A nickel-manganese aerogel catalyst and its application in electrocatalytic hydrogen production from alkaline biomass aqueous solution

Abstract

The present invention relates to the field of hydrogen production, and discloses a nickel-manganese aerogel catalyst and its application in the electrocatalytic production of hydrogen from alkaline biomass aqueous solution. The catalyst has a crystalline elemental nickel as a skeleton, and the surface is covered with amorphous nickel hydroxide and crystalline manganese oxide. The application uses the nickel-manganese aerogel catalyst as an electrocatalyst and an alkaline biomass aqueous solution as an electrolyte. When the nickel-manganese aerogel catalyst of the present invention is applied to the electrocatalytic production of hydrogen from alkaline biomass aqueous solution, it can promote charge transfer in the oxygen evolution reaction process and has ultra-high electrocatalytic oxidation performance. The hydrogen production system of the present invention uses the oxidation process of biomass such as ethylene glycol to replace the OER process to provide electrons, which can promote the hydrogen production of the HER process, and has the characteristics of high hydrogen production efficiency, mild hydrogen production conditions, safe catalytic process, and the ability to produce by-products with economic value while producing hydrogen.

Description

Technical Field

[0001] The present invention relates to the field of hydrogen production, and in particular to a nickel-manganese aerogel catalyst and application thereof in hydrogen production from an electrocatalytic alkaline biomass aqueous solution. Background Art

[0002] Growing global energy demand and serious concerns about climate change caused by fossil fuel use have prompted significant efforts to develop sustainable and clean energy storage and conversion technologies. Among various clean energy sources, hydrogen offers advantages such as high calorific value, abundant global reserves, widespread distribution, non-polluting combustion products, and environmental friendliness and regeneration. It is a reliable energy source that can address future energy and environmental challenges, leveraging renewable energy sources such as solar and wind power. Producing clean hydrogen through electrochemical or photoelectrochemical water splitting is considered a promising approach to meeting future energy needs.

[0003] Compared with traditional solutions such as steam reforming and coal gasification, high-purity hydrogen (H2) production based on water electrolysis is considered an environmentally friendly strategy that can promote the development of a future hydrogen economy. However, the inherently slow kinetics of the oxygen evolution reaction [OER; 4OH − =O2+2H2O+4e − , 1.23 V (compared to the reversible hydrogen electrode (RHE))] is considered a bottleneck for the future development of the hydrogen economy. The electrons in the hydrogen evolution process (HER) originate from the oxygen evolution reaction (OER) and are therefore limited by the slow OER process. In this case, the anodic OER can be replaced by the oxidation of biomass molecules with favorable thermodynamic potential to achieve energy-efficient hydrogen production. Coupling the oxidation of organic molecules with low oxidation potentials with the HER process of hydrogen production from water splitting to produce hydrogen can efficiently produce hydrogen at low potentials.

[0004] At the same time, using biomass molecular oxidation reactions instead of anode OER can decouple the overall water splitting reaction. This can avoid the simultaneous production of H2 and O2 in the same electrolytic cell during water electrolysis, which could lead to the formation of explosive H2 / O2 mixtures (gas crossover), reducing the dangers of the production process. At the same time, the coexistence of H2, O2, and the water splitting catalyst produced by the overall water splitting reaction may generate reactive oxygen species (ROS), which may oxidize the electrodes or electrolytic cell materials, leading to premature equipment failure and increasing the cost of large-scale commercialization of hydrogen production by electrolysis.

[0005] Aerogels are open-cell porous solid materials composed of interconnected nanostructured networks, with most pores less than 100 nm and a porosity exceeding 80%. They maintain a typical structure of pores and networks similar to hydrogels, with the pore medium of the gel replaced by air. Aerogels are increasingly recognized as materials with unique structures and properties, showing great promise in electrocatalysis. As highly active and durable electrocatalysts, these catalysts possess a large internal surface area providing abundant catalytically active sites, high porosity facilitating mass transfer and exposure of the active sites, high electrical conductivity facilitating electron transfer, and a deformed, extended surface imparting high durability during electrocatalysis.

[0006] Therefore, the development of high-performance non-noble metal aerogel electrocatalysts with high electrocatalytic activity and durability remains necessary and is of great significance from both fundamental and practical perspectives. Summary of the Invention

[0007] In order to solve the above technical problems, the present invention provides a nickel-manganese aerogel catalyst and its application in the electrocatalytic production of hydrogen from alkaline biomass aqueous solution.

[0008] The nickel and manganese oxide in the nickel-manganese aerogel catalyst of the present invention are crystalline, while the nickel hydroxide is amorphous. The nickel hydroxide acts as a reactive species, providing a source of divalent nickel and catalytic reaction sites. The manganese oxide regulates the overall electronic structure, making the surface electronic structure of the active sites provided by the nickel hydroxide conducive to the adsorption of reactive species. Ultimately, this allows for the rapid adsorption of biomass to form a catalytic system, oxidizing the biomass and achieving safe and efficient catalytic production of hydrogen. The nickel-manganese aerogel catalyst of the present invention has high electrical conductivity, can promote charge transfer during the oxygen evolution reaction, and exhibits ultra-high electrocatalytic oxidation performance when applied to hydrogen evolution in alkaline biomass aqueous solutions.

[0009] The hydrogen production system of the present invention uses the oxidation process of biomass such as ethylene glycol to replace the OER process to provide electrons, which can promote hydrogen production in the HER process. It has the characteristics of efficient hydrogen production, mild hydrogen production conditions (room temperature), safe catalytic process (no hydrogen and oxygen are produced at the same time), and the ability to produce by-products with economic value while producing hydrogen.

[0010] The specific technical solutions of the present invention are:

[0011] The present invention provides a nickel-manganese aerogel catalyst having an aerogel structure with a porosity greater than 75%. The structure comprises a crystalline nickel skeleton covered with amorphous nickel hydroxide and crystalline manganese oxide. The molar ratio of nickel to manganese in the raw materials of the nickel-manganese aerogel catalyst is 1:(0.2-1.8). Preferably, the molar ratio of nickel to manganese after the catalyst is prepared is 1:1.

