Flexible and extensive catalytic condensers for programmable catalysts

Abstract

A catalytic device includes a first electrically conductive layer, a second electrically conductive layer, an electrically insulating layer between the first electrically conductive layer and the second electrically conductive layer, and a metal on a surface of the first electrically conductive layer. The first electrically conductive layer and the second electrically conductive layer are configured to be electrically coupled. The catalytic device can be used to catalyze reactions by positioning the catalytic device in a medium comprising reactants, and applying a voltage across the first electrically conductive layer and the second electrically conductive layer, thereby catalyzing a chemical reaction of the reactants.

Description

FLEXIBLE AND EXTENSIVE CATALYTIC CONDENSERS FOR PROGRAMMABLE CATALYSTS

[0001] This application claims the benefit of U.S. Patent Application No. 63 / 538,797 filed on September 15, 2023, which is incorporated by reference herein in its entirety.STATEMENT OF GOVERNMENT SUPPORT

[0002] This invention was made with government support under DE-SC0023464 awarded by the U.S. Department of Energy. The government has certain rights in the invention.TECHNICAL FIELD

[0003] This invention relates to composition and fabrication of catalytic condensers for catalytic conversion of specific chemical reactions, which can be accelerated and manipulated with a controlled surface.BACKGROUND

[0004] Catalytic cycles on surfaces comprised of a sequence of elementary steps including adsorption, surface reaction, and desorption have historically been optimized by identifying catalytic materials that provide the best overall rate, independent of the fastest conditions for each elementary reaction step. This approach has identified optimal materials consistent with the Sabatier principle, whereby the fastest catalysts exhibit moderate characteristics in relevant reaction descriptors such as adsorbed species binding energy. Yet catalysts at the Sabatier maximum remain too slow for many important energy applications including ammonia synthesis, methanol synthesis, and hydrogen generation via electrolysis.SUMMARY

[0005] This disclosure describes catalytic condensers including ion gels separating a metal electrode from a platinum-on-carbon active layer are described. These catalytic condensers achieve more powerful, high surface area dynamic heterogeneous catalyst surfaces. Condensers are also fabricated on flexible, large area substrates allowing stacked or tubular form factors that facilitate high volumetric active site densities, ultimately enabling a fast and powerful catalytic condenser that can be fabricated for programmable catalysis applications.

[0006] A Pt on C ion gel catalytic condenser was fabricated, characterized, and evaluated for its thermal stability and its electronic ability to modulate the binding energy of carbon monoxide with varying applied potential. The ion gel condenser fdm stack is configured with exposed Pt / carbon active sites available to an external fluid for catalytic reactions and separation applications. Starting with an Au-deposited Si substrate, ion gel was first spin coated to yield a ~3.8 pm film. Conductive carbon was then sputtered on top of the ion gel followed by the deposition of Pt by electron beam deposition. Electron microscopy and X-ray photoelectron spectroscopy confirmed the surface structure and elemental makeup of the stack, showing no agglomerate formation. The thermal stability of three PVDF / [EMIM]+[Anion]‘ ion gels with differing anion species were assessed via transient and isothermal thermogravimetric measurements and isothermal infrared spectroscopy (IR) over 48 h. The isothermal IR measurement provided the best assessment of the thermal stability of the ion gel’s chemical structure, the most stable being the PVDF / [EMIM]+[TFSI]' ion gel. For electronic characterization, accumulation of charge in the Pt / C layer of the ion gel condensers of capacitance 2400 nF / cm2amounted to ~1014e7cm2under a potential bias of ±1 V with a cutoff frequency of 15 Hz. The capacitance and the cutoff frequency of the ion gel improved to 20,000 nF / cm2and 120 Hz respectively at 200 °C, providing a significant -10% charge per active site at + 1 V. CO binding on Pt was then evaluated by measuring adsorption isobars from temperatures of 25 to 200 °C under a fixed bias of -1.00 V to +0.25 V at 0.25 V increments. The CO binding energy, through fitting a Langmuir isobar, was estimated to shift from 68.2 to 84.4 kJ mol-1over the applied potential range; larger variation in CO binding was possible with higher voltages but was not detectable by spectroscopic methods. Finally, ion gel, with its excellent mechanical properties, can be fabricated via a scalable and low-cost manufacturing process such as roll-to- roll printing, creating more active sites over a volume of space and enabling dynamic perturbation with charge to become industrially relevant in catalytic applications.

[0007] Carbon sputtering provides for fast, large-scale fabrication of metal-carbon catalytic condensers. Carbon films were sputtered on HfCh dielectric / p-type Si with different thickness (1, 3, 6, 10 nm), and the enhancement of conductance and capacitance of carbon films was observed upon increasing carbon thickness following thermal treatment at 400 °C. After Pt deposition on the carbon films, the Pt catalytic condenser exhibited high capacitance of -210 nF / cm2that was maintained at a frequency -1,000 Hz, satisfying the requirement for a dynamic catalyst toimplement catalytic resonance. Temperature programmed desorption of carbon monoxide yielded CO desorption peaks which shifted in temperature with varying potential applied to the condenser (-6 V or 6 +V) indicating a shift in the binding energy of carbon monoxide on the Pt condenser surface. A substantial increase of capacitance (-2,000 nF / cm2) of the Pt-on-carbon devices was observed at elevated temperatures of 400 °C that can modulate- 10% of charge per metal atom when 10 V potential was applied. A large catalytic condenser of 42 cm2area Pt / C / HfCE / Si exhibited high capacitance of 9,393 nF with low leakage current / capacitive current ratio (<0.1), demonstrating the practicality and versatility of the facile, large-scale fabrication method for metal-carbon catalytic condensers.

[0008] The condenser technology can be used in applications including: catalytic chemistry, charge swing separations, and charge-swing redox chemistry. Examples include low cost production of H2, conversion of CO2, synthesis of ammonia, and large volume important reactions such as propylene epoxidation.

[0009] The details of one or more embodiments of the subject matter of this disclosure are set forth in the accompanying drawings and the description. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims.BRIEF DESCRIPTION OF DRAWINGS

[0010] FIG. 1 A is a schematic of an ion gel catalytic condenser configuration with exposed catalytic sites. PVDF is the polymer used to support the ionic liquids. FIG. IB depicts the chemical structure of the three ionic liquids with [EMTM]+as the cation and three different anions. In terms of thermal stability, the ion gel based on the anions are in the order: [TFSI]' > [HSO4] ' > [CH3COO] '. FIG. 1C is an image of a Pt / C ion gel catalytic condenser.

[0011] FIGS. 2A and 2B depict Pt / C on an ion gel catalytic condenser with negative and positive charge condensation, respectively, affecting adsorbate CO desorption.

[0012] FIG. 3A shows transient thermogravimetric analysis of polymer PVDF, ionic liquid [EMIM]+[TFSI]', and ion gel PVDF / [EMIM]+[TFSI]' under flowing air. T9o% is defined as the temperature that the change in mass reached 90%. FIG. 3B shows a comparison of the T9o% obtained from TGA for PVDF and three ion gels with differing anions. The stability based on anions are in the order: [TFSI]' > [HSO4]' > [CFECOO]'. FIG. 3C shows isothermalth erm ogravi metric analysis of the ion gel PVDF / [EMIM]+[TFSI]‘, ionic liquid [EMIM]+[TFSI]’ , and polymer PVDF over 48 h under flowing air. The ion gel maintained its mass at 100% after 48 h at 200 °C, and the ionic liquid is the least thermally stable material among the three. FIG. 3D shows IR spectra of the PVDF / [EMIM]+[TFSI]‘ ion gel held isothermally over a time. The symbol * denotes the bond stretches associated with the ion gel. The ion gel maintained its chemical structure at 200 °C after 48 h. FIG. 3E shows time-lapsed isothermal IR studies of PVDF / [EMIM]+[TFSI]' over time under flowing air for chemical stability assessment at 200 °C, 250 °C, and 300 °C. The symbol * denotes the bond stretches associated with the ion gel. The ion gel’s structure was maintained for 48 h at 200 °C. Despite better isothermal TGA profiles, the ion gel’s structure degraded completely at 250 °C under both flowing air and N2. N2 environment did not preserve the chemical structure. FIG. 3F shows chemical stability of the ion gel measured isothermally over time. Each point represents the integrated area within the ion gel fingerprint wavenumbers.

[0013] FIGS. 4A-4E relate to electronic properties of the Pt / C catalytic condenser with the ion gel PVDF / [EMIM]~[TFSI]‘. FIGS. 4A and 4B show I-V curves of C on the Ion Gel on Au- coated Si and Pt / C on the Ion Gel on Au-coated Si, respectively, at 25 °C. FIG. 4C shows charge density measured by I-V curves of both devices and a reference Pt / HfCE / Si device as a function of applied bias FCAT at 25 °C. FIG. 4D shows device capacitance with Pt / C / Ion Gel, Pt / HfCE / Si, and C / Ion Gel only. Charge accumulation at ± 1 V relative to the estimated Pt active site density range. FIG. 4E show measured device capacitance as a function of temperature with heating and cooling.

[0014] FIGS. 5A-5C relate to dynamic electronic properties of the Pt / C catalytic condenser with the ion gel PVDF / [EMIM]+[TFSI]'. FIG. 5A shows averaged capacitance of condenser devices as a function of applied frequency at 25 °C, 100 °C, and 200 °C, measured by an impedance analyzer with an inset showing cutoff frequency of each measurement. FIGS. 5B-5C depict the charging and discharging mechanism, respectively, of the ion gel catalytic condenser during a cyclic voltage sweep.

[0015] FIGS. 6A-6D relate to infrared spectroscopy of CO on Pt / C ion gel condenser. FIG. 6A depicts grazing incidence cell with reflected beam, heating stage, potential bias application, and gas introduction. FIG. 6B is a schematic depicting how CO binds to the Pt surface with a characteristic broad absorbance peak at —2080 cm1of CO after background subtraction at roomtemperature. FIG. 6C shows adsorption isobars of the normalized CO coverage on the Pt / C ion gel condenser measured as a function of temperature from -1.00 V to +0.25 V at 0.25 V increments. 200 °C was established as the maximum temperature before the ion gel begins to decompose. Points are experimental measurements, and lines are fitted Langmuir isobars. FIG. 6D shows binding energy of CO on the Pt ion gel condenser determined by fitting Langmuir isobars as a function of potential biases.

[0016] FIGS. 7A-7E relate to flexible ion gel and roll-to-roll printing for scalable, low-cost manufacturing. FIG. 7A shows a film stack of a Pt / C ion gel catalytic condenser on a flexible Kapton substrate. FIG. 7B shows illustration of the film stack of a Pt / C ion gel catalytic condenser on a flat Si substrate. FIG. 7C shows images of the ion gel condenser on a flat substrate and a flexible substrate for comparison. The square box marks a 1 cm2area where the Pt / C or Pt / Graphene was deposited. FIG. 7D shows capacitance as a function of curvature measured for the Pt / C on a flexible substrate undergoing tensile strain (i.e., the Pt / C / Ion Gel stack is located at the top of curved interface). FIG. 7E depicts roll-to-roll fabrication of the Pt / C / Ion Gel catalytic condenser with various printing technologies as options to create a film stack.

