Catalysis Apparatus and Method

Abstract

The present invention relates to a method for selecting an electrocatalyst array to achieve a desired product outcome. The method includes exposing an electrocatalyst system to an activator dissolved or suspended in a conductive solution and applying a voltage to the electrocatalyst system, the voltage being sufficient to cause multi-electron oxidation or multi-electron reduction of an active species. The electrocatalyst system includes a counter electrode and an electrocatalyst array. The array includes a support substrate and uniformly sized surface structures protruding from the surface of the support substrate, the uniformly sized surface structures having catalyst-containing edges and / or apexes. When the uniformly sized surface structures are micrometer-scale, a first product ratio is produced. When the uniformly sized surface structures are nanometer-scale, a second product ratio is produced, the first and second product ratios being different and requiring a higher order electronic process than the first product ratio. [Selected Figure] Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for catalyzing electrochemical redox reactions. More particularly, the present invention relates to a method for catalyzing electrochemical redox reactions using an electrocatalyst having a surface structure(s) that can reduce the costs typically associated with expensive catalyst materials. [Background technology]

[0002] Heterogeneous catalysis is used in a variety of important redox catalytic processes, including H2 production for energy storage and O2 reduction in fuel cells. However, catalysts are often expensive materials. For a given electrocatalytic reaction, it is desirable to have the catalytic reaction occur at a potential as close as possible to the reversible electrode potential (thermodynamic electrode potential) and with a satisfactory reaction rate. However, improving one aspect of a catalytic process typically has a detrimental effect on others; for example, improving the reaction rate often requires a larger driving force, resulting in a large deviation from the thermodynamic potential.

[0003] When optimizing a catalytic process, several parameters are considered, including the catalyst material, the solvent used (e.g., aqueous, organic), solution properties (e.g., pH, viscosity, electrolyte), fluid vs. static, cell design, and electrode material geometry and orientation. The primary component is an electrode containing a catalyst on the surface or within the bulk of the electrode matrix. Alternatively, in the case of metals, the electrode material may be the catalytic material.

[0004] The process of optimizing a catalyst typically involves optimizing each of the above parameters for their impact on the kinetic and thermodynamic responses within the system, providing an understanding of how each variable affects the catalytic efficiency in terms of rate and energy required. However, until now, little consideration has been given to the effect of the electrode surface topography on catalytic efficiency.

[0005] It is an object of the present invention to provide a method for catalyzing electrochemical redox reactions of active species in conductive solutions, to reduce the cost of catalyzing electrochemical redox reactions of active species in conductive solutions, or at least to provide the public with a useful choice. Summary of the Invention

[0006] According to a first aspect of the present invention, there is provided a method of catalyzing an electrochemical redox reaction of an active species in a conductive solution, the method comprising: a. providing an electrocatalytic array, the electrocatalytic array comprising: i. a support substrate; ii. a surface structure protruding from the support substrate, the surface structure comprising an electrocatalyst; iii. providing an electrocatalyst array comprising a functional surface on the electrocatalyst, the functional surface being on top of the surface structure, the functional surface being adapted to contact active species in the conductive solution; b. exposing the surface structure to a solution containing a counter electrode therein; c. establishing a current or voltage between the electrocatalyst and the counter electrode such that a charge density (voltage or current) concentrates at the functional surface and active species undergo a redox reaction following contact with said functional surface. In some embodiments, the redox reaction is selected from one or more of the following: hydrogen evolution from water; Oxygen generation from water Hydrogen generation from water, Hydrogen generation from protons, Hydrogen oxidation to water, hydrogen oxidation to protons, Hydrogen oxidation to hydrogen peroxide, oxygen reduction to water, oxygen reduction to peroxides, The reaction of carbon dioxide to carbon monoxide The reaction from carbon dioxide to methanol Reaction of carbon dioxide to carboxylic acid (e.g., formic acid), Reaction of carbon dioxide to aldehydes and / or ketones, Carbon dioxide to methane, ethane, propane, and / or up to C 21 Reaction to make higher carbon chains of Methane oxidation to methanol, Reaction of nitrogen to hydrazine, The reaction of nitrogen to ammonia Decomposing ammonia into hydrogen and nitrogen; The reaction from methane to methanol The reaction from nitrate to nitrogen, Reaction of nitrates to ammonia.

[0007] In some embodiments, the redox reaction is a combination of redox reactions, for example, water evolving hydrogen and oxygen, then the oxygen being reduced back to water, water evolving hydrogen, then the hydrogen combining with nitrogen to form ammonia.

[0008] In some embodiments, the redox reaction involves several steps where intermediates are preferably not isolated, for example, from carbon dioxide to carbon monoxide, and then from carbon monoxide to methanol, but the carbon monoxide is not isolated.

[0009] In some embodiments, the redox reaction is a two or more electron process. In some embodiments, the redox reaction is a two-electron process. In some embodiments, the two-electron process is selected from the following: Hydrogen generation from water Hydrogen generation from protons Hydrogen oxidation to hydrogen peroxide Oxygen reduction to peroxide The reaction of carbon dioxide to carbon monoxide Reaction of carbon dioxide to formic acid The reaction that converts methane into methanol.

[0010] In some embodiments, the redox reaction is a four or more electron process. In some embodiments, the redox reaction is a four electron process. In some embodiments, the four electron process is selected from the following: Oxygen generation from water Oxygen reduction to water Reaction of nitrogen to hydrazine The reaction of carbon dioxide to formaldehyde Hydrogen oxidation to water.

[0011] In some embodiments, the redox reaction is a six or more electron process. In some embodiments, the six electron process is selected from the following: The reaction from carbon dioxide to methanol The reaction of nitrogen to ammonia The decomposition of ammonia into hydrogen and nitrogen.

[0012] In some embodiments, the redox reaction is an eight or more electron process. In some embodiments, the eight or more electron process is selected from the following: Reactions of carbon dioxide to methane, ethane, propane, and / or higher carbon chains up to C21, reactions of carbon dioxide to acetic acid, Reaction of carbon dioxide to ketones The reaction from nitrate to nitrogen, Reaction of nitrates to ammonia.

[0013] In another aspect, a method for catalyzing an electrochemical redox reaction of an active species in a conductive solution is provided, the method comprising: a. providing an electrocatalytic array, the electrocatalytic array comprising: i. a support substrate; ii. a surface structure protruding from the support substrate, the surface structure comprising an electrocatalyst; iii. providing an electrocatalyst array comprising a functional surface on the electrocatalyst, the functional surface being on top of the surface structure, the functional surface being adapted to contact active species in the conductive solution; b. exposing the surface structure to a solution containing a counter electrode therein; c. establishing a current or voltage between the electrocatalyst and the counter electrode such that a charge density (voltage or current) concentrates on the functional surface and active species undergo redox reactions following contact with the functional surface; The active species is oxygen, which is reduced to water.

[0014] In another aspect, a method for catalyzing an electrochemical redox reaction of an active species in a conductive solution is provided, the method comprising: a. providing an electrocatalytic array, the electrocatalytic array comprising: i. a support substrate; ii. a surface structure protruding from the support substrate, the surface structure comprising an electrocatalyst; iii. providing an electrocatalyst array comprising a functional surface on the electrocatalyst, the functional surface being on top of the surface structure, the functional surface being adapted to contact active species in the conductive solution; b. exposing the surface structure to a solution containing a counter electrode therein; c. establishing a current or voltage between the electrocatalyst and the counter electrode such that a charge density (voltage or current) concentrates on the functional surface and active species undergo a redox reaction following contact with the functional surface; The active species is water or protons, which are reduced to hydrogen.

[0015] In another aspect, a method for catalyzing an electrochemical redox reaction of an active species in a conductive solution is provided, the method comprising: a. providing an electrocatalytic array, the electrocatalytic array comprising: i. a support substrate; ii. a surface structure protruding from the support substrate, the surface structure comprising an electrocatalyst; iii. providing an electrocatalyst array comprising a functional surface on the electrocatalyst, the functional surface being on top of the surface structure, the functional surface being adapted to contact active species in the conductive solution; b. exposing the surface structure to a solution containing a counter electrode therein; c. establishing a current or voltage between the electrocatalyst and the counter electrode such that a charge density (voltage or current) concentrates on the functional surface and active species undergo redox reactions following contact with the functional surface; The active species is nitrogen, which is reduced to ammonia. In another aspect, a method for catalyzing an electrochemical redox reaction of an active species in a conductive solution is provided, the method comprising: a. providing an electrocatalytic array, the electrocatalytic array comprising: i. a support substrate; ii. a surface structure protruding from the support substrate, the surface structure comprising an electrocatalyst; iii. providing an electrocatalyst array comprising a functional surface on the electrocatalyst, the functional surface being on top of the surface structure, the functional surface being adapted to contact active species in the conductive solution; b. exposing the surface structure to a solution containing a counter electrode therein; c. establishing a current or voltage between the electrocatalyst and the counter electrode such that a charge density (voltage or current) concentrates on the functional surface and active species undergo redox reactions following contact with the functional surface; The active species is carbon dioxide, which is reduced to methanol.

[0016] In another aspect, a method for catalyzing a redox reaction of an active species in a conductive solution is provided, the method comprising: exposing the electrocatalytic system to an active species; applying a voltage to the electrocatalytic system, where: applying a voltage sufficient to cause a multi-electron oxidation or multi-electron reduction of the active species; The electrocatalytic system is a counter electrode; 1. An electrocatalytic array comprising: A support substrate; uniformly sized surface structures protruding from a surface of a support substrate; The uniformly sized surface structures comprise an electrocatalytic array having catalyst-containing edges and apices.

[0017] In some embodiments, the edges and / or apexes comprise less than about 50%, less than about 40%, less than about 30%, less than about 20%, less than about 10%, less than about 1%, less than about 0.01%, less than about 0.001%, less than about 0.0001%, less than about 0.00001%, or less than about 0.000001% of the surface area of ​​the catalyst when viewed from above. In some embodiments, the edges and / or apexes comprise between about 0.0000001% and about 0.000001% of the surface area of ​​the catalyst when viewed from above. In some embodiments, the edges and / or apexes comprise between about 0.0001% and about 50% of the surface area of ​​the catalyst when viewed from above. In some embodiments, the edges and / or apexes comprise between about 0.1% and about 50% of the surface area of ​​the catalyst when viewed from above. In any of the embodiments herein, the uniformly sized surface structures may be of uniform geometric shape.

[0018] With respect to the surface structures, there may be a plurality of surface structures of substantially uniform size and / or geometry, and the plurality of surface structures may include a catalyst or catalytic material on one or more edges and / or apexes and / or tips and / or apexes of the structures.

[0019] In some embodiments, the multi-electron oxidation or reduction of the active species comprises a two-electron process, a four-electron process, a six-electron process, an eight-electron process, a ten-electron process, or a twelve-electron process.

[0020] In some embodiments, the multi-electron oxidation or reduction of the active species comprises two-electron processes, including: hydrogen evolution from water or protons, hydrogen oxidation to water or protons, hydrogen oxidation to hydrogen peroxide, oxygen reduction to hydrogen peroxide, conversion of carbon dioxide to carbon monoxide, or reduction of nitrogen (N) to hydrazine or methane to methanol.

[0021] In some embodiments, the multi-electron oxidation or reduction of the active species comprises a two-electron process involving the conversion of carbon dioxide to carbon monoxide.

[0022] In some embodiments, the multi-electron oxidation or reduction of the active species comprises a four-electron process including oxygen evolution from water, oxygen reduction to water, carbon dioxide reduction to an aldehyde, or carbon dioxide reduction to formic acid.

[0023] In some embodiments, the multi-electron oxidation or reduction of the active species comprises a four-electron process including carbon dioxide reduction to an aldehyde or carbon dioxide reduction to a carboxylic acid.

[0024] In some embodiments, the multi-electron oxidation or reduction of the active species comprises a six-electron process including carbon dioxide reduction to an alcohol, nitrogen (N) reduction to ammonia, or the production of hydrogen and nitrogen from ammonia. In some embodiments, the alcohol is methanol.

[0025] In some embodiments, the multi-electron oxidation or multi-electron reduction of the active species is carried out by reacting carbon dioxide with the compound of formula C n H 2n+2 (where n is 2 to 21) to an alkane, in a (2n + 6) electron process.

[0026] In some embodiments, the multi-electron oxidation or reduction of the active species comprises an eight-electron process from nitrate anion to ammonia.

[0027] In some embodiments, the multi-electron oxidation or reduction of the active species comprises a 10-electron process, including the oxidation of ethane.

[0028] In some embodiments, the multi-electron oxidation or reduction of the active species comprises an 11-electron process involving the conversion of nitrate anion to nitrogen.

[0029] In some embodiments, the multi-electron oxidation or reduction of the active species comprises a 12-electron process, including the oxidation of propane.

[0030] In another aspect, a method for catalyzing gas formation from an active species in a conductive solution is provided. Such a method includes exposing an electrocatalytic system to an active species and applying a voltage to the electrocatalytic system. The voltage is sufficient to cause multi-electron oxidation or multi-electron reduction of the active species. The electrocatalytic system further includes a counter electrode and an electrocatalytic array, the electrocatalytic array including a supporting substrate and uniformly sized surface structures protruding from a surface of the supporting substrate, the uniformly sized surface structures having catalyst-containing edges and / or apexes, and the rate of gas formation is increased by at least 1.5 times compared to the same electrocatalytic array without the uniformly sized surface structures protruding from a surface of the supporting substrate. In any of the embodiments herein, the uniformly sized surface structures may have a uniform geometric shape.

[0031] With respect to the surface structures, there may be a plurality of surface structures of substantially uniform size and / or geometry, and the plurality of surface structures may include a catalyst or catalytic material on one or more edges and / or apexes and / or tips and / or apexes of the structures.

[0032] In another embodiment, the rate of gas formation is increased by up to 1000 times, in another embodiment, by 1.5 to 1000 times, in another embodiment, by 10 to 1000 times, in another embodiment, by 20 to 500 times, in another embodiment, by 50 to 500 times, and in another embodiment, by 50 to 300 times.

[0033] In another aspect, a method is provided for enabling the selection of an electrocatalyst array based on a desired product outcome. The method includes exposing an electrocatalyst system to an activator dissolved or suspended in a conductive solution and applying a voltage to the electrocatalyst system. In the method, the voltage is sufficient to cause multi-electron oxidation or multi-electron reduction of an active species, and the electrocatalyst system includes a counter electrode and an electrocatalyst array. The electrocatalyst array includes a support substrate and uniformly sized surface structures protruding from the surface of the support substrate, the uniformly sized surface structures having catalyst-containing edges and / or apexes. When the uniformly sized surface structures are micrometer-scale, a first product is produced, whereas when the uniformly sized surface structures are nanometer-scale, a second product is produced, and the first and second products are different. The production of the second product requires a higher-order electronic process compared to the production of the first product. In other words, the production of the second product requires more electrons than the production of the first product. In any of the embodiments herein, the uniformly sized surface structures may have a uniform geometric shape.

[0034] With respect to the surface structures, there may be a plurality of surface structures of substantially uniform size and / or geometry, and the plurality of surface structures may include a catalyst or catalytic material on one or more edges and / or apexes and / or tips and / or apexes of the structures.