[0012] The nickel and manganese oxide in the nickel-manganese aerogel catalyst of the present invention are crystalline, while the nickel hydroxide is amorphous. The amorphous structure of the nickel hydroxide is structurally isotropic, and the catalytically active nickel centers are uniformly distributed in a single chemical environment. Furthermore, the amorphous material has a highly unsaturated surface, high surface energy, and a high concentration of highly coordinated unsaturated sites, resulting in strong activation ability and a high density of active centers. The crystalline manganese oxide structure of the crystalline nickel skeleton is stable, which stabilizes the nickel hydroxide and improves the stability of the catalyst.

[0013] When the catalyst of the present invention is applied to the electrocatalytic production of hydrogen from an alkaline biomass aqueous solution, nickel hydroxide serves as a reactive substance to provide a divalent nickel source and catalytic reaction active sites; manganese oxide regulates the overall electronic structure so that the electronic structure on the surface of the active sites provided by the nickel hydroxide is conducive to the adsorption of the reactive substance, ultimately achieving rapid adsorption of biomass (such as ethylene glycol) to form a catalytic system, oxidizing the biomass (such as ethylene glycol) and achieving safe and efficient catalytic production of hydrogen.

[0014] The nickel-manganese aerogel catalyst of the present invention has high conductivity, can promote charge transfer in the oxygen evolution reaction, and has ultra-high electrocatalytic oxidation performance (overpotential 120 mV@10 mA cm in ethylene glycol electrolyte) when applied to hydrogen evolution in alkaline biomass aqueous solution. -2 , overpotential in methanol electrolyte 141 mV@10 mA cm -2 、Overpotential in urea electrolyte 132mV@10 mA cm -2 ).

[0015] Furthermore, the inventors' team discovered through research that the ratio of nickel and manganese significantly influences catalytic performance, with optimal results achieved within a nickel-to-manganese molar ratio of 1:(0.2-1.8). If the Mn ratio falls below this range, it fails to effectively synergize with the Ni sites, rendering performance suboptimal. Conversely, excessive MnO coats the Ni(OH)2, reducing the number of Ni sites available for catalysis. Therefore, both excessively high and low Mn contents are detrimental to the catalytic reaction, with catalysts with a Ni1Mn1 structure exhibiting optimal catalytic performance.

[0016] Preferably, the aerogel structure has a porosity of 78.6%-85.2%.

[0017] Preferably, the preparation method of the nickel-manganese aerogel catalyst is as follows: mixing nickel salt with water to prepare a nickel solution; mixing manganese salt with water to prepare a manganese solution; taking sodium borohydride and adding water to prepare a sodium borohydride solution; pouring the sodium borohydride solution into the nickel solution at a uniform speed, and then quickly adding the manganese solution; gently rotating the container containing the obtained mixed solution, letting it stand and then washing, exchanging the washed supernatant with deionized water and anhydrous ethanol respectively, and vacuum drying to obtain the nickel-manganese aerogel catalyst; the molar ratio of the nickel and manganese elements is 1:(0.2-1.8); the molar ratio of the sodium borohydride and nickel elements is (2-3):1.

[0018] In the above preparation process, the amount of sodium borohydride must be strictly controlled. This prevents the reaction from producing excessive gas and potentially causing an explosion. Furthermore, a suitable amount of sodium borohydride prevents complete reduction to elemental nickel (controlling the ratio of elemental nickel to nickel hydroxide). At the same time, a surplus of sodium borohydride maintains an alkaline environment, ensuring the formation of nickel hydroxide and manganese oxide. Furthermore, during the preparation process, the sodium borohydride solution must be added to the nickel solution first, followed by the manganese solution. This order ensures that elemental nickel and nickel hydroxide are formed in the solution first, followed by the formation of manganese oxide.

[0019] The preparation method is further preferably as follows: nickel chloride hexahydrate or nickel nitrate hexahydrate is mixed with water to prepare a nickel solution with a concentration of 0.5-0.15 mol / L; manganese chloride tetrahydrate or manganese nitrate hexahydrate is mixed with water to prepare a manganese solution with a concentration of 0.5-0.15 mol / L; sodium borohydride is added to water to prepare a sodium borohydride solution with a concentration of 0.5-0.15 mol / L; the sodium borohydride solution is uniformly poured into the nickel solution, and then the manganese solution is quickly added; the container containing the obtained mixed solution is gently rotated for 0.5-1.5 minutes, allowed to stand for 10-12 hours, and then washed, the washed supernatant is exchanged with deionized water and anhydrous ethanol, respectively, and vacuum dried for 6-12 hours to obtain a nickel-manganese aerogel catalyst; the molar ratio of the nickel and manganese elements is 1:(0.2-1.8); and the molar ratio of the sodium borohydride and nickel elements is (2-3):1.

[0020] The present invention provides an application of the nickel-manganese aerogel catalyst in electrocatalytic hydrogen production from an alkaline biomass solution: the nickel-manganese aerogel catalyst is used as an electrocatalyst, and an alkaline biomass aqueous solution is used as an electrolyte; the electrolyte comprises methanol, ethylene glycol or urea at a concentration of 0.1-1 mol / L and sodium hydroxide or potassium hydroxide at a concentration of 0.5-2 mol / L.

[0021] As mentioned in the background technology section, in the water electrolysis hydrogen production reaction, the oxygen evolution reaction [OER; 4OH − =O2+2H2O+4e −, 1.23 V (compared to the reversible hydrogen electrode (RHE))] is the bottleneck of efficiency. The electrons in the hydrogen production process (HER) come from the OER process and are therefore limited by the slow OER process. The present invention replaces the traditional OER process with the oxidation process of biomass organic matter, which can avoid the production of oxygen to improve production safety. It can be applied to safe and efficient hydrogen production in an alkaline environment at room temperature. The hydrogen production efficiency is controlled by the concentration of the alkaline biomass aqueous solution. In order to improve the hydrogen production efficiency, the ethylene glycol concentration is 0.1-1 mol / L; preferably, the concentration of the alkaline ethylene glycol solution is 0.5-1 mol / L; more preferably, the concentration of the alkaline ethylene glycol solution is 0.5 mol / L.