[0017] FIGS. 8A-8B relate to implications of ion gel catalytic condensers. FIG. 8A show the capacitance of the catalytic condensers increases with different insulating dielectric layers of silica, amorphous and crystalline HfCL, and ion gel at room temperature and 200 °C for applied voltage of 1 V. FIG. 8B shows a combination of multiple catalytic condenser films can be combined with insulating spacers to permit high active site density and pores for flow of reactant gases.

[0018] FIG. 9 depicts multi-step fabrication of platinum-on-carbon catalytic condensers by sequential atomic layer deposition (ALD), carbon sputtering, thermal treatment, and evaporation of metal to form nanoclusters.

[0019] FIGS. 10A-10E relate to structural and electronic characterization of carbon (C) and treated carbon (TC) films on HfCL / Si. None of the films contained platinum. FIG. 10A shows Raman spectra of the C and TC devices. FIG. 10B shows conductance measured across the 1 cm2surface. FIG. 10C shows conductance versus carbon thickness. FIG. 10D shows capacitance of C / HfCL / Si and TC / HfCF / Si stacks versus carbon thickness obtained by I-V curves measured atdifferent sweep rates. FIG. 10E shows capacitance as a function of applied frequency for the same stacks measured by impedance spectroscopy.

[0020] FIGS. 11A-1 ID show capacitance of C / HfCE / Si devices as a function of applied frequency measured by impedance spectroscopy at different temperatures and sputtered carbon film thickness for 10 nm C / HfCE / Si, 6 nm C / HfCE / Si, 3 nm C / HfCE / Si, and 1 nm C / HfCE / Si, respectively. The insets indicate the temperature (°C) for measurement.

[0021] FIG. 12A shows capacitance of Pt / C / HfCE / Si devices as a function of applied frequency measured by impedance spectroscopy. FIG. 12B shows capacitance of Pt / 1 nm C / HfCE / Si device as a function of frequency measured by impedance spectroscopy at different temperatures. FIG. 12C shows I-V curves of Pt / 1 nm C / HfCE / Si catalytic condenser measured from 0 V to 15 V at different sweep rates. FIG. 12D shows charge condensation within Pt / 1 nm C / HfCE / Si at varying voltage bias. FIG. 12E show comparison of capacitance of C / HfCE / Si and Pt / C / HfCE / Si devices with different carbon thickness. FIG. 12F shows capacitance versus conductance from catalytic condensers of varying active layer on top of a 70 nm HfCE layer.

[0022] FIGS. 13 A and 13B relate to temperature programmed desorption (TPD) of carbon monoxide. FIG. 13A shows, 3CO-TPD profiles of Pt / 1 nm C / HfCE / Si device with varying potential bias (VCAT) of -6 V, 0 V and +6 V. FIG. 13B shows the TPD peak maximum temperature of13CO-TPD varied with VCAT; positive potential bias VCAT shifted the TPD peak to higher temperatures, while negative potential bias shifted the TPD peak to lower temperatures. The estimated binding energy of13CO (Ed, kJ / mol) was calculated by the Redhead equation.

[0023] FIG. 14A shows images of 42 cm2Pt / 1 nm C / HfCE / Si and 46 cm2Pt / 1 nm C / SiCE / Si catalytic condensers. FIG. 14B shows I-V curves of 42 cm2Pt / 1 nm C / HfCE / Si catalytic condenser measured from -1 V to 1 V at different sweep rates. FIG. 14C shows capacitance of Pt / 1 nm C / HfCE / Si and Pt / 1 nm C / SiCE / Si devices with different sizes obtained by I-V curves measured at different sweep rates. FIG. 14D shows leakage current / capacitive current ratio of Pt / 1 nm C / HfCE / Si device with different sizes at different sweep rates obtained at 1 V. FIG. 14E shows capacitance of Pt / 1 nm C / HfCE / Si devices with different sizes as a function of applied frequency measured by impedance spectroscopy. FIG. 14F shows capacitance of various metal (Pt, Pd, Ru, Ni) / C / HfCE / Si catalytic condensers.DETAILED DESCRIPTION

[0024] Programmable catalysts overcome the limited rate and selectivity of catalytic reactions by modulating the electronic states of the active site on the time scale of the catalytic cycle. Oscillating a heterogeneous catalyst between two or more states leads to resonance conditions at select frequencies, whereby the catalyst switches once per catalytic cycle to conditions favorable for each rate-controlling elementary reaction. This effect also controls the extent of reaction pathways for selectivity control and applies over a range of dynamic conditions. The mechanisms enabling active site dynamics and catalytic resonance include the application of light, charge, and physical strain, all of which can potentially modulate the binding energy of surface species in excess of 20 kJ mol1at frequencies above 100 Hz. These methods apply energy directly to the surface without changing overall (fluid-phase) reaction thermodynamics.

[0025] As described herein, catalytic devices (used interchangeably with catalytic condensers) are a platform device to implement programmable catalysis via the application of charge (electrons or holes) to an active site. As a stack device that includes multiple layers, the catalytic condenser uses an insulating (high-A dielectric layer to separate two conductive films. The exposed top catalytic film is sufficiently thin to permit stabilized charge to influence the electronic properties of the active site. The top catalytic layer typically includes a conductive carbon layer to conduct charge laterally across the device. Catalytic thin films or particles are deposited on top of the conductive carbon layer.Ion Gel Dielectric Layers

[0026] The dielectric constant of the insulating dielectric layer can limit the maximum charge density stabilized on the catalyst / carbon top layer. Ion gels are solid polymer electrolytes, typically prepared as a composite of a supporting polymer infiltrated with the cations and anions of an ionic salt or ionic liquid (IL). These solid-state materials provide higher capacitance and larger charge condensation than dielectric materials such as high-A HfCf. Ion gels exhibit high specific capacitance (e.g., Ci of 1 to 10 pF / cm2compared to high-A HfCh of 0.1 pF / cm2for -100 nm films) due at least in part to the migration of anions and cations within the gel to the electrodes, resulting in electrical double layer formation within nanometers of the electrolyte / gate electrode interface.

[0027] The high capacitance of ion gels in excess of 1-10 pF / cm2enables a higher density of condensed holes / electrons in semiconductors and metals. Moreover, the flexible and stretchable mechanical properties of ion gels have enabled wide applications in batteries, supercapacitors, bioelectronic devices, actuators, electrochromic devices, and more. When compared to liquid electrolytes, ion gels are functional at elevated temperatures (>100 °C), due at least in part to their low volatility and chemical / mechanical stability. The versatility of ion gels allows for convenient additive manufacturing processes such as drop casting, spin-coating, aerosol jet printing, ink-j et printing, electrohydrodynamic jet printing, and cut-and-stick lamination.

[0028] FIG. 1 A depicts an ion gel condenser architecture that exposes the active layer to an external fluid. Catalytic device 100 includes first electrically conductive layer 102 and second electrically conductive layer 104, electrically coupled or configured to be electrically coupled. Electrically insulating layer 106 is between first electrically conductive layer 102 and second electrically conductive layer 104. Metal 108 is disposed on (e.g., in direct contact with) a surface of first electrically conductive layer 102. Metal 108 can be in the form of nanoclusters or continuous layer on first electrically conductive layer 102. Metal 108 includes Pd, Ru, Rh, Ir, Ni, Co, Cu, Fe, or an alloy thereof. Catalytic device 100 can include substrate 110. In one example, substrate 110 is in direct contact with second electrically conductive layer 104. Substrate 100 is typically composed of silicon or a polymer (e.g., polyimide). In some cases, substrate 104 is flexible.

[0029] First electrically conductive layer 102 can be sputtered, deposited, or evaporated on electrically insulating layer 106, or disposed on the electrically insulating layer 106 by vacuum arc deposition, physical laser deposition, or e-beam evaporation. A thickness of first electrically conductive layer 102 is typically in a range of about 0.01 nm to about 100 nm, or about 1 nm to about 10 nm. A surface area of first electrically conductive area typically exceeds 20 cm2. In one example, first electrically conductive layer 102 is composed of amorphous carbon. In one example, second electrically conductive layer 104 is composed of silicon (e.g., in the form of a silicon wafer). In some examples, second electrically conductive layer 104 is composed of one or more metals. First and second electrically conductive layers 102, 104 can be electrically coupled via voltage source 112.

[0030] Electrically insulating layer 106 is composed of a high-K dielectric material.Examples of suitable high-K dielectric materials include metal oxides, polymer electrolytes, andionomers. Polymer electrolytes include ion gels. The ion gels can be formed from a molten salt or polymer and a molten salt, where the molten salt is an ionic liquid.

[0031] Examples of ionic components and polymers for the preparation of ion gels for use in the catalytic device are listed in Tables 1-8 below. Tables 1-3 list ionic liquids, molten salts, and acid-based / proton membrane electrolytes, respectively, all cationic. Tables 4-6 list ionic liquids, molten salts, and acid-based / proton membrane electrolytes, respectively, all anionic. Selected cationic and anionic components from Tables 1 and 4, Tables 2 and 5, and Tables 3 and 6 are combined with a polymer or mixture of polymers listed in Table 7 to yield ion gels suitable for use as electrically insulating layer 106. Table 8 lists ionomers suitable for use as electrically insulating layer 106.Table 1. Ionic liquids (cationic)Table 2. Molten salts (cationic)Table 3. Acid-based / proton membrane electrolyte (cationic)Table 4. Ionic liquids (anionic)Table 5. Molten salts (anionic)Table 6. Acid-based / proton membrane electrolyte (anionic)Table 7. PolymersTable 8. Ionomers

[0032] Fabricating catalytic device 100 includes disposing electrically insulating layer 106 on second electrically conductive layer 104, disposing first electrically conductive layer 102 on electrically insulating layer 106, and disposing metal 108 on the outer surface of first electrically conductive layer 102. Disposing electrically insulating layer 106 on second electrically conductive layer 104 can include forming a metal oxide layer or a layer including a polymer electrolyte on second electrically conductive layer 104. Disposing the first electrically conductive layer on the electrically insulating layer can include disposing a layer of carbon on the electrically insulating layer (e.g., by vacuum arc deposition, physical laser deposition, or e- beam evaporation). Disposing metal 108 on the surface of first electrically conductive layer 102can include forming nanoclusters of metal 108 on first electrically conductive layer 102 (e.g., by electron beam deposition, thermal evaporation, sputtering, vacuum arc deposition, or physical laser deposition).

[0033] In some cases, second electrically conductive layer 104 is disposed on substrate 110 before disposing electrically insulating layer 106 on second electrically conductive layer 104. Disposing second electrically conductive layer 104 on substrate 110 can include electron beam deposition, thermal evaporation, sputtering, vacuum arc deposition, or physical laser deposition of second electrically conductive layer 104 on substrate 110. Disposing electrically insulating layer 106 on second electrically conductive layer 104 can include printing, coating, or casting (e.g., dropcasting) the electrically insulating layer on the second electrically conductive layer. In some cases, disposing electrically insulating layer 106 on second electrically conductive layer 104, disposing first electrically conductive layer 102 on electrically insulating layer 106, and disposing metal 108 on the surface of first electrically conductive layer 102 occurs in a roll-to- roll fabrication process, as depicted in FIG. 7E.

[0034] Catalyzing a chemical reaction with catalytic device 100 can be achieved by positioning catalytic device 100 in a medium containing reactants, and applying a voltage across first electrically conductive layer 102 and second electrically conductive layer 104, thereby catalyzing a chemical reaction of the reactants.

