ag caused by the abundance of SF and GB in SS-Ag. (E) From the selected region in (D). The yellow and white lines in the image highlight GB and SF. The arrows in (F and E) highlight the steps. The arrow in (G) highlights GB in SS-Ag.

[0033] Figure 4 XRD patterns of SS-Ag, Ag-250, Ag-350 and Ag-450 on carbon paper and bare carbon paper.

[0034] Figure 5 In-situ heating TEM characterization. (A and B) TEM and HRTEM images of initial SS-Ag. (C and B) TEM and HRTEM images of initial SS-Ag heated at 250 °C for 10 min. (E and F) TEM and HRTEM images of samples further heated at 350 °C for 10 min. (G and H) TEM and HRTEM images of samples further heated at 450 °C for 10 min. (B, D, F, and H) Selected regions from (A, C, E, and G), respectively. (IL) In-situ heating TEM images of SS-Ag and SS-Ag directly heated at 450 °C for 10 min.

[0035] Figure 6 XAS measurements of SS-Ag, Ag-250, Ag-350, and Ag-450, as well as standard Ag foil references. (A) Ag K-edge XANES spectra. (B) Fourier transform of Ag K-edge EXAFS spectra.

[0036] Figure 7 Two-dimensional diagrams of wavelet transform EXAFS (2D WT EXAFS). (A) Standard Ag foil reference. (B) SS-Ag. (C) Ag-250. (D) Ag-350. (E) Ag-450.

[0037] Figure 8Ag K-edge EXAFS fitting curves in R and q-space, respectively. (A and B) Standard Ag foil reference. (C and D) SS-Ag. (E and F) Ag-250. (G and H) Ag-350. (I and J) Ag-450.

[0038] Figure 9 Tensile strain and coordination number of SS-Ag, Ag-250, Ag-350, Ag-450 and Ag foil reference. Values are means and error bars represent the highest and lowest values.

[0039] Figure 10 ECO2R performance of SS-Ag at different applied potentials in a flow cell with 1 M KOH as electrolyte. (A) Faradaic efficiency (FE) for ECO2R product. (B) Total and partial current densities. Values are means and error bars represent SD (n = 3 replicates).

[0040] Figure 11 ECO2R performance of Ag-250 at different applied potentials in a flow cell with 1 M KOH as electrolyte. (A) FE for ECO2R product. (B) Total and partial current densities. Values are means and error bars represent SD (n = 3 replicates).

[0041] Figure 12 ECO2R performance of Ag-350 at different applied potentials in a flow cell with 1 M KOH as electrolyte. (A) FE for ECO2R product. (B) Total and partial current densities. Values are means and error bars represent SD (n = 3 replicates).

[0042] Figure 13 ECO2R performance of Ag-450 at different applied potentials in a flow cell with 1 M KOH as electrolyte. (A) FE for ECO2R product. (B) Total and partial current densities. Values are means and error bars represent SD (n = 3 replicates).

[0043] Figure 14 Comparison of ECO2R performance of different samples at a range of applied potentials in a flow cell with 1 M KOH as electrolyte. (A) Total current density. (B) FE for CO. (C) Partial current density for CO. (D) FE for H2. (E) Partial current density for H2. Values are means and error bars represent SD (n = 3 replicates).

[0044] Figure 15 Strain, CN and peak j of ECO2R in a flow cell with 1 M KOH as electrolyte.CO (A), j H2 (B) between the products FE and the corresponding cell voltage. Values are means and error bars represent the highest and lowest values of CN. Values are means and error bars represent the SD of the partial current density (n = 3 replicates).

[0045] Figure 16 . Schematic of the anion exchange membrane and proton exchange membrane (AEM and PEM assembly: APMA) membrane electrode assembly (APMA MEA) system architecture for ECO2R.

[0046] Figure 17 . FE of products and corresponding cell voltage of the APMA MEA system for pure H2O feed at 100 mA / cm2total current density and different reaction temperatures. Low temperatures result in higher overpotentials, while too high temperatures inhibit ECO2R while increasing HER. Values are means and error bars represent the SD (n = 3 replicates). 2

[0047] Figure 18 . ECO2R performance of SS-Ag in the APMA MEA cell for pure H2O feed. (A) FE of SS-Ag for ECO2R products and corresponding cell voltage at a range of applied current densities and 60 °C. (B) FE of ECO2R and cell voltage of SS-Ag in the APMA MEA cell for pure H2O feed at 150 mA / cm2total current density, 60 °C and different CO2inlet flow rates. (C) CO2conversion to CO2R products of SS-Ag and cell voltage at different CO2inlet flow rates. (D and E) FE (G) and corresponding partial current density (H) for products for ECO2R at different CO2inlet flow rates. Values are means and error bars represent the SD (n = 3 replicates). 2

[0048] Figure 19 . Schematic of an exemplary free high-diffusivity flux gas diffusion electrode (HDF-GDE) according to certain embodiments described herein.

[0049] Figure 20 ​​ECO2R performance in membrane electrode assembly (APMA MEA) systems with pure H2O feed and different HDF-GDEs. (A) Digital photograph of SS-Ag HDF-GDE showing its hydrophobicity. (B) SEM image of SS-Ag HDF-GDE. (C) FE for ECO2R product and corresponding cell voltage of SS-Ag HDF-GDE at a range of applied current densities. (D-F) Comparison of CO FE (D), H2 FE (E), and cell voltage (F) of ECO2R of SS-Ag HDF-GDE and SS-Ag carbon paper (traditional GDE) at different current densities. (G) Comparison of CO2 conversion of SS-Ag traditional GDE and SS-Ag HDF-GDE. (H) In-situ Raman spectra of ECO2R of SS-Ag carbon paper GDE and SS-Ag HDF-GDE in APMA MEA cells with pure H2O feed. 2 . In-situ Raman spectra of ECO2R of SS-Ag carbon paper GDE and SS-Ag HDF-GDE in APMA MEA cells with pure H2O feed.

