Preparation method and application of high-activity NiCe (OH) n / NF

Abstract

The invention belongs to the technical field of electrocatalytic hydrolysis, and particularly relates to a preparation method and application of high-activity NiCe (OH) n / NF. A noble metal catalyst is not used, so that the use cost is greatly reduced. The positive electrode obtains glucaric acid in an electrooxidation mode, meanwhile, the active center NiOOH can stably exist in an alkaline environment in a circulation mode, and the negative electrode produces hydrogen. And due to the redox cycle between Ni (OH) 2 and NiOOH, the overpotential can be effectively reduced, and the electric energy loss is reduced. And due to the synergistic effect of a small amount of cerium, the system can realize high-efficiency hydrogen production while obtaining the glucaric acid with high additional value. According to the method, glucose is catalyzed by using a circulating system to obtain glucaric acid, meanwhile, the anode glucose yield reaches 70%, and the cathode hydrogen evolution efficiency is close to 100%. Compared with a traditional water electrolysis hydrogen production process, the glucose oxidation assisted low-potential couple circulation coupling hydrogen production method conforms to'green chemistry 'and is lower in cost, and harsh reaction conditions and complex separation steps are avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of electrocatalytic hydrolysis, and in particular relates to a preparation method of high-activity NiCe(OH)n / NF and application thereof. Background Art

[0002] Hydrogen energy is a renewable energy source with the advantages of high energy density, non-toxicity, and no pollution to the environment. It is hailed as a promising clean energy carrier to replace fossil fuels to solve the energy crisis and alleviate environmental problems.

[0003] Water electrolysis is currently the most promising way to produce hydrogen, because it can use electricity generated by various renewable energy sources such as solar energy and wind energy to drive water decomposition. In the traditional water electrolysis hydrogen production system, there are mainly two parts: one is the oxygen evolution reaction (OER) occurring at the anode, and the other is the hydrogen evolution reaction (HER) occurring at the cathode. OER is a relatively complex four-electron transfer process with inherently slow reaction kinetics and a high theoretical potential (1.23Vvs.RHE), which leads to a large overpotential for driving it, greatly reducing the energy conversion efficiency of water electrolysis, making water electrolysis have the defect of high energy consumption. At the same time, if the O2 and H2 produced by water electrolysis are cross-mixed, there is a risk of explosion. This limits its large-scale application. Therefore, it is very necessary to develop a low-cost, high-efficiency, green and safe electrocatalytic hydrogen production system.

[0004] In order to solve the above problems, some recent research works have replaced OER with thermodynamically more favorable anodic small molecule oxidation reactions, such as ethylene glycol oxidation, glycerol oxidation and 5-hydroxymethylfurfural oxidation. This hybrid water electrolysis system reduces the total energy consumption for effective hydrogen production and obtains value-added products at the anode. However, there are still many problems in its practical application. First, although the oxidation of organic small molecules can reduce the overall cell voltage to a certain extent, the system is relatively simple and is generally replaced by the oxidation of simple organic small molecules. Secondly, although the anode can obtain higher-value chemicals through design, the complexity of the product increases the cost of separation and purification. Third, the value of some anode products is even lower than that of the reactants. Therefore, the selection of suitable organic small molecules and the development of a coupled efficient hydrogen production system that can achieve both a lower electrolysis voltage and produce value-added chemicals at the anode are key technologies that must be solved. Summary of the invention

[0005] The present invention aims to overcome the defects of the prior art electrocatalytic hydrogen production system, such as too high anode reaction potential, high energy consumption for hydrogen production, high cost, low hydrogen production efficiency and difficulty in obtaining high value-added by-products. A method for preparing highly active NiCe(OH)n / NF is provided, and the method is applied to the electro-oxidation of glucose-assisted cycle coupling for efficient hydrogen production.