[0035] In another aspect, a method is provided that allows for the selection of an electrocatalyst array based on a desired product outcome, the method comprising: exposing an electrocatalyst system to an activator dissolved or suspended in a conductive solution; applying a voltage to the electrocatalytic system; where: applying a voltage sufficient to cause a multi-electron oxidation or multi-electron reduction of the active species; The electrocatalytic system is a counter electrode; 1. An electrocatalytic array comprising: A support substrate; uniformly sized surface structures protruding from a surface of a support substrate; an electrocatalytic array, the uniformly sized surface structures having catalyst-containing edges and / or apexes; a first product ratio is produced when the uniformly sized surface structures are of a micrometer scale, and a second product ratio is produced when the uniformly sized surface structures are of a nanometer scale, the first and second product ratios being different; The second product ratio requires a higher order of electronic processes than those required to produce the first product ratio.

[0036] In some embodiments, the active species is oxygen, the first product can be hydrogen peroxide (a two-electron process) (i.e., a product ratio of hydrogen peroxide to water of 100 to 0), and the second product can be water (a four-electron process) (i.e., a product ratio of hydrogen peroxide to water of 0 to 100).

[0037] In some embodiments, the width of the nanometer-scale surface structure that bonds with the support substrate is from about 25 nm to about 50,000 nm. In some embodiments, the width of the micrometer-scale surface structure that bonds with the support substrate is from about 5 μm to about 500 μm.

[0038] In some embodiments, a passive or passivating layer can be deposited between the surface structures to facilitate tailoring of product ratios.

[0039] In some embodiments, an inactive or passivating layer or a substantially less active layer may be deposited to a thickness that adjusts the relative ratio of products between the second product ratio and the first product ratio.

[0040] In some embodiments, the greater the thickness of the inactive or passivating layer, or the greater the thickness, the closer the relative ratio approaches the first product ratio.

[0041] In some embodiments, the relative ratio of the first product ratio to the second product ratio may be adjusted according to the relative thickness or height of the inert or passivation layer (by adjusting the exposure of the surface structures, such as a low amount of surface structures or a high amount of surface structures).

[0042] With respect to the thickness of the inert or passivating layer, the thickness is made relative to the height of the surface structure above the support surface.

[0043] The above adjustment of the thickness of the inert or passivating layer can be applied to the production of functional surfaces or catalysts.

[0044] In some embodiments, the thickness of the inert or passivating layer may be between about 5% and about 95% of the height of the surface structure.

[0045] In some embodiments, the thickness of the passive or passivating layer may be at least 99% of the height of the surface structures.

[0046] In some embodiments, the thickness of the inert or passivating layer can be proportional to the height of the surface features to expose the nanometer-scale size of the apex or tip or apexes of the surface features.

[0047] For example, in some embodiments of the method in which the active species is oxygen, the first product can be hydrogen peroxide (a two-electron process) and the second product can be water (a four-electron process).

[0048] In other embodiments of the method where the active species is CO2, the first product can be CO, the second product can be formic acid, and the third product can be methanol. In other embodiments of the method where the active species is nitrate, the first product can be ammonia and the second product can be nitrogen. In other embodiments of the method where the active species is nitrogen, the first product can be hydrazine and the second product can be ammonia.

[0049] In another aspect, a method for selecting an electrocatalyst array based on a desired product outcome is provided. The method includes exposing an electrocatalyst system to an activator dissolved or suspended in a conductive solution, applying a voltage to the electrocatalyst system, and recovering a redox product. The voltage is sufficient to cause a multi-electron oxidation or multi-electron reduction of the active species. The method also includes an electrocatalyst system including a counter electrode and an electrocatalyst array, the array including a supporting substrate and uniformly sized surface structures protruding from a surface of the supporting substrate, the uniformly sized surface structures having catalyst-containing edges and / or apexes. The method also includes selecting dimensions of the uniformly sized surface structures to vary the recovered redox product.

[0050] In some such embodiments, the activator is oxygen, the uniformly sized surface structures are micrometer-scale, and the redox product is hydrogen peroxide. In other such embodiments, the activator is oxygen, the uniformly sized surface structures are nanometer-scale, and the redox product is water.

[0051] In another aspect, a method for generating a gas from an electrode is provided. The method includes exposing the electrode to a conductive solution containing an active species and applying a voltage to the electrode sufficient to reduce or oxidize the active species to produce a gas. In this method, the electrode includes a nanostructure array, which in turn includes a supporting substrate and pyramidal surface structures protruding from the supporting substrate. In the array, each pyramidal surface structure has a base, an apex, and an edge between the base and the apex, the base is in contact with the supporting substrate, the base has a longest lateral dimension of 50 nm to about 4000 nm, the apex is about 1 nm to about 50 nm, the distance between adjacent apexes is about 50 nm to 1000 nm, and the edge and apex include a catalyst.

[0052] In some embodiments, the method further includes an electrolyte system including an electrode and a counter electrode. In some embodiments, the top portion is configured such that gas generation is initiated at the top portion. In any of these embodiments, the gas may be hydrogen, oxygen, or both hydrogen and oxygen. In any of the embodiments, the gas may be hydrogen, nitrogen, or both hydrogen and nitrogen. In any of the embodiments, the gas may be ammonia.

[0053] In some embodiments, the pyramidal surface structures of the nanostructure array are substantially the same in shape and height.

[0054] In another aspect, A support substrate; and uniformly sized surface structures protruding from a surface of a supporting substrate; The surface structure has uniformly arranged sizes and has edges and a top portion. and platinum and carbon deposited on at least a portion of the surface structure.

[0055] In another aspect, any one or more of the above aspects described herein, or the following embodiments described herein, can facilitate the substitution of a catalyst with either lower economic cost and / or activity, and / or reduced amount.

[0056] Here, the displaced catalyst is less reactive and / or less abundant than the catalyst it replaces or displaces.

[0057] For the avoidance of doubt, the following embodiments refer to all aspects described above.

[0058] In some embodiments, the cross-sectional area of ​​the surface structure decreases along an axis perpendicular to the top surface of the support substrate.

[0059] In some embodiments, the top of the surface structure has a convex upper surface.

[0060] In some embodiments, the surface structures have a triangular, convex, semicircular, or nipple-like cross section along a plane perpendicular to the top surface of the support substrate.

[0061] In some embodiments, the tops of the surface features have an angle of about 90° or less at the apex, hi some embodiments, the surface features are sharp peaks or ridges.

[0062] In some embodiments, the surface structures are pyramidal, conical, ridge, chevron, spike, cylinder, square pentahedron, flat-top pentahedron, pentagon, hexagon, or combinations thereof. Any of such structures can have edges, peaks, ridges, or any combination of two or more such features.

[0063] In some embodiments, the surface structures have a substantially triangular, substantially circular, or substantially square cross-section along a plane parallel to the top surface of the support substrate.

[0064] In some embodiments, the surface structures are uniformly disposed on the support substrate. Alternatively, the surface structures are randomly disposed on the support substrate.

[0065] In some embodiments, the surface structures are substantially uniform in size. It is believed that uniform size and / or geometry may provide substantially uniform results, such as, but not limited to, substantially the same current and / or voltage across each structure, producing substantially uniform products. In exemplary embodiments, the surface structures and catalysts may be tailored to provide for the production of a substantially predetermined primary or preferred product. Alternatively, the surface structures and catalysts may be tailored to provide for the production of one or more predetermined products, e.g., a preferred or primary product, and a secondary product (which may also be preferred). Similarly, the surface structures and catalysts may be tailored to minimize the production of non-preferential products.

[0066] With respect to the surface structures, there may be a plurality of surface structures of substantially uniform size and / or geometry, and the plurality of surface structures may include a catalyst or catalytic material on one or more edges and / or apexes and / or tips and / or apexes of the structures.

[0067] In some embodiments, the surface structures have at least one line of symmetry. In some embodiments, the surface structures have at least two lines of symmetry.

[0068] In some embodiments, the surface structure(s) is one or more of the following: i. at the same or different or different heights from the surface of the supporting substrate; ii. of the same or different shape or different geometric shape relative to other surface structure(s); iii. of regular or irregular geometric shapes; iv. Equally or unevenly spaced; v. The same or different or different densities vi. A population of a plurality of surface structures comprising a plurality of surface structures of any one of i to v.

[0069] In some embodiments, the surface structure(s) are provided at a predetermined spacing or density to provide a large number of peaks or points that act as functional surfaces, or to have functional surfaces formed thereon of the necessary size and density for the reduction or oxidation of active species as described herein.

[0070] In some embodiments, the surface structure(s) are provided at a predetermined uniform spacing or density to provide a large number of uniformly sized peaks and / or tips that act as functional surfaces, or to have functional surfaces formed thereon of the necessary size and density for the reduction or oxidation of active species as described herein. In any of the embodiments herein, the uniformly sized surface structures may be of uniform geometric shape.

[0071] With respect to the surface structures, there may be a plurality of surface structures of substantially uniform size and / or geometry, and the plurality of surface structures may include a catalyst or catalytic material on one or more edges and / or apexes and / or tips and / or apexes of the structures.

[0072] In some embodiments, the surface structure(s) comprise a distal end portion, the distal end portion being located furthest from the surface from which the surface structure(s) extend, the distal end portion being of a sharp, or peak, or spike, or apex, or ridge shape to act as or have a functional surface formed thereon.

[0073] In some embodiments, the surface structure(s) are provided as an array or arrays of surface structures provided on a surface of a supporting substrate.

[0074] In some embodiments, the or each array is a geometrically arranged uniform pattern.

[0075] In some embodiments, the or each array is a sequentially arranged pattern of a population of surface structure(s).

[0076] In some embodiments, the or each array is provided separately by molding tooling in a continuous molding machine, hot embossing, lithography, injection molding, forging, electroforming, lithography, or other molding techniques.

[0077] In some embodiments, the width of the surface structure at the location where the surface structure is bonded to the support substrate is about 20 nm to about 5000 μm. In some embodiments, the width is about 40 nm to about 4000 μm, about 55 nm to about 3000 μm, about 75 nm to about 2500 μm, about 100 nm to about 4000 μm, about 250 nm to about 3500 μm, about 20 nm to about 3500 μm, about 2 nm to about 4000 μm, about 20 nm to about 2500 μm, about 20 nm to about 4000 μm, about 20 nm to about 3000 μm, or about 20 nm to about 2000 μm. In some embodiments, the width is about 5 nm to about 750 μm, about 5 nm to about 500 μm, or about 5 nm to about 100 μm.

[0078] In some embodiments, the width of the micrometer-scale surface features where the surface features bond with the support substrate is about 5 μm to about 500 μm, hi some embodiments, the width of the micrometer-scale surface features is about 50 μm.

[0079] In some embodiments, the length of the micrometer-scale surface features where the surface features bond to the support substrate is between about 5 μm and about 500 μm, hi some embodiments, the length of the micrometer-scale surface features is about 50 μm.

[0080] In some embodiments, the width of the nanometer-scale surface features where the surface features bond with the supporting substrate is about 25 nm to about 5000 nm, hi some embodiments, the width of the micrometer-scale surface features is about 250 nm.

[0081] In some embodiments, the length of the nanometer-scale surface features where they bond to the supporting substrate is between about 25 nm and about 5000 nm, hi some embodiments, the length of the micrometer-scale surface features is about 250 nm.

[0082] In some embodiments, the height of the surface structure (i.e., the height of the protrusion from the support substrate) is about 20 nm to about 5000 μm. In some embodiments, it is about 40 nm to about 4000 μm, about 55 nm to about 3000 μm, about 75 nm to about 2500 μm, about 100 nm to about 4000 μm, about 250 nm to about 3500 μm, about 20 nm to about 3500 μm, about 2 nm to about 4000 μm, about 20 nm to about 2500 μm, about 20 nm to about 4000 μm, about 20 nm to about 3000 μm, or about 20 nm to about 2000 μm. In some embodiments, it is about 5 nm to about 750 μm, about 5 nm to about 500 μm, or about 5 nm to about 100 μm.

[0083] In some embodiments, the height of the micrometer-scale surface features where they bond to the support substrate is about 5 μm to about 500 μm, hi some embodiments, the height of the micrometer-scale surface features is about 50 μm.

[0084] In some embodiments, the micrometer-scale surface structures are provided at a density to provide about 180,000 to about 1,800 peaks or tips per square centimeter to provide a functional surface or have a functional surface formed thereon. In some embodiments, the micrometer-scale surface structures are provided at a density to provide about 18,000 peaks or tips per square centimeter to provide a functional surface or have a functional surface formed thereon.

[0085] In some embodiments, the height of the nanometer-scale surface features where the surface features bond with the supporting substrate is between about 25 nm and about 5000 nm, hi some embodiments, the height of the nanometer-scale surface features is about 250 nm.

[0086] In some embodiments, the nanometer-scale surface structures are provided at a density to provide about 160,000,000 to about 16,000,000,000 peaks or tips per square centimeter to provide a functional surface or have a functional surface formed thereon. In some embodiments, the nanometer-scale surface structures are provided at a density to provide about 1,600,000,000 peaks or tips per square centimeter to provide a functional surface or have a functional surface formed thereon.

[0087] In some embodiments, the functional surface is on top of or around the surface structure.

[0088] In some embodiments, the functional surface is at or around the apex of a surface structure, the surface structure tapering towards the apex and / or having a substantially triangular cross-section along a plane parallel to the top surface of the supporting substrate.

[0089] In some embodiments, the functional surface is located at or around the top of the surface structure, and the width of the top of each surface structure is about 1 nm to about 5,000 μm. In some embodiments, it is about 10 nm to about 10 μm, or about 20 nm to about 2 μm, or about 30 nm to about 1 μm. In some embodiments, it is about 1 nm to about 1,000 nm, or about 1 nm to about 500 nm, or about 1 nm to about 100 nm, or about 1 nm to about 50 nm. The width of the top of each surface structure is smaller than the location where it is bonded to the support substrate.

[0090] In some embodiments, the functional surface is at or around the apexes of the surface structures, and the apexes of the surface structures are separated from one another by an apex-to-apex length of about 5 nm to about 1000 μm, about 10 nm to about 1000 μm, about 25 nm to about 1000 μm, about 5 nm to about 750 μm, about 5 nm to about 500 μm, or about 5 nm to about 100 μm. In some embodiments, the apex-to-apex length is about 5 nm to about 2000 nm, about 5 nm to about 1000 nm, or about 5 nm to about 500 nm.

[0091] In some embodiments, the support substrate comprises a metal, a composite, a polymer, silicon, or glass.

[0092] In some embodiments, the support substrate comprises a single layer or multiple layers. In some embodiments, the support substrate is non-conductive, such as a non-conductive polymer, glass, and / or silica. In some embodiments, the support substrate is conductive. In some embodiments, the conductive material is doped Si, a semiconductor, a metal, a conductive polymer, a carbon-loaded polymer, or a composite material. In some embodiments, the metal is a transition metal, including Ni, Cu, Al, Pt, Au, Ag, Mg, and Mn.

[0093] In some embodiments, the surface structure is integral with the support substrate. In some embodiments, the surface structure is integrally formed with the support substrate. In some embodiments, the surface structure is the same material as the support substrate. In some embodiments, the surface structure and the support substrate comprise a metal. In some embodiments, the support substrate and the surface structure comprise a composite material, a polymer, silica, or glass.