[0035] In one example of catalytic device 100, metal 108 includes Pt nanoclusters (~2 nm thick) dispersed over first electrically conductive layer 102. First electrically conductive layer 102 is a continuous and conductive thin (~2 nm) carbon layer separated from second electrically conductive layer 104 (e.g., a bottom electrode) by electrically insulating layer 106 (an ion gel dielectric layer). A suitable ion gel is synthesized from the gelation of the polymer poly vinylidene difluoride (PVDF) and the ionic liquid l-ethyl-3-methylimidazolium bi s(trifluorom ethyl sulfonyl) imide ([EMIM]+[TFSI]‘). Other suitable ion gels can be synthesized using hydrogen sulfate [HSO4]' and acetate [CFECOO]’ as anions in the ionic liquid. The longterm thermal stabilities of these gels were assessed for their use in thermal catalytic applications, with [EMIM]+[TFSI]' being advantageously stable for catalytic operations over 48 h at 200 °C.

[0036] As shown in FIGS. 2A and 2B, when subjected to negative potential biases (FCAT < 0), electrons accumulating in the platinum / carbon reduce the binding energy of an adsorbate such as carbon monoxide. Likewise, positive bias (FCAT > 0) depleted electrons in the platinum / carbonand increase the adsorbate binding energy. This pl ati num / carb on ion gel condenser provides a tunable metal surface with significant charge condensation on the platinum sites (e.g., nearly two orders of magnitude greater than a similar condenser with HfCh dielectric layer. Additionally, printing or coating of ion gels on a flexible substrate allow for roll-to-roll manufacturing of condensers to achieve surface areas suitable for catalytic or separation applications.

[0037] In one example, a catalytic condenser with a layered Pt / C / ion gel / Au / Si structure such as depicted in FIG. 1 A was fabricated as follows. Starting with a silicon wafer substrate (~2 cm2), layers of Au on Ti were first deposited by electron beam deposition. Ion gel, prepared by the gelation of the polymer polyvinylidene difluoride (PVDF) and 1 -ethyl -3- methylimidazolium or [EMIM]+-based ionic liquid, was then spin coated on top of the Au layer followed by overnight baking in vacuum (70 °C). The ion gel thickness, as measured by a profilometer, decreased with increasing revolutions per minute, and the selected thickness of 3.8 pm was achieved at 4500 rpm for one minute. The primary ionic liquid component of interest was [EMIM]+[TFSI]‘, and gels of it were compared with two other ion gels made from similar ionic liquids with differing anionic components. Then, a ~1 cm2conductive carbon layer (thickness ~2 nm) was sputtered with the assistance of a shadow-mask on top of the ion gel layer. The sputtered conductive carbon layer has sp2characteristics, providing a conductive sheet for charge distribution across the surface of the gel while itself having low capacitance. Finally, 1 nm Pt was deposited on the carbon by electron beam evaporation of a pure Pt source followed by reduction in flowing Fh at 150 °C for an hour which resulted in ~2 nm Pt nanoclusters. The resulting catalytic condenser has exposed Pt / C active sites available for molecules to interact with the surface for catalytic applications.

[0038] With Pt / C successfully deposited on top of the ion gel, the catalytic condenser structure was confirmed with SEM and elemental mapping, which demonstrated that both Pt / C and the ion gel-relevant signals such as F, S, and N corresponding to the ion gel PVDF / [EMIM]+[TFSI]’ were evenly distributed across the condenser surface with no large agglomerate formations or significant surface defects. Finally, XPS measurements also confirmed the elemental presence of Pt, C, and the ion gel components of F, S, and N of the condenser device.

[0039] Thermal Stability of Ion Gels: Transient and Isothermal Measurements. The shortterm and long-term structural, thermal, and chemical stabilities of ion gels were measured under oxidative conditions. The short-term stability was evaluated using a thermogravimetric analyzer,measuring transiently the change in mass of the ion gel samples as a function of temperature under flowing air (100 mL / min) and a linear temperature ramp (3 °C / min). The long-term stability of the ion gels was evaluated via two methods: (i) isothermal thermogravimetric experiments, measuring the change in mass of the ion gel at specific temperatures as a function of time, and (ii) via infrared spectroscopy (IR) experiments, tracking the chemical structure / chemical bonds of the ion gel sample isothermally as a function of time. For the transient thermogravimetric study, as shown in FIG. 3A, the mass of the ion gel PVDF / [EMIM]+[TFSI]’ remained constant up to 300 °C before it decomposed completely at 450 °C. For the ionic liquid [EMIM]+[TFSI]‘ alone, the mass remained constant up to 225 °C before breaking down completely at 425 °C; for the polymer PVDF, the mass change remained unchanged up to 350 °C before breaking down completely at 500 °C. These results confirmed that the most stable component, polymer PVDF, imparted structural integrity to the ion gel at elevated temperatures.

[0040] Transient TGA measurements can be used to evaluate the thermal stability of ion gels. The thermogravimetric profiles of different measured ion gels typically vary depending on compositions, cationic components, anionic components, and preparation methods. The shape of the TGA profile varies for different ion gels and their corresponding ionic liquids, keeping the same cationic component in all the ionic samples and varying only the anionic components. Therefore, to systematically quantify these transient measurements, T9o% was defined as the temperature at which the measured mass reached 90% of its original amount. It was observed that the ion gel with the ionic liquid of [EMIM]+[TFSI]' was a stable ion gel with T9o% of 357 °C followed by that with [EMIM]+[HSO4]" at T9o% of 310 °C and [EMIM]+[CH3C00]’ at T9o% of 198 °C as shown in FIG. 3B.

[0041] The long-term stability of the ion gel made from PVDF and [EMIM]+[TFSI]' was evaluated as shown in FIG. 3C in isothermal thermogravimetric studies for 48 h in flowing air (100 mL / min) at temperatures of 200 °C to 300 °C in 25 °C increments. From FIG. 3C, the mass of the ion gel remained unchanged at 200 °C after 48 h under an oxidative environment. In contrast, at 300 °C, this ion gel decomposed completely after 48 h. Isothermal oxidation at temperatures 225, 250 and 275 °C decreased the mass of the ion gel to 98%, 89%, and 68% respectively. By fitting the decrease in mass over time to first order degradation kinetics, the activation energy of the ion gel degradation based on these isothermal gravimetric measurementswas approximately 175 kJ mol’1. The thermal stabilities of the ionic liquid [EMIM]+[TFSI]' and the polymer PVDF were also assessed isothermally for 48 h. From FIG. 3C, the mass of the ionic liquid and the polymer PVDF remained unchanged at 100% at 150 °C and 250 °C, respectively, after 48 h. Heating the ionic liquid in flowing air at 250 °C and 300 °C completely decomposed the material after 48 h; whereas, the polymer PVDF lost only 16% of its original mass at 300 °C. This result indicates that the polymer PVDF imparts structural support to the ionic liquid with the ionic liquid currently limiting the ion gel’s overall thermal stability. Moreover, it indicates that transient TGA studies may overpredict the thermal stability of ion gels and ionic liquids.

[0042] The chemical structure of the ion gel and its thermal stability were also evaluated via infrared spectroscopy as shown in FIGS. 3D-3F. The ion gel was first spin coated on an Au- coated Si substrate, baked, and then placed in an IR refractor reactor cell (grazing incidence) with the background of the Au-coated Si substrate subtracted. The ion gel samples were then heated to the setpoint temperatures under flowing air or flowing N2 at 100 mL / min, matching the conditions of the thermogravimetric analyzer. IR spectra of a pristine ion gel PVDF / [EMIM]+[TFSI]' and its related functional groups were then compared against IR spectra of the ion gel heated at different temperatures over time. The ion gel heated at 200 °C for 48 h and the pristine sample have similar IR spectra. At 250 °C, the same bond resonances were present after 1 h of heating, but they degraded completely over 5 h under flowing air. Comparing this result to the TGA, the mass change of the ion gel after 5 h had dropped to 98%. This small difference of 2% suggests that the change in mass is not as sensitive a descriptor for the ion gel’s thermal stability as IR spectroscopy. At 300 °C, the functional groups of the ion gel completely disappeared after 1 h (FIG. 3D).

[0043] A time-resolved IR measurement of the fingerprint region between 900 and 1500 cm'1under isothermal conditions was performed to characterize the stability of the ion gel’s chemical structure under flowing air and flowing N2 (FIG. 3E). At 200 °C, the ion gel’s spectra did not change after 48 h in both flowing air and flowing N2, in agreement with the isothermal thermogravimetric measurements. When maintained at 250 °C, however, the IR spectra showed an eventual degradation of the chemical structure under both flowing air and flowing N2 over 5 h and 8 h, respectively; at 300 °C, the chemical structure of the ion gel broke down completely in 1 h under both air and N2 conditions. These observations suggest that thermal decomposition may be the primary deactivation mechanism since the exposure to N2 environment was unable topreserve the chemical integrity of the ion gel. To evaluate the degradation kinetics of the gel’s chemical stability, the integrated area of each time-lapsed spectrum was plotted over time. This chemical stability descriptor exhibited first order degradation kinetics with an R2greater than 0.98, and the activation energy was calculated to be 82 + 5 kJ mol’1, a value lower than that from the isothermal thermogravimetric measurement above. This suggests that the ion gel structure breaks down at lower temperatures, since the energy barrier calculated from the isothermal IR measurement is lower than that calculated from the isothermal thermogravimetric measurement. Additional evidence of ion gel decomposition at lower temperatures than that suggested in the TGA measurement is surface deformation of a device after extensive heating at 250 °C. This highlights the benefit of infrared spectroscopy to characterize long term stability of the ion gel structure while acknowledging that thermogravimetric measurements could be used for rapid screening of different ionic liquids and ion gels.

[0044] Ion Gel Condenser Electronic Properties at Room Temperature. The electronic properties of the Pt / C / Ion Gel catalytic condenser were measured as shown in FIGS. 4A-4E. To determine the amount of charge stored in the Pt layer, current-voltage (I-V) measurements were performed on both a C / Ion gel catalytic condenser (without Pt) and the full Pt / C / Ion gel condenser from -1.0 V to +1.0 V at different voltage sweep rates. The measured displacement current densities of the carbon ion gel condenser without Pt, as shown in FIG. 4A, were in the range of 0.1 to 0.3 nA / cm2, increasing linearly with sweep rate, with a calculated average specific capacitance of 1.7 nF / cm2. The addition of Pt to the carbon ion gel condenser resulted in a significant increase in current densities, achieving -4000 nA / cm2, more than a thousand-fold increase over the carbon ion gel device, and a specific capacitance of 2400 nF / cm2when measured at room temperature (FIG. 4B). The Pt nanoparticles added to the carbon layer increased the total capacitance of the condenser, which is consistent with charge condensing in the Pt cluster. This measurement was also conducted over the range of -3.0 V and +3.0 V, and though standard capacitance determination yielded similar values, it produced consistently a duck-shaped curve. It is unclear whether this is caused by ions undergoing redox reaction at the interface or in the bulk, but it mimics the cyclic voltammetry curve of a typical electrochemical process.

