Nickel-based composite porous copper electrode for producing hydrogen through electro-catalysis of formaldehyde as well as preparation method and application of nickel-based composite porous copper electrode

Abstract

The invention relates to the technical field of electrode preparation, and particularly discloses a nickel-based composite porous copper electrode for producing hydrogen through electrocatalysis of formaldehyde and a preparation method and application thereof.The preparation method comprises the steps that a nickel net serves as a working electrode, the working electrode is electrically connected with an external negative electrode, and a counter electrode is electrically connected with an external positive electrode; the working electrode and the counter electrode are inserted into an electrolytic tank containing electrolyte, a two-electrode system is constructed, and the electrolytic tank comprises a copper-containing solvent and polyethylene glycol; and continuously electrifying the external negative electrode and the external positive electrode for 10 minutes to 10 hours, controlling the current density to be 5-50mA / cm < 2 >, and depositing and generating firm porous copper on the surface of the nickel net, so as to prepare the nickel-based composite porous copper electrode. The nickel-based composite porous copper electrode prepared by the invention not only retains high-activity sites, but also ensures that the structure is firm, and the paradox that activity and stability cannot be achieved at the same time is broken through.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrode preparation, in particular to a nickel-based composite porous copper electrode for electrocatalytic hydrogen production from formaldehyde and a preparation method and application thereof. BACKGROUND

[0002] Hydrogen is a clean energy carrier that can effectively reduce greenhouse gas emissions. Developing efficient hydrogen production methods is an important step towards realizing a hydrogen economy. Hydrogen has great potential as a sustainable energy carrier due to its high energy density and zero-emission characteristics. Producing hydrogen through water electrolysis using renewable energy is a promising method for achieving carbon neutrality. Water electrolysis involves the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), and due to the slow kinetics of OER, it results in high energy consumption, thus limiting the large-scale application of water splitting.

[0003] The formaldehyde oxidation reaction (FOR) can convert formaldehyde to hydrogen at the anode with very low thermodynamic potential, which first generates hydroxymethanol through the deprotonation of hydrated formaldehyde in a hydroxide solution, then generates hydrogen atoms through the cleavage of the C-H bond in hydroxymethanol, and finally generates hydrogen gas through the Tafel recombination of hydrogen atoms. Formaldehyde is a low-cost chemical that can be produced on a large industrial scale. In the presence of a catalyst, formaldehyde can efficiently produce hydrogen under alkaline conditions.

[0004] Copper-based materials have become the most active research materials for electrochemical formaldehyde hydrogen production due to their unique physical and chemical properties. However, it is often necessary to form high defects and high active sites to change their electronic states, thereby improving the performance of copper-based materials for electrolytic formaldehyde hydrogen production. Currently, the common method for preparing copper-based materials with high defects and high active sites is to construct nano-heterojunctions or alloys with other metals or copper oxides on purchased foam copper. Foam copper as a current collector is not resistant to hydrogen embrittlement and is easily broken; nano-heterojunctions and alloys have low mechanical stability, resulting in insufficient stability and inability to be used in actual industrial production.

[0005] Therefore, there is an urgent need in the prior art for an electrode with high stability and high hydrogen production efficiency. SUMMARY

[0006] In view of the deficiencies of the prior art described above, the purpose of the present application is to provide a nickel-based composite porous copper electrode for electrocatalytic hydrogen production from formaldehyde and a preparation method and application thereof, aiming to solve the problems of poor mechanical stability and low hydrogen production efficiency of existing electrodes for electrocatalytic hydrogen production.

[0007] The technical solution of the present application is as follows:

[0008] A preparation method of a nickel-based composite porous copper electrode for electrocatalytic hydrogen production from formaldehyde, comprising the following steps:

[0009] The nickel mesh is used as a working electrode, the working electrode is electrically connected with an external negative electrode, and the counter electrode is electrically connected with an external positive electrode;

[0010] The working electrode and the counter electrode are inserted into an electrolytic cell containing an electrolyte to construct a two-electrode system, and the electrolytic cell comprises a copper-containing solvent and polyethylene glycol;

[0011] The external negative electrode and the external positive electrode are continuously powered for 10 min to 10 h, and the current density is controlled to be 5-50 mA / cm 2 A firm porous copper is deposited on the surface of the nickel mesh, so as to obtain a nickel-based composite porous copper electrode.

[0012] The preparation method of the nickel-based composite porous copper electrode for electrocatalytic hydrogen production from formaldehyde, wherein the counter electrode is one of gold, platinum, silver, titanium, conductive carbon cloth, conductive glass and glassy carbon electrode.

[0013] The preparation method of the nickel-based composite porous copper electrode for electrocatalytic hydrogen production from formaldehyde, wherein the copper-containing solvent is one or more of copper sulfate, copper carbonate and copper chloride.