[0022] In the hydrogen production reaction of this invention, the hydrogen produced comes not only from biomass molecules such as ethylene glycol, but also partially from the solvent water and hydroxide ions in the alkaline environment. Ethylene glycol molecules and hydroxide ions adsorb on the catalyst surface, breaking carbon-hydrogen and oxygen-hydrogen bonds to produce a large number of hydrogen radicals, which then combine to produce hydrogen.

[0023] On the other hand, while hydrogen is produced at the cathode of the electrolytic cell, the anode produces ethylene glycol oxidation products such as formate and glycolate, which have additional economic value (taking biomass as ethylene glycol as an example, Figure 1 (The oxidation pathway of ethylene glycol in an alkaline environment) The production of formate results from the cleavage of the carbon-carbon bond in the ethylene glycol molecule, with the oxidation of the hydroxyl group to a carboxyl group; the production of glycolate results from the Concha Niro reaction of glyoxal generated by the oxidation of the hydroxyl group to an aldehyde group. Therefore, the nickel-manganese aerogel catalyst of the present invention can also be used in the production of formate and glycolate in the chemical industry. The electrolysis process achieves a selectivity of 96% for formate and 4% for glycolate. Preferably, the hydrogen production reaction temperature is room temperature, more preferably 25°C.

[0024] The hydrogen production system of the present invention has mild conditions and can produce hydrogen mildly at room temperature.

[0025] Preferably, the electrocatalyst is supported on a carrier, which is a conductive metal substrate or a non-metallic substrate. Further preferably, the carrier is selected from any one of a glassy carbon electrode, nickel foam, and a hydrophilic carbon cloth.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The nickel and manganese oxide in the nickel-manganese aerogel catalyst of the present invention are crystalline, while the nickel hydroxide is amorphous. When it is applied to the electrocatalytic production of hydrogen from alkaline biomass aqueous solution, it can promote the charge transfer during the oxygen evolution reaction and has an ultra-high electrocatalytic oxidation performance (overpotential of 120 mV@10 mA cm in ethylene glycol electrolyte). -2, overpotential in methanol electrolyte 141 mV@10 mA cm -2 、Overpotential in urea electrolyte 132 mV@10 mA cm -2 ).

[0028] (2) The hydrogen production system of the present invention replaces the OER process with the oxidation process of biomass such as ethylene glycol to provide electrons, which can promote the hydrogen production of the HER process. It has the characteristics of high hydrogen production efficiency, mild hydrogen production conditions (room temperature), and safe catalytic process (no hydrogen and oxygen are produced at the same time).

[0029] (3) The hydrogen production system of the present invention can produce by-products with economic value while producing hydrogen. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is the electrocatalytic oxidation pathway of ethylene glycol in an alkaline environment;

[0031] Figure 2 This is a comparison chart of the electrocatalytic performance of aerogels prepared in Examples 1-5 and Comparative Examples 1-2;

[0032] Figure 3 XRD pattern of the nickel-manganese aerogel catalyst prepared in Example 3 and after calcination and annealing at 400°C in nitrogen;

[0033] Figure 4 This is the FTIR test image of the nickel-manganese aerogel catalyst prepared in Example 3;

[0034] Figure 5 This is the XPS test chart of the nickel-manganese aerogel catalyst prepared in Example 3;

[0035] Figure 6 Polarization curves of nickel-manganese aerogel catalyst in different systems;

[0036] Figure 7 Polarization curves of nickel-manganese aerogel catalyst loaded on different supports;

[0037] Figure 8 is the Faradaic efficiency of nickel-manganese aerogel catalyst in alkaline ethylene glycol environment;

[0038] Figure 9 is the open circuit potential in different electrolyte solutions;

[0039] Figure 10 This is the ion chromatogram of the electrolyte after long-term electrolysis. DETAILED DESCRIPTION

[0040] The present invention will be further described below with reference to the embodiments.

[0041] Example 1

[0042] A nickel-manganese aerogel catalyst was prepared using nickel chloride hexahydrate, manganese chloride tetrahydrate, sodium borohydride, and deionized water as raw materials. The preparation method was as follows: 0.11885g of nickel chloride hexahydrate (NiCl2·6H2O) was placed in a 30ml glass bottle and 5ml of deionized water was added to prepare a 0.1mol / L nickel chloride solution. 0.0198g of manganese chloride tetrahydrate (MnCl2·4H2O) was placed in another container and 5ml of deionized water was added to prepare a 0.02mol / L solution for later use. 0.058g of sodium borohydride (NaBH4) was added to 15ml of deionized water to prepare a 0.1mol / L solution. This solution was then uniformly poured into the prepared nickel chloride solution, followed by the rapid addition of the manganese chloride solution. The glass bottle containing the mixed solution was gently swirled for 1 minute, allowed to stand for 12 hours, and then washed. The supernatant in the washing bottle was carefully exchanged three times with deionized water and anhydrous ethanol respectively, and stored with ethanol as the liquid phase. The solution was placed in a vacuum dryer and dried for 8 hours to obtain the catalyst.

[0043] Example 2

[0044] A nickel-manganese aerogel catalyst was prepared using nickel chloride hexahydrate, manganese chloride tetrahydrate, sodium borohydride, and deionized water as raw materials. The preparation method was as follows: 0.11885g of nickel chloride hexahydrate (NiCl2·6H2O) was placed in a 30ml glass bottle and 5ml of deionized water was added to prepare a 0.1mol / L nickel chloride solution. 0.0594g of manganese chloride tetrahydrate (MnCl2·4H2O) was placed in another container and 5ml of deionized water was added to prepare a 0.06mol / L solution for later use. 0.058g of sodium borohydride (NaBH4) was added to 15ml of deionized water to prepare a 0.1mol / L solution. This solution was then uniformly poured into the prepared nickel chloride solution, followed by the rapid addition of the manganese chloride solution. The glass bottle containing the mixed solution was gently swirled for 1 minute, allowed to stand for 12 hours, and then washed. The supernatant in the washing bottle was carefully exchanged three times with deionized water and anhydrous ethanol respectively, and stored with ethanol as the liquid phase. The solution was placed in a vacuum dryer and dried for 8 hours to obtain the catalyst.