[0045] The accumulation of charge in the C / Ion Gel condenser and the Pt / C / Ion Gel condenser are indicated by the box-shaped displacement current-voltage measurements as shownin FIGS. 4A-4B. Charge condensed on the C / Ion Gel condenser (without Pt) was determined to be only ~109(e‘ or h+) cm'2for VCAT of + 1.0 V. As shown in FIGS. 4C-4D, for the same potential applied on a Pt / C / Ion Gel condenser, the charge area density increased to ~1013(e' or h+) cm'2, with holes or electrons stabilized at VCAT greater or less than zero, respectively. This order of magnitude increase suggests that charge is primarily stored in the Pt layer. The Pt addition also allows the maximum amount of charge accumulation at the applied potential for the respective ion gel; this was verified by an alternative device with a thick Au contact layer, deposited by thermal evaporation on the ion gel, in place of Pt / C, which also stabilized -1013charges cm'2at room temperature as shown in FIG. 4D.

[0046] The accumulation of charge in Pt nanoclusters can modulate the binding energy of adsorbates such as carbon monoxide (CO) and alcohols on metals and metal oxides that have catalyst site densities of ~1015sites cm'2. The capacitance of the ion gel suggests that it should be able to condense ~1013cm'2holes or electrons a lower operating voltage of VCAT = + 1.0 V.

[0047] Temperature and Ion Gel Condenser Electronic Properties. The effects of temperature on the electronic properties of the ion gel condenser devices were assessed. The specific capacitance of the Pt / C / Ion gel condenser remained constant at -2400 nF / cm2from room temperature up to 50 °C, after which it increased gradually to -20,000 nF / cm2when heated to 200 °C with the total amount of charge stabilized increasing by about an order of magnitude. With this capacitance, under a potential bias of IV, an ion gel can provide more than 10% charge per active site. When cooled, the capacitance of the ion gel decreased reversibly with temperature gel within experimental error. Heating to temperatures above 200 °C to 250 °C yielded inconsistent measurements of capacitances owing to the breakdown of the chemical structure of the ion gel.

[0048] Leakage currents, defined as the flow of electrons flowing through the ion gel layer, were also evaluated to assess the possibility of resistive heating effects on the condenser devices. To determine the leakage current, the ion gel was modeled as an equivalent circuit. The extracted leakage current also increased with operating temperature, although at 200 °C and 1.0 V potential bias, it was below conditions that would lead to any significant temperature increase (ca. 0.3 °C increase min'1at 100 pA). Surface heating by leakage current was also determined to be negligible by an FLIR camera measuring the surface of the condenser device under potential application.

[0049] Catalytic turnover frequencies beyond the Sabatier limit can be achieved by oscillating the electronic properties of catalyst sites comparable to the natural frequencies of surface chemistry. Natural frequencies are defined as the inverse of the time constant of the rate limiting reaction step, which is typically in the range of 10 to 1,000 Hz based on models and real catalytic reactions. Therefore, a criterion to achieve dynamic oscillatory rate enhancement is that the catalyst must be able to sufficiently switch between the energetic states upon perturbation. The dynamic electronic properties of the ion gel catalytic condenser were experimentally measured using an impedance spectrometer, as shown in FIG. 5A. FIGS. 5B and 5C depict the charging and discharging mechanism, respectively, of the ion gel catalytic condenser during cyclic voltage sweep. The ion gel condenser at room temperature exhibited the expected -2000 nF / cm2capacitance at low frequencies up to 15 Hz (cutoff frequency) and decreased to 10 nF / cm2as the frequency increased to 10,000 Hz. At 100 °C, the initial capacitance increased to -4000 nF / cm2with the cutoff frequency also increasing to 30 Hz before the capacitance decreased again to 10 nF / cm2at high frequencies. At 200 °C, a capacitance of -27,000 nF / cm2was measured, a tenfold increase over that at room temperature, with the cutoff frequency increasing to 120 Hz. These cutoff frequencies of 15 to 120 Hz between 25 °C and 200 °C were within the target frequencies (10 to 1,000 Hz) needed to break the Sabatier limit.

[0050] The increase in the cutoff frequencies with temperature can be attributed to the increase in concentration of free ions within the ion gel and in ionic mobility. At elevated temperatures, interionic interactions such as hydrogen bonds deteriorate, which frees the number of ions for conduction and increases kinetic energy of mobile ions in the gel.

[0051] Infrared Spectroscopy and Isobars for CO Adsorption. With the Pt / C ion gel condenser, the effects of charge on the binding energy of carbon monoxide adsorbate were experimentally determined from adsorption isobars measured via variable temperature infrared spectroscopy (VTIR). The catalyst device was placed within a grazing incidence infrared spectroscopy cell (Harrick, Refractor Reactor) with the active surface of Pt / C exposed to the incident infrared light source (FIGS. 6A-6B). A HgCdTe detector detected absorption peaks associated with surface species on the Pt / C, subtracting the Pt / C spectrum as the background under vacuum condition. Electrical feedthroughs supplied a fixed potential bias, VCAT, to the surface of the condenser at each temperature for every isobar measurement with the bottom electrode of the condenser grounded with the entire setup. During each measurement, a fixedamount of pure CO gas (7.6 Torr) was maintained in the sample cell and over the condenser surface to maintain equilibrium between gaseous CO and surface-adsorbed species. This resulted in an adsorption spectrum with a broad peak for CO* on Pt at 2080 cm1under fixed CO(g) partial pressure, distinct from the two gaseous CO vibrational modes peaks at 2143 and 2269 cm’1.

[0052] To measure the CO adsorption isobars, the sample temperature (measured with a thermocouple within the sample cell) was allowed to equilibrate for one minute for each experimental data point to allow sufficient exposure of gaseous CO and the Pt surface. CO adsorption isobars were acquired for potential biases, VCAT, from -1.00 to +0.25 V at 0.25 V increments between 25 to 200 °C, the thermal stability limit of the ion gel (FIG. 6C). The isobars were normalized to the isobar area measurements obtained at 25 °C accounting also for drifts in the baseline at each temperature (i.e., IR spectrum of the sample only was obtained at every temperature increment to account for the thermal drift in baseline); the peak area decreased with increasing temperature consistent with reduced surface coverage of an exothermic CO adsorption on Pt. An in-situ displacement current measurement at a voltage sweep rate was obtained from the condenser device prior to each run. From the isobar data shown in FIG. 6D, negative biases (-1.00 V to -0.25 V) weakened the CO* binding energy, shifting the adsorption isobar to lower temperatures, while positive potential bias (+0.25V) strengthened the binding of CO* on the Pt surface, moving the isobars to higher temperatures. Higher positive voltages were not considered in this particular experiment, as the isobars could exceed the thermal stability limit established for the ion gel at 200 °C.

[0053] The change in the CO binding energy with applied potential bias was evaluated from the isobars using Langmuir isobar models. With the assumption that the adsorbed CO is immobilized on the Pt surface (ASads of 197 J mol'1K'1), the heat of adsorption of CO was determined for the potential bias from -1.00 V to +0.25 V (FIG. 6D). The ion gel condensers with a capacitance of 2400 nF / cm2modulated the CO binding energy from 68.2 to 84.4 kJ mol'1over a range of 16.2 kJ mol'1. This result highlights the considerable charge storage capacity of the ion gel that enables tuning of the energy profile of a catalytic cycle to enhance surface chemistry efficiently at low applied voltages.

[0054] Flexible and Extended Ion Gels for Roll-to-roll Fabrication. Fabrication of ion gel devices with high capacitance for portable and wearable electronics using printing processes androll-to-roll techniques has been reported over the last decade. This is possible in part due to the gel’s enabling features of excellent mechanical durability, flexibility, and large area scalability. Flexible substrates offer routes to higher-aspect-ratio structures when folded and coiled, which exhibit higher surface areas for applications in catalysis and separations in which the active surface must interact with a fluid phase. Increasing the total number of active sites using a flexible substrate is essential for future catalyst dynamics applications in important industrial chemistries such as ammonia synthesis, CO2 hydrogenation, and water-splitting. As depicted in FIGS. 7A-7B, a flexible ion gel condenser was fabricated on a Kapton substrate which supported the Pt / C / Ion Gel / Au film stack, prepared via the same procedure as that on the p-type Si substrate. Other metals such as Fe or Al could be used instead of Au as a back electrode for manufacturing feasibility, but for the purpose of comparison this film stack used Au. The photographs in FIG. 7C show that the flexible substrate combined with films of metal, carbon, and ion gel can bend and curl.

[0055] The electronic properties of the Pt / C / ion gel flexible condenser were evaluated for varying extent of curvature in FIG. 7D with respective I-V curves. To create curvature with the film stack, one side of the condenser was first held fixed by tape to a surface. Pressure was then applied on the other side of the flexible condenser to create curvature with the movable side of the condenser later held fixed by a weight. Tungsten probe tips were then placed gently on the Pt / C layer and the Au electrode layer. The capacitance of a 1 cm2flexible ion gel condenser remained constant at ~ 2000 nF / cm2for curvatures less than 1 cm'1(K < 1 cm'1) and decreased to 930 nF / cm2for high curvatures of K = 1.3 cm'1. A flexible metal substrate is also desirable for thermal catalytic applications, where elevated temperatures above 400 °C degrade substrates such as Kapton over time.

[0056] Ion gels provide versatility in ionic liquid composition selection, adaptability and self-healing, mechanical stability, and excellent electronic properties which surpass hi gh-A metal oxides such as HfCh for condensing charge in active layers to electronically modulate adsorbates on metals and metal oxides. Fabrication of the catalytic condenser film stack on flexible substrates using high-throughput, roll-to-roll techniques are manufacturing processes that can create foldable catalysts with higher aspect ratios and consequently higher active site density. FIG. 7E shows a proposed roll-to-roll process integrated with established deposition techniques such as e-beam metal deposition, printing, coating, and carbon sputtering to continuouslymanufacture the catalytic condenser film stacks. Among these techniques, printing offers a low- cost, scalable process that avoids vacuum operations. The scaling up of ion gels for dynamic and programmable modulation of catalysts may help achieve industrially important chemistries more efficiently.

[0057] Implications of Ion Gels for Catalytic Condensers. The ability to coat or print ion gels on flexible substrates enables significantly more powerful and scalable catalytic condenser devices (FIG. 8A). The common dielectric of silica with film thicknesses of ~100 nm exhibits capacitances below 0.1 pF / cm2; capacitance increases significantly when switching to either crystalline (C) or amorphous (Am) -100 nm HfCh films (FIG. 8A). Yet, HfCh dielectric films condense at most 5 x 1013e7cm2, which is 20X fewer electrons than the approximate areal density of active sites on metal surface (-1015sites / cm2). At room temperature ion gel films 3.8 pm thick exhibit capacitance above 1.0 pF / cm2, and for voltages above 1 V, they can condense -1013e’ / cm2. At higher temperatures of 200 °C relevant for catalysis applications, ion gel films can stabilize -1014e7cm2, which means nearly 0.1 electron or hole per metal active site. This extent of charge condensation is approximately an order of magnitude higher than earlier HfO devices, allowing for significant adsorbate binding energy variation on catalytic surfaces.Increases in binding energy amplitude in surface oscillation provide logarithmic increases in catalytic turnover frequency, making it one of the key characteristics of dynamic active sites.

[0058] The ability to mass produce condensers made of ion gels on continuous and flexible sheets also increases the ability to produce high active site density devices. The catalytic condenser architecture can be stacked as either single- or double-sided layers with insulating spaces between the films; for example, silica beads can pillar the layers while allowing for the flow of reactant gases to access active sites. This architecture can be implemented as stacked flat sheets or a rolled-up cylinder ‘jelly-roll’ device with electrical contacts extending axially out of the device.