[0006] To achieve the above-mentioned purpose, the present invention is implemented by the following technical solutions: A method for preparing highly active NiCe(OH)n / NF comprises the following steps: (S.1) dissolving nickel acetate tetrahydrate, cerium acetate tetrahydrate, ammonium fluoride and urea in deionized water under stirring, then transferring the mixture into a reaction kettle and adding nickel foam to carry out a hydrothermal reaction. After the reaction is completed, the nickel foam coated with nickel cerium hydroxide is taken out, washed, dried and subjected to potential scanning by cyclic voltammetry to obtain an anode material NiCe(OH)n / NF of nickel foam coated with nickel cerium hydroxide; (S.2) adding cobalt nitrate hexahydrate, sodium p-hydroxybenzenesulfonate dihydrate, urea and ammonium fluoride into deionized water and stirring to obtain a precursor solution, which is then transferred into a reactor and nickel foam is added to perform a hydrothermal reaction. After the reaction is completed, the solution is taken out and washed and dried to obtain a cobalt-phosphorus compound precursor Co(OH)n / NF. The cobalt-phosphorus compound precursor Co(OH)n / NF and sodium hypophosphite are then calcined. After the reaction is complete, the solution is cooled to room temperature to obtain a cathode material CoP / NF loaded with nickel foam containing a cobalt-phosphorus compound. (S.3) Using Hg / HgO as a reference electrode, the NiCe(OH)n / NF anode material obtained in step (S.1) and the CoP / NF cathode material obtained in step (S.2) are assembled into a coupling system in an alkaline electrolyte solution to obtain a highly active NiCe(OH)n / NF cyclic coupled hydrogen production system.

[0007] Since nickel oxyhydroxide (NiOOH) has high catalytic activity and is the key catalytic active site for many small molecule electro-oxidation reactions, it is extremely unstable in alkaline environments and easily decomposes to form nickel hydroxide (Ni(OH)2). The theoretical potential of the Ni(OH)2 / NiOOH couple is much lower than the theoretical potential required for OER. Therefore, by utilizing the Ni(OH)2 / NiOOH couple cycle, NiOOH can be stably present in a cyclic manner, and small molecule electro-oxidation can be used to assist the cycle of the couple. At the same time, the OER reaction is replaced to reduce the anode overpotential, thereby solving the problem of high energy consumption of hydrogen production by electrolysis of water.

[0008] Glucose (GLU) comes from biomass. Electrochemical oxidation of glucose produces glucaric acid (GRA), which is a key intermediate in the production of biodegradable polymers. GRA and its derivatives can also be used in medical treatments, such as cancer chemotherapy and lowering cholesterol. Therefore, the use of glucose as an organic small molecule has great application prospects. Glucose has a certain reducibility and can be used as a reducing agent for the redox cycle of the Ni(OH)2 / NiOOH electrode.

[0009] The present invention provides a method for producing hydrogen by dual-cycle coupling using glucose oxidation to assist low-potential electricity. The selected system uses a cycle to reduce the anode reaction potential, effectively reducing the energy consumption required by the system, and further obtaining glucaric acid with higher added value.

[0010] The present invention proposes a cyclic coupled hydrogen production system, wherein the anode uses NiCe(OH)n / NF as the electrode material, the cathode uses CoP / NF as the electrode material with lower cost, the anode electrolyte is an alkaline glucose solution (a mixed solution of 1M KOH solution and 0.5M glucose solution), the cathode electrolyte is an alkaline solution (1M KOH solution), and a double-chamber electrolytic cell with a proton exchange membrane as a diaphragm is used as a system device. In the anode reaction, due to the loss of electrons, a chemical reaction of Ni(OH)2 converting to NiOOH will first occur, and then due to the presence of NiOOH, the reducing glucose reacts with it, causing NiOOH to be reduced to Ni(OH)2 again, and glucose is converted into gluconic acid. Cerium can effectively enhance the oxidation progress of NiOOH on glucose, and can further convert the originally generated gluconic acid into gluconic acid. The cathode introduces the surfactant sodium p-hydroxybenzenesulfonate dihydrate to make the CoP / NF electrode material appear a new towel-like needle-like structure, which is regularly arranged and has gaps. This gap can effectively prevent the bubbles generated during the hydrogen production process from causing cobalt phosphide (CoP) to fall off the surface of the substrate. At the same time, this orderly multi-level nanoneedle array can provide a larger contact area with the electrolyte and expose more active centers, which will greatly improve the efficiency of the catalytic process. Combining the anode and cathode can obtain a coupled hydrogen production system with a recyclable anode.

[0011] Preferably, the molar ratio of nickel acetate tetrahydrate, cerium acetate tetrahydrate, ammonium fluoride and urea in step (S.1) is 0.5-1.5:0.05-0.15:3-5:15-18.

[0012] As further preferred, the molar ratio of nickel acetate tetrahydrate, cerium acetate tetrahydrate, ammonium fluoride and urea in step (S.1) is 1:0.1:4.16:16.6.