[0050] Figure 21 . Schematic of different GDEs. (A) Traditional carbon paper GDE. (B) HDF-GDE.

[0051] Figure 22 . Digital photographs of SS-Ag HDF-GDEs of different sizes.

[0052] Figure 23 . APMA MEA cell stack with HDF-GDEs assembled for ECO2R at scaled-up kilo- watt level with pure H2O feed. (A-C) Digital photograph of flow field plate in cell stack system (A), side view of assembled cell stack (B), and front view of cell stack (C). (D and E) System stability performance of ECO2R of SS-Ag HDF-GDE (D) and SS-Cu HDF-GDE (E).

[0053] Figure 24 . Structural characterization of SS-Ag after 1000 hours of ECO2R. (A and B) Typical HAADF-STEM images. (B) Selected area from (A).

[0054] Figure 25 . Crystal structure parameters of SS-Ag, Ag-250, Ag-350, Ag-450, and Ag foil reference produced from EXAFS fitting.

[0055] Figure 26 . Schematic of an exemplary electrochemical cell according to certain embodiments described herein. DETAILED DESCRIPTION

[0056] Definitions

[0057] The following terms will be used to describe the present application. Where no specific definition is provided in the text, the terms used to describe the present application will be given the general meaning as understood by one of ordinary skill in the art.

[0058] Throughout this disclosure, the word "comprise" or variations such as "comprises" or "comprising" shall mean the inclusion of the stated integer or integers, but not the exclusion of any other integer or integers. It is also to be noted that the terms such as "comprises", "comprised", "comprising" and the like can have the meaning ascribed to it in U.S. Patent Law i.e., they can mean "includes", "included", "including", and the like; and that the terms such as "consisting essentially of and "consists essentially of have the meaning ascribed to them in U.S. Patent Law i.e., they allow for elements not explicitly listed to be present but exclude elements that are found in the prior art or that affect a basic or novel characteristic of the application.

[0059] Further, throughout this disclosure and in the claims, the word "include" or variations such as "includes" and "including" shall not be construed so as to cover the only integers indicated expressly or by implication from the specification.

[0060] The singular includes the plural unless specifically stated otherwise. Further, when the term "about" is used in reference to a numerical value, the present teachings also include the specific numerical value itself, unless specifically stated otherwise. As used herein, unless otherwise stated or inferred, the term "about" means a variation of ±10%, ±7%, ±5%, ±3%, ±1% or ±0% of the nominal value.

[0061] As used herein, the term "soluble alkali metal electrolyte" refers to an alkali metal salt or an alkali metal hydroxide that is soluble in water. Suitable soluble alkali metal electrolytes for use in the present application include, but are not limited to, KHCO3, NaHCO3, CsHCO3, KOH, NaOH, and CsOH.

[0062] Provided herein is an electrode comprising: a plurality of metallic silver nanoparticles, wherein the plurality of metallic silver nanoparticles has an average coordination number of 8.9-11.6 and an average tensile strength strain of 0.14-0.81%.

[0063] The average coordination number of the plurality of metallic silver nanoparticles can be 8.9-11.6, 9.2-11.2, 9.2-10.5, 9.2-9.8, or 8.9-9.5. In certain embodiments, the average coordination number of the plurality of metallic silver nanoparticles is about 9.2.

[0064] The average tensile strength strain of the plurality of metallic silver nanoparticles can be 0.14-0.81%, 0.35-0.81%, 0.56-0.81%, 0.61-0.81%, 0.66-0.81%, 0.71-0.81%, or 0.76-0.81%. In certain embodiments, the average tensile strength strain of the plurality of metallic silver nanoparticles is about 0.81%.

[0065] Each of the plurality of metallic silver nanoparticles comprises a plurality of stacking faults and / or a plurality of grain boundaries.

[0066] The plurality of metallic silver nanoparticles can have an average diameter of 10-50 nm, 10-40 nm, 10-30 nm, 10-20 nm, 20-50 nm, 30-50 nm, 40-50 nm, 20-40 nm, 20-30 nm, 30-40 nm, or 15-25 nm. In certain embodiments, the plurality of metallic silver nanoparticles can have an average diameter of about 20 nm.

[0067] The plurality of metallic silver nanoparticles can be readily prepared from readily available, commercially available materials. In certain embodiments, the plurality of metallic silver nanoparticles is prepared by contacting a silver salt with an aliphatic primary amine, thereby forming the plurality of metallic silver nanoparticles.

[0068] The silver salt can be AgOAc, AgN03, AgOTf, AgOTFA, AgBF4, AgOS02Me, Ag2S04, AgPF6, and mixtures thereof. In certain embodiments, the silver salt is AgN03.

[0069] In certain embodiments, the aliphatic primary amine is a C8-C 24 alkyl primary amine, C 10 -C 24 alkyl primary amine, C 12 -C 24 alkyl primary amine, C 14 -C 24 alkyl primary amine, C 16 -C 24 alkyl primary amine, C 18 -C24 alkyl primary amines, C 18 -C 22 alkyl primary amines, C 16 -C 20 alkyl primary amines, C8-C 24 alkenyl primary amines, C 10 -C 24 alkenyl primary amines, C 12 -C 24 alkenyl primary amines, C 14 -C 24 alkenyl primary amines, C 16 -C 24 alkenyl primary amines, C 18 -C 24 alkenyl primary amines, C 18 -C 22 alkenyl primary amines, C 16 -C 20 alkenyl primary amines, or mixtures thereof. In certain embodiments, the aliphatic primary amine comprises octadecylamine, oleylamine, or mixtures thereof.

[0070] In certain embodiments, the method of making a plurality of metallic silver nanoparticles further comprises: contacting the silver salt and the aliphatic primary amine with a trialkylphosphine. Exemplary trialkylphosphines include, but are not limited to, tri(C6-C 12 alkyl)phosphine, tri(C6-C 10 alkyl)phosphine, tri(C6-C8alkyl)phosphine, tri(C8-C 12 alkyl)phosphine, tri(C8-C 10 alkyl)phosphine, or mixtures thereof. In certain embodiments, the trialkylphosphine is trioctylphosphine.