[0014] The preparation method of the nickel-based composite porous copper electrode for electrocatalytic hydrogen production from formaldehyde, wherein the relative molecular weight of the polyethylene glycol is 1000-10000.

[0015] The preparation method of the nickel-based composite porous copper electrode for electrocatalytic hydrogen production from formaldehyde, wherein the concentration of the polyethylene glycol is 0.1-10 mmol / L.

[0016] The preparation method of the nickel-based composite porous copper electrode for electrocatalytic hydrogen production from formaldehyde, wherein the copper ion concentration of the copper-containing solvent is 0.1-5 mol / L.

[0017] A nickel-based composite porous copper electrode for electrocatalytic hydrogen production from formaldehyde, wherein the electrode is prepared by the preparation method.

[0018] The application of a nickel-based composite porous copper electrode for electrocatalytic hydrogen production from formaldehyde, wherein the nickel-based composite porous copper electrode is used for electrocatalytic hydrogen production from formaldehyde.

[0019] The application, wherein the nickel-based composite porous copper electrode is used as an anode, a platinum sheet is used as a cathode, a potassium hydroxide aqueous solution containing formaldehyde is used as an electrolyte, an external power supply device is connected to the anode and the cathode, and electrocatalytic hydrogen production from formaldehyde is realized after power-on.

[0020] The application, wherein the concentration of formaldehyde in the electrolyte is 0.001-10 mol / L, and the concentration of potassium hydroxide is 0.001-10 mol / L.

[0021] Beneficial effects: The present application aims at the pain points of existing copper-based electrodes for electrocatalytic hydrogen production from formaldehyde, such as poor hydrogen embrittlement resistance, poor mechanical stability, difficult to balance activity and stability, and complex process. The present application achieves significant technical effects through an innovative preparation method: 1. Solving the problems of hydrogen embrittlement and mechanical stability, discarding the traditional foam copper substrate, and selecting a nickel mesh as the working electrode and depositing porous copper. The nickel mesh has excellent hydrogen embrittlement resistance and forms a firm metal bond with the porous copper, effectively preventing the integrated electrode from breaking and falling off; 2. Achieving the synergy of activity and stability by coupling regulation of PEG + 5-50 mA / cm 2 's current density, forming a uniform porous copper structure that not only retains high active sites but also ensures a firm structure, breaking the paradox of incompatibility between activity and stability; 3. Simplifying the process and reducing costs, using a one-step electrodeposition process without multiple modifications, using inexpensive nickel mesh, copper-containing salt, and PEG as raw materials, and shortening the production cycle from several days in existing technology to 10 min-10 h, which has industrialization potential; 4. Optimizing mass transfer efficiency, forming a multi-level structure with nickel mesh macro-pores and porous copper micro-pores to provide channels for electrolyte flow and reactant species transport, further ensuring stable hydrogen production efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The flow chart of the preparation method of the nickel-based composite porous copper electrode for electrocatalytic hydrogen production from formaldehyde according to the present application.

[0023] Figure 2 The electron microscope image of the nickel-based composite porous copper electrode prepared in Example 1 of the present application.

[0024] Figure 3 The electron microscope image of the nickel-based composite porous copper electrode prepared in Example 2 of the present application.

[0025] Figure 4 The electron microscope image of the nickel-based composite porous copper electrode prepared in Example 3 of the present application.

[0026] Figure 5 The electron microscope image of the nickel-based composite porous copper electrode prepared in Comparative Example 1 of the present application.

[0027] Figure 6 The electron microscope image of the nickel-based composite porous copper electrode prepared in Example 5 of the present application. DETAILED DESCRIPTION

[0028] The present application provides a nickel-based composite porous copper electrode for electrocatalytic hydrogen production from formaldehyde and its preparation method and application. To make the purpose, technical solution and effects of the present application more clear and explicit, the present application is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present application and not to limit the present application.

[0029] Please refer to Figure 1 , Figure 1A flow chart of a preparation method of a nickel-based composite porous copper electrode for electrocatalytic hydrogen production provided by the present application is shown in the figure, which comprises the following steps:

[0030] S10, using a nickel mesh as a working electrode, electrically connecting the working electrode with an external negative electrode and electrically connecting a counter electrode with an external positive electrode;

[0031] S20, inserting the working electrode and the counter electrode into an electrolytic cell containing an electrolyte to construct a two-electrode system, the electrolytic cell comprising a copper-containing solvent and polyethylene glycol;

[0032] S30, continuously powering the external negative electrode and the external positive electrode for 10 min to 10 h, and controlling the current density to be 5-50 mA / cm 2 , and depositing a firm porous copper on the surface of the nickel mesh to obtain a nickel-based composite porous copper electrode.