[0013] Preferably, the reaction temperature of the hydrothermal reaction in step (S.1) is 60 to 140°C, and the reaction time is 6 to 14 hours.

[0014] As a further preference, the reaction temperature for the hydrothermal reaction in step (S.1) is 100°C and the reaction time is 10 h.

[0015] Preferably, the scanning speed of the potential scanning process in step (S.1) is 5 to 20 mV / s, the potential interval is (0.3 to 0.6) V (vs. Hg / HgO), and the number of scanning cycles is 10 to 50 cycles.

[0016] As a further preference, the scanning speed of the potential scanning process in step (S.1) is 10 mV / s, and the number of scanning cycles is 20 cycles.

[0017] Preferably, the molar ratio of cobalt nitrate hexahydrate, sodium p-hydroxybenzenesulfonate dihydrate, urea and ammonium fluoride in step (S.2) is 0.6-3.6:0.2-1.2:15-18:3-5.

[0018] As further preferred, the molar ratio of cobalt nitrate hexahydrate, sodium p-hydroxybenzenesulfonate dihydrate, urea and ammonium fluoride in step (S.2) is 1.2:0.4:16.6:4.16.

[0019] Preferably, the reaction temperature of the hydrothermal reaction in step (S.2) is 90-110° C., and the reaction time is 2-8 h.

[0020] As a further preference, the reaction temperature for the hydrothermal reaction in step (S.2) is 105°C, and the reaction time is 4 hours.

[0021] Preferably, the mass ratio of the cobalt-phosphorus compound precursor Co(OH)n / NF to sodium hypophosphite in step (S.2) is 1-5:2-10.

[0022] As further preferred, the mass ratio of the cobalt-phosphorus compound precursor Co(OH)n / NF and sodium hypophosphite in step (S.2) is 1:2.

[0023] Preferably, the calcination temperature in the calcination process in step (S.2) is 280-350°C, and the calcination time is 2-4 hours.

[0024] As a further preference, the calcination temperature in the calcination process in step (S.2) is 280° C. and the calcination time is 2 h.

[0025] Preferably, the alkaline electrolyte solution in step (S.3) is any one or more combinations of potassium hydroxide solution, sodium hydroxide solution and alkaline glucose solution.

[0026] The preparation method of the highly active NiCe(OH)n / NF as described above is applied in the electro-oxidation of glucose-assisted cycle coupling for efficient hydrogen production.

[0027] Therefore, the present invention has the following beneficial effects: (1) The preparation method of the high-activity NiCe(OH)n / NF of the present invention does not use precious metal catalysts, which greatly reduces the cost of use; (2) The anode obtains glucaric acid by electro-oxidation, and at the same time, the active center NiOOH can be stably present in an alkaline environment in a cyclic manner, and hydrogen is produced at the cathode. Due to the redox cycle between Ni(OH)2 / NiOOH, the overpotential can be effectively reduced and the power loss can be reduced. And due to the synergistic effect of a small amount of cerium, the system can achieve efficient hydrogen production while obtaining high-value-added glucaric acid; (3) The present invention uses a circulation system to catalyze glucose to obtain glucaric acid. By testing the nuclear magnetic resonance hydrogen spectrum and carbon spectrum of the anode liquid after the reaction, it can be seen that gluconic acid is indeed generated. At the same time, the anode glucose yield reaches 70%, and the cathode hydrogen evolution efficiency is close to 100%; (4) Compared with the traditional water electrolysis hydrogen production process, the glucose oxidation-assisted low-potential electric couple cycle coupling hydrogen production method conforms to "green chemistry" and does not require harsh reaction conditions and complex separation steps; (5) This cyclic coupled hydrogen production system allows the entire cell voltage to reach 50 mA cm at a potential of only 1.4 V. -2 For the anode reaction, the potential can be reduced to about 1.2V by using a cycle to reach 50mA·cm -2 The current density is 282mV lower than that of the traditional OER reaction. The generation of gluconic acid can be seen from the carbon nuclear magnetic resonance spectrum. For the cathode reaction, the current density reaches 50mA·cm -2 When , the HER reaction only requires an overpotential of 98 mV. The chronopotentiometry shows that the cathode catalyst has good long-term stability and the Faradaic efficiency is close to 100%. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is the schematic diagram of the cyclic coupling system.