[0094] In some embodiments, the support substrate and surface structures comprise a first material, and the uniformly sized surface structures further comprise a layer coated thereon.

[0095] In some embodiments, the support substrate has a thickness of about 50 μm to 5 mm, or about 1 mm to 2 mm, about 85 μm to 2 mm, about 85 μm to 1 mm, about 1 mm to 4 mm, about 1 mm to 3 mm, or about 85 μm to 2 mm.

[0096] In some embodiments, the electrocatalyst is deposited on top of a support substrate. In some embodiments, the electrocatalyst is deposited on top of a surface structure. In some embodiments, the electrocatalyst is deposited on the tip of a surface structure. In some embodiments, the electrocatalyst is a different material than the surface structure and / or the support substrate.

[0097] In some embodiments, the electrocatalyst is deposited on less than about 50% to less than about 0.000001% of the surface when viewed from above. In some embodiments, the electrocatalyst is deposited on less than about 50%, less than about 40%, less than about 30%, less than about 20%, less than about 10%, less than about 1%, less than about 0.01%, less than about 0.001%, less than about 0.00001%, less than about 0.000001%, or less than about 0.000001% of the surface area. In some embodiments, the electrocatalyst is deposited on about 0.0000001% or about 0.000001% to about 50% of the surface area of ​​the catalyst when viewed from above. It will be apparent that the smallest possible surface area is a single atom on the supporting structure.

[0098] In some embodiments, the electrocatalyst is deposited on less than about 50% to less than about 0.0001% of the surface when viewed from above. In some embodiments, the electrocatalyst is deposited on less than about 50% to less than about 0.1% of the surface when viewed from above. In some embodiments, the electrocatalyst is deposited on less than about 30% to less than about 0.0001% of the surface of the array when viewed from above.

[0099] In some embodiments, the electrocatalyst comprises a layer of substantially constant thickness. In some embodiments, the thickness of the electrocatalyst is about 1 nm to 5 μm. In some embodiments, the thickness of the electrocatalyst is about 20 nm to 500 nm, or about 50 nm to 100 nm, about 50 nm to 500 nm, about 50 nm to 300 nm, about 1 nm to about 3 μm, 3 nm to about 5 μm, or about 2 nm to about 4 μm. In some embodiments, the thickness of the electrocatalyst is greater than 0 nm but less than about 1 nm.

[0100] In some embodiments, the electrocatalysts on the top surfaces of two or more surface structures are electrically connected in an array.

[0101] Alternatively, the electrocatalyst is integral with the surface structure(s). In some embodiments, the electrocatalyst is integrally formed with the support structure. In some embodiments, the electrocatalyst is the same material as the surface structure(s).

[0102] In some embodiments, the electrocatalyst comprises a material that produces a catalytic effect. In some embodiments, the electrocatalyst comprises a conductive material. The conductive material may include, but is not limited to, carbon (i.e., graphite, graphene, carbon fiber, carbon nanotubes, fullerenes), conductive polymers (i.e., polypyrrolidone (PPy)), polyacetylene, metals, alloys, organometallic complexes, or other such conductive materials. In some embodiments, the electrocatalyst comprises copper, a transition metal, an alloy, an organometallic complex, an organometallic complex containing a transition metal, or an organic material that can be oxidized or reduced. In some embodiments, the transition metal is selected from Ti, V, Cr, Fe, Co, Cu, Zn, Ga, Rb, Sr, Y, Zr, Nb, Mo, Tc, Ru, Ro, Pd, Ag, Cd, In, Sb, Sn, Cs, Ba, La, Ce, Pd, Nd, W, Os, Ir, Au, Pb, Bi, Ra, U, Pt, Au, and Ni. In some embodiments, the electrocatalyst comprises nickel. In some embodiments, the organometallic complex and / or organometallic complex comprising a transition metal is selected from ferrocene, porphyrin, phenanthroline, porphyrin imidazole, trispyridylamine, and / or triazole with a transition metal (the ferrocene already comprising a transition metal and a porphyrin may optionally include a transition metal).

[0103] In some embodiments, the conductive solution comprises water and / or an organic solvent, hi some embodiments, the organic solvent is selected from alcohol (e.g., ethanol), ether, acetonitrile, ethyl acetate, acetone, and / or DMSO.

[0104] In some embodiments, the conductive solution comprises an electrolyte. In some embodiments, the electrolyte is selected from buffer(s), a salt (e.g., NaCl), or an acid and base solution (e.g., H2SO4, HNO3, NaOH). In some embodiments, the solution comprises a buffer containing alkali metal chloride ions and copper 2+ ions.

[0105] In some embodiments, the active species is in a gaseous or liquid state. In some embodiments, the active species is a gas passing through the conductive solution. In some embodiments, the gas is selected from hydrogen, oxygen, nitrogen, methane, carbon monoxide and / or carbon dioxide or air, or a mixture of any two or more thereof. In some embodiments, the active species is a liquid. In some embodiments, the liquid is water, methanol, ethanol, propanol, acetone, ammonia, or a liquid short-chain hydrocarbon (e.g., up to C21). When the active species is water, the conductive solution is also preferably water containing an electrolyte or organic solvent. An organic solvent may be added to aid solubility or to participate in the oxidation or reduction process.

[0106] The counter electrode performs a charge-balancing redox (oxidation or reduction, anodic or cathodic) process that complements the redox (oxidation or reduction, anodic or cathodic) process occurring at the working electrode.

[0107] In some embodiments, the counter electrode, which preferably performs a charge-balancing redox (either oxidation or reduction) process and complements the redox (either oxidation or reduction) process occurring at the working electrode, is formed from a material selected from the group consisting of an inert conductive material, a conductive material, a metal, Pt, gold, carbon, graphite, graphene, carbon fiber, carbon nanotubes, fullerenes, conductive polymers PPy, PA, PA acetylene, or the same material as the working electrode. The counter electrode can be of various shapes, forms, and sizes, including fabrics, flat, perforated sheets, fibers, meshes, or 3D arrays, as defined herein. As described herein, the 3D structure is expected to enhance the redox properties, including catalysis, of the counter electrode in a manner similar to that performed at the working electrode.

[0108] In some embodiments, the counter electrode structure is a planar structure or an array structure. For example, an array of pyramids, an array of cones, a pyramidal shape, a conical shape, or a ridge shape. In some embodiments, the counter electrode comprises a surface structure as described herein. In some embodiments, the shape of the counter electrode reflects the shape of the surface structure. In some embodiments, the counter electrode comprises a surface structure in a manner opposite to the electrocatalyst array. In some embodiments, the counter electrode comprises a surface structure that differs in size, shape, or pattern from the electrocatalyst array.

[0109] In some embodiments, the counter electrode is (a) in a fixed orientation relative to the surface structure, or (b) attached to the electrode array, or (c) held in an orientation that minimizes the difference in distance between the surface structure(s) of the array, or (d) on top of the array, or (e) includes 3D surface features configured to facilitate placement of charge density (voltage or current) on the 3D working electrode, such as a series of tips that mirror the tips of the working electrode.

[0110] In some embodiments, the counter electrode is parallel to the surface structure.

[0111] The reaction at the counter electrode can be any redox process, such as the oxidation of an alcohol, water, or other moiety to complement the reduction at the surface structure, or vice versa.

[0112] In some embodiments, the counter electrode is formed from a material selected from the group consisting of an inert conductive material, a conductive material, a metal, Pt, Au, carbon, graphite, graphene, carbon fiber, carbon nanotubes, fullerenes, conductive polymers PPy, PA, PA acetylene, or the same material as the electrocatalytic array. In some embodiments, the counter electrode is a fabric, a planar perforated sheet, a fiber, a mesh, or a 3D array, as defined herein. As described herein, the 3D structure is expected to enhance the redox properties, including catalysis, of the counter electrode in a manner similar to that performed by the working electrode.

[0113] In some embodiments, the potential difference established between the counter electrode and the electrocatalyst is between about -2 V and +2 V. In some embodiments, it is between about -1 V and +1 V. In some embodiments, the potential difference is between about -200 mV and -1 V. Preferably, the potential difference is between about 0 mV and 1.8 V for oxidation.

[0114] In some embodiments, the current established between the electrocatalyst and the counter electrode is substantially constant.

[0115] In some embodiments, the current established between the electrocatalyst and the counter electrode is pulsed between an activation potential and a deactivation potential, hi some embodiments, the current established between the electrocatalyst and the counter electrode is pulsed between an activation potential and a deactivation potential within this range.

[0116] In one embodiment, the solution further comprises a reference electrode.

[0117] In some embodiments, the electrocatalytic array includes a bonding layer that is present at a significantly increased density on the functional surface of the electrode surface relative to the non-functional surface, or at a significantly increased density on the non-functional surface of the electrocatalytic array relative to the functional surface locations on the surface structure.

[0118] In some embodiments, the binding layer comprises a self-assembled monolayer (SAM). In some embodiments, the SAM is present on top of the electrocatalyst. In some embodiments, the SAM is present on top of the supporting substrate. In some embodiments, the SAM is present around the surface structure such that the surface structure, or a portion thereof, protrudes with the functional surface exposed thereon. In some embodiments, the SAM comprises a long-chain molecule comprising a C6-C24 carbon chain, which may be an alkane, alkene, alkyne, or aromatic, in some embodiments C6, C7, C8, C9, C10, C11, C12, C13, C14, C15, C16, C17, C18, C19, C20, C21, C22, C23, or C24, or a mixture thereof.

[0119] In some embodiments, the SAM comprises short chain molecules comprising carbon chains of C10 or less, in some embodiments C1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, or mixtures thereof.

[0120] In some embodiments, the SAM is a mixed SAM containing long-chain (C10-C24 as above) and short-chain (C1-C10 as above) molecules, which may be alkanes, alkenes, alkynes, or aromatics. In some embodiments, the mixed SAM contains long-chain molecules containing C6-C24 carbon chains (as above) and short-chain molecules of C1-C5 (as above).

[0121] In some embodiments, the long-chain SAM comprises a molecule selected from the group consisting of an azide, an amine, a carboxylate, an aldehyde, a ketone, an ester, or a carboxylic acid, or a mixture thereof. Such molecules are present in the backbone chain of the SAM. In some embodiments, the short-chain SAM comprises a molecule selected from the group consisting of an alkane, an azide, an amine, a hydroxyl, a carboxylate, or a carboxylic acid, or a mixture thereof. Such molecules are present in the backbone chain of the SAM.

[0122] In one embodiment, the SAM comprises a mixture of long chain molecules comprising carboxylic acid molecules greater than C6 and short chain molecules comprising hydroxyl molecules. In the above embodiment, the SAM long chain molecules are preferably selected from C6 to C24 molecules.

[0123] In some embodiments, the SAM is present on the electrocatalyst array, but not on top of a surface structure (including a functional surface) as defined above.

[0124] In some embodiments, the SAM comprises a short-chain molecule comprising a carbon chain of C5 or less, and the top portion of the surface structure(s) is either (a) free of the SAM, or (b) the SAM is adapted to be removed by establishing a current between the electrocatalytic layer and the counter electrode.

[0125] In some embodiments, the SAM comprises a long-chain SAM having a carbon chain of C6 to C24, and the top portion of the surface structure(s) is either (a) free of a SAM or (b) comprises a SAM adapted to be removed by establishing a current between the electrocatalyst layer and a counter electrode.

[0126] In one embodiment, the electrode array includes a SAM binding layer on the top and bottom of the surface structure, and contact of the active species with the functional surface results in selective removal of the SAM binding layer from the top of the surface structure where the charge density (voltage or current) is concentrated. In this embodiment, the method further includes selectively depositing an additional binding layer onto the now exposed portions of the electrocatalytic layer at the functional surface.

[0127] In some embodiments, the SAM is selected from the group consisting of methyl terminated alkanethiols, azides, thiols, aldehydes, cyanos, diazoniums, amines, alcohols, silanes, phosphonic acids, and carboxylic acids.

[0128] In certain embodiments, the SAM comprises: R-(aromatic), including both linear chains and chains composed of amide and ester bonds n -SH, alkane, alkene, alkyne or aromatic, R-(CH2) n -SH, R-(CH2) n -NH2, or R-(CH2) n -Si(OR')3, where R=alkyl, carboxylic acid, amine, aldehyde, alcohol, azide, quinone, or tetrazine; R' = Me, MeOH, Cl, (halides), Et, EtOH; In the formula, n=1 to 50.

[0129] In some embodiments, the conductive solution includes a solute reactant capable of binding to the binding layer. In some embodiments, the SAM includes a functional group that reacts with the solute reactant. In some embodiments, the functional group is a terminal functional group. In some embodiments, the SAM is functionalized with a functional group. In some embodiments, the functional group is selected from the group consisting of azide, carboxylic acid, amine, alcohol, ester, ketone, cyano, and aldehyde.

[0130] In some embodiments, the electrode array provided in step a) of the first aspect comprises a passivation layer deposited on a supporting substrate, covering the lower part of the surface structure and leaving the upper part exposed.

[0131] In some embodiments, applying a current or voltage to concentrate the charge density (voltage or current) results in the removal of a passivation layer on the functional surface on top of the surface structure.

[0132] In some embodiments, the passivation layer is removed by applying a reducing or oxidizing potential between the counter electrode and the electrode surface. In some embodiments, the potential is between -2 V and +2 V, in some embodiments, between -200 mV and -1 V, and in some embodiments, -400 mV relative to a silver / silver chloride reference electrode.

[0133] In some embodiments, the passivation layer comprises a functional group that binds to the electrode surface. In one embodiment, the passivation layer comprises a binding layer as described and defined herein. In one embodiment, the passivation layer comprises a SAM. In some embodiments, the SAM is linked to the electrode surface by a sulfur atom. In some embodiments, the electrode surface is gold. In some embodiments, the SAM further comprises a functional group, e.g., an alkyl chain, and in some embodiments, a carboxylic acid linked to an amine on the functional group.

[0134] The passivation layer between the tips can be a photoresist deposited by spin coating, painting, or spray coating. When this layer dries or crosslinks, it becomes a passivation layer and helps concentrate current. Ideally, this layer is a lacquer or a UV-crosslinkable photoresist such as SU8. In some embodiments, the passivation, or protective, layer can include catalytic material at non-active locations on the surface, such as at edges, ridges, and / or peaks, or immediately adjacent to such areas.

[0135] In some embodiments, the bonding layer is present on at least one of the functional surface, the surface structure, the passivation layer, or the supporting substrate.

[0136] In some embodiments, the method is carried out in a fuel cell.

[0137] Numerous modifications in structure and widely different embodiments and applications of the invention will suggest themselves to those skilled in the art to which this invention pertains without departing from the scope of the invention, which is defined in the appended claims. The disclosures and descriptions herein are merely illustrative and are not intended to be in any sense limiting.