[0071] In certain embodiments, the plurality of metallic silver nanoparticles is made according to a method comprising: contacting a silver salt, a first aliphatic primary amine, and a solvent, thereby forming a silver-based stock solution; and contacting the silver-based stock solution with a second aliphatic primary amine and a trialkylphosphine, wherein the first aliphatic primary amine and the second aliphatic primary amine are each independently C8-C 24 alkyl primary amines, C 10 -C 24 alkyl primary amines, C 12 -C 24 alkyl primary amines, C 14 -C 24 alkyl primary amines, C 16 -C 24 alkyl primary amines, C 18 -C 24 alkyl primary amines, C 18 -C 22 alkyl primary amines, C 16 -C 20 alkyl primary amines, C8-C 24alkyl amines, C 10 -C 24 alkyl amines, C 12 -C 24 alkyl amines, C 14 -C 24 alkyl amines, C 16 -C 24 alkyl amines, C 18 -C 24 alkyl amines, C 18 -C 22 alkyl amines, C 16 -C 20 alkyl amines, or mixtures thereof, and the silver salt and the trialkylphosphine are each independently defined as in any of the embodiments described herein.

[0072] The solvent can be any high boiling solvent in which the starting materials can be at least partially soluble. In certain embodiments, the solvent includes C 10 -C 30 alkanes, C 15 -C 30 alkanes, C 15 -C 25 alkanes, C 15- C 20 alkanes, C 10 -C 30 alkenes, C 15 -C 30 alkenes, C 15 -C 25 alkenes, C 15 -C 20 alkenes, and C 10 -C 14 aryl groups, or mixtures thereof. Exemplary solvents include, but are not limited to, 1- octadecene, diisopropyl biphenyl, diisopropyl naphthalene, dibenzyl ether, paraffin, alkyl stearates, alkyl oleates, squalane, and the like. In certain embodiments, the solvent includes squalane.

[0073] The step of contacting the silver salt, the first aliphatic primary amine, and the solvent can be performed at 60-100 °C, 70-90 °C, or 75-85 °C. In certain embodiments, the step of contacting the silver salt, the first aliphatic primary amine, and the solvent is performed at about 80 °C.

[0074] The step of contacting the silver-based stock solution with the second aliphatic primary amine and the trialkylphosphine can be performed at 100-220 °C, 120-220 °C, 140-220 °C, 160-220 °C, 180-220 °C, 150-190 °C, 160-180 °C, or 165-175 °C. In certain embodiments, the step of contacting the silver-based stock solution with the second aliphatic primary amine and the trialkylphosphine is performed at about 170 °C.

[0075] In certain embodiments, the silver salt is AgN03, the first aliphatic primary amine is octadecylamine, the second aliphatic primary amine is oleylamine, the trialkylphosphine is trioctylphosphine, and the solvent is squalane.

[0076] The plurality of metallic silver nanoparticles can be separated from the reaction mixture, for example, by centrifugation, filtration, decanting, and the like, and dried. Drying can be performed using conventional methods, for example, under reduced pressure, optionally at a temperature of 40-100 °C. As described in detail herein, the average coordination number and average tensile strength of the plurality of metallic silver nanoparticles can be altered at elevated temperatures. Thus, in certain embodiments, the method for preparing the plurality of metallic silver nanoparticles does not comprise annealing the plurality of metallic silver nanoparticles or subjecting the plurality of metallic silver nanoparticles to a temperature greater than 80 °C, 100 °C, 150 °C, 200 °C, 150 °C, 200 °C, 250 °C, 300 °C, 350 °C, 400 °C, or 450 °C.

[0077] In certain embodiments, the electrode is gas and liquid permeable. In certain embodiments, the electrode is a cathode.

[0078] In certain embodiments, the electrode further comprises a base electrode or substrate. In certain embodiments, the plurality of metallic silver nanoparticles is disposed on a surface of the base electrode or substrate.

[0079] The base electrode can be an inert electrode, for example, a glassy carbon electrode, a graphite electrode, an indium tin oxide (ITO) electrode, a fluorine-doped tin oxide (FTO) electrode, a carbon paper electrode, a carbon fiber electrode, a polycarbonate track-etched (PCTE)-based electrode, or a titanium-based electrode.

[0080] The electrode can optionally comprise a binder. The binder can optionally be cured to further adhere the SS-Ag particle or plurality of SS-Ag particles to the base electrode and can improve the electrical conductivity of the electrode. Typical binders include, for example, polyvinylidene fluoride (PVDF), basic ionomer (e.g., Nafion® XB-7), Nafion™ polymer dispersion (e.g., D520CS, D521CS, D2020CS, and D2021CS), polyvinyl alcohol (PVA), starch, sodium alginate, hydroxypropyl cellulose, carboxymethyl cellulose (CMC), regenerated cellulose, polyvinylpyrrolidone, polyimide, polyamide-imide, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), acrylic resin, sulfonated EPDM, styrene-butadiene rubber, polytetrafluoroethylene (PTFE), polyacrylic acid polymers, and combinations thereof. In certain embodiments, the binder is Nafion® XB-7. XA-9, XC-2 and XB-7), Nafion™ polymer dispersion (e.g., D520CS, D521CS, D2020CS, and D2021CS), polyvinyl alcohol (PVA), starch, sodium alginate, hydroxypropyl cellulose, carboxymethyl cellulose (CMC), regenerated cellulose, polyvinylpyrrolidone, polyimide, polyamide-imide, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), acrylic resin, sulfonated EPDM, styrene-butadiene rubber, polytetrafluoroethylene (PTFE), polyacrylic acid polymers, and combinations thereof. In certain embodiments, the binder is Nafion® XB-7. XA-9.

