Paired electrosynthesis process for (combined) production of hydroxylamine and ammonia

Abstract

The present invention relates to a paired electrosynthesis process for the production of hydroxylamine (HA) and / or ammonia from N2 or air and water (in combination). The invention also provides an electrolytic cell developed for the above-mentioned object, comprising a porous cathode and an anode with an active catalyst layer and based on a continuous flow process. The method and the electrolytic cell according to the invention are particularly suitable for the efficient conversion of reactants such as NO3-, NO2-, NOx and N2 at the cathode and anode.

Description

Technical Field

[0001] The present invention relates to N 2 A paired electrosynthetic method for producing hydroxylamine (HA) and / or ammonia from oxygen or air and water (combined). The present invention also provides an electrolyzer developed for the above purpose, comprising a porous cathode and an anode with an effective catalyst layer and based on a continuous flow process. The method and electrolyzer of the present invention are particularly suitable for effectively converting reactants such as NO at the cathode and anode. 3 - 、NO 2 - , NOx and N 2 . Background Art

[0002] The electrosynthesis of nitrogen species such as ammonia and HA is promising in view of the storage of renewable energy and the electrification of the chemical industry. Specifically, the current ammonia production, due to the Haber-Bosch process using fossil fuels, generates a large amount of CO 2 Emissions. When renewable electricity is used, nitrogen dioxide / NO 3 - The electrochemical reduction of 2 Sustainable ammonia synthesis process with low emissions. In addition, the production of HA is important for the production of caprolactam, a precursor for nylon-6. Since the wastewater stream contains nitrates and nitrites, the wastewater stream can also be used for the electrochemical production of ammonia and / or HA.

[0003] However, the current electrochemical nitrogen reduction reaction (NRR) technology faces the problem of poor product selectivity, resulting in the generation of NH 3 Or the amount of HA product is very small. In addition, due to the small amount of product generated, it is impossible to accurately confirm N 2 or NO 3 - or NO 2 - The conversion rate of HA has been questioned, and the reliability of many experiments in this field has been questioned. 3 RR) can still only be realized on a laboratory scale using intermittent cells.

[0004] Therefore, currently N 2 The main bottlenecks of electrosynthesis of nitrogen species from ammonia or air and water are: (1) poor selectivity of electrocatalysts; and (2) the electrochemical system (electrodes, membranes, reactors) is not suitable for long-term (continuous) operation, which is ultimately required for an economically viable process. Both factors limit the expected / achievable current or production rates of ammonia and HA, hindering the applicability, operation, and scale-up of this process.

[0005] The object of the present invention is to solve the above problems and to provide a method for effectively converting reactants such as NO 3 - 、NO 2 - , NOx and N 2 As described in further detail below, the electrochemical flow cell provided herein and the method implemented herein can realize the conversion of N-containing nitrogen into industrially valuable nitrogen species such as ammonia and HA. 2 In the prior art, a separate nitrogen oxidation unit is required. Alternatively, a common nitrogen-containing gas can be used at the cathode and anode. 2 Gas. In conventional nitrogen-containing fertilizer production systems, such as provided in PCT Publication WO 2012 / 051507, the anode system is based on the supply of hydrogen-containing gas, and thus an integrated system for the combined synthesis of ammonia and HA cannot be provided. Summary of the invention

[0006] In a first aspect, the present invention provides a method for electrosynthesizing NH 3 An electrochemical flow reactor for the production of hydroxylamine (HA) and / or hydroxylamine (HA), the reactor comprising a metal electrocatalyst-based porous gas diffusion electrode (GDE) as a cathode and an anode.

[0007] In one embodiment, the electrochemical flow cell reactor is characterized in that the metal electrocatalyst is selected from bismuth / molybdate, bismuth / tin-based catalysts, copper-based catalysts, ruthenium-based catalysts, platinum-based catalysts, cobalt-based catalysts, nickel-based catalysts, palladium-based catalysts, iron-based catalysts, titanium-based catalysts, tungsten-based catalysts, cobalt / iron / zinc / oxide alloy-based catalysts, iron / tin alloy-based catalysts and combinations or alloys thereof.