[0029] Figure 2 The SEM and XRD patterns of the anode material NiCe(OH)n / NF.

[0030] Figure 3 SEM and XRD images of cathode material CoP / NF.

[0031] Figure 4 Figure (a) shows the LSV curves of NiCe(OH)n / NF in mixed solutions of glucose and KOH at different concentrations; Figure 4 Figure (b) shows the comparison of GOR and OER polarization curves of NiCe(OH)n / NF; Figure 4Figure (c) shows the GOR polarization curves of NiCe(OH)n / NF and comparative samples (Ni(OH)n / NF, NF substrate).

[0032] Figure 5 Figure (a) is a comparison of the HER polarization curves of CoP / NF and the comparative samples (Ni2P / NF, NF substrate); Figure 5 Figure (b) shows the EIS graphs of CoP / NF and comparative samples (Ni2P / NF, NF substrate); Figure 5 Figure (c) shows the CoP / NF in Example 1 at a current density of 50 mA·cm -2 Chronopotentiometry curve after 20 h of action.

[0033] Figure 6 This is the SEM image of the cathode material Ni2P / NF.

[0034] Figure 7 Figure (a) shows the GOR / / HER anode reaction diagram; Figure 7 Figure (b) is a comparison of the LSV curves of GOR / / HER and OER / / HER.

[0035] Figure 8 The carbon NMR spectra before and after the reaction.

[0036] Fig. 9 Figure (a) shows the conversion rate of glucose and the yield of glucaric acid; Fig. 9 Figure (b) is the Faraday efficiency diagram of HER; Fig. 9 Figure (c) shows the HER / / GOR at [1.3V (vs. RHE)] (10mA·cm -2 ) 24h stability test chart. DETAILED DESCRIPTION

[0037] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments of the specification. Those of ordinary skill in the art will be able to implement the present invention based on these descriptions. In addition, the embodiments of the present invention involved in the following description are generally only embodiments of a part of the present invention, rather than all embodiments. Therefore, based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work should fall within the scope of protection of the present invention.

[0038] Example 1 A method for preparing highly active NiCe(OH)n / NF comprises the following steps: (S.1) Preparation of anode electrode material NiCe(OH)n / NF: Ni(C2H3O2)2·4H2O (1 mmol), Ce(C2H3O2)3·4H2O (0.1 mmol), NH4F (4.16 mmol), and urea (16.6 mmol) were dissolved in 40 mL of deionized water for 30 min under vigorous stirring. 2 The nickel foam (NF) was transferred to a stainless steel autoclave lined with polytetrafluoroethylene, sealed, and subjected to a hydrothermal reaction, and maintained at 100°C for 10 hours. After the reaction was completed, the nickel foam coated with nickel cerium hydroxide was taken out, thoroughly washed with deionized water and ethanol, and vacuum dried at 60°C for 12 hours. Then, by electrolytic conversion, cyclic voltammetry (CV) was used to scan the potential for 20 cycles in the potential range of (0.3-0.6) V (vs. Hg / HgO) at a scanning speed of 10 mV / s to obtain a nickel foam anode material NiCe(OH)n / NF coated with nickel cerium hydroxide with more active sites; (S.2) Preparation of cathode electrode material CoP / NF: Co(NO3)2·6H2O (1.2mmol), sodium p-hydroxybenzenesulfonate dihydrate (0.4mmol), urea (16.6mmol) and NH4F (4.16mmol) were added to 40mL of deionized water and stirred vigorously to obtain a precursor solution. The precursor solution and a piece of (1cm*1.5cm) nickel foam (NF) were placed in a reactor for hydrothermal reaction and kept at 105°C for 4h. After the reaction was completed, it was taken out, washed with deionized water and ethanol several times, and then dried to obtain the cobalt-phosphorus compound precursor Co(OH)n / NF. 0.0102g of sodium hypophosphite and 0.0051g of cobalt-phosphorus compound precursor Co(OH)n / NF were weighed respectively, and the cobalt-phosphorus compound precursor Co(OH)n / NF and sodium hypophosphite were placed in different ceramic boats and then placed in a tube furnace, heated to 280°C at a rate of 2°C / min and calcined for 2h. After the reaction was complete, it was cooled to room temperature to obtain a cathode material CoP / NF of nickel foam loaded with cobalt-phosphorus compound; (S.3) Assembly of paired coupling system: The anode material NiCe(OH)n / NF of nickel foam coated with nickel cerium hydroxide obtained in step (S.1) is used as the anode of the coupling system to generate redox cycle reaction, and the cathode material CoP / NF of nickel foam loaded with cobalt phosphorus compound obtained in step (S.2) is used as the cathode to generate hydrogen. The whole system is carried out in an alkaline environment, and Hg / HgO is used as the reference electrode to obtain a highly active NiCe(OH)n / NF cyclic coupled hydrogen production system. Among them, the anode electrolyte is an alkaline glucose solution (a mixed solution of 1M KOH solution and 0.5M glucose solution), and the cathode electrolyte is an alkaline solution (1M KOH solution). The principle of the cyclic coupling system is as follows: Figure 1 As shown. Figure 1 It can be seen that the present invention establishes a hybrid water electrolysis system combining hydrogen evolution reaction (HER) and glucose oxidation cycle reaction (GOR), thereby solving the problems of slow kinetics and high energy consumption of oxygen evolution reaction (OER). CoP / NF and NiCe(OH)n / NF are used for cathode hydrogen evolution reaction and anode glucose oxidation cycle reaction, respectively.