[0059] FIG. 8B depicts catalytic assembly 200. Catalytic assembly 200 includes two or more catalytic devices 202. Catalytic devices 202 include first electrically conductive layers 102, second electrically conductive layers 104, and electrically insulating layers 106 (e.g., ion gels). Catalytic devices 202 are separated by one or more spacers 204 to provide an opening between catalytic devices 100 and allow a flow of fluid between catalytic devices 202. The catalyst active site density can be approximated geometrically (see the dashed line box of FIG. 8B). For aflat double-sided condenser sheet stack with silica bead spacers of 5 pm diameter, a conductive substrate of 15 pm, an ion gel thickness of 3.8 pm, with a metal areal density of 1015sites / cm2, the active site density is approximately 4 x 1017sites / cm3. Further folding or rolling the substrates may increase the volumetric site density by an order of magnitude or more in the goal of attaining site densities viable for industrial applications. Introductions of grooved surfaces to the conductive substrate to build the condenser stack can also increase the site density.

[0060] Experimental Methods. The platinum carbon ion gel catalytic condenser was fabricated, and its structure, thermal stability, electronic property, and catalytic property were determined using microscopy, profdometry, infrared spectroscopy, displacement current measurement, and impedance spectroscopy.

[0061] Ion Gel Catalytic Condenser Fabrication. The catalytic condensers were fabricated on a conductive p-type Si substrate (WaferPro) with sequential deposition of Au / Ti, ion gel, conductive carbon, and Pt layer. First, a 45 nm Au and 5 nm Ti contact layer were deposited on the Si substrate by e-beam deposition of pure Au and Ti sources, respectively. The Au layer includes a 45 nm Au layer with a 5 nm Ti adhesion layer. Subsequently, a solution of the ion gel (7.7 wt. % polyvinylidene difluoride or PVDF polymer, 30.8 wt. % l-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide or [EMIM]+[TFSI]' ionic liquid, 61.5 wt. % acetone solvent) was spin coated (4500 rpm, 60 s) on the Au-coated substrate at 60 °C until polymer dissolution. The deposited gel on the substrate was then dried in a vacuum oven for 24 h at 70 °C to remove the acetone. With a shadow mask as a template, a 1 .0 cm2area of conductive carbon (1 .8 nm thick) was sputtered on top of the ion gel using a sputter coater (Leica EM ACE600) by pulsing carbon thread at 140 W under high vacuum (-IO3torr). A Pt layer (target of 1 nm) was then grown on the conductive carbon by e-beam evaporation of a pure Pt source. Two other ionic liquids were also explored in the thermal studies. For the flexible substrate, the same procedure of spin coating ion gel, carbon sputtering, and e-beam deposition of Pt was repeated on a Kapton substrate (American Durafilm).

[0062] Profilometry and Scanning Electron Microscopy. The thickness of the ion gel was measured using a profilometer (KLA-Tencor P-7) over a scan area of 500 pm at a scan speed of 10 pm / s and rate of 1000 Hz. SEM images and SEM-EDX maps were acquired using JEOL 6500 FEG-SEM. SEM images and SEM-EDX elemental maps were acquired under 5 kV. The SEM- EDX maps were quantified using the Aztec EDX analytical system (Oxford Instruments).

[0063] Spectroscopy. XPS spectra collection was performed on a PHT Versa Probe III XPS system (ULVAC-PHI) using a mono-chromated Al Ka X-ray source (1486.6 eV). The measurements were conducted using an X-ray spot size of 0.1 x 0.1 mm2with a power of 25 W under 15 kV. The survey spectra were measured using 280 eV pass energy and 1.0 eV / step. The data was processed with the Multipak software. Infrared spectra of the ion gel and the platinum ion gel condenser devices exposed to CO were collected using a Thermo Scientific Nicolet i S50 FT-IR with a Mercury-Cadmium-Telluride (MCT) detector and a tailored Refractor Reactor Grazing Angle setup (Harrick Scientific). The incident angle of the reactor was fixed at 75°, and the windows used were wedged ZnSe. To measure the effects of temperature with IR, the background was first collected at every experimental temperature. For the thermal stability study involving ion gel deposited on the Au coated substrate, an Au-only substrate was used as the background for subtraction. For CO desorption, the Pt ion gel catalytic condenser device was used as the background for subtraction. During an experimental run, pure CO (~7.6 Torr) was dosed into the sample chamber and the IR spectrum was then collected and subtracted.

[0064] Device Electronic Characterization. Capacitance measurements were collected from a probe station equipped with a source meter (Keithley 261 IB and Keithley Test Script Builder). Conductive metal probes were carefully placed on the surface of the sample for the electrical measurements. Different voltage sweep-rates (2.00 V / s, 1.75 V / s, 1.50 V / s, 1.25 V / s, 1.00 V / s) were used to collect the I-V curves. For temperature-based experiments, a conductive sample stage was placed on top of a ceramic non-conductive hot plate. Probes were carefully placed on the sample’s surface and on the conductive stage to measure capacitance and leakage current. The impedance spectra of the devices were recorded in the same two-electrode configuration, like the setup used in capacitance measurement as described above. These measurements were performed with a Newtons PSM3750 multimeter equipped with an Impedance Analysis Interface 2 from the frequency range of 10 Hz to 10 MHz.Amorphous Carbon Layers

[0065] Amorphous carbon films of different thicknesses (1-10 nm) were deposited by carbon sputtering on HfCh / Si substrates in the fabrication of large (>5 cm2) catalytic condensers, as shown in FIG. 9. The carbon films were further thermally treated (400 °C) to induce ordering of amorphous carbon to more graphitic carbon structure with higher sp2 / sp3ratios, which increased both the conductance and capacitance. After depositing Pt on top of the carbon films,the resulting Pt-on-carbon device showed high capacitance (-210 nF / cm2) maintained at applied frequencies up to -1,000 Hz. The temperature programmed desorption experiments with13CO as a probe molecule showed that the electronic states of the top Pt layer can be modulated by an external voltage bias, indicating that catalytic condensers can function with amorphous carbon films thicker than graphene. Large area Pt-on-carbon devices (8-42 cm2) were fabricated by the same process, and the linear increment of capacitance with device area with low leakage current / capacitive current ratio (<0.1) was confirmed, indicating that the fabrication of high- quality metal-carbon catalytic condensers is reproducible and functional for programmable catalysis applications.

[0066] The fabrication process for Pt / C / HfCL / Si catalytic condensers is depicted in FIG. 9. 70 nm of HfO2as a dielectric material was grown on a highly conductive p-type Si wafer by atomic layer deposition (ALD). Different thicknesses (1, 3, 6, 10 nm) of carbon film with -1 cm2area were obtained by carbon sputtering on HfCL / Si (C / HfCh / Si) for different durations; carbon films were thermally annealed at 400 °C in air to make thermally treated carbon (TC) devices (TC / HfCh / Si).

[0067] To explore the structural properties of C and TC films, C / HfCh / Si and TC / HfO2 / Si devices were analyzed by Raman spectroscopy (FIG. 10A). The C films showed a broad peak centered at - 1500 cm which is generally observed in amorphous carbon materials. After thermal treatment, the Raman spectra of all carbon film thicknesses showed two distinct bands, D and G peaks at 1358 and 1583 cm ’, which originated from the disordered carbon structure and in-plane stretching vibration of sp2carbons, respectively. This indicates that the thermal treatment induced re-ordering of amorphous carbon films to form semi-graphitic carbon films. The same result was obtained when the C / HfO2 / Si was heated under N2flow, indicating that the re-ordering process occurred by thermal heating.

[0068] The electronic properties of C / HfO2 / Si and TC / HfO2 / Si devices were characterized for variation in film thickness and thermal treatment. FIG. 10B shows the conductance of C and TC films measured across the 1.0 cm2top surface of the device plotted in log scale. The comparison of carbon film conductance versus thickness of C and TC is summarized in FIG. 10C, indicating that the conductance exponentially increased with carbon film thickness. Furthermore, the thermal treatment process enhanced the conductance of carbon films by about an order of magnitude. The amount of accumulated charge in the top layer of a device wasdetermined from the current density-voltage (I-V) curves measured from -1 V to 1 V at different sweep rates, from which capacitance was calculated. The maximum capacitance of metal / HfCh / Si device was measured to be 207 nF / cm2by depositing Au / Ti (45 / 5 nm) on HfCh / Si by e-beam evaporation, and the corresponding dielectric constant (k) of 70 nm HfO was 16.7.

[0069] FIG. 10D summarizes the capacitance of the C / HfCh / Si and TC / HfCh / Si devices determined from I-V curves. The capacitance of carbon films significantly increased with film thickness and after the thermal treatment process. The 1 and 3 nm C films have low capacitance (0.068 nF / cm2and 1.2 nF / cm2), while the 6 and 10 nm C film have high capacitance (45 nF / cm2and 143 nF / cm2). After thermal treatment, 6 nm TC and 10 nm TC are able to store most of the charges stabilized by 70 nm HfCh dielectric, reaching the maximum capacitance of 206 nF / cm2and 208 nF / cm2. The amorphous HfO did not crystallize after thermal treatment process, thus preserving its dielectric constant. This is evidenced by the high capacitance observed in 6 and 10 nm TC / HfCh / Si devices, similar to that of the Au-Ti / HfCE / Si device. The 1 and 3 nm TC films still exhibited low capacitance (0.36 nF / cm2and 6.8 nF / cm2) following thermal treatment.

[0070] FIG. 10E shows the capacitance of the carbon films as a function of applied frequency (i.e., dynamic conditions) measured by impedance spectroscopy from 10 Hz to 10 MHz with a 2 V amplitude sinusoidal potential. The capacitance measured at 10 Hz is comparable with the capacitance measured by I-V measurements, consistently showing that capacitance at varied frequencies increased with carbon thickness and thermal treatment. The 6 and 10 nm TC / HfCE / Si maintained high capacitance (-210 nF / cm2) up to -100 Hz. However, the devices with thinner carbon films showed negligible capacitance or immediate loss of capacitance with increasing frequency indicating that the charge response to the applied frequency is slow due to both low conductance and low capacitance of the thin carbon films.

[0071] Amorphous carbon consists of four-fold coordinated sp3carbons with no free electrons and three-fold coordinated sp2carbons with -U* bonding with one free electron. The conduction in the amorphous carbon predominantly originates from the hopping between nanocrystalline graphitic clusters (sp2carbons) rather than the non-crystalline sp3carbon rings or branches. The higher conductance of TC film than C film can therefore be explained at least in part by the reduced distance between graphitic clusters consistent with an increase of their size. The measured capacitance of C / HfCh / Si and TC / HfCh / Si devices (except for 6 and 10 nm TC / HfCE / Si) are smaller than the maximum capacitance obtained from 70 nm HfCh dielectric;the sputtered carbon films must therefore be semi conductive materials having low density of states. Therefore, an increase of conductance and capacitance after thermal treatment is ascribed to the more graphitic structure (high sp2 / sp3ratio) of TC films relative to the C films as evidenced by Raman spectroscopy observed in FIG. 10A.