[0045] Example 3

[0046] A nickel-manganese aerogel catalyst material was prepared using nickel chloride hexahydrate, manganese chloride tetrahydrate, sodium borohydride, and deionized water as raw materials. The preparation method was as follows: 0.11885g of nickel chloride hexahydrate (NiCl2·6H2O) was placed in a 30ml glass bottle and 5ml of deionized water was added to prepare a 0.1mol / L nickel chloride solution. 0.099g of manganese chloride tetrahydrate (MnCl2·4H2O) was placed in another container and 5ml of deionized water was added to prepare a 0.1mol / L solution for later use. 0.058g of sodium borohydride (NaBH4) was added to 15ml of deionized water to prepare a 0.1mol / L solution. This solution was uniformly poured into the prepared nickel chloride solution, followed by the rapid addition of the manganese chloride solution. The glass bottle containing the mixed solution was gently swirled for 1 minute, allowed to stand for 12 hours, and then washed. The supernatant in the washing bottle was carefully exchanged three times with deionized water and anhydrous ethanol respectively, and stored with ethanol as the liquid phase. The solution was placed in a vacuum dryer and dried for 8 hours to obtain the catalyst.

[0047] Example 4

[0048] A nickel-manganese aerogel catalyst was prepared using nickel chloride hexahydrate, manganese chloride tetrahydrate, sodium borohydride, and deionized water as raw materials. The preparation method was as follows: 0.11885g of nickel chloride hexahydrate (NiCl2·6H2O) was placed in a 30ml glass bottle and 5ml of deionized water was added to prepare a 0.1 mol / L nickel chloride solution. 0.1386g of manganese chloride tetrahydrate (MnCl2·4H2O) was placed in another container and 5ml of deionized water was added to prepare a 0.14 mol / L solution for later use. 0.058g of sodium borohydride (NaBH4) was added to 15ml of deionized water to prepare a 0.1 mol / L solution. This solution was then uniformly poured into the prepared nickel chloride solution, followed by the rapid addition of the manganese chloride solution. The glass bottle containing the mixed solution was gently swirled for 1 minute, allowed to stand for 11 hours, and then washed. The supernatant in the washing bottle was carefully exchanged three times with deionized water and anhydrous ethanol respectively, and stored with ethanol as the liquid phase. The solution was placed in a vacuum dryer and dried for 8 hours to obtain the catalyst.

[0049] Example 5

[0050] A nickel-manganese aerogel catalyst was prepared using nickel chloride hexahydrate, manganese chloride tetrahydrate, sodium borohydride, and deionized water as raw materials. The preparation method was as follows: 0.11885g of nickel chloride hexahydrate (NiCl2·6H2O) was placed in a 30ml glass bottle and 5ml of deionized water was added to prepare a 0.1mol / L nickel chloride solution. 0.1782g of manganese chloride tetrahydrate (MnCl2·4H2O) was placed in another container and 5ml of deionized water was added to prepare a 0.18mol / L solution for later use. 0.058g of sodium borohydride (NaBH4) was added to 15ml of deionized water to prepare a 0.1mol / L solution. This solution was then uniformly poured into the prepared nickel chloride solution, followed by the rapid addition of the manganese chloride solution. The glass bottle containing the mixed solution was gently swirled for 1 minute, allowed to stand for 10 hours, and then washed. The supernatant in the washing bottle was carefully exchanged three times with deionized water and anhydrous ethanol respectively, and stored with ethanol as the liquid phase. The solution was placed in a vacuum dryer and dried for 8 hours to obtain the catalyst.

[0051] Comparative Example 1

[0052] A nickel-manganese aerogel catalyst was prepared using nickel chloride hexahydrate, manganese chloride tetrahydrate, sodium borohydride, and deionized water as raw materials. The preparation method was as follows: 0.11885g of nickel chloride hexahydrate (NiCl2·6H2O) was placed in a 30ml glass bottle and 5ml of deionized water was added to prepare a 0.1mol / L nickel chloride solution. 0.0099g of manganese chloride tetrahydrate (MnCl2·4H2O) was placed in another container and 5ml of deionized water was added to prepare a 0.01mol / L solution for later use. 0.058g of sodium borohydride (NaBH4) was added to 15ml of deionized water to prepare a 0.1mol / L solution. This solution was uniformly poured into the prepared nickel chloride solution, followed by the rapid addition of the manganese chloride solution. The glass bottle containing the mixed solution was gently swirled for 1 minute, allowed to stand for 12 hours, and then washed. The supernatant in the washing bottle was carefully exchanged three times with deionized water and anhydrous ethanol respectively, and stored with ethanol as the liquid phase. The solution was placed in a vacuum dryer and dried for 8 hours to obtain the catalyst.

[0053] Comparative Example 2

[0054] A nickel-manganese aerogel catalyst was prepared using nickel chloride hexahydrate, manganese chloride tetrahydrate, sodium borohydride, and deionized water as raw materials. The preparation method was as follows: 0.11885g of nickel chloride hexahydrate (NiCl2·6H2O) was placed in a 30ml glass bottle and 5ml of deionized water was added to prepare a 0.1mol / L nickel chloride solution. 0.198g of manganese chloride tetrahydrate (MnCl2·4H2O) was placed in another container and 5ml of deionized water was added to prepare a 0.2mol / L solution for later use. 0.058g of sodium borohydride (NaBH4) was added to 15ml of deionized water to prepare a 0.1mol / L solution. This solution was then uniformly poured into the prepared nickel chloride solution, followed by the rapid addition of the manganese chloride solution. The glass bottle containing the mixed solution was gently swirled for 1 minute, allowed to stand for 12 hours, and then washed. The supernatant in the washing bottle was carefully exchanged three times with deionized water and anhydrous ethanol respectively, and stored with ethanol as the liquid phase. The solution was placed in a vacuum dryer and dried for 8 hours to obtain the catalyst.