[0008] In a particular embodiment, the metal electrocatalyst of the cathode is different from the metal electrocatalyst of the anode. Thus, in one embodiment, the metal electrocatalyst of the cathode is selected from bismuth / molybdate-based catalysts, bismuth / tin-based catalysts, copper-based catalysts, ruthenium-based catalysts, platinum-based catalysts, cobalt-based catalysts, nickel-based catalysts, palladium-based catalysts, and combinations thereof; and the metal electrocatalyst of the anode is selected from ruthenium and ruthenium / manganese oxide-based catalysts, platinum-based catalysts, palladium-based catalysts, cobalt / iron / zinc / oxide alloy-based catalysts, rhodium-based catalysts, tungsten-based catalysts, iron / tin alloy-based catalysts, (supported) boron-doped diamond, (supported) nitrogen-doped carbon, and combinations thereof.

[0009] In a preferred embodiment, the metal electrocatalyst of the cathode is selected from bismuth / molybdate alloys, bismuth / tin alloys, copper, platinum / ruthenium alloys, platinum / tin alloys, cobalt, nickel and palladium; more specifically, the metal electrocatalyst of the cathode is selected from bismuth / molybdate alloys, copper, platinum / ruthenium alloys, platinum / tin alloys, cobalt, nickel and palladium; even more specifically, the metal electrocatalyst of the cathode is selected from bismuth / molybdate alloys, copper, platinum / ruthenium alloys, platinum / tin alloys, cobalt and nickel.

[0010] In another preferred embodiment, the metal electrocatalyst of the anode is selected from platinum, ruthenium / titanium alloy, palladium, cobalt / iron / zinc / oxide alloy, iron / tin alloy and palladium / ruthenium alloy; more specifically, the metal electrocatalyst of the anode is selected from platinum, ruthenium / titanium alloy, ruthenium / manganese oxide alloy, rhodium, cobalt / iron / zinc / oxide alloy, iron / tin alloy, palladium / ruthenium alloy, (supported) boron-doped diamond, (supported) nitrogen-doped carbon; even more specifically, the metal electrocatalyst of the anode is selected from platinum, ruthenium / titanium alloy, cobalt / iron / zinc / oxide alloy, iron / tin alloy and palladium / ruthenium alloy.

[0011] Electrochemical flow cell reactors typically include an anode chamber and a cathode chamber separated by an ion exchange membrane, or a single chamber system in which the cathode and anode are not separated from each other. Those skilled in the art are aware of ion exchange membrane separators used in electrochemical flow cell reactors, including cation exchange membranes, anion exchange membranes, and bipolar membranes. A metal electrocatalyst-based porous GDE is used as an anode and a cathode, and the anode chamber and the cathode chamber preferably each include an electrolyte chamber and a gas chamber, which are separated from each other by a metal electrocatalyst-based porous GDE, and the gas in the gas chamber is designed to reach the metal electrocatalyst of the GDE, wherein the metal electrocatalyst layer is designed to contact the electrolyte in the electrolyte chamber.

[0012] In one embodiment, the electrolyte chamber of the anode chamber and the electrolyte chamber of the cathode chamber contain a common electrolyte (alkaline or acidic electrolyte, especially alkaline), wherein the outlet of the electrolyte chamber of the anode chamber is fluidically connected to the inlet of the electrolyte chamber of the cathode chamber. In this way, a continuous flow of electrolyte can be achieved. 3 In the electrochemical synthesis of HA, the gas chamber of the anode chamber and the gas chamber of the cathode chamber both contain nitrogen-containing gas (such as N 2 ,NO,NO 2 、N 2 O and their mixtures), especially dinitrogen (N 2 ) Gas inlet for gas.

[0013] In another aspect, the present invention provides a method for electrosynthesizing NH from a nitrogen-containing gas in pairs. 3 and / or hydroxylamine (HA) in an electrochemical flow cell reactor, wherein dinitrogen (N 2) is oxidized at the anode to form NOx and nitrate (NO 3 - ) and / or nitrite (NO 2 - ), wherein the nitrate-containing (NO 3 - ) is fed into the electrolyte chamber of the cathode chamber, and the cathode is heated by nitrogen (N) in the nitrogen-containing gas from the gas chamber of the cathode chamber. 2 ) is reduced to form ammonia (NH 3 ) and / or hydroxylamine (HA), and removing the thus obtained ammonia (NH 3 ) and / or hydroxylamine (HA) electrolytes.

[0014] In one embodiment, the electrochemical flow cell reactor further comprises a separator for separating the ammonia (NH 3 ) and / or hydroxylamine (HA) electrolyte recovery ammonia (NH 3 ) and / or hydroxylamine (HA), and the electrolyte is circulated back to the electrolyte compartment of the anode compartment.