[0138] Further aspects of the present invention, which should be considered in all its novel aspects, will become apparent to those skilled in the art upon reading the following description, which provides at least one example of a practical application of the invention. [Brief explanation of the drawings]

[0139] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [Figure 1] 1 shows a cross-sectional view of an electrode array according to the present invention having a triangular cross-section. [Figure 2a] Rapid electrochemical desorption of SAMs from a 3D pyramidal electrode surface is shown. [Figure 2b]1 shows the slower electrochemical desorption of SAMs from planar electrode surfaces. [Figure 2c] Kinetic traces of electrochemical desorption of SAMs on 3D and planar electrode surfaces are shown. [Figure 3] 1 shows an SEM image illustrating Pt deposition on top of a group of surface structures. [Figure 4a] 1 shows an SEM image illustrating Pt deposition on top of a group of surface structures. [Figure 4b] 1 shows an SEM image illustrating Pt deposition on top of a group of surface structures. [Figure 5a] We demonstrate a systematic change in the mechanism of the O2 reduction reaction from a pure two-electron process on planar electrocatalysts to partial two-electron and partial four-electron processes on micropyramidal-structured electrocatalysts with and without insulating layers, to a pure four-electron process on nanopyramidal-structured electrocatalysts. [Figure 5b] The various gold electrodes used in the example of Figure 5a are displayed in Figure 5b. [Figure 6] The background CV shows the absence of current (top line) and the increase in catalytic current with CO2 introduction (bottom line). [Figure 7a] CVs of an organometallic catalyst (ferrocene) on planar and 3D pyramidal electrode surfaces are shown. [Figure 7b] Tafel plots corresponding to the CVs in Figure 7a are shown. [Figure 8] CV of oxygen reduction using planar and 3D pyramidal gold electrodes. [Figure 9] 1 shows linear sweep voltammetry plots at 1600 rpm for various Pt-coated gold electrodes. [Figure 10] Oxygen reduction by 30% Pt / C deposited on a planar surface and nanopyramids is shown. [Figure 11] 1 shows the effect of three-dimensionality on the reduction of nitrate to nitrogen. [Figure 12] The scan rate dependence of ferrocene immobilized on a pyramidal electrode surface (a: upper plot) and a planar electrode surface (b: lower plot) is shown. [Figure 13] Peak potentials versus scan rate for both the oxidation and reduction of ferrocene are shown. [Figure 14] The rotation number pendant of the Pt-coated pyramidal surface is shown. [Figure 15] Koutecky-Levich plots are shown for both pyramidal and planar surfaces. [Figure 16] 1 shows a step-by-step process for fabricating a 3D electrode array. [Figure 17a] An SEM image of the silicon master is shown. [Figure 17b] Shows an SEM image of a nickel master generated from a silicon master. [Figure 17c] 1 shows an SEM of an embossed gold coated array. [Figure 18] Hydrogen gas production under identical conditions is shown for A) flat versus 50 μm pyramids, and B) flat versus 250 nm pyramids. SEM images of each of the pyramids are shown below in C (50 μm pyramids) and D (250 nm pyramids). [Figure 19] CVs of PBS buffer bubbled with both argon (top line) and argon plus nitrogen (bottom line) are shown. [Figure 20] Reduction of CO2 is shown. A) shows the CV for argon (top trace) and CV for argon + CO2 (bottom trace), B) and C)) show the analysis of the products in the headspace, confirming the appearance of CO and formic acid. [Figure 21] Oxygen reduction on a flat surface, Pt-pyramids (50 μm) and Pt-nanopyramids (250 nm) is shown. [Figure 22] Cyclic voltammetry is used to demonstrate the long-term O2 reduction by Pt-coated nanopyramid surfaces. [Figure 23] 10 shows the long-term O2 reduction by Pt-coated nanopyramid surfaces using chronoamperometry. [Figure 24]1 shows controlled deposition of Pt catalyst on top of pyramids using A) 5 pulses and B) 10 pulses. [Figure 25] The structures mentioned in Table 2 are shown. [Figure 26] The structures mentioned in Table 2 are shown. DETAILED DESCRIPTION OF THE INVENTION

[0140] definition "Attach" or "bind" means a covalent bond, electrostatic bond, or other mode of attachment in which a species is bound to a support in some way. Attachment can be direct or via another species.

[0141] "Tapered" means going from a wide surface structure to a narrow surface structure.

[0142] "Deposited" means formed on a surface and refers to the formation, layering, or production of any form. In one embodiment, deposition is achieved by sputtering, e-beam, or thermal evaporation. Preferably, the deposited layer has some degree of adhesion to the layer on which it is deposited. This adhesion may be covalent, electrostatic, or may involve van der Waals forces.

[0143] "Substantially constant thickness" with respect to an electrocatalyst means that the electrocatalyst does not vary significantly across its coverage of the supporting substrate or bonding layer. Unintentional variations in layer thickness that do not substantially affect the function of the sensor are intended to be encompassed by the term substantially constant thickness.

[0144] The words "comprise," "comprising," and the like, are to be construed in their inclusive sense, i.e., "including but not limited to," and not in their exclusive or exhaustive sense, unless the context clearly requires otherwise.

[0145] The terms "surface structure" and "functional surface" referred to herein are intended to refer to one or more structures / surfaces.

[0146] The "width" of a surface structure is measured by the maximum distance across the cross-sectional area of ​​the surface structure when a cross-section is taken along a plane substantially parallel to the top surface of the supporting substrate. When width is mentioned, the point on the surface structure where the parallel plane occurs is also described (e.g., at the junction between the supporting substrate and the surface structure).

[0147] "Catalyst" refers to a species that increases the rate of a chemical reaction.

[0148] "Electrochemically modified" with respect to the active species means that the active species undergoes reduction or oxidation, i.e., the gain or loss of electrons.

[0149] "Solute reactant" means a reactant found in solution that participates in a reaction catalyzed by a catalytically active species. The solute reactant is preferably in a separate conductive solution (i.e., different from the conductive solution containing the active species) or may be in the same solution, and upon reaction with the active species serves to bind / react with a target molecule that is detected by the sensor.

[0150] A "binding layer" includes a layer of molecules bound to the surface of the electrode array. The binding layer may be formed from a cross-linked polymer, a photoresist, or a self-assembled monolayer (SAM). Preferably, the cross-linked polymer is an epoxy-based negative photoresist such as SU-8. The binding layer can be deposited on the surface of the electrode array by means known to those skilled in the art, for example, by spin coating, spray coating, dip coating, wiping, or painting. In an alternative embodiment, the binding layer is bound to the surface of the electrode array by electrochemical modification of a precursor to the binding layer (i.e., active species), preferably according to the methods described herein.

[0151] "Concentrated" with respect to current or voltage means that the charge density (voltage or current) is stronger at the concentrated location on the surface compared to another location on the surface. The charge density (voltage or current) on the surface can be measured according to methods known to those skilled in the art. However, in one embodiment, the charge density (voltage or current) is measured by modeling and then directed to direct binding of fluorophores or platinum deposition on the surface.

[0152] A "counter electrode" can be any conductive entity that facilitates the flow of current from the electrode layer through the solution. In one embodiment, the counter electrode comprises a wire or other form of electrode structure held in the solution. Preferably, the counter electrode is formed from a material selected from the group consisting of metal, Pt, gold, nickel, copper, iron, carbon, graphite, graphene, carbon fiber, carbon nanotubes, fullerenes, conductive polymers PPy, PA, polyacetylene, and stainless steel. The counter electrode can be fabricated from a solid layer or a conductive layer deposited on a suitable support, such as a polymer, glass, or metal. The counter electrode can be bare metal (Au, Pt, stainless steel, copper) or an Au- or Pt-plated substrate (metal, polymer, or glass) and configured to facilitate the placement of charge density (voltage or current) on the 3D working electrode. For example, it can be a series of tips that mirror the tip of the working electrode.

[0153] "Activating" or "activate" refers to converting an active species from an inactive form to a reactive form. Thus, "electrochemical activation" refers to converting an active species to a reactive form by oxidizing or reducing the active species by applying a current to an electrode. "Activation potential" refers to the voltage (oxidation or reduction, typically in the range of +2 V to -2 V) required to initiate a coupling / binding / modification reaction. Typically, the reduction activation potential for clicks is between -500 mV and -100 mV.

[0154] "Inactivation potential" means the voltage required to stop a coupling / binding / modification reaction.

[0155] "Active species" refers to an entity present in solution that can undergo electrochemical modification. In one embodiment, the active species is a catalyst or catalyst precursor. In another embodiment, the active species is a component of a binding layer. In another embodiment, the active species is a charged particle that can bind to a functional surface. In another embodiment, the active species is a binding agent that can detect a target analyte in solution.

[0156] "Oxidation" means a chemical reaction involving the loss of electrons. Thus, "oxidative" means promoting the loss of electrons in a chemical reaction.

[0157] "Reduction" refers to a chemical reaction that involves the gain of electrons. Thus, "reductive" means promoting the gain of electrons in a chemical reaction.

[0158] "Pulse" or "pulsing" means adjusting the voltage or current from an activation potential to an inactivation potential. Pulsing may be regular or intermittent.

[0159] "Self-assembled monolayer (SAM)" means a molecular assembly comprising a head group linked to a tail group terminating in a functional group.

[0160] "Selective removal," with respect to removal of entities from a functional surface, means enhanced removal compared to other surfaces on the array where the current is not concentrated. For example, removal of the SAM occurs at a faster rate or a higher concentration of entities is removed compared to other surfaces. This term does not imply that removal is complete or that removal occurs to a lesser extent on other surfaces.

[0161] "Preferential deposition," with respect to deposition of entities on a functional surface, means enhanced deposition compared to other surfaces on the array where the current is not concentrated. For example, deposition of the SAM occurs at a faster rate or a higher concentration of entities is deposited on the other surfaces compared to the other surfaces. This expression does not exclude the possibility that other surfaces may be less heavily deposited.

[0162] "And / or" means "and" or "or," or both.

[0163] The "(s)" following a noun refers to the plural and / or singular form of the noun. Reference to a numerical range disclosed herein (e.g., 1 to 10) is also intended to encompass reference to all rational numbers within that range (e.g., 1, 1.1, 2, 3, 3.9, 4, 5, 6, 6.5, 7, 8, 9, and 10) and to any range of rational numbers within that range (e.g., 2 to 8, 1.5 to 5.5, and 3.1 to 4.7).

[0164] explanation The inventors have discovered that the method of the present invention is one that allows for a reduction in costs typically associated with expensive catalyst materials. The cost reduction is achieved by one or more of the following: 1. Increasing the activity of catalytic materials; 2. Reducing the amount of catalyst material required; 3. The ability to substitute lower cost, less active catalysts without loss of effectiveness; 4. Lowering the energy required to cause a reaction 5. Increasing exchange current density 6. Increasing the rate of mass transfer between the reactants and the catalyst 7. Increasing the mass transfer rate of the product(s) from the catalyst

[0165] The present inventors have discovered that by modifying the surface of an electrode to form an electrocatalyst with an array of surface structures, when a current or voltage is passed through the electrocatalyst exposed to a conductive solution, the charge density (voltage or current) can be concentrated toward the top (or tips) of the surface structures. This can result in dramatic improvements in the electrocatalyzed reaction. Not only have the inventors observed kinetic improvements, i.e., a dramatic increase in the rate of catalysis, and thermodynamic improvements (e.g., a more than 100-fold increase in the production of hydrogen from water), i.e., a dramatic decrease in the energy required to drive the redox-catalyzed reaction over a similar flat electrocatalyst, but unexpectedly, the inventors also observed changes in the reaction mechanism. For example, electrochemical oxygen reduction in aqueous alkaline media typically produces pure peroxide (H2O2). However, using the method of the present invention, surprisingly, water was produced. Possible reduction pathways are as follows: O2+2e - +2H + →H2O20.7V O2+4e - +4H + →2H2O 1.2V

[0166] The method of the present invention surprisingly promotes a more efficient four-electron process (see Example 3). This results in reduced energy loss and / or overcoming problems with O2 reduction as the rate-determining step. This can be particularly advantageous when used in, for example, fuel cells, as this can result in improved cell performance.

[0167] This four-electron pathway appeared to be almost universally observed when nanostructures were used, but was also particularly evident when microstructures were used.

[0168] Further redox reactions to which this method can be applied include: Hydrogen generation from water, Oxygen generation from water Hydrogen oxidation, The reaction of carbon dioxide to carbon monoxide The reaction from carbon dioxide to methanol Reaction of carbon dioxide to carboxylic acid (e.g., formic acid), Reaction of carbon dioxide to aldehydes and / or ketones, Carbon dioxide to methane, ethane, propane, and / or up to C 21 Reaction to make higher carbon chains of Methane oxidation to methanol, The reaction of nitrogen to ammonia and decomposing ammonia into hydrogen and nitrogen.

[0169] Applications of the methods of the present invention include (but are not limited to) electrodes, batteries, fuel cells and / or hydrogen production.

[0170] A standard electrode comprises a conductive solid support having a catalyst immobilized on its surface, examples of which include, but are not limited to: Metallized polymer, glass or silicon Carbon mesh Carbonaceous materials (fibers, vulcanized, powders, glassy, ​​edge planes, basal planes, fullerenes, nanotubes, graphene) Perforated and non-perforated metal sheets ITO or FTO coated sheets (polymer, glass, silicon) Conductive polymers

[0171] The inventors believe that catalysis depends on a combination of factors: 1. Diffusion of reactants and products to and from the site of catalysis 2.Electronic supply: a. An oxidation process that requires the supply of electrons to a catalytic site B reduction process requiring the removal of electrons from the site of catalysis 3. The voltage at the site of catalysis must be large enough to carry out the catalytic process. 4. Easy electron transfer between reactants and catalysts; 5. Lowering the activation energy for conversion 6. The catalyst material used.

[0172] Three-dimensionality provides a platform for achieving the above in a controllable manner, improving the performance of existing catalysts that are either deposited directly on top of the 3D structure or suspended in a matrix surrounding the tip. This allows access to previously inaccessible multi-electron transfer transformations (oxidative or reductive), allowing the same catalyst to be used to controllably produce a wider range of products from a single starting material.

[0173] As will be apparent to those skilled in the art, when the description of the present invention refers to a solution containing both an active species and a counter electrode, this refers to a solution having a counter electrode position therein.

[0174] Without wishing to be bound by theory, the inventors believe that the observed increases in kinetic and thermodynamic rates, the dramatic increase in electrocatalytic reactivity at the top of the tip, and / or alternative reaction pathways are likely due to one or more of the following mechanisms: 1. The combination of high density voltage and current distribution results in less wasted voltage (i.e., effectively higher voltage at the top, resulting in lower resistance) and more reactive electrons being generated. 2. Hot electrons are generated via the plasmonic effect, making electron injection easier. 3. The combined effect of higher voltage, higher current density, lower resistance, and more rapid diffusion of catalytic species creating a supercharged state of catalytic species. 4. Combination of the above with electromagnetic effects that affect constants such as potential field, concentration gradient, temperature, and pH. 5. Quantum effects, which increase with decreasing effective tip size or particle size, are achieved within and induced by the hot electron environment, resulting in increased hot electron current density and enhanced reaction. These quantum effects increase with decreasing tip dimensions. 6. Rapid diffusion between the above environment and the small effective surface area changes the bonding mode of the substrate, resulting in enhanced reactivity. 7. Reduction of IR drop due to reduction in "wasted energy" by the combination of the above, and therefore reduction in the energy cost of the reaction. 8. Reduction in solution resistance due to the environment caused by a combination of the above effects. 9. Quantum effects improve substrate bond orientation 10. Quantum effects due to changes in the bonding modes of the substrate, which result in different current and potential densities, resulting in the formation of a substrate (e.g., H + ) becomes higher. 11. Reducing the activation energy of catalytic processes 12. Changing the density of states of a catalyst 13. Changing the Gibbs free energy of an equilibrium process 14. To increase the enthalpy of a reaction, thereby making the reaction easier to carry out. a. Entropy effect b. Higher order 15. High current density and / or high temperature at the tip.