[0055] Example 6

[0056] A nickel-manganese aerogel catalyst was prepared using nickel nitrate hexahydrate, manganese nitrate hexahydrate, sodium borohydride, and deionized water as raw materials. The preparation method was as follows: 0.145g of Ni(NO₃)₂·6H₂O was placed in a 30ml glass bottle and 5ml of deionized water was added to prepare a 0.1 mol / L nickel chloride solution. 0.0287g of manganese nitrate hexahydrate (Mn(NO₃)₂·6H₂O) was placed in another container and 5ml of deionized water was added to prepare a 0.02 mol / L solution for later use. 0.058g of sodium borohydride (NaBH₄) was added to 15ml of deionized water to prepare a 0.1 mol / L solution. The experiment was performed in a fume hood. The sodium borohydride solution was uniformly poured into the prepared nickel chloride solution, followed by the rapid addition of the manganese chloride solution. The glass bottle containing the mixed solution was gently swirled for 1 minute, allowed to stand for 10 hours, and then washed. The supernatant in the washing bottle was carefully exchanged three times with deionized water and anhydrous ethanol respectively, and stored with ethanol as the liquid phase. The solution was placed in a vacuum dryer and dried for 8 hours to obtain the catalyst.

[0057] Example 7

[0058] A nickel-manganese aerogel catalyst was prepared using nickel nitrate hexahydrate, manganese nitrate hexahydrate, sodium borohydride, and deionized water as raw materials. The preparation method was as follows: 0.145g of Ni(NO₃)₂·6H₂O was placed in a 30ml glass bottle and 5ml of deionized water was added to prepare a 0.1 mol / L nickel chloride solution. 0.0862g of manganese nitrate hexahydrate (Mn(NO₃)₂·6H₂O) was placed in another container and 5ml of deionized water was added to prepare a 0.06 mol / L solution for later use. 0.058g of sodium borohydride (NaBH₄) was added to 15ml of deionized water to prepare a 0.1 mol / L solution. The experiment was performed in a fume hood. The sodium borohydride solution was uniformly poured into the prepared nickel chloride solution, followed by the rapid addition of the manganese chloride solution. The glass bottle containing the mixed solution was gently swirled for 1 minute, allowed to stand for 10 hours, and then washed. The supernatant in the washing bottle was carefully exchanged three times with deionized water and anhydrous ethanol respectively, and stored with ethanol as the liquid phase. The solution was placed in a vacuum dryer and dried for 8 hours to obtain the catalyst.

[0059] Example 8

[0060] A nickel-manganese aerogel catalyst was prepared using nickel nitrate hexahydrate, manganese nitrate hexahydrate, sodium borohydride, and deionized water as raw materials. The preparation method was as follows: 0.145g of Ni(NO₃)₂·6H₂O was placed in a 30ml glass bottle and 5ml of deionized water was added to prepare a 0.1 mol / L nickel chloride solution. 0.1437g of manganese nitrate hexahydrate (Mn(NO₃)₂·6H₂O) was placed in another container and 5ml of deionized water was added to prepare a 0.1 mol / L solution for later use. 0.058g of sodium borohydride (NaBH₄) was added to 15ml of deionized water to prepare a 0.1 mol / L solution. The experiment was performed in a fume hood. The sodium borohydride solution was uniformly poured into the prepared nickel chloride solution, followed by the rapid addition of the manganese chloride solution. The glass bottle containing the mixed solution was gently swirled for 1 minute, allowed to stand for 10 hours, and then washed. The supernatant in the washing bottle was carefully exchanged three times with deionized water and anhydrous ethanol respectively, and stored with ethanol as the liquid phase. The solution was placed in a vacuum dryer and dried for 8 hours to obtain the catalyst.

[0061] Example 9

[0062] A nickel-manganese aerogel catalyst was prepared using nickel nitrate hexahydrate, manganese nitrate hexahydrate, sodium borohydride, and deionized water as raw materials. The preparation method was as follows: 0.145g of Ni(NO₃)₂·6H₂O) was placed in a 30ml glass bottle and 5ml of deionized water was added to prepare a 0.1 mol / L nickel chloride solution. 0.201g of manganese nitrate hexahydrate (Mn(NO₃)₂·6H₂O) was placed in another container and 5ml of deionized water was added to prepare a 0.14 mol / L solution for later use. 0.058g of sodium borohydride (NaBH₄) was added to 15ml of deionized water to prepare a 0.1 mol / L solution. The experiment was performed in a fume hood. The sodium borohydride solution was uniformly poured into the prepared nickel chloride solution, followed by the rapid addition of the manganese chloride solution. The glass bottle containing the mixed solution was gently swirled for 1 minute, allowed to stand for 10 hours, and then washed. The supernatant in the washing bottle was carefully exchanged three times with deionized water and anhydrous ethanol respectively, and stored with ethanol as the liquid phase. The solution was placed in a vacuum dryer and dried for 8 hours to obtain the catalyst.

[0063] Example 10

[0064] When using glassy carbon electrodes, nickel foam, and hydrophilic flexible carbon cloth as test carriers, the carriers were pretreated. For the glassy carbon electrode, 0.05 μm alumina powder was added with a small amount of water and polished until smooth. For the nickel foam and flexible carbon cloth, they were soaked in 1M hydrochloric acid, acetone, and water, followed by ultrasonic cleaning for 5 minutes each, and then dried for use to remove surface oxides and oil stains.

[0065] Example 11

[0066] Take 5g of each catalyst prepared in Examples 1-5 and Comparative Examples 1-2, mix them with 50μl Nafion117 solution, 250μl isopropanol, and 700μl water, respectively, and place them in an ultrasonic instrument for ultrasonic dispersion for 5-10min to prepare catalyst ink. Take 50μl of ink respectively, drop it on a glassy carbon electrode with a diameter of 3mm in 5 times and dry it as the anode working electrode, the stone mill rod as the cathode electrode, and the silver / silver chloride electrode as the reference electrode, which together constitute a three-electrode system. The electrolyte solution uses 50ml of alkaline ethylene glycol solution, the potassium hydroxide concentration is 1mol / L, and the ethylene glycol concentration is 0.5mol / L. The electrolytic cell is connected to the Chenhua electrochemical workstation for electrochemical testing to test the different electrocatalytic properties of nickel-manganese aerogels under different nickel-manganese ratios.