[0015] In a second aspect, the present invention provides a method for electrosynthesizing NH in pairs in an electrochemical flow cell reactor. 3 and hydroxylamine (HA), the reactor comprising an anode chamber and a cathode chamber separated by an ion exchange membrane, the method comprising:

[0016] ·Use metal electrocatalyst-based porous gas diffusion electrode (GDE) as anode to oxidize dinitrogen (N 2 ), forming nitrate (NO 3 - ) and / or nitrite (NO 2 - ) or forming NOx in the gas chamber of the anode chamber,

[0017] The nitrate-containing (NO 3 - ) / nitrite (NO 2 - ) / NO x The electrolyte is fed into the electrolyte compartment of the cathode compartment,

[0018] ·Use metal electrocatalyst-based porous gas diffusion electrode (GDE) as cathode, 3 - ) in the electrolyte (NO 3 - ) / nitrite (NO 2- ) using nitrogen (N 2 ) is reduced to form ammonia (NH 3 ) and hydroxylamine (HA), and

[0019] The thus obtained ammonia (NH 3 ) and hydroxylamine (HA) electrolyte.

[0020] In one embodiment, the paired electrosynthesis of NH 3 and / or hydroxylamine (HA) further comprising:

[0021] ·From ammonia (NH 3 ) and hydroxylamine (HA) to separate ammonia (NH 3 ) and hydroxylamine (HA), and

[0022] • Circulate the electrolyte back into the electrolyte compartment of the anode compartment.

[0023] In one embodiment, the paired electrosynthesis of NH 3 The method of producing and / or hydroxylamine (HA) is characterized in that the metal electrocatalyst of the cathode is selected from bismuth / molybdate-based catalysts, copper-based catalysts, ruthenium-based catalysts, platinum-based catalysts, cobalt-based catalysts, nickel-based catalysts, palladium-based catalysts and combinations thereof; and wherein the metal electrocatalyst of the anode is selected from ruthenium-based catalysts, platinum-based catalysts, palladium-based catalysts, cobalt / iron / zinc / oxide alloy-based catalysts, iron / tin alloy-based catalysts and combinations thereof. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Attached Figure 1 (also referred to here as Figure 1 ) provides a method for producing NH 3 Schematic diagram of the paired electrosynthesis method of / HA. DETAILED DESCRIPTION

[0025] As described above, the present invention specifically relates to 2 A paired electrosynthetic method for producing hydroxylamine (HA) and / or ammonia from air and water (combined). To this end, the present invention provides a continuous flow method and a continuous electrochemical flow reactor with porous electrodes at the anode and cathode, wherein each porous electrode contains a metal electrocatalyst layer.

[0026] refer to Figure 1 As described in detail below, such a continuous electrochemical flow reactor includes a membrane or diaphragm that separates the anode and cathode chambers, and incorporates metal electrocatalyst layers into gas diffusion electrodes (GDEs) on each side to enhance mass transfer and increase electrochemically active surface area.

[0027] Since it is difficult to obtain suitable nitrate (NO 3 - ) source (wastewater can be used, but the concentrations of nitrate and nitrite in wastewater are usually too low to produce large amounts of ammonia and / or HA). So far, electrochemical methods for HA and / or ammonia synthesis have been technically impeded by the following obstacles:

[0028] Very low current density, especially at the cathode (hence low productivity),

[0029] NRR electrocatalysts have poor product selectivity for HA or ammonia,

[0030] The anodic reaction (usually the oxygen generation reaction) results in a high overpotential (and therefore low energy efficiency),

[0031] Long process duration due to the interaction of processes occurring simultaneously at both electrodes and the passage of substances through the membrane, and

[0032] Stability of electrode structure.

[0033] The paired electrosynthesis method and continuous electrochemical flow reactor of the present invention solve this problem. A paired electrosynthesis method is applied, wherein the anode reaction produces nitrate, nitrite and / or NOx, which are then used as reactants for the cathode reaction to produce NH 3 and / or HA, thereby solving the above-mentioned suitable nitrate (NO 3 - ) source problem. In the reactor of the present invention, N-containing 2 - Gases such as air, or even gaseous reactants such as NOx, can be used, optionally with liquid reactants or solvents such as NO 3 - 、NO 2 - and N 2 H 4 ) electrolyte. A paired electrosynthesis process is applied, in which the anode reaction produces nitrate, nitrite and / or NOx, which are then used as reactants in the cathode reaction to produce NH 3 or HA, which also leads to a decrease in the battery potential, thereby improving energy efficiency. 2 and NO 3 - or NO 2 - The synergistic effect of the co-reduction at the cathode, which can be controlled by the potential window, leads to high product yields of HA and / or ammonia compared to the prior art.