[0033] Specifically, the existing copper-based materials for electrocatalytic hydrogen production from formaldehyde have two fatal defects: first, foamed copper is generally used as a current collector, but it is not resistant to hydrogen embrittlement and is easy to break, because hydrogen atoms are easy to diffuse in the copper lattice and form hydride, causing the lattice to expand and break; second, in order to improve the activity, a nano-heterojunction or alloy is constructed on the surface of the foamed copper, and such structure has low mechanical stability and cannot be used for industrial production. These two defects directly lead to the fact that copper-based materials have been in the laboratory research stage for a long time and are difficult to realize industrial application, which is a core technical bottleneck that needs to be broken through in the field.

[0034] Therefore, the present application discards the traditional foamed copper substrate and selects a nickel mesh as a working electrode (deposition substrate), forms a firm porous copper layer on the surface of the nickel mesh through an electrodeposition process, and constructs a nickel mesh-porous copper integrated electrode. This selection is not a simple substrate replacement, but a precise matching based on material properties and electrocatalytic requirements. First, as a transition metal, the face-centered cubic crystal structure of nickel endows it with excellent hydrogen embrittlement resistance: on the one hand, the diffusion coefficient of hydrogen atoms in nickel (about 10 - 10 cm2 / s) is much lower than that in copper (about 10 -8 cm2 / s), and hydrogen atoms are difficult to migrate and gather in the nickel lattice; on the other hand, the binding energy of nickel and hydrogen (about 2.8 eV) is lower than that of copper (about 3.2 eV), and it is not easy to form stable hydride to cause lattice distortion. The stability test data of subsequent examples 1-3 (all reaching 100 h) directly verify this advantage, compared with subsequent comparative example 1 (dendritic copper without PEG assistance, with a stability of only 9 h), the stability of the nickel mesh substrate electrode is improved by more than 10 times, completely solving the core pain point of the easy breakage of the current collector in the prior art.

[0035] Further, the interface bonding force of the nickel mesh and the porous copper of the present application is significantly better than that of the foam copper. During the electrodeposition process, nickel atoms on the surface of the nickel mesh can form partial metal bond with the deposited copper atoms. The electronegativity of nickel and copper is 1.91 and 1.90 respectively, and the difference in atomic radius is only 5%, which is easy to form a solid solution transition layer, and the interface bonding energy is as high as 2.5 J / m 2 ; while the foam copper itself has a loose porous structure, and the deposition of copper atoms is only physical adhesion, and the bonding energy is less than 0.5 J / m 2 . Subsequent experiments fully prove the firm combination of the nickel mesh substrate and the porous copper, which fundamentally solves the defect of low mechanical stability of the existing nano-heterojunction / alloy.

[0036] Further, the nickel-based composite porous copper electrode prepared by the present application has a multi-level porous structure of "macro-porous nickel mesh hole + micro-porous copper": the macro-porous mesh hole (about 200 μm) of the nickel mesh substrate provides a fast flow channel for the electrolyte, and the micro-porous copper (10-50 μm) provides active sites for the reaction, and the two realize efficient matching of mass transfer-reaction, and the multi-level porous structure can effectively reduce the mass transfer resistance of formaldehyde molecules and hydrogen atoms; while the single porous structure of the foam copper easily leads to mass transfer bottleneck (such as formaldehyde molecules cannot quickly reach the deep active sites) or uneven current distribution, and cannot achieve this effect.

[0037] In the prior art, there is a core technical paradox in the electrodeposition of copper-based materials: high-activity structure must be accompanied by low stability, and high-stability structure must be accompanied by low activity, which is specifically manifested as:

[0038] High current density deposition: when the current density is > 50 mA / cm 2 , the reduction speed of copper ions is too fast, and the plating layer is easy to form dendritic copper. This kind of structure has large specific surface area and rich active sites, but the structure is loose and the branch is fragile, and the mechanical stability is very poor, which is easy to fall off in the process of electrocatalysis;

[0039] Low current density + polyethylene glycol (PEG) auxiliary: when the current density is < 5 mA / cm 2 and PEG is added, PEG as a leveling agent is adsorbed on the surface of the electrode to inhibit local excessive growth, and a high-crystalline copper plating layer is formed. This kind of structure has high crystallinity and mechanical stability, but the surface is smooth and lacks active sites, which cannot meet the demand of electrocatalysis;

[0040] No PEG auxiliary: even if the current density is moderate (such as 20 mA / cm 2 ), without PEG, the reduction of copper ions is non-selective, and dendritic structure is still formed, which cannot balance the activity and stability.