[0081] The electrode further comprising a base electrode or substrate can be prepared using methods known in the art. In certain embodiments, the electrode further comprising a base electrode or substrate is prepared by depositing a solution comprising a plurality of metallic silver nanoparticles, a binder, and a solvent on at least one surface of a substrate, thereby forming a coated substrate; and calcining the coated substrate, thereby forming the electrode.

[0082] The solvent can be any organic solvent in which the binder is at least partially soluble. Exemplary organic solvents include, but are not limited to, ethers, alcohols, alkanes, ketones, aromatic solvents, formaldehyde, esters, sulfoxides, and mixtures thereof. In certain embodiments, the organic solvent comprises a-pinene and 2-(2-butoxyethoxy)ethanol.

[0083] The step of depositing the solution on at least one surface of the substrate can be accomplished using any method known to one of skill in the art. Exemplary methods of depositing the solution on the substrate include, but are not limited to, spin coating, printing, screen printing, spraying, painting, doctor blading, inkjet printing, roller printing, or flexographic fabric printing, and dip coating. In certain embodiments, the solution is deposited by screen printing.

[0084] Optionally, the solvent can be removed from the coated substrate prior to calcination, for example, by subjecting the coated substrate to reduced pressure (vacuum) and / or heat. Further improvement in the adhesion of the plurality of silver nanoparticles to the substrate can be advantageously achieved by compressing the coated substrate prior to calcination, for example, by directly compressing the coated substrate or compressing the coated substrate after the solvent has been removed. Compression of the coated substrate can include applying a pressure of, for example, up to 10,000, 5,000, 4,000, 3,000, 2,000, or 1,000 pounds to the coated substrate for a period of time, for example, 1-5 hours, 1-4 hours, 1-3 hours, or 1-2 hours.

[0085] Calcination of the coated substrate can include heating the coated substrate at a temperature of 100-400 °C, 150-400 °C, 200-400 °C, 250-400 °C, 300-400 °C, or 325-375 °C. The calcination step can be performed for 15-120 minutes, 15-90 minutes, 15-60 minutes, or 15-45 minutes. In certain embodiments, the coated substrate is calcined at a temperature of about 350 °C for about 30 minutes.

[0086] The present disclosure also provides an electrochemical cell comprising: an electrode as described herein; a counter electrode (or a counter / reference electrode); an optional reference electrode (for example, in a three-electrode system); and an electrolyte solution positioned between and in contact with the electrode, the counter electrode, and the optional reference electrode. In certain embodiments, the electrolyte solution comprises an aqueous solution.

[0087] A counter electrode is an electrode that is paired with the electrode described herein, through which current passes that is equal in magnitude and opposite in sign to the current through the electrode. The counter electrode can include a counter electrode that also functions as a reference electrode (i.e., a counter / reference electrode). Any suitable counter electrode known in the art can be used in conjunction with the methods described herein. For example, the counter electrode can include carbon (e.g., highly oriented pyrolytic graphite), a metal (e.g., Al, Au, Ag, Bi, Cd, Co, Cr, Cu, Cu alloys (e.g., brass and bronze), Ga, Hg, In, Mo, Nb, Ni, NiCo2O4, Ni alloys, Ni-Fe alloys, Pb, Pd alloys, Pt, Pt alloys, Rh, Sn, Sn alloys, Ti, V, W, Zn, or stainless steel), glassy carbon, or a conductive polymer, among others. In certain embodiments, the counter electrode is a mixture of IrO x , RuO x , Ir, Pt, or IrO x and RuO x . In certain embodiments, the counter electrode is Ir.

[0088] The reference electrode can be selected from a standard hydrogen electrode, a calomel electrode, a copper-copper(II) sulfate electrode, a silver chloride electrode, a palladium-hydrogen electrode, a mercury-mercurous sulfate electrode, among others.

[0089] The electrolyte solution can include a saturated solution of carbon dioxide or any concentration less than saturated or pure H2O.

[0090] Carbon dioxide can be added to the electrolyte prior to the step of applying a current between the electrode and the counter electrode, and / or continuously introduced into the electrolyte during the electrochemical reduction, and / or introduced to the back of the gas diffusion electrode, for example, by bubbling CO2 into the electrolyte solution.

[0091] The electrolyte solution can comprise an aqueous solvent, a non-aqueous solvent (e.g., methanol and acetonitrile), or a mixture thereof, and an electrolyte. Suitable electrolytes include salts comprising one or more cations selected from lithium, sodium, potassium, cesium, calcium, magnesium, and tetraalkylammonium; and one or more anions selected from halide, carbonate, bicarbonate, perchlorate, silicate, borate, phosphate, sulfate, polyphosphate, and nitrate. Exemplary electrolytes include, but are not limited to, M2SO4, M2CO3, MHCO3, MCI, M'SO4, M'CO3, M'(HCO3)2, and M'CI2, where M is independently in each instance lithium, sodium, potassium, cesium, or tetra(Ci-C4)alkylammonium, and M' is calcium or magnesium. In certain embodiments, the electrolyte salt is K2CO3, KHCO3, KOH, Na2CO3, NaHCO3, NaOH, or a mixture thereof. In certain embodiments, the electrolyte consists of water or is an aqueous solution comprising KOH.

[0092] The concentration of the electrolyte salt in the electrolyte solution can be 0.1 to 5 M, 0.1 to 4.5 M, 0.1 to 4 M, 0.1 to 3.5 M, 0.1 to 3 M, 0.1 to 2.5 M, 0.1 to 2 M, 0.5 to 1.5 M, 0.6 to 1.4 M, 0.7 to 1.3 M, 0.8 to 1.2 M, or 0.9 to 1.1 M. In some embodiments, the electrolyte salt is present in the electrolyte solution at a concentration of about 1 M.