[0034] In other words, the present invention utilizes the anode reaction product to produce HA and ammonia in a paired electrosynthesis concept. Although it has been reported that NRR electrodes can be used to produce ammonia, there is no indication in the literature that only ammonia or HA can be co-produced with 100% selectivity. Nitrogen oxidation has not been electrochemically implemented in a continuous flow cell, which is the key to our anode reaction. Therefore, the purpose of the present invention is to apply nitrogen oxidation, i.e., the electrochemical nitrogen oxidation reaction (NOR), in the electrochemical synthesis of ammonia and / or hydroxylamine, and more specifically, to apply NOR in a continuous flow cell structure in the electrochemical synthesis of ammonia and / or hydroxylamine. Therefore, the present invention uses the product obtained by nitrogen oxidation at the anode as a reactant for the cathode reaction to generate NH 3 Therefore, in one embodiment, the present invention uses the product obtained by oxidation of nitrogen at the anode as a reactant for the cathode reaction in a continuous flow cell to produce NH 3 and / or HA, more specifically, used as reactants in the cathode reaction in a continuous flow cell to produce NH 3 and / or HA.

[0035] Figure 1 The schematic diagram provides a paired electrosynthesis of ammonia and / or HA using the anode reaction product as a reactant for cathode reduction in a continuous electrochemical flow cell reactor (1). The electrochemical flow cell reactor comprises an anode chamber (2) and a cathode chamber (3) separated from each other by an ion exchange membrane (4). Both the anode chamber and the cathode chamber are configured as continuous flow cells and respectively comprise electrolyte chambers (5, 6) containing a common electrolyte (20) (in this case an alkaline electrolyte), and gas chambers (7, 8) separated from each other by metal electrocatalyst-based porous GDEs (9, 10). The GDE of the anode chamber (9) is designed to allow the N-containing gas in the gas chamber (7) to be 2 The gas (13) reaches the metal electrocatalyst layer (11) of the anode, which is in contact with the alkaline electrolyte (20) of the anode electrolyte chamber (5). At the interface between the liquid alkaline electrolyte and the metal electrocatalyst layer (11) of the anode, nitrogen is oxidized to form nitrate (NO 3 - ) / nitrite (NO 2 - The nitrate-containing (NO 3 - ) is fed to the electrolyte chamber of the cathode cell (6) via a fluid connection (19). In the cathode chamber (3), there is another GDE (10) designed to allow the N-containing gas in the gas chamber (8) to 2 The gas (14) reaches the metal electrocatalyst layer (12) of the cathode, which reacts with the nitrate-containing (NO 3- ) is in contact with an alkaline electrolyte (21). 3 - ) at the interface between the alkaline electrolyte (21) and the metal electrocatalyst layer (12) of the cathode, dinitrogen (N 2 ) and / or nitrate / nitrite are reduced to form ammonia (NH 3 ) and / or hydroxylamine (HA). 3 ) and / or hydroxylamine (HA) is removed from the cathode electrolyte chamber (6) through the outlet (18). The double arrows indicate a separator for removing the ammonia (NH 3 ) and / or hydroxylamine (HA) in an alkaline electrolyte (22) to separate ammonia (NH 3 ) and / or hydroxylamine (HA), and it is possible to recycle the alkaline electrolyte (20) back to the electrolyte compartment of the anode (5). The circulation of the alkaline electrolyte (20) is an optional step of the disclosed method. In addition, the separator used only represents the separation of the ammonia (NH 3 ) and / or hydroxylamine (HA) in an alkaline electrolyte (22) to obtain a reaction product ammonia (NH 3 ) and / or hydroxylamine (HA) in any possible method and steps.