[0175] As can be seen, the surface structures protruding from the supporting substrate create three-dimensional (3D) structures on the array.

[0176] In one embodiment, the surface structure(s) are integral with the support substrate. This means that the surface structure(s) are formed of and protrude from the same material as the support substrate. In this embodiment, the top surface of the support substrate can comprise an array of surface structures arranged in a regular or random configuration. In this embodiment, the electrocatalyst may be formed / deposited on the top surface of the surface structure (and the support substrate to which it is exposed), or the electrocatalyst may be the same material as the surface structure and / or the support substrate. The support substrate with integrated surface structures may be formed by known methods, such as hot embossing, CFT processing, injection molding, forging, electroforming, lithography, and other similar techniques.

[0177] In an alternative embodiment, the surface structure is formed from a different material than the support substrate and is deposited or attached onto the support substrate. In this embodiment, the surface structure may be integral with the electrocatalyst, meaning that the surface structure is part of the electrocatalyst and is formed from the same material as the electrocatalyst.

[0178] Alternatively, the electrocatalyst may be deposited or otherwise formed on a surface structure, which is deposited on, integrated with, or otherwise formed on a supporting substrate. Support substrates having surface structure(s) formed from various materials may be formed by known methods, for example, hot embossing, CFT processing, laser processing of photoresist, forging or lithography techniques, and deposition techniques such as growth or evaporation of carbonaceous materials.

[0179] It is particularly preferred that the electrode catalyst can be deposited or otherwise formed on the surface structure. The inventors have found that this is cost-effective because less catalyst needs to be used. The catalyst is often an expensive material such as platinum and / or gold. The ability to use a small amount of catalyst is highly beneficial. The inventors have found that using a small amount of catalyst still results in the same or even better performance than a planar electrode using much more catalyst.

[0180] The present invention also, or alternatively, allows for the substitution of an active but typically more expensive catalyst with a less expensive catalyst that is less active under standard conditions. For example, if cost is a consideration, the catalyst may be copper, titanium, or nickel instead of platinum, palladium, rhodium, iridium, or gold. It is believed that the increased efficiency of electron transfer from the surface structures to the activator allows for the use of lower-cost catalysts, such as nickel, to replace more expensive catalysts, such as platinum. Furthermore, the amount of catalyst concentrated at the tips, peaks, ridges, and / or edges of the surface structures, and the amount of extraneous catalyst that might otherwise be located on other structural features or in the valleys between structures, is minimized, again resulting in cost savings even when more expensive catalyst materials are used. The cost and activity of various catalysts are shown in Table 1. [Table 1]

[0181] In some embodiments, the cross-sectional area of ​​the surface structure decreases along an axis perpendicular to the upper surface of the support substrate. In some embodiments, the upper portion of at least one surface structure has a convex upper surface. In more preferred forms, the surface structure has a triangular, convex, semicircular, or nipple-shaped cross-section along a plane perpendicular to the upper surface of the support substrate.

[0182] The top of the surface structure preferably has an angle of about 90° or less at the apex, e.g., the surface structure points to a point. It is believed that the sharper the angle, i.e., the sharper the point, the greater the effect on the electrocatalyst. In some embodiments, the surface structure is pyramidal, conical, ridged, or a combination thereof. In some embodiments, the surface structure has a substantially triangular, substantially circular, or substantially square cross section along a plane parallel to the top surface of the support substrate.

[0183] In a preferred embodiment, the surface structures are uniformly distributed on the support substrate, although this can be varied as needed. Uniformity is preferred as it provides more predictable behavior and results. Also, the amount of catalyst is restricted to a limited area above the tip. This allows for consistent catalyst activity and high product purity.

[0184] In some embodiments, a catalyst can be controllably deposited on a functional surface (such as an edge, a top, a tip, a top, and / or other surfaces of a surface structure) by exposing the functional surface to one or more of, but not limited to, electroplating, electroforming, electrodeposition, sputtering, e-beam, vapor deposition, thermal evaporation, plasma deposition.

[0185] In some embodiments, controlled deposition can be performed by varying one or more of the following deposition parameters, including, but not limited to, voltage, current, time (residence time of the functional surface exposed to the deposition technique, e.g., time immersed in the electroplating solution), pulse rate (such as electrodeposition pulse rate), and passivation layer (such as using a passivation layer to expose a partial surface of the surface structure, which can, for example, change the current density of electrodeposition). It will be understood that any of the fabrication techniques described herein can be used to control the deposition of catalysts, such as lithographic masking, SAMs, etc.

[0186] The surface structures are preferably substantially uniform in size. As the inventors have shown, the size of the surface structures affects the activity of the catalyst and the redox reaction product. A uniform surface structure size is preferred because it results in a more predictable and reproducible product. The size of the surface structures can be selected based on the desired product or product ratio. The product produced can also be substantially homogeneous.

[0187] In exemplary embodiments, the surface structure and catalyst may be tailored to provide for the production of substantially a predetermined primary or preferred product. Alternatively, the surface structure and catalyst may be tailored to provide for the production of one or more predetermined products, e.g., a preferred or primary product, and a secondary product (which may also be preferred). Similarly, the surface structure and catalyst may be tailored to minimize the production of non-preferential products.

[0188] The surface structures preferably have at least one line of symmetry, and more preferably have at least two lines of symmetry, which is preferred to allow the conductive solution to surround the tips of the surface structures.

[0189] The width of the surface structure at which the surface structure is bonded to the support substrate is, in some embodiments, about 20 nm to about 5000 μm, and in some embodiments, about 40 nm to about 4000 μm, about 55 nm to about 3000 μm, about 75 nm to about 2500 μm, about 100 nm to about 4000 μm, about 250 nm to about 3500 μm, about 20 nm to about 3500 μm, about 2 nm to about 4000 μm, about 20 nm to about 2500 μm, about 20 nm to about 4000 μm, about 20 nm to about 3000 μm, or about 20 nm to about 2000 μm. In some embodiments, the width is about 5 nm to about 750 μm, about 5 nm to about 500 μm, or about 5 nm to about 100 μm. Nanostructures are particularly preferred, although microstructures may also be beneficial depending on the desired product.

[0190] The functional surface is preferably at or near the top of the surface structure. While the entire surface structure may be made of electrocatalytic material, the top or tip is considered to be the functional surface, providing the majority of the catalytic effect for the redox reaction. Preferably, electrochemical activation of the catalyst occurs at a substantially faster rate at the functional surface than activation occurs at other surface locations on the electrocatalytic layer.

[0191] In some embodiments, the functional surface is located at or around the top of the surface structure, and the surface structure is tapered toward the top and / or has a substantially triangular cross-section along a plane parallel to the top surface of the support substrate. In some embodiments, the functional surface is located at or around the top of the surface structure, and the width of the top of each surface structure is about 1 nm to about 5000 μm, and in some embodiments, about 10 nm to about 10 μm, or about 20 nm to about 2 μm, or about 30 nm to about 1 μm. In some embodiments, the width is about 1 nm to about 1000 nm, or about 1 nm to about 500 nm, or about 1 nm to about 100 nm, or about 1 nm to about 50 nm. The width of the top of each surface structure is smaller than where it joins the support substrate.

[0192] In some embodiments, the peaks of the surface structures are separated from one another by a peak-to-peak distance of about 5 nm to about 1000 μm, about 10 nm to about 1000 μm, about 25 nm to about 1000 μm, about 5 nm to about 750 μm, about 5 nm to about 500 μm, or about 5 nm to about 100 μm. In some embodiments, the peak-to-peak distance is about 5 nm to about 2000 nm, about 5 nm to about 1000 nm, or about 5 nm to about 500 nm.

[0193] The surface structure(s) of any of the embodiments herein should be understood to encompass any suitable surface features that effectively increase the relative surface area and / or provide an array of peaks or points compared to a planar smooth area of ​​comparable dimensions. The size, shape, density, uniformity, arrangement, and proportions of the elemental portions of the array of surface structures may vary from the illustrated embodiment.

[0194] In one embodiment, the surface structures can have a uniform shape and / or geometry, density and / or size. The surface structures may be shaped, sized, and / or provided at a specific density according to predetermined characteristics, such as providing a number or size of peaks or tips for a particular solution to be catalyzed, or a desired peak or tip shape, size, density, or uniformity, as needed.

[0195] In alternative embodiments, the surface structures may be provided with non-uniform sizes, shapes, and / or densities. For example, the surface structures may comprise protrusions of uniform protrusion height and shape but varying spacing or density. Alternatively, the surface structures may comprise varying heights but uniform shapes and spacing or density. It will be appreciated that any variation in the shape, size, and / or density of the surface structures can be provided to facilitate specific reactions or catalysis by providing a peak or tip, or an array of peaks or tips, that function as a functional surface, or by having a functional surface formed thereon.

[0196] Examples of surface structure shapes can be substantially conical, cylindrical, or pyramidal, pointed, spiked, square, pentahedral, flat-top pentahedral, pentagonal, or hexagonal. In preferred embodiments, any shape that creates a peak or tip suitable for acting as or receiving a functional surface for catalysis can be used.

[0197] In preferred embodiments, a uniform array of surface structures can advantageously provide substantially uniform product or solution catalytic results, which can be attributed to the uniform size and shape of the ridges, peaks, and / or tips of each surface structure, providing a uniform current density across the peaks or tips of each surface structure.

[0198] In an alternative embodiment, a non-uniform array of surface structures can advantageously provide the ability to generate multiple products or catalytic results from a solution. This can be due to the different sizes of the apexes or tips of the variously shaped surface structures in such a non-uniform array, which can result in different current densities at the apexes or tips. For example, a first group of surface structures can be uniform in size, and a second group, which is different in size from the first group, can also be uniform in size within the second group.

[0199] 1 illustrates an embodiment of the present invention in which an electrocatalyst array 400 comprises a supporting substrate 410, a surface structure 415, and a functional surface 420. The functional surface is formed from an electrocatalyst (e.g., Pt, Au, Ni), which is activated via electrochemical modification by applying a current or voltage between the electrocatalyst and a counter electrode.

[0200] The array optionally comprises a catalyst on the peaks of the surface structures and a co-catalyst in the valleys between the surface structures.

[0201] In some embodiments, the active species are electrochemically modified after contact with the functional surface, and the thermodynamic and kinetic efficiency of the electrochemical modification is improved compared to a corresponding planar electrode.

[0202] In some embodiments, the electrocatalytic array constitutes part of a system. The system includes appropriate wiring, seals, electrodes, and solutions that allow the sample to contact the functional surface and electrochemically modify the active species. The system preferably includes a reservoir, channel (e.g., in or for an electrode stack configuration), or other container for holding the conductive solution on the functional surface. The array system also preferably further includes a reference electrode and a counter electrode configured to contact the conductive solution during the redox reaction. Preferably, the reference electrode and / or counter electrode are stationary and at a fixed distance from the functional surface. Suitable systems and configurations will be known to those skilled in the art.

[0203] Those skilled in the art will appreciate that an electrocatalytic array ("working electrode") can function as an anode, where an oxidation reaction occurs, or as a cathode, where a reduction reaction occurs. The term "working electrode" is often used in the art to describe the electrode where the reaction of interest occurs. However, a counter electrode is required to balance the redox charge. For example, if oxidation occurs at the working electrode, reduction will occur at the counter electrode.

[0204] In some embodiments, a counter electrode can also be used to carry out useful redox reactions. In such cases, the counter electrode can be a planar or array structure. In some embodiments, the counter electrode comprises a supporting substrate and a surface structure, as described in connection with the electrocatalyst array. All features of the surface structure described herein in connection with the electrocatalyst can be applied to the counter electrode. The surface structure of the counter electrode can be the same size and / or geometry as the electrocatalyst, or can be a different size and / or geometry than the electrocatalyst.

[0205] Alternatively, the counter electrode of any embodiment of the present invention comprises a substantially inert conductive material. In this case, the term inert means that the mass and state of the counter electrode do not substantially change after the establishment and passage of a current from the electrocatalyst to the counter electrode. Thus, an "inert" counter electrode is substantially unreactive with the components of the solution. Preferably, the counter electrode is formed from a material selected from the group consisting of metal, Pt, gold, nickel, copper, iron, carbon, graphite, graphene, carbon fiber, carbon nanotubes, fullerenes, conductive polymers PPy, PA, polyacetylene, and stainless steel. The counter electrode may be fabricated from a conductive layer deposited on a solid layer or a suitable support, such as a polymer, glass, or metal. The counter electrode may be fabricated from a conductive layer deposited on a solid layer or a suitable support, such as a polymer, glass, or metal. Preferably, the counter electrode is bare metal (such as Au, Pt, stainless steel, and / or copper) or an Au- or Pt-plated substrate (such as a metal, polymer, and / or glass). Preferably, the counter electrode of any embodiment of the present invention is in a fixed orientation relative to the surface structure.

[0206] Preferably, the counter electrode of any embodiment of the present invention is attached to an electrode array.

[0207] Preferably, the counter electrodes are held in an orientation that minimizes the difference in distance between each of the surface structures of the array. Preferably, the counter electrodes are oriented above the top surface of the array. In these embodiments, the distance from the counter electrodes to the top of each surface structure is substantially equidistant. This minimizes detection noise due to the placement of the counter electrodes.

[0208] Therefore, the counter electrode is preferably either (a) in a fixed orientation relative to the surface structure, (b) attached to the electrode array, (c) held in an orientation that minimizes the difference in distance between each surface structure, or (d) on top of the array.

[0209] In one embodiment, the solution further comprises a reference electrode, which aids in measuring and controlling the voltage while the current is flowing, for example, during the deposition process. The properties and placement of the reference electrode will be known to those skilled in the art.

[0210] Preferably, the electrode array further comprises a reference electrode in contact with the solution. Preferably, the reference electrode comprises an electrode formed from Ag / AgCl. Other options would include a standard hydrogen electrode (SHE), a normal hydrogen electrode (NHE), a reverse hydrogen electrode (RHE), a dynamic hydrogen electrode (DHE), a standard calomel electrode (SCE), a copper-copper(II) sulfate electrode (CSE), a mercury-mercury sulfate electrode, Pt, stainless steel, or Au.

[0211] Preferably, the current established between the electrocatalyst and the counter electrode measured at the electrocatalyst is an oxidation or reduction current, which facilitates the electrochemical modification of the active species after contact with the functional surface of each surface structure.

[0212] Preferably, the current includes a reduction or oxidation potential between the counter electrode and the electrode surface. Preferably, the potential is about −2 V to +2 V, about −200 mV to −1 V, or about −400 mV relative to a silver / silver chloride reference electrode.