[0041] To break the above paradox, the present application precisely regulates the PEG concentration (0.1-10 mmol / L) and the current density (5-50 mA / cm2 ) to achieve the controllable deposition of porous copper structure with high activity and stability, and the regulation mechanism is as follows:

[0042] In the prior art, the role of PEG in electrodeposition is only as a leveling agent, which uniformly adsorbs on the electrode surface to inhibit the growth of local protrusions, and a smooth plating layer is obtained; in the present application, the role of PEG is to selectively regulate the reduction kinetics of copper ions, and the core mechanism is as follows: when the PEG concentration is 0.1-10 mmol / L, the PEG molecules will selectively adsorb on the high-activity sites (such as grain boundaries and defects) on the surface of the nickel mesh, but will not completely cover the electrode surface, and the low-activity sites that are not adsorbed become the preferential reduction sites of copper ions, while the high-activity sites adsorbed by PEG are inhibited from growing, forming the initial structure of core site-gap; as the deposition proceeds, the core sites continuously grow to form a copper skeleton, and the gaps develop into a porous structure, and finally form a porous copper; in the present application, if the PEG concentration exceeds the upper limit (such as 15 mmol / L), the PEG molecules will completely cover the surface of the nickel mesh, and all the active sites will be inhibited, and the copper ions can only be slowly reduced in the interstices between the PEG molecules and stacked in the order of the crystal lattice to form a "high-crystalline copper plating layer (no porosity, low activity); if the PEG concentration is lower than the lower limit (0.05 mmol / L), the PEG adsorption amount is insufficient to completely inhibit the excessive growth of high-activity sites, and the copper ions are rapidly reduced in the local area to form dendritic copper (poor stability). Obviously, the precise regulation of PEG concentration is the core of the formation of the porous structure, rather than the simple leveling effect in the prior art.

[0043] Further, the present application selects a current density range of 5-50 mA / cm 2 , which is not randomly selected, but forms a dynamic balance with the PEG concentration, and the specific logic is as follows: if the current density is too low (such as 4 mA / cm 2 ), even if the PEG concentration is within the range, the reduction speed of copper ions is too slow, and the inhibition effect of PEG adsorption area dominates, and copper atoms can only be slowly stacked in the core sites, and cannot form pores, and finally a dense high-crystalline layer is formed; if the current density is too high (such as 60 mA / cm 2 ), the reduction speed of copper ions far exceeds the inhibition ability of PEG, and the local excessive growth cannot be controlled, and even if the PEG concentration is within the range, dendritic copper will still be formed; only within the range of 5-50 mA / cm 2 , the reduction speed of copper ions and the inhibition effect of PEG reach a balance, the core sites grow rapidly to form a copper skeleton, and the PEG adsorption area is inhibited to form pores, and finally a "porous and firm" structure is formed. Through the above coupling regulation, the nickel-based composite porous copper electrode of the present application achieves the activity and stability synergy that the prior art cannot achieve.

[0044] In the prior art, the preparation of copper-based materials requires multiple modification steps: first, a copper foam substrate is prepared, then other metals or alloys are deposited through processes such as electroplating or sputtering, and finally a nano-heterojunction is constructed. The entire process takes several days, is complex, costly, and has poor reproducibility (performance fluctuations of more than 20% between different batches), making it difficult to industrialize. In contrast, the preparation method of the present application only requires one step of electrodeposition: immerse a nickel mesh as the working electrode into an electrolyte containing a copper-containing solvent (copper sulfate, copper chloride, etc.) and PEG, and continuously apply electricity (10 min-10 h) to obtain a porous copper electrode without the need for subsequent modification steps. This process simplification has clear industrial value: short process, high efficiency: only 1 step of deposition, the production cycle is shortened from several days in the prior art to 10 min-10 h, and the production efficiency is increased by more than 10 times.

[0045] In some embodiments, the counter electrode is one of gold, platinum, silver, titanium, conductive carbon cloth, conductive glass, and a glassy carbon electrode, but is not limited thereto.

[0046] In some embodiments, the copper-containing solvent is one or more of copper sulfate, copper carbonate, and copper chloride, but is not limited thereto.

[0047] In some embodiments, the relative molecular weight of the polyethylene glycol is 1000-10000, but is not limited thereto. In the present application, the core role of PEG is to adsorb on the high active sites on the electrode surface (such as grain boundaries, defects), inhibit local excessive growth, and form a micro-zoning of PEG adsorption area (gap) in the copper skeleton growth area. PEG with a molecular weight of 1000-10000 can precisely achieve this selectivity: if the PEG molecular weight is less than 1000 (low molecular weight): the molecular chain is too short, the adsorption force (van der Waals force, hydrogen bond) with the nickel mesh surface is weak, and it is easy to desorb from the high active site, which cannot continuously inhibit Cu 2+ reduction in this area; if the PEG molecular weight is higher than 10000 (high molecular weight): the molecular chain is too long and has a large space volume, which is easy to form a "dense adsorption layer" on the nickel mesh surface, covering not only the high active sites but also the low active sites, leading to Cu 2+ only slow reduction in the gap between the adsorption layer, forming a high-crystalline dense copper plating layer with no porous structure and very low activity; only PEG with a molecular weight of 1000-10000: the molecular chain length and adsorption strength are moderate, allowing stable adsorption on high active sites without covering low active sites, precisely constructing the initial zoning of "copper skeleton-gap", laying the foundation for the subsequent formation of porous structure.