[0036] In this schematic diagram, the alkaline electrolyte is an aqueous alkaline electrolyte, so that the electrochemical flow cell reactor can also be used as an electrolyzer, in which oxygen (O 2 ), and hydrogen (H 2 ). However, these side reactions can be minimized by selective electrocatalysts and by choosing the optimal reaction conditions (potential, electrolyte composition, etc.). Moreover, the formation or consumption of NOx gases cannot be excluded on either side.

[0037] abbreviation

[0038] CL-catalyst layer

[0039] GDE - Gas Diffusion Electrode

[0040] GDL - Gas Diffusion Layer

[0041] HA-Hydroxyamine

[0042] HER - Hydrogen Generation Reaction

[0043] NRR - Electrochemical Nitrogen Reduction Reaction

[0044] NOR - Electrochemical Nitrogen Oxidation Reaction

[0045] NO 3 RR-Electrochemical Nitrate Reduction Reaction

[0046] NO 2 RR-Electrochemical Nitrite Reduction Reaction

[0047] OER - Oxygen Evolution Reaction

[0048] ORR - oxygen reduction reaction

[0049] Reference numerals

[0050] 1-Electrochemical flow cell reactor

[0051] 2- Anode chamber, also called anode cell

[0052] 3-Cathode chamber, also called cathode cell

[0053] 4-Membrane

[0054] 5- Electrolyte compartment of anode cell

[0055] 6-Cathode battery electrolyte compartment

[0056] 7-Gas chamber of anode cell

[0057] 8-Gas chamber of cathode cell

[0058] 9-GDE of anode battery or anode GDE

[0059] 10-Cathode battery GDE or cathode GDE

[0060] 11-Metal electrocatalyst layer of anode GDE

[0061] 12-Metal electrocatalyst layer of cathode GDE

[0062] 13-Gas inlet of anode cell gas chamber

[0063] 14-Gas inlet of cathode cell gas chamber

[0064] 15-Electrolyte inlet of the electrolyte chamber of the anode cell

[0065] 16-Electrolyte outlet of the electrolyte chamber of the anode cell

[0066] 17-Electrolyte inlet of the electrolyte chamber of the cathode cell

[0067] 18-Electrolyte outlet of electrolyte chamber of cathode cell

[0068] 19- Fluid connections between electrolyte chambers

[0069] 20-Alkaline Electrolyte

[0070] 21-containing nitrate (NO 3 -) / nitrite (NO 2 - ) of alkaline electrolyte

[0071] 22-containing ammonia (NH 3 ) and / or hydroxylamine (HA) alkaline electrolyte

Claims

1. An electrochemical flow reactor designed for electrosynthesis of NH3 and / or hydroxylamine (HA) in pairs, the reactor comprising: -Metal electrocatalyst-based porous gas diffusion electrodes (GDE) as cathode and anode, - an anode chamber and a cathode chamber each comprising an electrolyte chamber and a gas chamber separated from each other by a metal electrocatalyst-based porous GDE designed so that the gas in the gas chamber reaches the metal electrocatalyst of the GDE and contacts the electrolyte of the electrolyte chamber; and Features include: The electrolyte chamber outlet of the anode chamber is in fluid communication with the electrolyte chamber inlet of the cathode chamber.

2. The electrochemical flow cell reactor of claim 1, wherein the metal electrocatalyst is selected from the group consisting of bismuth / molybdate-based catalysts, copper-based catalysts, ruthenium-based catalysts, platinum-based catalysts, cobalt-based catalysts, nickel-based catalysts, palladium-based catalysts, cobalt / iron / zinc / oxide alloy-based catalysts, iron / tin alloy-based catalysts, and combinations thereof.

3. An electrochemical flow cell reactor as described in claim 1 or 2, wherein the metal electrocatalyst of the cathode is selected from bismuth / molybdate-based catalysts, bismuth / tin-based catalysts, copper-based catalysts, ruthenium-based catalysts, platinum-based catalysts, cobalt-based catalysts, nickel-based catalysts, palladium-based catalysts and combinations thereof; and the metal electrocatalyst of the anode is selected from ruthenium and ruthenium / manganese oxide-based catalysts, platinum-based catalysts, rhodium-based catalysts, palladium-based catalysts, cobalt / iron / zinc / oxide alloy-based catalysts, tungsten-based catalysts, iron / tin alloy-based catalysts, (supported) boron-doped diamond, (supported) nitrogen-doped carbon and combinations thereof.