[0093] In some embodiments, the electrochemical cell further includes an anion exchange membrane and a proton exchange membrane, wherein the electrode is in contact with the anion exchange membrane, the anode is in contact with the proton exchange membrane, and the anion exchange membrane and the proton exchange membrane are in contact with each other.

[0094] Figure 26 An exemplary electrochemical cell (100) according to certain embodiments described herein is shown, comprising: an electrode (101) as described herein, a counter electrode (102), an optional proton exchange membrane (104), an optional anion exchange membrane (103), an optional CO2 inlet (105), an optional water inlet (106), a CO outlet (107), and an optional product outlet (108).

[0095] This disclosure also provides an electrochemical cell comprising: a plurality of cells, each cell including an electrode as described herein; a counter electrode (or counter / reference electrode), an anion exchange membrane, and a proton exchange membrane, wherein the electrode is in contact with the anion exchange membrane, the counter electrode is in contact with the proton exchange membrane, and the anion exchange membrane and the proton exchange membrane are in contact with each other; and an electrolyte solution located between and in contact with the plurality of cells, wherein each electrode, each counter electrode, and the electrolyte are each independently defined as in any embodiment described herein.

[0096] Proton exchange membranes may include, but are not limited to, those marketed under the brand name Nafion. TM NR 50, Nafion TM 117. Nafion TM 211 and Nafion TM 212 sells proton exchange membranes. In some embodiments, the proton exchange membrane is Nafion. TM 117.

[0097] In some implementations, the anion exchange membrane includes, but is not limited to, those marketed under trademarks. X-37-50 Grade RT X-37-50 Grade 60 X-37 Grade FA, X-37Grade T、Sustainion E-30Grade T、 E-28 Grade T, B-22 Grade T and MT CP-50 sold anion exchange membranes (described in Wanjie Song et al., Alkaline Membranes toward Electrochemical Energy Devices: Recent Development and Future Perspectives ACS Cent. Sci. 2023, 9, 8, 1538-1557, which is incorporated by reference herein in its entirety), quaternary ammonium poly(N-methyl-piperidine-co-p-terphenyl) (QAPPT), and quaternary ammonium poly(ether ether ketone) (QAPEEK). In certain embodiments, the anion exchange membrane is X-37-50 Grade 60.

[0098] In certain embodiments, the electrochemical cell further comprises: a CO2 inlet in fluid communication with the electrode for introducing CO2 into the electrochemical cell; an electrolyte inlet in fluid communication with the counter electrode for introducing an electrolyte into the counter electrode; a product outlet in fluid communication with the electrode for removing carbon monoxide from the electrochemical cell; and a product outlet in fluid communication with the counter electrode for removing a product (e.g., O2) from the electrochemical cell.

[0099] The current between the electrode and the counter electrode can be applied at a voltage of -0.1 to -1 V, -0.1 to -0.9 V, -0.1 to -0.8 V, -0.1 to -0.7 V, -0.1 to -0.6 V, -0.1 to -0.5 V, -0.1 to -0.4 V, -0.1 to -0.3 V, -0.1 to -0.2 V, -0.2 to -0.9 V, -0.3 to -0.9 V, -0.4 to -0.9 V, -0.5 to -0.9 V, -0.6 to -0.9 V, -0.7 to -0.9 V, -0.8 to -0.9 V, -0.2 to -0.7 V, or -0.32 to -0.65 V (vs. RHE). In certain embodiments, the current between the electrode and the counter electrode is applied at about -0.32 V to about -0.65 V (vs. RHE). Advantageously, the yield of CO can be optimized when the current between the electrode and the counter electrode is applied at about -0.32 V to about -0.65 V (vs. RHE).

[0100] In other embodiments, the current between the electrode and the counter electrode is applied at a voltage of 0.1-10 V, 0.1-9 V, 0.1-8 V, 0.1-7 V, 0.1-6 V, 0.1-5 V, 0.1-4 V, 0.1-3 V, 0.1-2 V, 0.1-1 V, 0.1-0.5 V, 0.5-10 V, 1-10 V, 2-10 V, 3-10 V, 4-10 V, 5-10 V, 6-10 V, 7-10 V, 8-10 V, 9-10 V, 1-5 V, 2-5 V, 3-5 V, 3-4.5 V, 3.5-4.5 V, 4-4.5 V, or 3.5-4 V.

[0101] In cases where the electrochemical cell comprises multiple cells, the current between each electrode and each counter electrode is applied at a voltage of 1-100 V, 10-100 V, 20-100 V, 20-90 V, 20-80 V, 20-70 V, 20-60 V, 20-50 V, 20-40 V, 25-40 V, 30-40 V, 35-40 V, 20-35 V, 20-30 V, 20-25 V, 25-35 V, 30-35 V, or 25-30 V.

[0102] The electrical energy used for the electrochemical reduction of carbon dioxide can come from any energy source, including nuclear energy, alternative energy sources (e.g., hydroelectric, wind, solar, geothermal, etc.), solar energy, coal, natural gas, or other sources of electricity.

[0103] The carbon dioxide can be obtained from any source (e.g., an exhaust stream from a power plant or factory that burns fossil fuels, a gas from a geothermal or natural gas well, a natural gas stream, a flue gas of a fossil fuel, a cement plant exhaust, or the atmosphere itself).

[0104] Also provided is a method for reducing carbon dioxide, the method comprising: providing an electrochemical cell as described herein; contacting CO2 and the electrode, and contacting water and the counter electrode; and applying a current between the electrode and the counter electrode to electrolytically reduce the CO2, thereby forming CO.

[0105] In certain embodiments, the electrochemical cell has a CO Faraday efficiency (FE) of 90-99% at -0.32 V to -0.65 V vs. a reversible hydrogen electrode (RHE).