[0048] In some embodiments, the concentration of the polyethylene glycol is 0.1-10 mmol / L, but is not limited thereto.

[0049] In some embodiments, the copper ion concentration of the copper-containing solvent is 0.1-5 mol / L, but not limited thereto. The electrodeposition of the present application is carried out at a current density of 5-50 mA / cm 2 The copper ion concentration of 0.1-5 mol / L is the copper ion concentration under the current density. 2+ The key to balance the supply rate and the reduction rate: if the copper ion concentration is lower than 0.1 mol / L: the Cu 2+ The total amount is insufficient, even if the current of 5-50 mA / cm2 is applied (the Cu 2+ must be continuously supplied), the Cu 2+ diffusion rate < reduction rate” causes the Cu 2+ depletion on the surface of the nickel mesh, at this time, the copper atoms can only slowly accumulate at the limited active sites, and cannot form a porous structure of “copper skeleton-gap”, but rather a dense thin copper layer, the active sites are severely insufficient, and the hydrogen production efficiency will be greatly reduced; if the copper ion concentration is higher than 5 mol / L: the Cu 2+ supply is excessive, and the reduction rate is too fast under the current of 5-50 mA / cm 2 , which will break through the inhibition of PEG on the high active sites. The Cu 2+ grows rapidly at the high active sites, forming a dendritic copper-like structure, which is loose and has fragile branches, and the stability is reduced; only the concentration of 0.1-5 mol / L: the Cu 2+ supply is precisely matched with the demand of the current density, which can not only meet the continuous reduction of Cu 2+ under the current of 5-50 mA / cm2, but also will not cause excessive growth due to excessive supply, and finally form a uniform porous structure under the cooperation of PEG.

[0050] In some embodiments, a nickel-based composite porous copper electrode for electrocatalytic hydrogen production from formaldehyde is also provided, wherein the preparation method of the present application is used.

[0051] In some embodiments, the application of a nickel-based composite porous copper electrode for electrocatalytic hydrogen production from formaldehyde is also provided, wherein the nickel-based composite porous copper electrode is used for electrocatalytic hydrogen production from formaldehyde, wherein the nickel-based composite porous copper electrode is used as an anode, a platinum sheet is used as a cathode, a potassium hydroxide aqueous solution containing formaldehyde is used as an electrolyte, an external power supply device is connected to the anode and the cathode, and after power-on, electrocatalytic hydrogen production from formaldehyde is realized. Preferably, in the electrolyte, the concentration of formaldehyde is 0.001-10 mol / L, and the concentration of potassium hydroxide is 0.001-10 mol / L.

[0052] The present application will be further explained and described below through specific examples:

[0053] Example 1

[0054] A method for preparing a nickel-based composite porous copper electrode for electrocatalytic hydrogen production from formaldehyde includes the following steps:

[0055] A nickel mesh with a pore density of 100 mesh was used as the working electrode. A platinum sheet (2*2cm) was used as the counter electrode, connected to the negative and positive electrode wires respectively. The electrode was immersed in an electrolyte composed of 0.1mol / L copper sulfate and 0.1mmol / L polyethylene glycol, forming a two-electrode system together with the electrolytic cell. Copper deposition was carried out continuously for 10 hours at a current density of 5mA / cm². 2 , to obtain Figure 2 The nickel-based composite porous copper electrode shown is from... Figure 2 As can be seen, the nickel mesh surface is covered with a uniform and continuous porous copper layer, with interconnected and regularly distributed pores. On a 100μm scale, the pore size of the porous copper is concentrated between 15-30μm, with no obvious localized dense areas or signs of breakage; the interface between the copper layer and the nickel mesh is seamless, presenting an integrated "nickel mesh-porous copper" structure, without any copper layer peeling or cracking. This is due to the low current density (5mA / cm²). 2 Copper atoms grow slowly under the substrate, and combined with the selective adsorption of PEG (0.1 mmol / L), a porous structure with matching copper framework and gaps is formed. The deposition time is as long as 10 hours to ensure that the copper layer and nickel mesh are fully bonded.

[0056] Example 2

[0057] A method for preparing a nickel-based composite porous copper electrode for electrocatalytic hydrogen production from formaldehyde includes the following steps:

[0058] A nickel mesh with a pore density of 100 mesh was used as the working electrode. A platinum sheet (2*2cm) was used as the counter electrode, connected to the negative and positive electrode wires respectively. The electrode was immersed in an electrolyte composed of 5mol / L copper sulfate and 10mmol / L polyethylene glycol, forming a two-electrode system together with the electrolytic cell. Copper deposition was carried out continuously for 10 minutes at a current density of 50mA / cm². 2 , to obtain Figure 3 The nickel-based composite porous copper electrode shown is from... Figure 3 It can be seen that the deposited copper still has a uniform porous structure, but with a higher pore density, slightly smaller pore size (10-20 μm), and a thinner but more continuous copper layer. On a 100 μm scale, the pore distribution of the porous copper is more... Figure 2 More dense, without dendritic protrusions or localized clusters. Despite a current density of 50 mA / cm². 2The deposition time was only 10 min (upper limit), but the PEG concentration was simultaneously increased to 10 mmol / L (upper limit). Its stronger selective adsorption inhibited the excessive reduction of copper ions and avoided the formation of dendritic structures. The high copper ion concentration (5 mol / L) quickly replenished the copper ion consumption under the current density, ensuring the continuous growth of the copper layer.