[0213] Preferably, the current in any embodiment of the present invention is pulsed between an activation potential and a deactivation potential. This pulsing allows for localization of the reaction occurring at the functional surface. Pulsing also maximizes the amount of active species attached to the top of each surface structure and minimizes the diffusion of active species from the top of each surface structure into the solution. The pulsing frequency and its duty cycle define the extent of localization of the functional surface. Regular on / off cycling results in deactivation of the active species, thus minimizing the spread of activated active species from the functional surface to other locations on the array.

[0214] Before the current is applied, the sensate remains inactive and active species present in the solution cannot bind to the sensate. Application of an activation potential increases the charge density (voltage or current) at the functional surface, thus activating any active species that diffuse to the functional surface.

[0215] Thus, the current in any embodiment of the present invention is pulsed between an activation potential and an inactivation potential.

[0216] The entire disclosures of all applications, patents and publications, cited above and below, if any, are hereby incorporated by reference.

[0217] The reference herein to any prior art is not, and should not be construed as, an acknowledgment or any form of implication that that prior art forms part of the common general knowledge in the field of endeavor in any country in the world.

[0218] The present invention may also be broadly described as consisting of the parts, elements and features referred to or shown in the specification of this application, individually or collectively, any or all combinations of two or more of said parts, elements or features.

[0219] Where the foregoing description has referred to components having wholes or their known equivalents, those wholes are incorporated herein as if individually set forth.

[0220] It should be noted that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present invention and without diminishing its attendant advantages. Accordingly, such changes and modifications are intended to be included within the scope of the present invention. [Example]

[0221] material PBS pallets, K3FeCN6, K4FeCN6, K2PtCl4 and thiols were purchased from Sigma Aldrich and used as received.

[0222] The electrodes used in these experiments were gold-coated polycarbonate, and the electrode array was made from polycarbonate embossed with a series of pyramids. The micropyramid structures had a tip-to-tip (top-to-bottom) spacing of 70 μm and a base of 50 μm x 50 μm. The tip size was 1-5 microns. The height of the micropyramid was approximately 35 microns.

[0223] The nanopyramids were purchased as nickel stampers and consisted of a series of tips measuring 250 nm at the base and approximately 3-10 nm at the tip. The spacing between tips (from the top of one surface feature to the top of the next) was approximately 250 nm, and the tip size ranged from 3-10 nm. The height of the nanopyramids was approximately 250 nm.

[0224] Electrochemical studies Electrochemical studies were performed using a Pine E-chem bipotentiostat station via a three-electrode setup with platinum as the counter electrode. All electrochemical potentials presented in this work are measured and reported using a leak-free Ag / AgCl miniature reference electrode (eDAQ). The electrochemical cell was confined by a cylindrical bore Teflon cone (4 mm inner diameter) pressed against the sample. All measurements were performed at room temperature without air exclusion.

[0225] Self-assembled monolayer (SAM) formation The deposition solution was prepared by dissolving the desired amount of alkanethiol in ethanol. The total thiol concentration was maintained between 0.1 and 1 mM. Freshly prepared gold substrates were immersed in the deposition solution for 24 hours. Deposition was performed in the absence of light to eliminate any photon oxidation on the thiol monolayer. The substrates were then rinsed with ethanol and deionized water to remove excess adsorbate and dried with N2 to remove residual solvent.

[0226] Example 1 - Removal of SAM at the tip Objective: To demonstrate that the charge density (voltage or current) distribution of an electrode array bearing a surface structure can be used to selectively remove self-assembled monolayers from the top of the surface structure.

[0227] Methods: The SAM-coated electrode was immersed in PBS solution. Desorption was performed by chronoamperometry by applying a reducing potential (-1.1V for cumulative durations of 0, 2.5, 5, 10, 20, 40, 80, 160, 320, 640, and 900 seconds), and the desorption rate was monitored using cyclic voltammetry of KFeCN at 20 mV / s.

[0228] Results: The gold-coated surface structure on the electrode array confirmed a faster desorption profile, with the maximum oxidation peak occurring after approximately 10 seconds (Fig. 2a) compared to the planar electrode, where the maximum oxidation peak was observed after approximately 20–30 minutes (Fig. 2b).

[0229] Conclusion: The differential charge density (voltage or current) distribution on three-dimensional surfaces resulted in significantly faster desorption of SAMs from the tips of surface structures compared to planar surfaces (Figure 2c). This occurred due to the concentration of charge density (voltage or current) at or near the top of the surface structures. This provides an opportunity to modify the functional surface of the electrocatalyst or to expose only the tips, i.e., the functional surface of the electrocatalyst.

[0230] Example 1b - SU8 passivation layer Objective: To demonstrate that the distribution of charge density (voltage or current) in an electrode array can be increased by applying a photoresist coating to the valleys between the tips.

[0231] Methods: Gold-coated electrodes were spin-coated with SU8 at 2000-5000 rpm and cross-linked by UV exposure to provide a passivation layer thickness ranging from 10 μm to 30 μm.

[0232] Results: As a result of the current concentration, platinum was electrochemically reduced to the exposed tip, which formed as a series of nanoparticles (see Figure 3).

[0233] Conclusion: The differential charge density (voltage or current) was enhanced by the passivation layer, inducing the formation of nanoparticles instead of films, which can enhance catalytic activity.

[0234] Example 2: Pt functionalization at the tip Objective: To demonstrate that the differential charge density (voltage or current) distribution of an electrode array with surface structures can be used to selectively deposit metal on top of the structures.

[0235] Method: Surface structures with gold electrocatalytic layers were cleaned using reactive ion etching (RIE) with O2 plasma (2 min) and then immersed in a solution of platinum(IV) chloride (1 mM) in PBS. Pt mesoparticle growth was performed using a square-wave potential as follows: a reduction potential (-500 mV) was applied to reduce the Pt(II) on the surface to Pt(0) for 15 s, followed by an oxidation potential (300 mV) to stop the process. This cycle was continued until the desired amount of deposited Pt was achieved.

[0236] Results: As shown in Figures 4a and 4b (without passivation layer) and Figure 3 (with SU8 passivation layer), Pt deposition occurred primarily at or near the top of the surface structure.

[0237] Conclusion: Due to the high distribution of charge density (voltage or current) at or near the top of the surface structure, Pt is deposited at a higher density than on other surfaces. This provides an opportunity to modify the functional surface of the electrocatalyst.

[0238] Example 3: Nanoscale Catalysis and Mechanism Modification by Transition Metals Objective: To demonstrate that the three-dimensionality of electrocatalysts alters the mechanism of reactions and the efficiency of their conversion to products by minimizing electron "leakage" through by-product formation, which can reduce catalytic efficiency and lead to the production of reactive and damaging by-products.

[0239] Methods: A four-electrode system (Pt, HO collector working electrode 2, and Au electrode as O reduction catalyst working electrode 1) was used with Pt as the counter electrode and Ag / AgCl as the reference electrode to measure the level of hydrogen peroxide produced during the oxygen reduction reaction using planar, micropyramidal, and nanopyramidal structured surfaces. The height of the collector (Pt) was calibrated by lowering the Pt working electrode until it reached the surface of the Au electrode. From this baseline, it was raised to a distance of 200 μm. Cyclic voltammograms were performed at the gold electrode while the Pt electrode was held at an oxidation potential sufficient for HO oxidation. The efficiency of O reduction was then evaluated as the ratio of the Pt current to the Au current.

[0240] Results: Results for various gold electrodes (as shown in Figure 5b): flat, micropyramid, micropyramid separated by an inert layer between the pyramid tips (referred to in the figure as pyramid lacquer), and nanopyramid at pH 13 are shown in Figure 5a. Typically, under these conditions, gold is known to produce pure HO (hydrogen peroxide) in electrochemical O reduction in alkaline media. Therefore, hydrogen peroxide would be the expected product of this type of reaction. Introducing three-dimensionality, particularly nanostructures and, to a lesser extent, microstructures, unexpectedly alters the behavior of the mechanism by moving from a two-electron reduction (100% HO) to a four-electrode reduction (100% HO). This was only apparent when measuring the recovery of hydrogen peroxide.

[0241] The above examples (shown in Figures 5 and 5a) demonstrate that varying the size and / or shape of the 3D structures can lead to the generation of different products from the catalytic process, e.g., O2 to peroxide or water. This also applies to all of the following examples: N2 to NH3, NO3 to N2, CO2 to HCOOH, etc.

[0242] The tip size selected depends on the desired product: smaller feature sizes result in more efficient conversion to the final product and a higher concentration of high energy products, especially if multiple products are considered.

[0243] The apex and / or tip and / or edge of the structure (functional surface) is believed to be one of the most important factors in determining the activity of the electrocatalyst. It is believed that the size of the apex section and / or tip can be used to select the desired redox product. In general terms, the sharper, smaller or more acute the angle of the apex or apexes (or edges) and / or tip, the greater the current and voltage focusing and the higher the catalyst turnover.

[0244] Conclusion: The surface topography of the electrocatalyst leads to dramatic changes in the reaction mechanism.

[0245] Example 4: Electrocatalytic reduction of CO Objective: To demonstrate the versatility of nanoscale electrocatalysis by CO2 reduction.

[0246] Methods: A three-electrode system was used, with the nanostructured Au surface as the working electrode, Pt as the counter electrode, and Ag / AgCl as the reference electrode. The solution was first degassed by purging with Ar gas, and background measurements were performed by cyclic voltammetry. CO2 was then introduced by vigorous bubbling, and the CO2 reduction activity was measured by cyclic voltammetry.

[0247] Results: The results are shown in Figure 6. In Figure 6, a significant current was observed when CO2 was introduced, resulting in the formation of CO and methanol.

[0248] Conclusion: The electrocatalyst used here demonstrated the capability for CO2 reduction.

[0249] Example 5: Electrocatalytic reduction of O2 by Pt Objective: To demonstrate that the three-dimensionality of mechanistically efficient electrocatalysts enhances catalytic activity while reducing the energy cost (thermodynamic) of the process and increasing its kinetic efficiency.

[0250] Methods: Pt catalyst (30 nm) was sputtered onto the surfaces of flat surfaces, micropyramids, and nanopyramids. A three-electrode system was used to measure the O2 reduction activity of each surface, using a Pt wire as the counter electrode and Ag / AgCl as the reference electrode. Cyclic voltammograms were performed on the Pt-coated electrode. The efficiency of O2 reduction was then evaluated by the onset potential (a measure of thermodynamic gain) and maximum current (a measure of kinetics).

[0251] Results: Results for various Pt-coated electrodes are shown in Figure 21. We observed a significant shift in onset potential in the order planar < micropyramid < nanopyramid surface. This trend (planar < micropyramid < nanopyramid) was also observed in the relative currents generated.

[0252] Conclusion: Surface topography of electrocatalysts provides dramatic improvements over heterogeneous catalysis in both energy cost and catalytic reaction rate.

[0253] Example 6: pH Dependence, Tafel, and Concentration Dependence of Ascorbic Acid Aim: To demonstrate the generality of potential shifts under various conditions.

[0254] Methods: A three-electrode system was used, with a pyramidal Au surface as the working electrode, a Pt counter electrode, and an Ag / AgCl reference electrode. Ferrocene was immobilized on both the planar and pyramidal electrodes using differential current distribution electrochemical surface modification. Experiments were performed to ensure equivalent surface coverage of ferrocene on both the planar and pyramidal electrodes (Figure 7a). Electrochemical conversion of 1 (Figures 7a and b) and 100 mM sodium ascorbate was performed over a pH range of 1 to 14.

[0255] Results: Ferrocene is known to promote the oxidation of ascorbate when incorporated into a SAM-modified gold electrode. The oxidation of ascorbic acid is known to be a two-electron, two-proton oxidation process yielding a single product. As a result, there is an expected pH shift during the oxidation process. When ferrocene was attached to N3-C11SH / C10SH, the current rose, peaked, and then decreased, indicating a diffusion-limited process. Enhanced catalytic performance was observed for both hydrogen production and oxygen reduction using a significant reduction in the voltage required to initiate the oxidation process (Figure 8a). This catalytic improvement is observed across all pH units.

[0256] The Tafel plot clearly showed a decrease in both the thermodynamic cost and the exchange current density (Fig. 7b).

[0257] Conclusion: 3D geometries differentiate electrochemical activity at the tip from the base, even for the same material. Catalysis is improved by reducing the activation energy, thereby reducing the energy cost of conversion and improving the rate at which reactions occur in different environments.

[0258] Example 7: O2 reduction by Au electrodes Methods: A three-electrode system was used, with a pyramidal Au surface as the working electrode, a Pt counter electrode, and an Ag / AgCl reference electrode. Cyclic voltammetry was performed on the gold electrode in O2-saturated perchloric acid.

[0259] Results: Results for the planar and micropyramidal surfaces at pH 1 are shown in Figure 8. At this pH, Au is known to reduce O2 to water with four electrons and four protons. By introducing three-dimensionality, the onset potential is dramatically reduced, and two peaks are observed: one at a low overpotential at the apex, followed by one at a high overpotential in the planar region.

[0260] Conclusion: The surface topography of the electrocatalyst leads to dramatic improvements over heterogeneous catalysis in both energy cost and catalytic reaction rate (Figure 8).

[0261] Example 8: Mass activity of catalysts under steady state conditions Objective: To study the effect of three-dimensionality on the mass activity of catalysts.

[0262] Methods: A three-electrode system was used with a pyramidal structure. Pt was electrodeposited onto the pyramidal microstructure as in Example 2, and a planar Au electrode was placed in a 5 mm insert used for the rotating disk electrode. Cyclic voltammograms were performed at 1600 rpm in O2-saturated perchloric acid.

[0263] Results: Similar thermodynamic shifts were observed for O2 reduction at 1600 rpm as in the case of static surfaces (Figure 9).

[0264] Conclusion: Rotation improves mass transport of O2 to the electrode, minimizing the enhancement produced by a three-dimensional surface. Thus, rotating disk electrode experiments allowed a direct comparison of mass activity on both planar and 3D surfaces, without being influenced by diffusion effects.

[0265] Example 8: Catalytic activity of Pt / C with three-dimensionality Objective: To study the electrocatalytic enhancement of three-dimensionality of Pt / C in the current state-of-the-art technology.

[0266] Methods: 10% Pt / C ink was prepared from a previously reported procedure. 10 μL of ink was drop-cast onto planar and nanopyramid surfaces. O2 reduction activity was then performed in an O2-saturated NaOH solution. Results: A significant improvement in the catalytic activity of Pt / C was observed on the three-dimensional platform (Figure 10) compared to planar surfaces.

[0267] Conclusion: Three-dimensionality can be used to improve the catalytic performance of existing materials.

[0268] Example 9: Conversion of nitrate to nitrogen Objective: To apply the 3D catalytic surface to the reduction of nitrate.

[0269] Methods: A three-electrode system was used with nanopyramid-structured Au surface as the working electrode, Pt as the counter electrode, and Ag / AgCl as the reference in PBS buffer. CVs were performed with and without the addition of 6 mmol of sodium nitrate.

[0270] Results: Addition of sodium nitrate to the solution resulted in a peak in the CV at approximately -0.85 mV compared to Ag / AgCl (Figure 11). Holding the voltage at -0.8 mV released an odorless gas, which was believed to correspond to nitrogen.