[0106] In a typical synthesis, 0.07 g of AgN03and 0.02 g of octadecylamine were dissolved in 0.8 mL of squalane and the solution was heated at 80 °C under inert gas (Ar) for 0.5 h to form a silver-based stock solution. Meanwhile, a mixed solution of 10 mL of oleylamine and 0.04 mL of trioctylphosphine was heated to 170 °C under Ar atmosphere by strong magnetic stirring. Subsequently, the silver-based stock solution was injected into the above mixed solution and kept at 170 °C for 5 h. After natural cooling, the resulting sample was collected by centrifugation and washed with n-hexane several times. Finally, the sample was dried in vacuum at 80 °C before use. This sample is denoted as SS-Ag.

[0107] In a tube furnace, the SS-Ag sample was annealed at different temperatures (250, 350 and 450 °C) for 2 h under mixed gas (H2 / Ar: 5 v / v%; 200 seem (standard cubic centimeter per minute)), denoted as Ag-250, Ag-350 and Ag-450, respectively.

[0108] Model catalyst SS-Ag (-20 nm) with a large number of stacking faults (SFs) and grain boundaries (GBs) was prepared by a simple oil-bath method. Figure 1 Four-dimensional aberration-corrected high-angle annular dark-field (HAADF) scanning TEM (STEM) (4D-STEM) showed that a large number of SFs and GBs in SS-Ag intersected with each other and led to the formation of step-like surfaces. Figure 1 High-resolution TEM (HR-TEM) and HAADF-STEM showed a large number of SFs and GBs in SS-Ag, GBs contained Σ3 coincidence site lattice grain boundaries (twin grain boundaries), and some of them formed some typical five-fold twin structures. Figure 2 and Figure 3 SFs and GBs led to the formation of step-like surfaces at the surface exits of GBs and SFs. Figure 1 C and Figure 3 According to the powder X-ray diffraction (XRD) pattern, the synthesized SS-Ag was in a cubic phase (JCPDS No. 04-0783) and remained as metallic Ag. Figure 4

[0109] ​To investigate the effect of SF and GB on Ag catalyst, SS-Ag was treated with different high temperatures (250 °C, 350 °C and 450 °C; corresponding to Ag-250, Ag-350 and Ag-450) to reduce or eliminate SF and GB in SS-Ag, since atoms would rearrange at high temperatures to reach a more thermodynamically favorable state, thus minimizing surface energy. In-situ heating TEM showed that SF and GB were reduced or even disappeared at high temperatures, and the higher the temperature, the lower the density of SF and GB, and there was no significant change in sample size after high-temperature treatment Figure 5 ).

[0110] X-ray absorption spectroscopy (XAS) was used to investigate the fine structure of the samples Figures 6-8 ). The Ag K-edge X-ray absorption near-edge structure (XANES) spectra and wavelet-transformed EXAFS (2D WT EXAFS) two-dimensional maps of the samples presented the near-edge features of metallic Ag phase Figure 6 A and Figure 7 ). The Fourier transform χ(R) function of the extended X-ray absorption fine structure (EXAFS) data in the frequency domain (R) revealed that the coordination number (CN) increased with increasing treatment temperature Figure 6 B). The fine structure information from the EXAFS fitting results showed that the average CN of Ag gradually increased (from about 9.2 to 11.2) while the average tensile strain gradually decreased (from about 0.81% to 0.14%) with increasing treatment temperature Figure 8 and Figure 25 ). Due to the thermodynamic effect (high-temperature treatment), the tensile strain and CN showed a strong linear correlation with the change of annealing temperature Figure 9 ).

[0111] For ECO2R, the FE of CO on SS-Ag reached about 99% in a flow electrolysis cell with conventional electrolyte (1 M KOH) at a wide potential window (-0.32 V to -0.65 V vs. reversible hydrogen electrode (RHE)) Figure 10 ). It was also found that low CN and high tensile strain improved the ECO2R performance Figures 10-14 ). With the increase of CN and the decrease of tensile strain, the ECO2R performance of the samples showed a significant decrease Figure 15 ). More importantly, the CO partial current density (j CO ) monotonically increased with the decrease of CN and the increase of tensile strain of Ag Figure 15 A), which means that j COwith a strong linear correlation with the function of tensile strain and CN. This strong linear correlation can reflect the potential reason that SF and GB can improve the ECO2R (electrolysis CO2 reduction) activity can be due to lower CN and higher tensile strain. In addition, the HER (hydrogen evolution reaction) activity seems to be independent of SF and GB Figure 15 B).

[0112] To suppress the formation of carbonates during the ECO2R process and improve the stability of the electrolysis system, a pure H2O-fed MEA architecture with anion exchange membrane and proton exchange membrane (AEM and PEM assembly: APMA) was employed to evaluate the ECO2R performance of SS-Ag Figure 16 Since pure H2O was used as the anode electrolyte, the reaction temperature was first increased (from about 25 °C to 80 °C) to reduce the reaction overpotential. At a total current density of 100 mA / cm 2 The optimal reaction temperature was 60 °C, the FE CO was about 91%, the FE H2 was about 8%, and the cell voltage was about 3.61 V Figure 17 , which indicates that too high a temperature will suppress ECO2R and favor HER. Therefore, the following ECO2R tests were conducted at 60 °C (unless otherwise specified).

[0113] In the APMA MEA system with pure H2O feed, SS-Ag achieved CO and H2 FE 2 of about 93% and 6%, respectively, at 150 mA / cm Figure 18 A). The cell voltage was about 3.88 V (all tests of MEA cells in the full text were without iR compensation). Although this system can effectively suppress the formation of carbonates, the low current density (150 mA / cm 2 ) results in a low CO2 conversion rate, greatly limiting its feasibility.