[0059] Example 3

[0060] A method for preparing a nickel-based composite porous copper electrode for electrocatalytic hydrogen production from formaldehyde includes the following steps:

[0061] A nickel mesh with a pore density of 100 mesh was used as the working electrode. A platinum sheet (2*2cm) was used as the counter electrode, connected to the negative and positive electrode wires respectively. The electrode was immersed in an electrolyte composed of 2mol / L copper sulfate and 5mmol / L polyethylene glycol, forming a two-electrode system together with the electrolytic cell. Copper deposition was carried out continuously for 4 hours at a current density of 20mA / cm². 2 , to obtain Figure 4 The nickel-based composite porous copper electrode shown is from... Figure 4 It can be seen that the deposited copper exhibits the most regular porous structure, with pore sizes (12-25 μm), uniform copper layer thickness (approximately 5-8 μm), and no structural defects. On a 100 μm scale, the pore distribution uniformity is superior to that of the deposited copper. Figure 2 , Figure 3 There are no areas with excessively large or small pores. Under intermediate parameter combinations, the copper ion reduction rate (20 mA / cm²) is... 2 The optimal balance between PEG inhibition (5 mmol / L) and copper ion supply (2 mol / L) is achieved: there is neither the risk of slow growth due to low current density nor the risk of excessive reduction due to high current density, thus forming the most regular porous structure.

[0062] Comparative Example 1 (Polyethylene glycol concentration too high)

[0063] A method for preparing a copper electrode for electrocatalytic hydrogen production from formaldehyde includes the following steps:

[0064] A nickel mesh with a pore density of 100 mesh was used as the working electrode. A platinum sheet (2*2cm) was used as the counter electrode, connected to the negative and positive electrode wires respectively. The electrode was immersed in an electrolyte composed of 5mol / L copper sulfate and 15mmol / L polyethylene glycol, forming a two-electrode system together with the electrolytic cell. Copper deposition was carried out continuously for 10 minutes at a current density of 50mA / cm². 2 , to obtain Figure 5 The image shows a highly crystalline copper plating. From Figure 5As can be seen, the deposited copper surface is smooth and dense, without any obvious pores, exhibiting a highly crystalline layered structure. Under 2000x magnification, the copper layer surface shows only extremely fine lattice textures, lacking the porous characteristics of a "copper skeleton-interstitial" structure. In this comparative example, when the PEG concentration exceeds the upper limit (15 mmol / L), the molecular chains form a dense adsorption layer on the nickel mesh surface, completely covering both highly active and inactive sites. Copper ions can only be slowly reduced in the interstices of PEG molecules, accumulating in a lattice order to form a dense coating, rather than a porous structure.

[0065] Comparative Example 2 (Polyethylene glycol concentration too low)

[0066] A method for preparing a copper electrode for electrocatalytic hydrogen production from formaldehyde includes the following steps:

[0067] A nickel mesh with a pore density of 100 mesh was used as the working electrode. A platinum sheet (2*2cm) was used as the counter electrode, connected to the negative and positive electrode wires respectively. The electrode was immersed in an electrolyte consisting of 5 mol / L copper sulfate and 0.05 mmol / L polyethylene glycol, forming a two-electrode system together with the electrolytic cell. Copper deposition was carried out continuously for 10 min at a current density of 50 mA / cm². 2 Dendritic copper electrodes were obtained.

[0068] Comparative Example 3 (Current Density Too High)

[0069] A method for preparing a copper electrode for electrocatalytic hydrogen production from formaldehyde includes the following steps:

[0070] A nickel mesh with a pore density of 100 mesh was used as the working electrode. A platinum sheet (2*2cm) was used as the counter electrode, connected to the negative and positive electrode wires respectively. The electrode was immersed in an electrolyte consisting of 5 mol / L copper sulfate and 10 mmol / L polyethylene glycol, forming a two-electrode system together with the electrolytic cell. Copper deposition was carried out continuously for 10 min at a current density of 60 mA / cm². 2 Dendritic copper electrodes were obtained.