[0067] like Figure 2 As shown in Figure 3, the catalyst prepared in Example 3 has the best performance, with an overpotential of only 120 mV@10 mA cm in ethylene glycol electrolyte. -2 In sharp contrast, the overpotentials of comparative examples 1 and 2, which have poor performance, reached 300 mV @ 10 mA cm -2and 330mV@10mAcm -2 Because the nickel ratio in Comparative Example 1 exceeded the specified range, the relatively small amount of manganese oxide on the surface was insufficient to form an effective synergistic effect with the large amount of nickel material. This weakened synergistic effect made it difficult for the catalyst to form an effective catalytic effect. In Comparative Example 2, the manganese ratio exceeded the specified range, and a large amount of manganese oxide covered the surface of the material, reducing the number of catalytically effective nickel sites in contact with the electrolyte solution. Therefore, it was also difficult to form an effective catalytic effect.

[0068] Test of catalytic hydrogen production effect of nickel-manganese aerogel catalyst in different alkaline biomass solutions

[0069] Example 12

[0070] The nickel-manganese aerogel material prepared in Example 3 has an aerogel structure with a high porosity greater than 75%. Figure 3 The prepared nickel-manganese aerogel material and the XRD pattern after calcination and annealing at 400°C in nitrogen show that crystalline nickel oxide, crystalline manganese oxide, and crystalline nickel are present in the calcined material; Figure 4 The infrared spectrum of the material is shown as follows. The nickel-manganese aerogel has an infrared spectrum of 764 cm -1 , 618.21cm -1 There are characteristic peaks, which are metal hydroxide -OH and MOM. The results show that metal hydroxide exists on the surface of the catalyst; Figure 5 The XPS test results of the material shown in Figure 2 show that there are zero-valent and divalent states of Ni, and the valence state of Mn is divalent, which proves that the existence of Ni and Mn in the material is Ni 0 、Ni 2+ 、Mn 2+ XRD refers to X-ray diffraction, SEM refers to scanning electron microscopy, TEM refers to transmission electron microscopy, and XPS refers to X-ray photoelectron spectroscopy.

[0071] Take 5 mg of the nickel-manganese aerogel powder prepared in Example 3, mix it with 50 μl of Nafion117 solution, 250 μl of isopropanol, and 700 μl of water, and place it in an ultrasonic instrument for ultrasonic dispersion for 10 minutes to prepare a catalyst ink. Take 50 μl of ink, drop it on a 1cm×1cm×5mm nickel foam and dry it as the anode working electrode, the stone mill rod as the cathode electrode, and the silver / silver chloride electrode as the reference electrode, which together constitute a three-electrode system. The electrolyte solution uses 50 ml of alkaline ethylene glycol solution, the potassium hydroxide concentration is 1 mol / L, and the ethylene glycol concentration is 0.5 mol / L. The electrolytic cell is connected to the Chenhua electrochemical workstation for electrochemical testing to test the electrocatalytic performance of the nickel-manganese aerogel.

[0072] Example 13

[0073] Take 5 mg of the nickel-manganese aerogel powder prepared in Example 3, mix it with 50 μl of Nafion117 solution, 250 μl of isopropanol, and 700 μl of water, and place it in an ultrasonic instrument for ultrasonic dispersion for 10 minutes to prepare a catalyst ink. Take 50 μl of ink, drop it on a 1cm×1cm×5mm nickel foam and dry it as the anode working electrode, the stone mill rod as the cathode electrode, and the silver / silver chloride electrode as the reference electrode, together forming a three-electrode system. The electrolyte solution uses 50 ml of alkaline urea solution, the potassium hydroxide concentration is 1 mol / L, and the urea concentration is 0.5 mol / L. The electrolytic cell is connected to the Chenhua electrochemical workstation for electrochemical testing to test the electrocatalytic performance of the nickel-manganese aerogel.

[0074] Example 14

[0075] Take 5 mg of the nickel-manganese aerogel powder prepared in Example 3, mix it with 50 μl of Nafion117 solution, 250 μl of isopropanol, and 700 μl of water, and place it in an ultrasonic instrument for ultrasonic dispersion for 5-10 minutes to prepare a catalyst ink. Take 50 μl of ink, drop it on a 1cm×1cm×5mm nickel foam and dry it as the anode working electrode, the stone mill rod as the cathode electrode, and the silver / silver chloride electrode as the reference electrode, which together constitute a three-electrode system. The electrolyte solution uses 50 ml of alkaline methanol solution, the potassium hydroxide concentration is 1 mol / L, and the methanol concentration is 0.5 mol / L. The electrolytic cell is connected to the Chenhua electrochemical workstation for electrochemical testing to test the electrocatalytic performance of the nickel-manganese aerogel.

[0076] Examples 12-14 studied the effects of using different alkaline biomass solutions as electrolyte solutions in hydrogen production systems on the electrocatalytic results. Different biomasses have different oxidation potentials and will produce different results. Figure 6 The data shows that catalytic hydrogen production in alkaline ethylene glycol, alkaline urea, and alkaline methanol solutions significantly improves compared to traditional alkaline aqueous solutions, demonstrating the effectiveness of replacing the OER process with biomass molecules in promoting the overall reaction. Among them, the nickel-manganese aerogel catalyst is most effective in catalyzing hydrogen production in alkaline ethylene glycol solutions, and its performance remains stable even after long periods of catalysis.