[0271] Conclusion: The CV clearly shows a peak corresponding to the reduction of nitrate. Although the exact identity of the released gas has not yet been obtained, the fact that it is odorless rules out the formation of ammonia and supports the production of nitrogen.

[0272] Example 10: Enhanced kinetics of electron transfer to ferrocene through a monolayer Objective: To demonstrate the enhancement of the kinetics of electron transfer (KET) to ferrocene SAMs immobilized on three-dimensional surfaces versus planar surfaces.

[0273] Methods: Mixed self-assembled monolayers (SAMs) composed of equimolar 1-decanethiol and an azide-terminated monolayer with an 11-carbon chain were formed on sputtered planar and pyramidal gold surfaces. A three-electrode system was used with a Pt wire as the counter electrode and an Ag / AgCl reference electrode to attach ferrocene to the surfaces via chronoamperometry. Cyclic voltammograms at different scan rates were performed on the electrodes to evaluate the electron transfer mechanism on the planar and pyramidal surfaces.

[0274] Results: Results for pyramidal (a) and planar (b) surfaces at neutral pH are shown in Figure 12. We observed faster electron transfer using the pyramidal surface, as evidenced by the smaller difference in peak-to-peak splitting between the oxidation and reduction peak potentials as a function of scan rate (Figure 13). These results demonstrate easier movement for electrons to jump between the chemical species and the microstructured electrode surface, while the planar surface exhibited slower rates throughout the experiment.

[0275] Conclusion: The surface topography of the electrode leads to a dramatic improvement in the electron transfer kinetics by reducing the required energy cost.

[0276] Example 11: Electrocatalytic reduction of O2 by Pt through rotating disk electrode (RDE) experiments Objective: To demonstrate that three-dimensionality produces kinetic enhancement and maintains steady-state mass transport conditions using (RDE).

[0277] Methods: Both planar and pyramidal electrodes (5 mm disks) were prepared as in Example 5, where Pt catalyst was sputtered. The three-electrode system used a Pt wire as the counter electrode and Ag / AgCl as the reference electrode. The O2 reduction activity of each surface was measured by cyclic voltammetry at rotation speeds of 400, 900, 1600, 2500, 3600, and 4900 rpm (Figure 14). The efficiency of O2 reduction was then evaluated by the onset potential, maximum current, and the Koutecky-Levich equation (Figure 15).

[0278] Results: Results for the Pt-coated micropyramid electrode are shown in Figure 15. We observed a significant shift in the onset potential as the rotation rate increased, accompanied by higher currents at both surfaces due to reduced mass transfer within the system. The Koutecky-Levich equation shows a similar slope with the pyramidal electrode exhibiting higher electron transfer.

[0279] Conclusion: The surface topography of the electrocatalyst leads to dramatic improvements in both energy cost and catalytic kinetics over heterogeneous catalysis using three-dimensional pyramidal electrodes.

[0280] Example 12: Representative fabrication of gold-coated 3D polycarbonate arrays (Figure 16) Inverted pyramid arrays were fabricated on silicon (Si) wafers by modifying a previously reported anisotropic wet etching methodology. In this report, inverted pyramid array microstructures were fabricated using silicon nitride (Si3N4) in three steps (Figure 16): photolithography was used to define the pyramid bases (50 μm × 50 μm) and spacing (75 μm tip-to-tip). The Si3N4 layer was isotropically etched using buffered hydrofluoric acid, followed by anisotropic etching of the Si using a KOH solution. Anisotropic etching using an alkaline etchant (30% KOH) resulted in the formation of an array of inverted pyramid microstructures at a 54.7° angle. This angle depends on the orientation of the crystal planes and varies from material to material. It is noted that achieving a controlled etching rate over a large area was difficult, and reproducibility was poor due to the complex wet etching parameters.

[0281] A polished Si wafer coated with Si3N4 (resistivity of 4-7 Ω·cm) was cleaned with isopropanol. AZ nLOF2070 negative photoresist was then spin-coated onto the wafer at 3000 rpm to obtain a thickness of 6.5 μm. The resist was then baked on a hotplate at 110 °C for 60 seconds. After cooling to room temperature, the substrate was transferred to a mask aligner (model) and irradiated with UV light (180 mJ / cm) through a square array patterned mask. 2 ) to define the size and spacing of the inverted array. The substrate was then re-baked at 110 °C for 60 seconds. After cooling to room temperature, the photoresist was developed by exposure to AZ326 MIF for 60 seconds, and the surface was then rinsed with deionized water and dried under a stream of nitrogen. The integrity of the lithography process was then inspected using an optical microscope after an additional cure at 140 °C for 5 minutes.

[0282] To minimize overetching, the photoresist pattern was etched into the Si3N4 layer using a buffered hydrogen fluoride solution for 8 hours. The wafer was then rinsed with copious amounts of deionized water. After rinsing, residual photoresist was removed with acetone, rinsed with deionized water, and dried under a stream of nitrogen. Next, the inverted pyramid array microstructures were etched through the Si3N4 mask by anisotropic etching. This was achieved by immersing the wafer in a mixture of 30% aqueous KOH and 16% isopropanol at 70 °C for 75 minutes with constant agitation at 300 rpm. Under these conditions, the Si substrate etched at approximately 60 microns per hour. The wafer was then rinsed with copious amounts of deionized water, dried under a stream of nitrogen, and examined by scanning electron microscopy (SEM) (Figure 17a).

[0283] A Ni stamper with an inverted pyramidal array was prepared from a Si master by two sequential electroforming processes using a previously reported methodology. The first inversion was performed by sputtering a thin layer of Ni (100 nm) onto the Si master of the inverted pyramidal array (3 mTorr argon atmosphere, 200 W for 180 seconds). The Ni-coated substrate was then immediately immersed in a nickel sulfamate solution containing nickel chloride. A direct current (DC) of 2.7 A was then applied to the Ni-coated Si cathode (0.015 cm). 2 Electric current was applied between the Ni-coated Si master and the Ni anode at 55 °C for 12 hours. During electroforming, the cathode (Ni-coated Si master) was rotated at 60 rpm to ensure uniform and continuous electrodeposition. When the thickness of the Ni pyramidal array reached approximately 350 μm, the power supply was switched off, and the electroformed Ni was separated from the Si master, rinsed with copious amounts of water, and dried under a stream of nitrogen. The Ni pyramidal array was then inspected by SEM. A second Ni-to-Ni inversion was performed by repeating the above electroforming process to obtain an inverted pyramidal array Ni stamper (Figure 17b).

[0284] An inverted pyramid array Ni stamper was stamped into polycarbonate using a hot embossing machine (YPL-NIL-SI402 customized model, Wu Xi Imprint Nano Tech. Ltd.). A sheet of PC (0.5 mm thick) was placed on top of the Ni stamper, sandwiched between two polished stainless steel plates, and placed in the embossing chamber with the heater facing the Ni side of the stack. The imprint was performed under vacuum (1.5 × 102 Pa) at 220 °C and 1.5 MPa / cm. 2 The embossing was performed at a pressure of 0.05 MPa for 15 minutes. The substrate was then cooled to room temperature, and the embossed polycarbonate was separated and examined under an optical microscope. The polycarbonate substrate was then immediately coated with gold using a direct current magnetron sputtering machine (Torus Sputtering Machine, Kurt J. Lesker) at 200 W under a 3 mTorr argon atmosphere with rotation for 180 seconds, ensuring uniform deposition to a thickness of approximately 60 nm (Figure 17c).

[0285] Example 13: Hydrogen generation by Pt particles on planar and 3D electrodes Objective: To demonstrate that three-dimensionality creates improved catalytic performance for catalysts located at the apex of the tip.

[0286] Methods: K2(PtCl4) (6 mmol) in PBS buffer was electrochemically deposited onto both planar and 3D SAM-coated electrodes using chronoamperometry at -0.4 V versus Ag / AgCl.

[0287] Results: This method deposited Pt as particles on both planar and 3D electrodes (see Table 2). On the planar electrode, the particles were relatively evenly distributed across the entire electrode surface, whereas on the 3D electrode, the Pt particles were located only on top of the peaks and ridges. Table 2 details the parameters for the Pt-coated electrode and the current densities obtained for the reduction of water to produce hydrogen.

[0288] Conclusion: These results show that Pt particles located on top of the tip are over 100 times more active than those located at the apex. The large difference in current density per platinum area indicates that the activity of the platinum molecules on the structure is 130 times greater than the activity of the same platinum molecules on a planar electrode. The current density can be considered as equal to the activity of the catalyst and the production rate of hydrogen production.

[0289] The data in Table 2 are for micron-sized pyramids; nano-sized pyramids have significantly greater turnover. [Table 2]

[0290] Example 14: Conversion of Nitrogen to Ammonia Objective: To apply the 3D catalytic surface to the reduction of nitrogen.

[0291] Methods: A three-electrode system was used with nanopyramid-structured Au surfaces as the working electrode, Pt as the counter electrode, and Ag / AgCl as the reference in PBS buffer. CVs were performed with and without the addition of nitrogen to the solution.

[0292] Results: Upon addition of nitrogen gas, a clear yet reversible deviation in the CV was observed, as shown in Figure 19. This was believed to correspond to the production of ammonia, as confirmed by the appearance of a peak at 420 nm in the UV-Vis spectrum.

[0293] Conclusion: The CV clearly shows peaks corresponding to the reduction of nitrogen. Although the exact identity of all products has not yet been fully confirmed, the appearance of peaks in UV-Vis supports the formation of ammonia.

[0294] Example 15: Hydrogen gas generation at planar and 3D electrodes Objective: To demonstrate that three-dimensionality results in more gas production than planar electrodes, with finer structures resulting in greater production. Also, 3D structures generate bubbles that are efficiently and consistently cleared from the surface of the 3D electrode, with smaller features resulting in smaller bubbles.

[0295] Methods: K2(PtCl4) (6 mml) in PBS buffer was electrochemically deposited onto both planar and 3D SAM-coated electrodes using chronoamperometry at -0.4 V versus Ag / AgCl. The electrodes were set up in the cell shown in Figure 18 to allow hydrogen production of both 50 μm and 250 nm pyramids for comparison against planar electrodes.

[0296] Results: The setup also allowed us to investigate the bubbling rate and relative size of the bubbles, confirming that the 3D surface effectively removes hydrogen from the tip and does not interfere with fabrication.

[0297] Conclusion: These results demonstrated that 3D surfaces overcome one of the major limitations of hydrogen gas generation and efficiently remove hydrogen from the surface.

[0298] Example 16: Conversion of CO to CO and formic acid Objective: To apply 3D catalytic surfaces to the reduction of CO2.

[0299] Methods: A three-electrode system was used with nanopyramid-structured Au surfaces as the working electrode, Pt as the counter electrode, and Ag / AgCl as the reference in PBS buffer. CVs were performed with and without the addition of CO2 in argon to the solution.

[0300] Results: Upon addition of CO2 gas, a clear yet reversible deviation in the CV was observed, as shown in Figure 20A. Headspace analysis confirmed that this corresponded to the production of CO2 and the appearance of a CO2-myoglobin complex in the UV-Vis (Figure 20B), and formic acid due to the appearance of a peak at 320 nm in the UV spectrum (Figure 20C).

[0301] Conclusion: The CV clearly shows peaks corresponding to the reduction of nitrogen. Although the exact identity of all products has not yet been fully confirmed, the appearance of peaks in UV-Vis supports the formation of ammonia.

[0302] Example 17: Stability of Pt-coated nanopyramid arrays with redox cycling Objective: To demonstrate the stability of Pt-coated nanopyramid arrays under prolonged catalytic conditions using cyclic voltammetry.

[0303] Methods: A Pt catalyst (30 nm) was sputtered onto the nanopyramid surface. A three-electrode system was used, with a Pt wire as the counter electrode and an Ag / AgCl as the reference electrode. The surface was cycled continuously from 200 mV to -300 mV at 10 mV / s for 500 cycles to reduce O2 in a pH 13 solution.

[0304] Results: Figure 22 showed no measurable decrease in Pt activity as the maximum O2 reduction current remained constant at -300 mV.

[0305] Conclusion: Long-term cyclic voltammetry showed no signs of degradation at the surface. If the catalyst had degraded, one would observe a decrease in the catalytic current towards the underlying Ni substrate.

[0306] Example 18: Stability of Pt-coated nanopyramid arrays with constant current Objective: To demonstrate the stability of Pt-coated nanopyramid array electrodes under prolonged catalytic conditions using chronoamperometry.

[0307] Methods: A Pt catalyst (30 nm) was sputtered onto the surface of the nanopyramids. A three-electrode system was used, with a Pt wire as the counter electrode and Ag / AgCl as the reference electrode. A reduction potential of -150 mV was applied for 2.5 days to continuously reduce O2 in a pH 13 solution.

[0308] Results: Figure 23 showed no measurable decrease in Pt activity as the maximum O2 reduction current remained constant at -5 mA.

[0309] Conclusion: The surface showed no signs of degradation during the long catalytic process.

[0310] Example 19: Control of catalyst deposition Objective: To demonstrate that the 3D structure allows the deposition of a controlled amount of catalyst onto the tip.

[0311] Method: Surface structures with a gold layer were cleaned using reactive ion etching (RIE) with O2 plasma (2 min) and then immersed in a solution of platinum(IV) chloride (1 mM) in PBS. Pt mesoparticle growth was performed using a square-wave potential as follows: a reduction potential (-500 mV) was applied to reduce the Pt(II) on the surface to Pt(0) for 15 s, followed by an oxidation potential (300 mV) to stop the process. This cycle was continued until the desired amount of deposited Pt was achieved.

[0312] Results: As shown in Figure 24 (for 5 pulses (Figure 24A) and 10 pulses (Figure 24B)), Pt deposition occurred primarily at or near the top of the surface structure. As shown in the figure, the amount of Pt deposited clearly increases proportionally with the number of pulses at and around the tip.

[0313] Conclusion: The ability to precisely place and control the amount of catalyst is important for minimizing the catalyst material that needs to be deposited on a surface and therefore minimizing the manufacturing costs of the catalyst system.

[0314] Without wishing to be bound by theory, it is believed that the present invention is based on one or more of the following non-limiting concepts. Exchange current density It is an important kinetic parameter that describes the rate of an electrochemical reaction at equilibrium and determines how quickly an electrochemical reaction can occur. The exchange current density of an electrochemical reaction depends on the reaction and the electrode surface on which the electrochemical reaction occurs, and is therefore related to the true electrode area and the reactant concentration. The 3D surface has a higher exchange current density than a planar electrode. Electron Transfer Coefficient It is defined as the proportion of electrostatic potential energy that influences the reduction rate in an electrode reaction. 3D surfaces have higher electron transfer coefficients than planar surfaces. activation energy Reducing activation reduces the energy cost of a given catalytic process, thereby reducing thermodynamic costs 3D surfaces have a lower overpotential than planar surfaces.