[0039] Example 2 This embodiment provides a method for preparing high-activity NiCe(OH)n / NF.

[0040] The difference between this embodiment and embodiment 1 is that: A method for preparing a highly active NiCe(OH)n / NF, wherein in step (S.1), Ni(C2H3O2)2·4H2O (0.5 mmol), Ce(C2H3O2)3·4H2O (0.05 mmol), NH4F (3 mmol), and urea (15 mmol) are added; a hydrothermal reaction is carried out and maintained at 60°C for 14 h; a scanning speed of 5 mV / s is used to scan the electric field at (0.3-0.6) V (vs. Hg / HgO) to obtain a NiCe(OH)n / NF having a high activity. The potential was scanned for 10 cycles in the potential interval; Co(NO3)2·6H2O (0.6mmol), sodium p-hydroxybenzenesulfonate dihydrate (0.2mmol), urea (15mmol) and NH4F (3mmol) were added in step (S.2); a hydrothermal reaction was carried out and maintained at 90°C for 8h; 0.017g of sodium hypophosphite and 0.0017g of cobalt phosphorus compound precursor Co(OH)n / NF were weighed respectively; the mixture was heated to 320°C at a rate of 2°C / min and calcined for 3h. The rest was the same as in Example 1.

[0041] Example 3 This embodiment provides a method for preparing high-activity NiCe(OH)n / NF.

[0042] The difference between this embodiment and embodiment 1 is that: A method for preparing highly active NiCe(OH)n / NF, wherein in step (S.1), Ni(C2H3O2)2·4H2O (1.5 mmol), Ce(C2H3O2)3·4H2O (0.15 mmol), NH4F (5 mmol), and urea (18 mmol) are added; a hydrothermal reaction is carried out and maintained at 140°C for 6 hours; a potential of (0.3-0.6) V (vs. Hg / HgO) is measured at a scanning speed of 20 mV / s. The potential was scanned for 50 cycles in the interval; Co(NO3)2·6H2O (3.6mmol), sodium p-hydroxybenzenesulfonate dihydrate (1.2mmol), urea (18mmol) and NH4F (5mmol) were added in step (S.2); a hydrothermal reaction was carried out and maintained at 110°C for 2h; 0.00172g of sodium hypophosphite and 0.0043g of cobalt phosphorus compound precursor Co(OH)n / NF were weighed respectively; the mixture was heated to 350°C at a rate of 2°C / min and calcined for 4h. The rest was the same as in Example 1.

[0043] Comparative Example 1 This comparative example provides a method for preparing an anode electrode material Ni(OH)n / NF.

[0044] The difference between this comparative example and Example 1 is: In step (S.1), Ce(C2H3O2)3·4H2O is not added, and steps (S.2) to (S.3) are omitted. The rest is the same as in Example 1. Finally, anode material Ni(OH)n / NF of nickel foam coated with nickel hydroxide is obtained.

[0045] Comparative Example 2 This comparative example provides a method for preparing a cathode electrode material Ni2P / NF.