[0114] To improve the CO2 conversion rate, the CO2 inlet flow rate was first reduced from 30 sccm to 2 sccm Figure 18 B). As expected, the CO2 conversion rate gradually increased from 3.23% to 42.97% Figure 18 C). However, the FE and partial current density of CO gradually decreased (FE CO : from about 92.70% to 82.26%; j CO : from about 139.04 mA / cm 2 to 123.40 mA / cm 2 ) and the FE and partial current density of H2 gradually increased (FE H2: from ~ 6.49% to 17.29%; j H2 : from 9.74 mA / cm 2 to 25.94 mA / cm 2 Figure 18 D and Figure 18 E). These indicate that the increase in by-product (H2) FE is at the expense of product (CO) FE under this CO2 mass transport limited regime (i.e., lower CO2 flow rates). The cell voltage also slightly decreases (from ~ 3.88 V to 3.49 V) Figure 18 B and Figure 18 C) due to the thermodynamic driving force favoring HER. These indicate that over-reducing the CO2 inlet flow rate will slow down the CO2 mass transfer driving force, resulting in lower CO2 / *CO coverage on the catalyst surface, thus decreasing ECO2R activity and increasing HER.

[0115] For the ECO2R system, further drastic changes in CO2 mass transfer are needed to achieve higher CO2 conversion. Since the CO2 and key intermediate *CO coverage on the catalyst surface is determined by the total flux of species in and out of the GDE surface, the HDF-GDE was redesigned and assembled by screen printing to increase the CO2 / *CO coverage, thus increasing the ECO2R current density and ultimately improving the CO2 conversion efficiency Figure 19 ) instead of traditional GDEs (e.g., carbon paper or porous polytetrafluoroethylene (PTFE)).

[0116] To strengthen the mechanical strength of the HDF-GDE, stainless steel mesh (SSM) was employed as the supporting skeleton for the catalyst sheet Figure 20 A, Figure 21 and Figure 22 ). The porous SS-Ag HDF-GDE exhibits hydrophobicity Figure 20 A and Figure 20 B) and its thickness is controlled to be ~ 300 pm. The SS-Ag HDF-GDE contains only catalyst and SSM skeleton in the middle layer of catalyst, which can allow CO2 to directly contact the catalyst without going through a substrate (e.g., carbon paper and PTFE). This can increase the total flux of CO2 / *CO in and out of the HDF-GDE surface, thus accelerating the CO2 mass transfer driving force.

[0117] ​For HDF-GDE, the cathode catalyst (SS-Ag or SS-Cu) was printed on the SSM scaffold by screen printing, followed by drying in vacuum overnight. After that, the SSM scaffold loaded catalyst was pressed under 1000 pounds of pressure for 2 hours, and the thickness of HDF-GDE was controlled to be about 300 pm. Finally, it was calcined at 350 °C for 30 minutes. The printing ink was prepared by mixing the prepared catalyst and PTFE solution in an organic solution consisting of a-terpineol, 2-(2-butoxyethoxy)ethanol, and acrylic resin (weight ratio of about 65: 15:20). The loading of catalyst in HDF-GDE was controlled to be about 10 mg / cm 2 .

[0118] After obtaining the desired SS-Ag HDF-GDE, its ECO2R performance was evaluated in an APMA MEA cell with pure H2O feed including Ir counter electrode. The SS-Ag HDF-GDE still maintained a high CO FE (about 90%) ( Figure 20 C). More importantly, the peak current density was significantly increased to 400 mA / cm 2 at a cell voltage of about 3.91 V. Compared to SS-Ag assembled on a conventional carbon paper GDE under the same testing conditions (e.g., 30 seem CO2inlet flow rate), although the SS-Ag HDF-GDE exhibited a negligible decrease in CO FE (from about 93% to about 90%) and a slight increase in cell voltage (from about 3.88 V to about 3.91 V) ( Figure 20 D and Figure 20 F), the peak current density was increased from 150 mA / cm 2 to 400 mA / cm 2 . Moreover, the H2 FE was effectively suppressed, especially at higher current densities (from about 70% to about 14% at 500 mA / cm 2 ( Figure 20 E). These indicate that more CO2 / *CO can occupy the active sites in the SS-Ag HDF-GDE, while reducing the *H coverage on the catalyst surface, thus improving the ECO2R activity and suppressing the HER. Therefore, compared to the conventional GDE (SS-Ag carbon paper GDE), the CO2conversion efficiency of the SS-Ag HDF-GDE was significantly improved by about 2.6 times (from about 3.2% to about 8.5%) at the peak CO FE without the need to reduce the CO2inlet flow rate ( Figure 20 G).

[0119] In addition, in-situ Raman experiments were also conducted to investigate the ECO2R product (CO / *CO) concentration on different GDEs ( Figure 20H) because if the HDF-GDE can facilitate CO2 mass transfer and diffusion, the CO2 concentration on the surface of the HDF-GDE will be higher than that on the carbon paper GDE, which will lead to a higher CO2 / *CO concentration during the ECO2R process. For the SS-Ag HDF-GDE, the peak intensity of CO2 / *CO at about 237 cm -1 is significantly higher than that of the SS-Ag carbon paper GDE, which directly proves that the total flux of the material in and out of the HDF-GDE is increased (HDF-GDE significantly accelerates the CO2 mass transfer kinetics). Efficient CO2 mass transfer can suppress the accumulation of *H due to the transfer of H2O on the catalyst surface, resulting in a higher CO2 / *CO coverage on the catalyst surface, increasing the peak current density, and significantly increasing the CO2 conversion rate.

[0120] After demonstrating the ECO2R CO production performance of the APMA MEA cell with pure H2O feed (SS-Ag HDF-GDE area of 1 x 1 cm 2 ), a cell stack was designed and customized, which contains 6 MEA cells (each MEA cell contains the electrode described herein, an Ir counter electrode, and an APMA with an area of 150 cm 2 stacked in a series circuit structure, to verify the practical application possibility of the HDF-GDE combined APMA MEA system with pure H2O feed Figure 23 A- Figure 23 C). The scale-up demonstration and stability measurement can reflect its actual feasibility, thereby further promoting the development of the ECO2R technology towards industrial deployment.