[0072] To measure the capacitance of carbon devices at elevated temperatures, the C / HfCh / Si devices were measured by impedance spectroscopy at temperatures from 25 °C to 400 °C as shown in FIGS. 11 A-l ID. The surface temperature of the device surface was confirmed by FLIR camera. Notably, 10 nm C / HfCh / Si and 6 nm C / HfCh / Si exhibited significant increase of capacitance from 143 nF / cm2and 45 nF / cm2at 25 °C to 2,020 nF / cm2and 1,625 nF / cm2at 400 °C, respectively. These capacitances corresponded to charge (e or h+) densities of ~1013cm2and ~1014cm2when +1 V or +5 V of voltage bias was applied. Considering the number of surface-active sites in continuous metal layer is estimated to be ~1015cm2. the obtained result indicates that 1-10% of charge per surface atom can be condensed when the catalytic condenser was operated at 400 °C. This result indicates an increase of the dielectric constant of HfCh with temperature and demonstrates that 6-10 nm carbon films can store significant charge density at higher temperatures. The 3 nm C / HfCh / Si also showed an increase of capacitance from 0.36 nF / cm2to 321 nF / cm2. The capacitance of 1 nm C / HfCh / Si increased slightly (0.24 nF / cm2to 0.61 nF / cm2) due at least in part to the limited density of states in the 1 nm C film.

[0073] The increase in capacitance of HfCh-based catalytic condensers is consistent with the known electronic properties of HfCh. The dielectric constant of a material is determined by the polarizability of its constituents as expressed by the Clausius-Mossotti relation. The thermal coefficient of capacitance can be derived from this, which describes the changes of capacitance with temperature due to: (i) decreased number of polarizable electrons from the volume expansion, (ii) increased polarizability of a constant number of electrons from the increased volume available, (iii) temperature dependence of electron polarizability, and (iv) increased material inhomogeneities from defects and disorder. Consistent with these factors, the dielectric constant of HfCf dielectric materials is known to increase with temperature. Indeed, the impedance spectroscopy measurements at elevated temperatures revealed that the charge-storing capability of the catalytic condenser under reaction conditions (i.e., elevated temperatures) can be much higher than the capacitance of a device at room temperature.

[0074] Platinum Catalytic Condensers. Having confirmed the structural and electronic characteristics of C / HfCf / Si and TC / HfCE / Si devices, Pt as the catalytic material was deposited on top of C / HfCh / Si and TC / HfCh / Si by e-beam evaporation. To explore the structure of the Pt catalytic condenser, the devices were characterized by transmission electron microscopy (TEM), high-angle annular dark-field scanning TEM (HAADF-STEM) images, and corresponding energy-dispersive X-ray spectroscopy (EDS) analysis, for which cross-sectional devices were prepared by using focused ion beam (FIB). The device stacks consist of a Si wafer, ~1.6 nm native SiCh, -70 nm HfCh, 0.8-8 nm carbon film, and Pt nanoclusters in the TEM images. The elements comprising each layer were distinguished by EDS maps. The topmost thick carbon layer is the amorphous carbon protection layer added for preparation of the sample in the FIB process. The Pt layer was composed of - 2.5 nm Pt nanoclusters, and the (111) planes of Pt (fee) structure were observed from these Pt nanoclusters. The surface roughness of HfCh increased with the carbon thickness due to the high energy of carbon sputtering process, which in turn affected the roughness of the carbon and Pt layers on it.

[0075] Based on the 7-Ecurves of Pt / C / HfCE / Si and Pt / TC / HfCE / Si devices, the capacitances of all Pt devices were about the same (195 - 210 nF / cm2), and they matched with the capacitance of Au-Ti / HfCh / Si device (207 nF / cm2). This result indicates that the top conductive Pt / C or Pt / TC layers store the maximum amount of charge that can be stabilized with the 70 nm HfCh dielectric film. In addition to the capacitance measured through Z-E curves, the capacitance relevant to the dynamic conditions necessary for programmable catalysis applications can be estimated by measuring capacitance as a function of applied frequency. As shown in FIG. 12A, measurements via impedance spectroscopy showed that all Pt devices have a capacitance of -210 nF / cm2at 10 Hz. Notably, the capacitance was maintained up to -1,000 Hz, except for the Pt / 1 nm C / HfCE / Si device that showed slightly lower cut-off frequency of -500 Hz.

[0076] The observed increase in conductance and capacitance of condenser devices containing Pt in FIG. 12A indicates the viability of thin amorphous carbon films for programmable catalysis applications. The Pt nanoclusters provide additional states for charge condensation, thereby allowing for Pt / C condenser devices to achieve the maximum capacitance possible with a 70 nm HfO film. A benefit of the Pt deposition is increased conductance of the top layer, which then gives rise to a larger cut-off frequency above 1000 Hz for capacitance as seen in FIG. 12A. Prior reaction simulations have shown that a catalytic condenser switchingelectronic states at frequencies of 10-1000 Hz should be sufficiently fast to promote the ratelimiting step (a specific elementary reaction or product desorption), thereby potentially exceeding the Sabatier rate.

[0077] To explore the capacitance changes of the Pt condenser at high temperatures, a Pt / 1 nm C / HfCh / Si device was electronically characterized by impedance spectroscopy at elevated temperatures as shown in FIG. 12B. The result indicated a significant increase of capacitance from 201 nF / cm2at 25 °C to 1,544 nF / cm2at 400 °C, similar in trend to the carbon C / HfCh / Si devices (FIGS. 11A-1 ID). The capacitance obtained from I- V measurement at 400 °C was 1,513 nF / cm2similar to the impedance result. Considering that 1 nm C / HfCh / Si had negligible capacitance (less than 1 nF / cm2) at any considered temperature, most of the condensed charges in Pt-containing devices must be in the Pt nanoclusters in the Pt / 1 nm C / HfCh / Si. FIG. 12C shows the I-V curves of Pt / 1 nm C / HfCh / Si measured from 0 V to 15 V at different sweep rates (1-2 V / s). Box-shaped I-V curves were obtained, indicating that the majority of the current is accumulated in the Pt layer and the Pt / 1 nm C / HfCh / Si catalytic condenser has low leakage current even at 15 V. Based on the measured capacitance, the charge areal density (charge per cm2) was calculated as shown in FIG. 12D. With 1 V voltage bias, the condensed charge in the Pt layer was about ~1012(e or h+) cm2, while -1013(e or h+) cm2charge amount could be accumulated when 5-10 V was applied, which can effectively modify the electron density of metal sites by -1% at room temperature. FIG. 12E compares the measured capacitance of carbon-only (C / HfCh / Si) versus platinum-on-carbon (Pt / C / HfCh / Si) devices. The capacitance of carbon was largely dependent on its thickness, but after Pt deposition, all the devices achieved the maximum capacitance of -210 nF / cm2. By this comparison, more charge accumulated in Pt under voltage bias with thinner carbon film layers.

[0078] FIG. 12F summarizes the capacitance and conductance of several device compositions. The capacitance and conductance were generally proportional on a logarithmic scale, but they also depended on the material characteristics. Amorphous carbon films (6 and 10 nm C) exhibited high conductance (7.6 pS / cm2and 23.9 pS / cm2) that is slightly less than graphene (54 pS / cm2), but they are not ideal candidate materials for the Pt catalytic condenser due to a large extent of charge condensation within carbon itself. In contrast, although 1 and 3 nm C films exhibited low conductance on their own, they also had negligible capacitance; theresult when adding Pt to carbon films (FIG. 12E) is a highly conductive composite film where most of the condensed charge resides in the Pt nanoclusters.

[0079] Temperature Programmed Desorption ofI3CO. To evaluate charge modulation of the Pt active layer and examine the Pt / C / HfCh / Si device as a catalytic condenser, the Pt / 1 nm C / HfCh / Si device was examined by the method of temperature programmed desorption (TPD) using13CO as a probe molecule. The CO binding energy on the metal surface can be greatly affected by the electronic structure of the metal surface, typically observed from bimetal alloy or metal-support interaction; increasing the electron density in the metals weakens the bond strength between CO molecule and metal atom, which results in lowered CO desorption temperature. Alternatively, depleting electrons in Pt nanoclusters via positive applied bias (VCAT > 0) strengthens the binding energy of13CO to the surface.

[0080] After inserting the catalytic condenser device into a TPD reactor chamber with electronic connections, the system was sealed and preheated at 400 °C in a vacuum to remove any adsorbed molecules on the surface and reactor walls; thereafter the system and device were cooled to room temperature followed by dosing of13CO to saturate the Pt surface. The reactor was then heated from 20 °C to 400 °C via a linear ramp of 10 K min1to observe the desorption of13CO by tracking the mass-to-charge (m / z) of 29 with the quadrupole mass spectrometer.

[0081] FIG. 13 A depicts the13CO-TPD profdes of the Pt / 1 nm C / HfCh / Si device at different applied external voltages (VCAT) of 0 V, -6 V, and +6 V. The results showed that the maximum peak temperature for13CO desorption from the Pt surface varied with the applied VCAT. Without an external applied voltage (0 V), the measured13CO desorption peak temperature was 102.4 °C. When negative bias potential was applied (VCAT = “6 V), the peak temperature decreased to 78.9 °C due to the accumulation of additional electrons on the exposed Pt layers. In contrast, the peak temperature increased to 112.7 °C when a positive potential bias was applied (VCAT = +6 V), due to the depletion of electrons in the Pt layer. From the obtained peak desorption temperatures, the estimated desorption activation energy of13CO was calculated by the Redhead equation as shown in FIG. 13B (assuming 1storder kinetics and pre-exponential factor of 1013s '). The13CO desorption binding energies were 99.8 kJ / mol, 106.7 kJ / mol, and 114.5 kJ / mol when VCAT was -6 V, 0 V, and +6 V. The observation of a shift in13CO binding energy indicates that the amorphous-carbon catalytic condensers have comparable capability for controlling surface chemistry as the earlier graphene-based devices.

[0082] Large Area Device Fabrication. Large area Pt / 1 nm C / HfCL / Si devices were next fabricated by taking advantage of the carbon sputtering process. On top of a 4” wafer of HfCh / Si, a large square area was outlined with polyimide tape for carbon sputtering and Pt deposition. The obtained large area devices are shown in a photograph in FIG. 14A using both HfO and SiO2 as the dielectric film. These devices exhibited purple and blue colors, respectively. FIG. 14B and show the I-V curves (y-axis is not normalized to the area) of different-sized Pt / 1 nm C / HfO2 / Si devices at different sweep rates; all devices featured box-shaped curves, indicating low leakage current even for large area devices. The capacitance of each device was then calculated, and the result was an expected linear increase of capacitance as the area of devices increased as shown in FIG. 14C. The 8, 21, 29, and 42 cm2Pt / 1 nm C / HfCh / Si devices exhibited high capacitance of 1,822, 4,421, 6,497, and 9,393 nF, and these values corresponded to -210 nF / cm2after area normalization. This indicated that the large area fabricated device had the same electronic characteristics as the smaller -1 cm2device.

[0083] The same large-area fabrication procedures were also performed on different sizes (1, 14, 28 and 46 cm2) of 100 nm SiCL / Si substrate to produce Pt / 1 nm C / SiCL / Si devices. These also showed box shaped I-V curves and a linear increase of capacitance with the device size as shown in FIG. 14C. The ability to switch between dielectric films indicates the versatile utility of carbon sputtering-based large area catalytic condenser fabrication process and the uniformity of the deposited Pt nanoclusters and carbon films on the entire wafer area.

[0084] The measured current of a catalytic condenser can be divided into current that passes through the HfCh insulator (leakage current) and current that accumulates charge in the top Pt / C layer (capacitive current). From the I-V curves (FIG. 14B), the relative ratio of the leakage current to the capacitive current at each sweep rate was calculated as shown in FIG. 14D. All devices exhibited low leakage current / capacitive current values less than 0.1 at every sweep rate, demonstrating that the majority of the current is accumulated in the Pt layer rather than passing through HfCh insulator even for large devices.