[0315] In conclusion, the results are The smaller tip dimensions indicate a greater effect at the tip both with and without an additional catalytic coating. The tip size makes it ideal for application in a microfluidic setting for both catalytic separation and recombination of a range of carbon-, oxygen-, and nitrogen-containing species. It is expected that the MF environment will improve reaction rates and the overall efficiency of the conversion. A range of catalytic processes can be set up using both microfluidic and non-microfluidic setups. Furthermore, aspects of the invention disclosed in this specification include aspects described in the following clauses. <Clause> [Article 1] 1. A method for selecting an electrocatalyst array based on a desired product outcome, said method comprising: exposing the electrocatalytic system to an activator dissolved or suspended in a conductive solution; applying a voltage to the electrocatalytic system; the voltage is sufficient to cause a multi-electron oxidation or multi-electron reduction of the active species; the electrocatalytic system comprising: a counter electrode; 1. An electrocatalytic array comprising: A support substrate; uniformly sized surface structures protruding from a surface of the support substrate; the uniformly sized surface structures have edges and / or peaks that include a catalyst; an electrocatalytic array; a first product ratio is produced when the uniformly sized surface structures are of a micrometer scale, and a second product ratio is produced when the uniformly sized surface structures are of a nanometer scale, wherein the first and second product ratios are different; The method, wherein the second product ratio requires a higher electronic process than does producing the first product ratio. [Clause 2] 10. The method of claim 1, wherein the first product is hydrogen peroxide when the active species is oxygen and the uniformly sized surface structures are of a micrometer scale. [Article 3] 3. The method of clause 1 or clause 2, wherein the first product is water when the active species is oxygen and the uniformly sized surface structures are of nanometer scale. [Article 4] 4. The method according to any one of clauses 1 to 3, wherein the width of the nanometer-scale surface structure bonded to the support substrate is from about 25 nm to about 50,000 nm. [Article 5] 5. The method according to any one of clauses 1 to 4, wherein the width of the nanometer-scale surface structure bonded to the support substrate is from about 5 μm to about 500 μm. [Article 6] 6. The method of claim 4 or 5, further comprising a passivation layer deposited between the surface structures to provide a predetermined exposure of the surface structures. [Article 7] 6. The method of clause 4 or 5, further comprising a passivation or inert layer deposited between the surface structures to facilitate adjustment of the product ratio. [Article 8] 8. The method of clause 7, wherein the inert or passivating layer is deposited to a thickness that adjusts the relative ratio of products between the second product ratio and the first product ratio. [Article 9] 9. The method of claim 8, wherein the greater the thickness of the inactive or passivating layer or the greater the thickness, the closer the relative ratio approaches the first product ratio. [Article 10] 10. The method of clause 9, wherein the relative ratio between the first product ratio and the second product ratio is adjusted according to the relative thickness or height of the passivation or passivation layer. [Article 11] 11. The method of any one of clauses 6 to 10, wherein the thickness of the passivation layer is about 5% to about 95% of the height of the surface structures. [Article 12] 12. The method of any one of clauses 1-11, wherein the counter electrode comprises a counter electrode support substrate and uniformly sized counter electrode surface structures protruding from a counter electrode surface of the counter electrode support substrate. [Article 13] 1. A method for catalyzing a redox reaction of an active species in a conductive solution, said method comprising: exposing the electrocatalytic system to said active species; applying a voltage to the electrocatalytic system; the voltage is sufficient to cause a multi-electron oxidation or multi-electron reduction of the active species; the electrocatalytic system comprising: a counter electrode; 1. An electrocatalytic array comprising: A support substrate; uniformly sized surface structures protruding from a surface of the support substrate; the uniformly sized surface structures have edges and / or peaks that include a catalyst; an electrocatalytic array. [Article 14] 1. A method for catalyzing gas formation from activated species in a conductive solution, the method comprising: exposing the electrocatalytic system to said active species; applying a voltage to the electrocatalytic system; the voltage is sufficient to cause a multi-electron oxidation or multi-electron reduction of the active species; the electrocatalytic system comprising: a counter electrode; 1. An electrocatalytic array comprising: A support substrate; and uniformly sized surface structures protruding from a surface of the support substrate, an electrocatalytic array, wherein the uniformly sized surface structures have catalyst-containing edges and / or peaks; The method, wherein the rate of gas formation is increased by at least 1.5 times compared to the same electrocatalyst array without the uniformly sized surface structures protruding from the surface of the support substrate. [Article 15] 15. The method of claim 14, wherein the rate of gas formation is increased by 1.5 to 1000 times. [Article 16] 1. A method for catalyzing an electrochemical redox reaction of an active species in a conductive solution, said method comprising: a. providing an electrocatalytic array, said electrocatalytic array comprising: i. a support substrate; ii. a surface structure protruding from the support substrate, the surface structure comprising an electrocatalyst; iii. providing an electrocatalyst array comprising a functional surface on the electrocatalyst, the functional surface being on top of the surface structure, the functional surface being adapted to contact active species in the conductive solution; b. exposing the surface structure to the solution containing the counter electrode therein; c. establishing a current or voltage between the electrocatalyst and the counter electrode such that a charge density (voltage or current) is concentrated at the functional surface and the active species undergoes the redox reaction following contact with the functional surface. [Article 17] 17. The method of claim 16, wherein the surface structures are uniformly sized and have substantially the same shape. [Article 18] 18. The method of any one of clauses 1 to 17, wherein the surface structure is of the same material as the support substrate. [Article 19] 19. The method of any one of clauses 1 to 18, wherein the catalyst is deposited on top of a surface structure and is a different material from the surface structure. [Article 20] 20. The method of clause 19, wherein the electrocatalyst is deposited on less than about 50% to less than about 0.000001% of the surface of the array when viewed from above. [Article 21] 1. A method for catalyzing an electrochemical redox reaction of an active species in a conductive solution, said method comprising: a. providing an electrocatalytic array, said electrocatalytic array comprising: i. a support substrate; ii. a surface structure protruding from the support substrate, the surface structure comprising an electrocatalyst; iii. providing an electrocatalyst array comprising a functional surface on the electrocatalyst, the functional surface being on top of the surface structure, the functional surface being adapted to contact active species in the conductive solution; b. exposing the surface structure to the solution so as to contain a counter electrode therein; c. establishing a current or voltage between the electrocatalyst and the counter electrode such that a charge density (voltage or current) is concentrated on the functional surface and the active species undergoes the redox reaction following contact with the functional surface; The redox reaction Oxygen generation from water Hydrogen generation from protons, Hydrogen oxidation to water, hydrogen oxidation to protons, oxygen reduction to water, oxygen reduction to peroxides, The reaction of carbon dioxide to carbon monoxide The reaction from carbon dioxide to methanol Reaction of carbon dioxide to carboxylic acid (e.g., formic acid), Reaction of carbon dioxide to aldehydes and / or ketones, Reaction of carbon dioxide to methane, ethane, propane, and / or higher carbon chains up to C21, Methane oxidation to methanol, Reaction of nitrogen to hydrazine, The reaction of nitrogen to ammonia Decomposing ammonia into hydrogen and nitrogen; The reaction from methane to methanol The reaction from nitrate to nitrogen, A method selected from the reaction of converting nitrates to ammonia. [Article 22] 22. The method of clause 21, wherein the redox reaction includes several steps in which intermediates are not isolated. [Article 23] 23. The method of claim 21 or 22, wherein the surface structure is of the same material as the support substrate. [Article 24] 24. The method of any one of clauses 21 to 23, wherein the electrocatalyst is deposited on top of the surface structure and is a different material from the surface structure. [Article 25] 25. The method of clause 24, wherein the electrocatalyst is deposited on less than about 50% to less than about 0.000001% of the surface of the array when viewed from above. [Article 26] 1. A method for catalyzing gas formation from activated species in a conductive solution, comprising: exposing the electrocatalytic system to said active species; applying a voltage to the electrocatalytic system; the voltage is sufficient to cause a multi-electron oxidation or multi-electron reduction of the active species; the electrocatalytic system comprising: a counter electrode; 1. An electrocatalytic array comprising: A support substrate; uniformly sized surface structures protruding from a surface of the support substrate; the uniformly sized surface structures have edges and / or peaks that include a catalyst; an electrocatalytic array; The method, wherein the rate of gas formation is increased by at least 1.5 times compared to the same electrocatalyst array without the uniformly sized surface structures protruding from the surface of the support substrate. [Article 27] 1. A method for generating gas from an electrode, said method comprising: exposing the electrode to a conductive solution containing an active species; applying a voltage to the electrodes sufficient to reduce or oxidize the active species to produce a gas; The electrode is 1. A nanostructured array comprising: A support substrate; pyramidal surface structures protruding from the support substrate; each of the pyramidal surface structures having a base, an apex, and an edge between the base and the apex; the base is in contact with the support substrate; the base has a longest side dimension of 50 nm to about 4000 μm, an apex of about 1 nm to about 50 nm, and a distance between adjacent apexes of about 50 nm to 1000 nm; The method wherein the edge and top include a catalyst. [Article 28] 28. The method of claim 27, wherein the gas is hydrogen, oxygen, or both hydrogen and oxygen. [Article 29] 29. The method of claim 27 or 28, wherein the gas is hydrogen, nitrogen, or both hydrogen and nitrogen. [Article 30] 30. The method of any one of clauses 27 to 29, wherein the gas is ammonia.

Claims

1. 1. A method for catalyzing an electrochemical redox reaction of an active species in a conductive solution, said method comprising: a. providing an electrocatalytic array, said electrocatalytic array comprising: i. a support substrate; ii. a surface structure protruding from the support substrate, the surface structure having an electrocatalyst formed thereon; iii. Providing an electrocatalyst array comprising a functional surface on the electrocatalyst, the functional surface being on top of the surface structure, the functional surface being adapted to contact active species in the conductive solution; b. exposing the surface structure to the conductive solution containing the counter electrode therein; c) establishing a current or voltage between the electrocatalyst and the counter electrode such that a charge density (voltage or current) is concentrated at the functional surface and the active species undergoes the redox reaction following contact with the functional surface; the uniformly sized surface structures have edges and / or peaks; the electrocatalyst is deposited on the top surface of the surface structure, the material of the electrocatalyst being different from the material of the surface structure; the electrocatalyst is deposited on the tips of the surface structures; the electrocatalyst is deposited on the edges and / or the top of the surface structure; the electrocatalyst is deposited on 0.000001% to 50% of the surface of the electrocatalyst array when viewed from above; The method, wherein the surface structure is only partially covered by the electrocatalyst, and at least a portion of the surface structure is contactable with the conductive solution.

2. 10. The method of claim 1, wherein the surface structure(s) are one or more of the following: i. at the same or different heights from the surface of the supporting substrate; ii. of the same or different geometric shape relative to other surface structure(s); iii. Regular or irregular geometric shapes; iv. Evenly or unevenly spaced; v. of the same or different density; vi. A population of a plurality of surface structures comprising a plurality of surface structures of any one of i to v.

3. The method of claim 1 or 2, wherein the surface structures are uniform in size and have substantially the same shape.

4. The method of any one of claims 1 to 3, wherein the surface structure is of the same material as the supporting substrate.

5. The method of any one of claims 1 to 4, wherein the surface structure is integral with the supporting substrate.

6. The redox reaction is a two or more electron process, or the redox reaction is a four or more electron process, or the redox reaction is a six or more electron process, or The method of any one of claims 1 to 5, wherein the redox reaction is an eight or more electron process.

7. 7. The method according to claim 1, wherein the functional surface is at or around the apex of the surface structure, and the width of the apex of each surface structure is between 1 nm and 5000 μm.

8. 10. The method of claim 1, wherein the voltage is sufficient to cause a multi-electron oxidation or multi-electron reduction of the active species; a first product is generated when the uniformly sized surface structures are on a micrometer scale, and a second product is generated when the uniformly sized surface structures are on a nanometer scale; the first product and the second product are different; 10. The method of claim 1, wherein the production of the second product requires a higher order electronic process compared to the production of the first product.

9. 9. The method of claim 8, wherein the width of the micrometer-scale surface structure where the surface structure joins with the support substrate is 5 μm to 500 μm and / or the width of the nanometer-scale surface structure where the surface structure joins with the support substrate is 25 nm to 5000 nm.

10. 1. A method of catalyzing gas formation, comprising: the voltage being sufficient to cause a multi-electron oxidation or multi-electron reduction of the active species; 10. The method of claim 1, wherein the rate of gas formation is increased by at least 1.5 times compared to the same electrocatalyst array without the uniformly sized surface structures protruding from the surface of the supporting substrate.

11. 8. The method of any one of claims 1 to 7, wherein the redox reaction comprises several steps in which the intermediates are not isolated.

12. The method of any one of claims 1 to 7, wherein the redox reaction is selected from one or more of the following: Hydrogen generation from water, Oxygen generation from water Hydrogen generation from water, Hydrogen generation from protons, Hydrogen oxidation to water, hydrogen oxidation to protons, Hydrogen oxidation to hydrogen peroxide, oxygen reduction to water, oxygen reduction to peroxides, The reaction of carbon dioxide to carbon monoxide The reaction from carbon dioxide to methanol Reaction of carbon dioxide to carboxylic acid (e.g., formic acid), Reaction of carbon dioxide to aldehydes and / or ketones, Reaction of carbon dioxide to methane, ethane, propane, and / or higher carbon chains up to C21; Methane oxidation to methanol, Reaction of nitrogen to hydrazine, The reaction of nitrogen to ammonia Decomposing ammonia into hydrogen and nitrogen; The reaction from methane to methanol The reaction from nitrate to nitrogen, Reaction of nitrates to ammonia.

13. The method of any one of claims 1 to 12, wherein the electrocatalyst comprises a transition metal, an alloy, an organometallic complex, an organometallic complex containing a transition metal, or an organic material that can be oxidized or reduced.

14. 14. The method of any one of claims 1 to 13, wherein the dimensions of the uniformly sized surface structures are selected to modify the redox product recovered as a result of the electrochemical redox reaction.

15. 15. The method of any one of claims 1 to 14, wherein a first product or a first product ratio is generated when the surface structures are of a micrometer scale, and a second product or a second product ratio is generated when the surface structures are of a nanometer scale, and the first product and the second product, and the first product ratio and the second product ratio are different, respectively.

16. 16. The method of claim 15, wherein the second product requires a higher order electronic process compared to the production of the first product.

17. The method of any one of claims 1 to 16, wherein the electrocatalyst comprises a transition metal, an alloy, an organometallic complex, an organometallic complex containing a transition metal, or an organic material that can be oxidized or reduced.

18. 18. The method of any one of claims 1 to 17, wherein the active species are electrochemically modified after contact with the functional surface, and the thermodynamic and kinetic efficiency of the electrochemical modification compared to a planar electrode is increased compared to a corresponding planar electrode.

19. 19. The method of any one of claims 1 to 18, wherein electrochemical activation of the electrocatalyst occurs at the functional surface at a faster rate than activation occurs at other surface locations on the electrocatalyst array.

20. 20. The method of any one of claims 1 to 19, wherein the activation energy required to drive the redox reaction is reduced compared to a similar flat plate electrocatalyst.

21. The method according to any one of claims 1 to 20, wherein the nanometer-scale surface structure has a width or length of 25 nm to 5000 nm at a portion that bonds with the support substrate, or the micrometer-scale surface structure has a width or length of 5 μm to 500 μm at a portion that bonds with the support substrate.

22. 22. The method of claim 21, wherein the activation energy required to drive a redox reaction when the nanometer-scale surface structures are used is reduced compared to the activation energy required to drive a redox reaction when the micrometer-scale surface structures are used.

Images