[0121] During the scale-up, various engineering problems will occur. For example, under high power operation, the temperature of the MEA core will be significantly increased due to resistive heating, and for the series circuit, the voltage distribution of the entire stack must be uniform. Since the power of the scaled-up pure H2O-fed APMA MEA cell stack assembled with SS-Ag HDF-GDE is scaled up to the kilowatt level, the initial temperature of the pure H2O anolyte is reduced to 30°C to balance the temperature of the MEA core, and the CO2 inlet flow rate is increased to 3000 sccm.

[0122] In order to examine the durability of the stack, the scaled-up pure H2O-fed APMA MEA cell stack assembled with SS-Ag HDF-GDE was operated for 1000 hours at a total current of 60 A Figure 23D). The total cell stack voltage was very stably maintained at 21 V to 22 V, and the working power was up to about 1.29 kW. Throughout the stability test, the 6 SS-Ag HDF-GDEs provided a relatively stable CO FE of about 89-80%. The slight increase in voltage and slight decrease in CO FE could be due to slight GDE flooding at high power.

[0123] At a CO2inlet flow rate of 3000 seem, the CO2conversion of the kilowatt-scale cell stack assembled with SS-Ag HDF-GDE was up to about 81%, which was about 25 times higher than that of SS-Ag carbon paper GDE in a single pure H2O-fed APMA MEA cell (about 3.2%) ( Figure 20 G). In addition, the stability of SS-Ag with SF and GB was also investigated. The HAADF-STEM images showed that SS-Ag maintained its structural integrity (GB and SF) Figure 24 ) after 1000 hours of ECO2R. The stable SS-Ag catalyst, the durable pure H2O-fed MEA system, and the efficient HDF-GDE synergistically improved the ECO2R performance.

Claims

1. An electrode comprising: a plurality of metallic silver nanoparticles, wherein the plurality of metallic silver nanoparticles have an average coordination number of 8.9-11.6 and an average tensile strain of 0.14-0.81%.

2. The electrode according to claim 1, wherein each of the plurality of silver nanoparticles comprises a plurality of stacking faults and a plurality of grain boundaries.

3. The electrode according to claim 1, wherein the plurality of metallic silver nanoparticles have an average diameter of 10-50 nm.

4. The electrode according to claim 1, wherein each of the plurality of silver nanoparticles has an average coordination number of 9.2-9.8 and an average tensile strain of 0.56-0.81%.

5. The electrode according to claim 1, wherein each of the plurality of silver nanoparticles has an average coordination number of about 9.2 and an average tensile strain of about 0.81%.

6. The electrode according to claim 1, wherein the plurality of silver nanoparticles are prepared by a method comprising the steps of contacting AgNO3, octadecylamine, oleylamine, squalane and trioctylphosphine to form the plurality of silver nanoparticles.

7. The electrode according to claim 1, wherein the plurality of silver nanoparticles are prepared by a method comprising the following steps: contacting an organic solvent such as AgNO3, octadecylamine, and squalane at 60-100°C to form a silver-based reserve solution; and contacting the silver-based reserve solution, oleylamine, and trioctylphosphine at 100-200°C to form the plurality of silver nanoparticles.

8. The electrode according to claim 1, wherein the plurality of silver nanoparticles are not annealed at a temperature above 250°C.

9. The electrode of claim 1, wherein the electrode further comprises a base electrode or a substrate, wherein the plurality of metallic silver nanoparticles are disposed on the surface of the base electrode or the substrate.

10. The electrode of claim 9, wherein the substrate comprises a breathable metal mesh.

11. A method for preparing the electrode according to claim 9, the method comprising: A solution comprising the plurality of metallic silver nanoparticles, a binder, and a solvent is deposited on the surface of the substrate to form a coated substrate; The electrode is formed by calcining the coated substrate.

12. The method of claim 11, wherein the solvent comprises an organic solvent.

13. The method of claim 11, wherein the solution is deposited by screen printing.

14. The method of claim 11, further comprising: The coated substrate is compressed before it is calcined.

15. An electrochemical battery, comprising: The electrode according to claim 1; Counter electrode; as well as An electrolyte solution containing an electrolyte, wherein the electrolyte solution is located between and in contact with the electrode and the counter electrode.

16. The electrochemical cell of claim 15, wherein the electrode further comprises a base electrode or a substrate, wherein the plurality of metallic silver nanoparticles are disposed on the surface of the base electrode or the substrate.

17. The electrochemical cell according to claim 15, wherein the base electrode is selected from glassy carbon electrode, graphite electrode, indium tin oxide (ITO) electrode, fluorine-doped tin oxide (FTO) electrode, carbon paper electrode, carbon fiber electrode, polycarbonate track etching (PCTE) based electrode, and titanium-based electrode; and the substrate comprises a breathable metal mesh.

18. The electrochemical cell of claim 15, wherein the electrolyte comprises water and optionally a metal hydroxide and a soluble alkali metal electrolyte.

19. The electrochemical cell according to claim 15, further comprising at least one ion exchange membrane disposed between the electrode and the counter electrode.

20. The electrochemical cell of claim 15, further comprising an anion exchange membrane and a proton exchange membrane, wherein the electrode is in contact with the anion exchange membrane, the anode is in contact with the proton exchange membrane, and the anion exchange membrane and the proton exchange membrane are in contact with each other.

21. The electrochemical cell of claim 15, wherein the electrochemical cell further comprises a CO2 inlet and a water inlet, the CO2 inlet being in fluid communication with the electrode and the water inlet being in fluid communication with the counter electrode.

22. A method for reducing carbon dioxide, the method comprising: Provide an electrochemical cell according to claim 15; Make CO2 contact with the electrode and water contact with the counter electrode; And apply current between the electrode and the counter electrode to electrolyze and reduce CO2, thereby forming CO.

23. The method of claim 22, wherein the electrochemical cell has a CO faradaic efficiency (FE) of 50-99%.

24. The method of claim 22, wherein the electrochemical cell has a CO Faradaic efficiency (FE) of 90-99%.

Images