[0071] Comparative Example 4 (Current Density Too Low)

[0072] A method for preparing a copper electrode for electrocatalytic hydrogen production from formaldehyde includes the following steps:

[0073] A nickel mesh with a pore density of 100 mesh was used as the working electrode. A platinum sheet (2*2cm) was used as the counter electrode, connected to the negative and positive electrode wires respectively. The electrode was immersed in an electrolyte composed of 5 mol / L copper sulfate and 10 mmol / L polyethylene glycol, forming a two-electrode system together with the electrolytic cell. Copper deposition was carried out continuously for 10 min at a current density of 4 mA / cm². 2 This yields a highly crystalline copper plating layer.

[0074] Comparative Example 5 (without polyethylene glycol)

[0075] A method for preparing a copper electrode for electrocatalytic hydrogen production from formaldehyde includes the following steps:

[0076] A nickel mesh with a pore density of 100 mesh was used as the working electrode. A platinum sheet (2*2cm) was used as the counter electrode, connected to the negative and positive electrode wires respectively. The electrode was immersed in 5mol / L copper sulfate solution, forming a two-electrode system together with the electrolytic cell. Copper deposition was carried out continuously for 10 minutes at a current density of 50mA / cm². 2 , to obtain Figure 6 The dendritic copper electrode shown. From Figure 6 As can be seen, the deposited copper in Comparative Example 5 exhibits an irregular dendritic branching structure, lacking uniform porosity, and the branches are loose and easily broken. On a macroscopic scale, the copper layer grows in a main-branch-lateral-branch form, with no interconnected structure between branches, and some branches are not firmly bonded to the nickel mesh substrate (with minute gaps). This indicates that...

[0077] During PEG, copper ions are rapidly reduced without inhibition at highly active sites (grain boundaries, defects) on the nickel mesh, forming "dendritic growth". Although this structure has a large specific surface area, its mechanical stability is extremely poor.

[0078] The electrodes prepared in Examples 1-3 and Comparative Examples 1-5 of this invention were subjected to stability tests and hydrogen production efficiency tests. For the stability test: the electrodes prepared in the above examples and comparative examples were used as working electrodes, a platinum sheet as a control electrode, and Hg / HgO as a reference electrode. An aqueous solution containing 0.1 mol / L formaldehyde and 1.0 mol / L potassium hydroxide was used as the electrolyte. The stability test was performed using constant voltage technology, with an applied voltage of 0.5 V / L. The test time was based on the actual stability time of the sample; the test was stopped immediately when the performance became unstable. The testing instrument was a Chenhua electrochemical workstation CHI760C. For the hydrogen production efficiency test: the electrodes prepared in the above examples and comparative examples were used as working electrodes, a platinum sheet as a control electrode, and Hg / HgO as a reference electrode. An aqueous solution containing 0.1 mol / L formaldehyde and 1.0 mol / L potassium hydroxide was used as the electrolyte. The hydrogen production efficiency test was performed using polarization curve technology, with a test voltage of -0.2 to 0.9 V. The testing instrument was a Chenhua electrochemical workstation CHI760C. The measurement results are shown in Table 1.

[0079] Table 1 Performance Test Results

[0080] Stability (h) Hydrogen production efficiency (mA / cm 2 @0.4 V) Example 1 100 520 Example 2 100 586 Example 3 100 553 Comparative Example 1 150 13 Comparative Example 2 10 540 Comparative Example 3 13 601 Comparative Example 4 145 16 Comparative Example 5 9 600

[0081] As shown in Table 1, the nickel-based composite porous copper electrodes prepared in Examples 1-3 exhibited better stability and higher hydrogen production efficiency, breaking the paradox of high activity necessarily leading to low stability and high stability necessarily leading to low activity in existing technologies. Their stability reached 100 hours, indicating that all three methods achieved stability through "PEG selective adsorption (inhibiting excessive growth of highly active sites) + appropriate current density (5-50 mA / cm²)". 2 Control Cu 2+ The reduction rate forms a uniform, interconnected porous copper structure (corresponding to) Figures 2-4 (Electron microscopy image) The porous copper and nickel mesh are firmly bonded together by metallic bonds, effectively resisting hydrogen embrittlement and electrolyte erosion, avoiding the fragility of traditional foamed copper; hydrogen production efficiency ≥520 mA / cm² 2 The porous structure provides ample active sites. The macroscopic pores of the nickel mesh and the microscopic pores of the copper layer form a "multi-level mass transfer channel", allowing formaldehyde molecules to quickly reach the active center and hydrogen atoms to desorb efficiently, thus increasing the formaldehyde oxidation reaction (FOR) rate.

[0082] Comparative Examples 1-4 all failed to simultaneously meet the stability + high activity criteria because a single parameter exceeded the limits of this invention. Their data directly verified the necessity of the parameter range of this invention.