4. The electrochemical flow cell reactor of claim 1, wherein the metal electrocatalyst of the cathode is selected from bismuth / molybdate alloys, bismuth / tin alloys, copper, platinum / ruthenium alloys, platinum / tin alloys, cobalt, nickel and palladium; more specifically, the metal electrocatalyst of the cathode is selected from bismuth / molybdate alloys, copper, platinum / ruthenium alloys, platinum / tin alloys, cobalt and nickel.

5. The electrochemical flow cell reactor of claim 1, wherein the metal electrocatalyst of the anode is selected from platinum, ruthenium / titanium alloy, ruthenium / manganese oxide alloy, rhodium, palladium, cobalt / iron / zinc / oxide alloy, iron / tin alloy, palladium / ruthenium alloy, (supported) boron-doped diamond, (supported) nitrogen-doped carbon; more specifically, the metal electrocatalyst of the anode is selected from platinum, ruthenium / titanium alloy, cobalt / iron / zinc / oxide alloy, iron / tin alloy and palladium / ruthenium alloy.

6. An electrochemical flow cell reactor as claimed in any preceding claim, wherein the anode chamber and the cathode chamber are separated by an ion exchange membrane.

7. The electrochemical flow cell reactor of claim 1, wherein the gas chamber of the anode chamber and the gas chamber of the cathode chamber both comprise a gas inlet for a nitrogen (N2)-containing gas.

8. The electrochemical flow cell reactor of claim 7, wherein nitrogen (N2) in the nitrogen-containing gas from the gas chamber of the anode chamber is oxidized at the anode to form nitrate (NO3) in the electrolyte of the anode chamber. - ), nitrite (NO2 - ) and / or NOx, wherein the nitrate-containing (NO3 - ), nitrite (NO2 - ) and / or NOx is fed into the electrolyte chamber of the cathode chamber, is reduced at the cathode by nitrogen (N2) in the nitrogen-containing gas from the gas chamber of the cathode chamber, forms ammonia (NH3) and hydroxylamine (HA) in the electrolyte of the cathode chamber, and the electrolyte containing ammonia (NH3) and hydroxylamine (HA) thus obtained is removed from the electrolyte chamber of the cathode chamber.

9. The electrochemical flow cell reactor of claim 8 further comprises a separator for recovering ammonia (NH3) and hydroxylamine (HA) from the electrolyte containing ammonia (NH3) and hydroxylamine (HA) in the cathode chamber and recycling the electrolyte back to the electrolyte chamber of the anode chamber.

10. A method for electrosynthesizing NH3 and hydroxylamine (HA) in pairs in an electrochemical flow cell reactor, the reactor comprising an anode chamber and a cathode chamber separated by an ion exchange membrane, the method comprising: A metal electrocatalyst-based porous gas diffusion electrode (GDE) is used as the anode to oxidize nitrogen (N2) in the nitrogen-containing gas to form nitrate (NO3 - ), nitrite (NO2 - ) and / or NOx, · The nitrate-containing (NO3 - ) is fed into the electrolyte compartment of the cathode compartment, ·Use metal electrocatalyst-based porous gas diffusion electrode (GDE) as cathode to reduce (NO3 - ) in an alkaline electrolyte (NO3 - ), forming ammonia (NH3) and hydroxylamine (HA) in the alkaline / acidic electrolyte in the cathode compartment, and • Removing the alkaline / acidic electrolyte containing ammonia (NH3) and hydroxylamine (HA) thus obtained from the electrolyte compartment of the cathode chamber.

11. The method for paired electrosynthesis of NH3 and / or hydroxylamine (HA) according to claim 10, further comprising: Separation of ammonia (NH3) and hydroxylamine (HA) from an alkaline electrolyte containing ammonia (NH3) and hydroxylamine (HA), and • Circulate the alkaline electrolyte back into the electrolyte compartment of the anode compartment.

12. The method of claim 10 or 11, wherein the metal electrocatalyst of the cathode is selected from the group consisting of bismuth / molybdate-based catalysts, bismuth / tin alloys, copper-based catalysts, ruthenium-based catalysts, platinum-based catalysts, cobalt-based catalysts, nickel-based catalysts, palladium-based catalysts, and combinations thereof, and wherein the metal electrocatalyst of the anode is selected from the group consisting of ruthenium-based catalysts, platinum-based catalysts, palladium-based catalysts, cobalt / iron / zinc / oxide alloy-based catalysts, iron / tin alloy-based catalysts, and combinations thereof.

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