[0085] The capacitance of the different sized condensers was measured via impedance spectroscopy as a function of frequency as shown in FIG. 14E. The obtained capacitances of devices at 1 Hz agree with the capacitances obtained from I-V measurements (FIG. 14B), but the large area devices exhibited a gradual reduction of capacitance at higher frequencies. This can be attributed to the resistance of the Pt / C layer across the large area of a device; the smaller areadevices (1 cm2) exhibited the highest corner frequency consistent with current traveling the shortest distance.

[0086] Application of Metal-Carbon Catalytic Condenser. The wafer-scale fabrication method of catalytic condensers by successive ALD (HfO2growth), carbon sputtering, and e- beam evaporation (Pt deposition) processes described herein provide benefits including timeefficiency, reduced cost, reproducibility, uniformity, and scalability. Securing high capacitance (210 nF / cm2) at -1000 Hz frequency and low leakage current / capacitive current ratio (< 0.1) even for large-area (42 cm2) devices demonstrated that the metal-carbon catalytic condenser is a suitable platform device for dynamic catalysis. The large-area catalytic condenser enables the exploration of catalytic activity as a function of device area, or the amount of catalyst, while modifying their electronic states via steady-state or oscillating applied potential.

[0087] The accessibility of other catalytically active metal sources from physical vapor deposition methods such as e-beam evaporation, thermal evaporation, or sputtering, allows facile fabrication of diverse metal-on-carbon catalytic condensers. In addition to Pt / C / HfCh / Si device, devices of Pd / C, Ru / C, and Ni / C on top of HfOz / Si were fabricated. As shown in FIG. 14F, the capacitances of each metal / C / HfO2 / Si device was identical to that of Pt / C / HfCh / Si. These metal- on-carbon catalytic condensers can be utilized individually or can be combined as a multi-metal catalytic condenser. A metallic alloy catalytic condenser (e.g., AuPd / C), can be produced by depositing alloy sources or by depositing multiple thin metal layers, followed by a heat treatment (reduction) process for the formation of desired metallic alloy phase with exposed different (or more) metal sites. These metal-on-carbon catalytic condensers can be utilized by applying different voltage bias or oscillation frequency to each metal surface to control the adsorption and desorption behavior of complicated catalytic reactions more precisely, by reducing catalyst poisoning, or by controlling product selectivity.EXAMPLES

[0088] The metal / carbon catalytic condensers were fabricated and characterized as below.

[0089] The metal / carbon catalytic condensers are fabricated by growing HfO2on a conductive p-type Si+++ substrate, followed by carbon sputtering, and metal deposition. 70 nm of HfO2fdm was grown by 500 cycles of ALD process at 100 °C using tetrakis(dimethylamido)hafnium (IV) and water as the HfO2and oxygen precursor. Differentthickness of carbon film was deposited using a sputter coater (Leica EM ACE600) for 1cm2device. Carbon thread as the carbon source was pulsed at 140 W under vacuum (5.0 / 105torr) until the set thickness (1 nm, 3 nm, 6 nm, 10 nm) of carbon films were achieved by quartz crystal microbalance in the sputtering machine. For large-scale fabrication, graphitic carbon target (99.999%) was used as the carbon source, and the sputtering was conducted with DC sputtering machine (AJA ATC 2000) at 250 W under vacuum (5. Ox 106torr) for 300 seconds. Pt layer was grown on the carbon films by e-beam evaporation (CHA evaporator) by using Pt target source.

[0090] Raman spectra were obtained from a Witec Alpha 300R confocal Raman microscope equipped with a UHTS300 spectrometer and a DV401 CCD detector. The spectra collection was carried out with an excitation laser wavelength of 532 nm, grating of 600 g / mm at 40x lens (laser spot size of 0.5 pm in the x-y directions and 1 um in the z direction). The integration time was 5 s and each spectrum was obtained via 10 accumulations. XRD patterns were recorded on a Bruker D8 Discover 2D diffractometer equipped with a Co Kot source (2 = 0.179 nm).

[0091] The cross-sections of the devices for STEM studies were prepared using focused-ion beam (FEI Helios NanoLab G4 dual beam). The protective amorphous carbon and Pt layers were deposited, and the FIB ion beam was operated at 30 kV with 2 kV electron beam. STEM analysis was performed with an aberration-corrected FEI Titan G2 60-300 STEM microscope equipped with a CEOS DCOR probe corrector, a monochromator, and a super-X EDS spectrometer. HAADF-STEM images were obtained at 200 kV with 150 pA probe current. STEM-EDS elemental maps were obtained via Bruker Esprit.

[0092] The electronic measurements of the devices were collected by placing the conductive metal probe tips on the surface of the device that connected with a probe station equipped with a source meter (Keithley 261 IB and Keithley Test Script Builder). For / -E measurements, five different voltage sweep rates (1.00 V / s, 1.25 V / s, 1.50 V / s, 1.75 V / s, 2.00 V / s) were used, and 2.00 V / s sweep rate was used for conductance measurements. The impedance spectra were collected with a Newtons PSM3750 multimeter equipped with an Impedance Analysis Interface 2 from the frequency range from 10 Hz (or 1 Hz) to 10 MHz. For impedance measurements at elevated temperatures, the devices were placed on a conductive metal stage on top of a ceramic hot plate.

[0093] 13CO-TPD experiment was performed in a customized ultrahigh vacuum chamber connected with voltage bias-capable setup and a mass spectrometer. The temperature inside thechamber for actual sample temperature (Tint) and the exterior temperature (Text) were different, and a standard temperature calibration curve was made. Prior to each TPD experiment, the chamber preheated at Text = 400 °C under vacuum, followed by cooling to room temperature. Then, 200 Torr of13CO vapor was introduced to the TPD chamber for 10 min for complete saturation on the device’s surface, and then the TPD chamber was evacuated at Text =100 °C for 1 h to remove any physisorbed13CO on the device’s surface and the chamber wall. After the TPD chamber cooled to room temperature, TPD experiment was conducted by applying a voltage bias (-6 V, 0 V, +6 V) and heating the chamber to Text= 400 °C at a ramp rate of 10 °C / min. The desorbed13CO with m / z ratio of 29 was monitored by a quadrupole mass spectrometer during the temperature ramping.

[0094] A facile and effective fabrication process was developed for large-area (~42 cm2) metal-on-carbon catalytic condensers by successive ALD, carbon sputtering, and an e-beam evaporation process. A significant enhancement of conductance and capacitance of carbon films after thermal treatment was observed, which was ascribed to the increase of sp2 / sp3ratio by graphitization. Thick carbon (C) and treated carbon (TC) films (6 and 10 nm) had large capacitance, but the capacitance of thin C and TC films (1 and 3 nm) were low, which is desirable for a metal-on-carbon catalytic condensers to enable the condensation of charge predominately in metal clusters. After Pt deposition, the resulting Pt / C / HfCh / Si and Pt / TC / HfCh / Si showed the maximum capacitance (-210 nF / cm2) independent of the supporting carbon film thickness. Impedance spectroscopy measurements of C / HfCh / Si and Pt / C / HfCh / Si devices at elevated temperatures showed high capacitance (-2,000 nF / cm2) at 400 °C, demonstrating that the capacitance of catalytic condensers under real reaction conditions (i.e., elevated temperatures) are much higher than the capacitance measured at room temperature. The13CO-TPD experiments demonstrated shifts of13CO desorption temperatures when an external potential bias was applied (-6 V and +6 V), which indicates that the electronic state of Pt layer was modulated in a Pt / 1 nm C / HfCh / Si catalytic condenser. The large-area Pt / 1 nm C / HfCh / Si devices exhibited a linear increase of capacitance as the device area increased, maintaining low leakage current / capacitive current ratio below 0.1. This indicates the uniform distribution of Pt nanoclusters on sputtered carbon films with a high-quality dielectric film within the Pt / C / HfCh / Si stack even in wafer-scale, thereby demonstrating a practical large-area fabrication process for metal / carbon catalytic condenser. The developed method was also applied to a SiC>2 / Si substrateand different metal sources to further demonstrate the versatility of the application for making metal-carbon catalytic condenser.

[0095] Although the disclosed inventive concepts include those defined in the attached claims, it should be understood that the inventive concepts can also be defined in accordance with the following embodiments.

[0096] In addition to the embodiments of the attached claims and the embodiments described above, the following numbered embodiments are also innovative.

[0097] Embodiment 1 is catalytic device comprising: a first electrically conductive layer; a second electrically conductive layer; an electrically insulating layer between the first electrically conductive layer and the second electrically conductive layer; and a metal on a surface of the first electrically conductive layer, wherein the first electrically conductive layer and the second electrically conductive layer are configured to be electrically coupled.

[0098] Embodiment 2 is the catalytic device of embodiment 1, wherein the first electrically conductive layer comprises an amorphous carbon layer.

[0099] Embodiment 3 is the catalytic device of embodiment 2, wherein the amorphous carbon layer is disposed on the electrically insulating layer.

[0100] Embodiment 4 is the catalytic device of embodiment 3, wherein the amorphous carbon layer is sputtered, deposited, or evaporated on the electrically insulating layer.

[0101] Embodiment 5 is the catalytic device of embodiments 3 or 4, wherein the amorphous carbon layer is disposed on the electrically insulating layer by vacuum arc deposition, physical laser deposition, or e-beam evaporation.

[0102] Embodiment 6 is the catalytic device of any one of embodiments 2-5, wherein a thickness of the amorphous carbon layer is in a range of 0.01 nm to 100 nm.

[0103] Embodiment 7 is the catalytic device of embodiment 6, wherein a thickness of the amorphous carbon layer is in a range of 1 nm to 10 nm.

[0104] Embodiment 8 is the catalytic device of any one of embodiments 1-7, wherein the second electrically conductive layer comprises a silicon wafer.

[0105] Embodiment 9 is the catalytic device of any one of embodiments 1-7, wherein the second electrically conductive layer comprises a metal.

[0106] Embodiment 10 is the catalytic device of embodiment 9, further comprising a substrate in contact with the second electrically conductive layer.

[0107] Embodiment 11 is the catalytic device of embodiment 10, wherein the substrate comprises silicon.

[0108] Embodiment 12 is the catalytic device of embodiment 10, wherein the substrate comprises a polymer.

[0109] Embodiment 13 is the catalytic device of embodiment 12, wherein the polymer comprises polyimide.

[0110] Embodiment 14 is the catalytic device of embodiment 12 or 13, wherein the polymer is flexible.

[0111] Embodiment 15 is the catalytic device of any one of embodiments 1-14, wherein the electrically insulating layer comprises a high-K dielectric material.

[0112] Embodiment 16 is the catalytic device of embodiment 15, wherein the high-K dielectric material comprises a metal oxide.

[0113] Embodiment 17 is the catalytic device of embodiment 15, wherein the high-K dielectric material comprises a polymer electrolyte.

[0114] Embodiment 18 is the catalytic device of embodiment 17, wherein the polymer electrolyte comprises an ion gel.

[0115] Embodiment 19 is the catalytic device of embodiment 18, wherein the ion gel is formed from a molten salt.

[0116] Embodiment 20 is the catalytic device of embodiment 19, wherein the molten salt comprises an ionic liquid.