[0077] Catalytic effect test of nickel-manganese aerogel catalyst under different catalyst supports

[0078] Example 15

[0079] Take 5 mg of the nickel-manganese aerogel powder prepared in Example 3, mix it with 50 μl of Nafion117 solution, 250 μl of isopropanol, and 700 μl of water, and place it in an ultrasonic instrument for ultrasonic dispersion for 10 minutes to prepare a catalyst ink. Take 50 μl of ink, drop it 5 times on a hydrophilic flexible carbon cloth of size 1 cm × 1 cm and dry it as the anode working electrode, the stone mill rod as the cathode electrode, and the silver / silver chloride electrode as the reference electrode, which together constitute a three-electrode system. The electrolyte solution uses 50 ml of alkaline ethylene glycol solution, the potassium hydroxide concentration is 1 mol / L, and the ethylene glycol concentration is 0.5 mol / L. The electrolytic cell is connected to the Chenhua electrochemical workstation for electrochemical testing to test the electrocatalytic performance of the nickel-manganese aerogel.

[0080] Example 16

[0081] Take 5 mg of the nickel-manganese aerogel powder prepared in Example 3, mix it with 50 μl of Nafion117 solution, 250 μl of isopropanol, and 700 μl of water, and place it in an ultrasonic instrument for ultrasonic dispersion for 10 minutes to prepare a catalyst ink. Take 50 μl of ink and drop it 5 times on a nickel foam of size 1 cm × 1 cm × 5 mm and dry it as the anode working electrode, the stone mill rod as the cathode electrode, and the silver / silver chloride electrode as the reference electrode, which together constitute a three-electrode system. The electrolyte solution uses 50 ml of alkaline ethylene glycol solution, the potassium hydroxide concentration is 1 mol / L, and the ethylene glycol concentration is 0.5 mol / L. The electrolytic cell is connected to the Chenhua electrochemical workstation for electrochemical testing to test the electrocatalytic performance of the nickel-manganese aerogel.

[0082] Example 17

[0083] Take 5 mg of the nickel-manganese aerogel powder prepared in Example 3, mix it with 50 μl of Nafion117 solution, 250 μl of isopropanol, and 700 μl of water, and place it in an ultrasonic instrument for ultrasonic dispersion for 10 minutes to prepare a catalyst ink. Take 50 μl of ink, drop it on a glassy carbon electrode with a diameter of 3 mm in 5 times and dry it as the anode working electrode, the stone mill rod as the cathode electrode, and the silver / silver chloride electrode as the reference electrode, which together constitute a three-electrode system. The electrolyte solution uses 50 ml of alkaline ethylene glycol solution, the potassium hydroxide concentration is 1 mol / L, and the ethylene glycol concentration is 0.5 mol / L. The electrolytic cell is connected to the Chenhua electrochemical workstation for electrochemical testing to test the electrocatalytic performance of the nickel-manganese aerogel.

[0084] Examples 12 and 15-17 studied the effects of different catalyst supports on the catalytic effect of the electrodes of the electrolytic cell system in the hydrogen production system ( Figure 7 ), and the catalytic effect of blank carriers without loaded catalysts on alkaline ethylene glycol aqueous solution has been tested, eliminating the influence of the carrier on the catalytic hydrogen production effect of nickel-manganese aerogel catalyst.

[0085] Actual hydrogen production efficiency (i.e., Faraday efficiency) of nickel-manganese aerogel catalyst when catalyzing hydrogen production from alkaline ethylene glycol solution

[0086] Example 18

[0087] Take 5 mg of the nickel-manganese aerogel powder prepared in Example 3, mix it with 50 μl of Nafion117 solution, 250 μl of isopropanol, and 700 μl of water, and place it in an ultrasonic instrument for ultrasonic dispersion for 10 minutes to prepare a catalyst ink. Take 50 μl of ink, drop it on a hydrophilic flexible carbon cloth of size 1 cm × 1 cm in 5 times and dry it as the anode working electrode. Take 5 mg of commercial platinum / carbon catalyst, make ink according to the above operation and make the cathode working electrode according to the same operation, together forming a two-electrode electrolytic cell system. The electrolyte solution uses 50 ml of alkaline ethylene glycol solution, with a potassium hydroxide concentration of 1 mol / L and an ethylene glycol concentration of 0.5 mol / L. The electrolytic cell is connected to the Chenhua electrochemical workstation for electrochemical testing to test the electrocatalytic hydrogen production efficiency of the nickel-manganese aerogel. Seal the electrolytic cell with a polytetrafluoroethylene film and pass nitrogen for 1 hour to remove the air in the electrolytic cell. Electrochemical tests were performed at an applied voltage of 1.7 V. The hydrogen content in the system was tested every 5 minutes after the start of the catalytic reaction. The generation of hydrogen was detected by GC-TCD gas chromatography (the filling column was a Porapak Q column or a 5A molecular sieve column).

[0088] Example 19

[0089] Take 5 mg of the nickel-manganese aerogel powder prepared in Example 3, mix it with 50 μl of Nafion 117 solution, 250 μl of isopropanol, and 700 μl of water, and place it in an ultrasonic instrument for ultrasonic dispersion for 10 minutes to prepare a catalyst ink. Take 50 μl of ink, drop it on a hydrophilic flexible carbon cloth of size 1 cm × 1 cm in 5 times and dry it as the anode working electrode. Take 5 mg of commercial platinum / carbon catalyst, make ink according to the above operation and make the cathode working electrode according to the same operation, together forming a dual-electrode electrolytic cell system. The electrolyte solution uses 50 ml of alkaline ethylene glycol solution, with a potassium hydroxide concentration of 1 mol / L and an ethylene glycol concentration of 0.5 mol / L. The electrolytic cell is connected to the Chenhua electrochemical workstation for electrochemical testing to test the electrocatalytic hydrogen production efficiency of the nickel-manganese aerogel. Seal the electrolytic cell with a polytetrafluoroethylene film and pass nitrogen for 1 hour to remove the air in the electrolytic cell. Electrochemical tests were carried out at applied voltages of 1.5 V, 1.6 V, 1.7 V, and 1.8 V, respectively. The hydrogen content in the system was tested 5 minutes after the start of the catalytic reaction. The generation of hydrogen was detected by GC-TCD gas chromatography (the filling column was Porapak Q column or 5A molecular sieve column).