[0083] In Comparative Example 1, an excessive amount of PEG formed a "dense adsorption layer" that completely covered all active sites on the nickel mesh, and Cu... 2+ It can only slowly accumulate into a highly crystalline and dense copper layer. Figure 5 (Electron microscopy image) It lacks a porous structure, meaning it has no active sites. Its high stability is solely due to its dense structure, but it cannot be used for electrocatalytic hydrogen production due to extremely low efficiency. Comparative Example 2, due to insufficient PEG, cannot completely cover the highly active sites; Cu... 2+ Over-reduction at highly active sites forms loose dendritic copper. The dendritic structure is fragile, has weak bonding with the nickel mesh, and is prone to breakage during the reaction, resulting in a sharp drop in stability. Although it has high activity, it has no practical value. Comparative Example 3 showed that excessively high current density led to Cu… 2+ The reduction rate far exceeds the inhibition ability of PEG (even if the PEG concentration of 10 mmol / L is compliant), overcoming the steric hindrance of PEG to form dendritic copper. This results in a large specific surface area and extremely high activity, but the loose structure leads to a stability of only 13 hours, making long-term use unsuitable. Comparative Example 4 shows that the Cu reduction was caused by excessively low current density. 2+ The reduction rate is too slow. Even with a PEG concentration of 10 mmol / L, which is within the acceptable range, copper atoms can only slowly accumulate into a dense copper layer at a limited number of sites. This results in a lack of porous structure and therefore no active sites, leading to high stability but no electrocatalytic value. Comparative Examples 1-4 demonstrate that only when all parameters (PEG concentration, current density) are within the limits specified in this application can the imbalance between "stable but inactive" and "active but unstable" be avoided. A deviation from even a single parameter will disrupt the "PEG-current density-Cu" relationship. 2+The synergistic mechanism of "concentration" cannot meet the demand for hydrogen production from formaldehyde in electrocatalysis.

[0084] Comparative Example 5 served as a blank control, "without PEG," with all other parameters identical to Example 2. Comparative Example 5 showed no PEG inhibition, resulting in the formation of dendritic copper (…). Figure 6 (Electron microscopy image) shows that the branches are loose and the bonding force is weak, and it breaks after 9 hours; its dendritic structure has a larger specific surface area, which means slightly higher activity, but the structure is unstable and cannot be converted into practical performance; Comparative Example 1 represents the pain point that existing copper-based materials cannot achieve both activity and stability.

[0085] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for preparing a nickel-based composite porous copper electrode for electrocatalytic hydrogen production from formaldehyde, characterized in that, Including the following steps: A nickel mesh is used as the working electrode, which is electrically connected to an external negative electrode, and the counter electrode is electrically connected to an external positive electrode. The working electrode and the counter electrode are inserted into an electrolytic cell containing electrolyte to construct a two-electrode system. The electrolytic cell includes a copper-containing solvent and polyethylene glycol. The external negative and positive electrodes are continuously energized for 10 minutes to 10 hours, with the current density controlled at 5-50 mA / cm². 2 A robust porous copper electrode is formed by depositing copper on the surface of a nickel mesh, thereby producing a nickel-based composite porous copper electrode.

2. The method for preparing the nickel-based composite porous copper electrode for electrocatalytic formaldehyde hydrogen production according to claim 1, characterized in that, The counter electrode is one of gold, platinum, silver, titanium, conductive carbon cloth, conductive glass, and glassy carbon electrode.

3. The method for preparing the nickel-based composite porous copper electrode for electrocatalytic formaldehyde hydrogen production according to claim 1, characterized in that, The copper-containing solvent is one or more of copper sulfate, copper carbonate, and copper chloride.

4. The method for preparing the nickel-based composite porous copper electrode for electrocatalytic formaldehyde hydrogen production according to claim 1, characterized in that, The relative molecular weight of the polyethylene glycol is 1000-10000.

5. The method for preparing the nickel-based composite porous copper electrode for electrocatalytic formaldehyde hydrogen production according to claim 1, characterized in that, The concentration of the polyethylene glycol is 0.1-10 mmol / L.

6. The method for preparing the nickel-based composite porous copper electrode for electrocatalytic formaldehyde hydrogen production according to claim 1, characterized in that, The copper ion concentration of the copper-containing solvent is 0.1-5 mol / L.

7. A nickel-based composite porous copper electrode for electrocatalytic hydrogen production from formaldehyde, characterized in that, It is prepared by any one of the preparation methods described in claims 1-6.

8. The application of a nickel-based composite porous copper electrode for electrocatalytic formaldehyde hydrogen production as described in claim 7, characterized in that, The nickel-based composite porous copper electrode was used for electrocatalytic hydrogen production from formaldehyde.

9. The application according to claim 8, characterized in that, Using the nickel-based composite porous copper electrode as the anode, a platinum sheet as the cathode, and a potassium hydroxide aqueous solution containing formaldehyde as the electrolyte, an external power supply is connected to the anode and cathode to achieve electrocatalytic hydrogen production from formaldehyde after energization.

10. The application according to claim 8, characterized in that, The electrolyte contains formaldehyde at a concentration of 0.001-10 mol / L and potassium hydroxide at a concentration of 0.001-10 mol / L.

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