[0117] Embodiment 21 is the catalytic device of embodiment 18, wherein the ion gel is formed from a polymer and a molten salt.

[0118] Embodiment 22 is the catalytic device of embodiment 21, wherein the molten salt comprises an ionic liquid.

[0119] Embodiment 23 is the catalytic device of embodiment 15, wherein the high-K dielectric material comprises an ionomer.

[0120] Embodiment 24 is the catalytic device of any one of embodiments 1-23, wherein the metal comprises Pd, Ru, Rh, Ir, Ni, Co, Cu, Fe, or an alloy thereof.

[0121] Embodiment 25 is the catalytic device of any one of embodiments 1-24, wherein metal comprises nanoclusters.

[0122] Embodiment 26 is the catalytic device of any one of embodiments 1-25, wherein the metal is in the form of a layer.

[0123] Embodiment 27 is the catalytic device of any one of embodiments 1-26, wherein the first electrically conductive layer and the second electrically conductive layer are electrically coupled.

[0124] Embodiment 28 is the catalytic device of any one of embodiments 1-27, wherein the first electrically conductive layer and the second electrically conductive layer are electrically coupled to a voltage source.

[0125] Embodiment 29 is the catalytic device of any one of embodiments 1-28, wherein a surface area of the catalytic device exceeds 20 cm2.

[0126] Embodiment 30 is a catalytic device comprising two or more of the catalytic devices of any one of embodiments 1-29, wherein each of the two or more of the catalytic devices is separated from another one of the two or more of the catalytic devices by one or more spacers.

[0127] Embodiment 31 is the catalytic device of embodiment 30, wherein the one or more spacers allow a flow of a fluid between each of the two or more of the catalytic devices.

[0128] Embodiment 32 is method of making the catalytic device of any one of embodiments 1-31, the method comprising: disposing the electrically insulating layer on the second electrically conductive layer; disposing the first electrically conductive layer on the electrically insulating layer; and disposing the metal on the surface of the first electrically conductive layer.

[0129] Embodiment 33 is the method of embodiment 32, wherein disposing the electrically insulating layer on the second electrically conductive layer comprises forming a metal oxide layer on the second electrically conductive layer.

[0130] Embodiment 34 is the method of embodiment 32, wherein disposing the electrically insulating layer on the second electrically conductive layer comprises forming a layer comprising a polymer electrolyte on the second electrically conductive layer.

[0131] Embodiment 35 is the method of any one of embodiments 32-34, wherein disposing the first electrically conductive layer on the electrically insulating layer comprises disposing a layer of carbon on the electrically insulating layer.

[0132] Embodiment 36 is the method of embodiment 35, wherein disposing the layer of carbon on the electrically insulating layer comprises vacuum arc deposition, physical laser deposition, or e-beam evaporation.

[0133] Embodiment 37 is the method of any one of embodiments 32-36, wherein disposing the metal on the surface of the first electrically conductive layer comprises forming nanoclusters of the metal on the first electrically conductive layer.

[0134] Embodiment 38 is the method of any one of embodiments 32-37, wherein disposing the metal on the surface of the first electrically conductive layer comprises electron beam deposition, thermal evaporation, sputtering, vacuum arc deposition, or physical laser deposition.

[0135] Embodiment 39 is the method of any one of embodiments 32-38, further comprising disposing the second electrically conductive layer on a substrate before disposing the electrically insulating layer on the second electrically conductive layer.

[0136] Embodiment 40 is the method of embodiment 39, wherein disposing the second electrically conductive layer on the substrate comprises electron beam deposition, thermal evaporation, sputtering, vacuum arc deposition, or physical laser deposition of the second electrically conductive layer on the substrate.

[0137] Embodiment 41 is the method of any one of embodiments 32-40, wherein disposing the electrically insulating layer on the second electrically conductive layer comprises printing, coating, or casting the electrically insulating layer on the second electrically conductive layer.

[0138] Embodiment 42 is the method of embodiment 41, wherein casting comprises dropcasting.

[0139] Embodiment 43 is the method of any one of embodiments 32-42, wherein disposing the electrically insulating layer on the second electrically conductive layer, disposing the first electrically conductive layer on the electrically insulating layer, and disposing the metal on the surface of the first electrically conductive layer occurs in a roll-to-roll fabrication process.

[0140] Embodiment 44 is a method of catalyzing a chemical reaction with the catalytic device of any one of embodiments 1-31, the method comprising: positioning the catalytic device in a medium comprising reactants; andapplying a voltage across the first electrically conductive layer and the second electrically conductive layer, thereby catalyzing a chemical reaction of the reactants.

[0141] Although this disclosure contains many specific embodiment details, these should not be construed as limitations on the scope of the subject matter or on the scope of what may be claimed, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in this disclosure in the context of separate embodiments can also be implemented, in combination, in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments, separately, or in any suitable sub-combination. Moreover, although previously described features may be described as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can, in some cases, be excised from the combination, and the claimed combination may be directed to a sub-combination or variation of a sub-combination.

[0142] Particular embodiments of the subject matter have been described. Other embodiments, alterations, and permutations of the described embodiments are within the scope of the following claims as will be apparent to those skilled in the art. While operations are depicted in the drawings or claims in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed (some operations may be considered optional), to achieve desirable results.

[0143] Accordingly, the previously described example embodiments do not define or constrain this disclosure. Other changes, substitutions, and alterations are also possible without departing from the spirit and scope of this disclosure.

Claims

WHAT IS CLAIMED IS:

1. A catalytic device comprising: a first electrically conductive layer; a second electrically conductive layer; an electrically insulating layer between the first electrically conductive layer and the second electrically conductive layer; and a metal on a surface of the first electrically conductive layer, wherein the first electrically conductive layer and the second electrically conductive layer are configured to be electrically coupled.

2. The catalytic device of claim 1, wherein the first electrically conductive layer comprises an amorphous carbon layer.

3. The catalytic device of claim 2, wherein the amorphous carbon layer is disposed on the electrically insulating layer.

4. The catalytic device of claim 3, wherein the amorphous carbon layer is sputtered, deposited, or evaporated on the electrically insulating layer.

5. The catalytic device of claim 3 or 4, wherein the amorphous carbon layer is disposed on the electrically insulating layer by vacuum arc deposition, physical laser deposition, or e-beam evaporation.

6. The catalytic device of any one of claims 2-5, wherein a thickness of the amorphous carbon layer is in a range of 0.01 nm to 100 nm.

7. The catalytic device of claim 6, wherein a thickness of the amorphous carbon layer is in a range of 1 nm to 10 nm.

8. The catalytic device of any one of claims 1-7, wherein the second electrically conductive layer comprises a silicon wafer.

9. The catalytic device of any one of claims 1-7, wherein the second electrically conductive layer comprises a metal.

10. The catalytic device of claim 9, further comprising a substrate in contact with the second electrically conductive layer.

11. The catalytic device of claim 10, wherein the substrate comprises silicon.

12. The catalytic device of claim 10, wherein the substrate comprises a polymer.

13. The catalytic device of claim 12, wherein the polymer comprises polyimide.

14. The catalytic device of claim 12 or 13, wherein the polymer is flexible.

15. The catalytic device of any one of claims 1-14, wherein the electrically insulating layer comprises a high-K dielectric material.

16. The catalytic device of claim 15, wherein the high-K dielectric material comprises a metal oxide.

17. The catalytic device of claim 15, wherein the high-K dielectric material comprises a polymer electrolyte.

18. The catalytic device of claim 17, wherein the polymer electrolyte comprises an ion gel.

19. The catalytic device of claim 18, wherein the ion gel is formed from a molten salt.

20. The catalytic device of claim 19, wherein the molten salt comprises an ionic liquid.

21. The catalytic device of claim 18, wherein the ion gel is formed from a polymer and a molten salt.

22. The catalytic device of claim 21, wherein the molten salt comprises an ionic liquid.

23. The catalytic device of claim 15, wherein the high-K dielectric material comprises an ionomer.

24. The catalytic device of any one of claims 1-23, wherein the metal comprises Pd, Ru, Rh, Ir, Ni, Co, Cu, Fe, or an alloy thereof.

25. The catalytic device of any one of claims 1-24, wherein metal comprises nanoclusters.

26. The catalytic device of any one of claims 1-25, wherein the metal is in the form of a layer.

27. The catalytic device of any one of claims 1-26, wherein the first electrically conductive layer and the second electrically conductive layer are electrically coupled.

28. The catalytic device of any one of claims 1-27, wherein the first electrically conductive layer and the second electrically conductive layer are electrically coupled to a voltage source.

29. The catalytic device of any one of claims 1-28, wherein a surface area of the catalytic device exceeds 20 cm2.

30. A catalytic device comprising two or more of the catalytic devices of any one of claims 1-29, wherein each of the two or more of the catalytic devices is separated from another one of the two or more of the catalytic devices by one or more spacers.31 . The catalytic device of claim 30, wherein the one or more spacers allow a flow of a fluid between each of the two or more of the catalytic devices.

32. A method of making the catalytic device of any one of claims 1-31, the method comprising: disposing the electrically insulating layer on the second electrically conductive layer; disposing the first electrically conductive layer on the electrically insulating layer; and disposing the metal on the surface of the first electrically conductive layer.

33. The method of claim 32, wherein disposing the electrically insulating layer on the second electrically conductive layer comprises forming a metal oxide layer on the second electrically conductive layer.

34. The method of claim 32, wherein disposing the electrically insulating layer on the second electrically conductive layer comprises forming a layer comprising a polymer electrolyte on the second electrically conductive layer.

35. The method of any one of claims 32-34, wherein disposing the first electrically conductive layer on the electrically insulating layer comprises disposing a layer of carbon on the electrically insulating layer.

36. The method of claim 35, wherein disposing the layer of carbon on the electrically insulating layer comprises vacuum arc deposition, physical laser deposition, or e-beam evaporation.

37. The method of any one of claims 32-36, wherein disposing the metal on the surface of the first electrically conductive layer comprises forming nanoclusters of the metal on the first electrically conductive layer.

38. The method of any one of claims 32-37, wherein disposing the metal on the surface of the first electrically conductive layer comprises electron beam deposition, thermal evaporation, sputtering, vacuum arc deposition, or physical laser deposition.

39. The method of any one of claims 32-38, further comprising disposing the second electrically conductive layer on a substrate before disposing the electrically insulating layer on the second electrically conductive layer.

40. The method of claim 39, wherein disposing the second electrically conductive layer on the substrate comprises electron beam deposition, thermal evaporation, sputtering, vacuum arc deposition, or physical laser deposition of the second electrically conductive layer on the substrate.

41. The method of any one of claims 32-40, wherein disposing the electrically insulating layer on the second electrically conductive layer comprises printing, coating, or casting the electrically insulating layer on the second electrically conductive layer.

42. The method of claim 41, wherein casting comprises dropcasting.

43. The method of any one of claims 32-42, wherein disposing the electrically insulating layer on the second electrically conductive layer, disposing the first electrically conductive layer on the electrically insulating layer, and disposing the metal on the surface of the first electrically conductive layer occurs in a roll-to-roll fabrication process.

44. A method of catalyzing a chemical reaction with the catalytic device of any one of claims 1-31, the method comprising: positioning the catalytic device in a medium comprising reactants; and applying a voltage across the first electrically conductive layer and the second electrically conductive layer, thereby catalyzing a chemical reaction of the reactants.

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