[0090] Examples 18-19 studied the actual hydrogen production efficiency, ie, the Faraday efficiency, of the nickel-manganese aerogel catalyst when catalyzing hydrogen production from an alkaline ethylene glycol solution. Figure 8The data show that the two methods of testing Faraday efficiency prove that the Faraday efficiency of this system is above 90%, proving that the nickel-manganese aerogel catalyst has a high energy conversion rate in actual catalytic hydrogen production applications, can efficiently carry out reactions, avoid the waste of external energy, and prove the high efficiency and feasibility of catalytic hydrogen production of this system.

[0091] Example 20

[0092] 5 mg of the nickel-manganese aerogel powder prepared in Example 3 was mixed with 50 μl of Nafion 117 solution, 250 μl of isopropyl alcohol, and 700 μl of water. The mixture was then ultrasonically dispersed in an ultrasonicator for 10 minutes to prepare a catalyst ink. 50 μl of the ink was then dropped onto two 1 cm × 1 cm hydrophilic flexible carbon cloths in five separate drops and dried. These served as the anode working electrode, a stone mill rod served as the cathode electrode, and a silver / silver chloride electrode served as the reference electrode, forming a three-electrode system. The electrolytes used were the alkaline ethylene glycol aqueous solution described in Example 8 and a 1 mol / L sodium hydroxide aqueous solution, respectively. The open-circuit potential changes under the two conditions were measured. Figure 9 The results of the open circuit potential changes under the two environments show that the nickel-manganese aerogel material catalyst can react in advance in the alkaline ethylene glycol solution, which is beneficial to the catalytic process.

[0093] Example 20 studies the strategy of using alkaline ethylene glycol aqueous solution instead of traditional pure alkaline aqueous solution for electrolytic hydrogen production, which has the advantages of fast reaction start and high reaction efficiency, and has the feasibility of optimizing practical applications.

[0094] Example 21

[0095] Taking the catalytic system constructed in Example 18 as an example, the catalytic system was maintained at a current of 100 mA for 36 hours, and 50 ml of electrolyte was taken for ion chromatography test. The results are as follows: Figure 10 As shown, the selectivity for formate is 96% and the selectivity for glycolate is 4%. The nickel-manganese aerogel catalyst has good selectivity for the oxidation of alkaline ethylene glycol solution, and can efficiently produce products with additional economic benefits while producing hydrogen through electrolysis.

[0096] Unless otherwise specified, the raw materials and equipment used in the present invention are commonly used in the art; the methods used in the present invention are conventional methods in the art unless otherwise specified.

[0097] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent transformation made to the above embodiment based on the technical essence of the present invention still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A nickel-manganese aerogel catalyst, characterized in that: The invention relates to an aerogel structure having a porosity greater than 75%, with a crystalline nickel skeleton, the skeleton surface of which is covered with amorphous nickel hydroxide and crystalline manganese oxide. The molar ratio of nickel to manganese in the raw materials of the nickel-manganese aerogel catalyst is 1:(0.2-1.8). The nickel-manganese aerogel catalyst is prepared by the following method: mixing a nickel salt with water to prepare a nickel solution; mixing a manganese salt with water to prepare a manganese solution; adding sodium borohydride to water to prepare a sodium borohydride solution; uniformly pouring the sodium borohydride solution into the nickel solution, and then quickly adding the manganese solution; gently rotating the container containing the obtained mixed solution, letting it stand and then washing, exchanging the washed supernatant with deionized water and anhydrous ethanol respectively, and vacuum drying to obtain the nickel-manganese aerogel catalyst.

2. The nickel-manganese aerogel catalyst according to claim 1, wherein: After the catalyst is prepared, the molar ratio of nickel to manganese elements is 1:

1.

3. The nickel-manganese aerogel catalyst according to claim 1, wherein: The aerogel structure has a porosity of 78.6%-85.2%.

4. The nickel-manganese aerogel catalyst according to claim 1, wherein: The molar ratio of the sodium borohydride to the nickel element is (2-3):

1.

5. The nickel-manganese aerogel catalyst according to claim 1, wherein: Nickel chloride hexahydrate or nickel nitrate hexahydrate is mixed with water to prepare a nickel solution with a concentration of 0.5-0.15 mol / L; manganese chloride tetrahydrate or manganese nitrate hexahydrate is mixed with water to prepare a manganese solution with a concentration of 0.5-0.15 mol / L; sodium borohydride is added to water to prepare a sodium borohydride solution with a concentration of 0.5-0.15 mol / L; The sodium borohydride solution is uniformly poured into the nickel solution, and then the manganese solution is quickly added; the container containing the obtained mixed solution is gently rotated for 0.5-1.5 minutes, allowed to stand for 10-12 hours, and then washed. The washed supernatant is exchanged with deionized water and anhydrous ethanol, respectively, and vacuum dried for 6-12 hours to obtain a nickel-manganese aerogel catalyst; the molar ratio of the nickel and manganese elements is 1: (0.2-1.8); and the molar ratio of the sodium borohydride and nickel elements is (2-3):

1.

6. Application of nickel-manganese aerogel catalyst in electrocatalytic hydrogen production from alkaline biomass aqueous solution, characterized by: The nickel-manganese aerogel catalyst according to any one of claims 1 to 5 is used as an electrocatalyst, and an alkaline biomass aqueous solution is used as an electrolyte; the electrolyte includes methanol, ethylene glycol or urea with a concentration of 0.1-1 mol / L and sodium hydroxide or potassium hydroxide with a concentration of 0.5-2 mol / L.

7. The use according to claim 6, characterized in that: The electrolyte includes ethylene glycol at a concentration of 0.5-1 mol / L; The reaction temperature of the hydrogen production is room temperature.

8. The use according to claim 6, characterized in that: The electrocatalyst is loaded in a carrier; the carrier is a metal substrate or a non-metal substrate with conductive properties.

9. The use according to claim 8, characterized in that: The carrier is selected from any one of a glassy carbon electrode, nickel foam and hydrophilic carbon cloth.

10. Use of nickel-manganese aerogel catalyst in the preparation of formate or glycolate, characterized in that: The nickel-manganese aerogel catalyst according to any one of claims 1 to 5 is used as an electrocatalyst, and an alkaline biomass aqueous solution is used as an electrolyte; the electrolyte includes methanol, ethylene glycol or urea.

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