[0046] The difference between this comparative example and Example 1 is: In step (S.2), Co(NO3)2·6H2O (1.2 mmol) was replaced by Ni(NO3)2·6H2O (1.2 mmol), and steps (S.1) and (S.3) were omitted. The rest was the same as in Example 1. Finally, a cathode material Ni2P / NF of nickel foam loaded with nickel-phosphorus compound was obtained.

[0047] Comparative Example 3 This comparative example provides a commercially available nickel foam NF substrate, which was purchased from Chengnan Jinyihe New Materials Business Department of Wuzhong Economic Development Zone.

[0048]

Test instruments and methods

Physical Characterization

[0049] The SEM and XRD patterns of the anode material NiCe(OH)n / NF are shown in Figure 2. Figure 2 The SEM and XRD patterns of the cathode material CoP / NF are shown in Figure 3 The SEM image of the cathode material Ni2P / NF is shown in Figure 6 shown.

[0050] from Figure 2 It can be seen that the NiCe(OH)n / NF nanoflower balls are stacked and grown on nickel foam. The hydrothermal reaction will make the in-situ grown catalyst uneven, so it is necessary to expand the contact area between the material and the organic matter. The flexible sheet-like nanoflowers grown by this material can further expand the surface area of ​​the material and improve the efficiency of the electrical reaction. Then the crystal structure of NiCe(OH)n / NF was analyzed by X-ray diffractometer (XRD). The diffraction peaks at 11.4°, 22.9°, 34.7°, 39.0°, 46.9°, 60.2° and 62.6° all belong to Ni(OH)2NiOOH (JCPDS No.21-0288), and correspond to the (003), (006), (009), (015), (0012), (110) and (1013) crystal planes of Ni(OH)2NiOOH, respectively.

[0051] from Figure 3 It can be seen that the present invention studies the changes in the surface morphology of the cathode electrode material CoP / NF during the preparation process through SEM images. Since the surfactant sodium p-hydroxybenzenesulfonate dihydrate participates in the preparation reaction, unlike the smooth surface of nickel foam (NF) and other needle-shaped deposits, the CoP in the present invention is loaded on the NF to present a towel-shaped needle. This needle grows continuously on the NF, arranged in a cylindrical shape with gaps. This gap leaves enough space for the hydrogen evolution reaction to prevent the bubbles generated during the reaction from causing the CoP to fall off the surface of the substrate. At the same time, this ordered multi-level nanoneedle array can provide a larger contact area with the electrolyte and expose more active centers, which will greatly improve the efficiency of the catalytic process. The crystal structure of CoP is as follows Figure 3As shown, in addition to the peaks associated with NF, diffraction peaks at 31.6°, 48.1°, and 56.0° corresponding to CoP (PDF#29-0497) were observed, corresponding to the (011), (211), and (020) crystal planes, respectively.

[0052] from Figure 6 It can be seen that the cathode material Ni2P / NF is in the shape of nanosheet flowers, and a large number of small particles are accumulated on the nanosheets, making the surface relatively rough, the thickness increased, and some electroactive sites covered, making its activity slightly lower than that of the cathode material CoP / NF of the nanoneedle array.

[0053]

Electrochemical characterization

[0054] In order to verify that glucose can promote the redox cycle between Ni(OH)2 and NiOOH, the present invention conducted a series of controllable electrochemical tests. Before testing the GOR cycle performance of NiCe(OH)n / NF, the linear sweep voltammetry (LSV) curve of NiCe(OH)n / NF prepared in Example 1 in a mixed solution of glucose (Glucose) and potassium hydroxide (KOH) at different concentrations was tested to determine the optimal electrolyte ratio. The Ni(OH)n / NF prepared in Comparative Example 1 and the NF substrate prepared in Comparative Example 3 were used as comparative samples. Figure 4 As shown in Figure (a), the GOR performance of NiCe(OH)n / NF increases with the increase of glucose concentration, but after reaching a concentration node, the GOR performance of NiCe(OH)n / NF decreases due to the increase of glucose concentration. Therefore, the present invention selects 1M KOH and 0.5M glucose electrolyte concentrations as the subsequent GOR performance test. Figure 4 As shown in Figure (b), the present invention compares the GOR and OER performance of NiCe(OH)n / NF. Due to the thermodynamic advantage of GOR, the onset potential of GOR is greatly reduced compared with OER. Specifically, the NiCe(OH)n / NF electrode requires a potential of 1.6V (vs.RHE) to provide 50mA·cm in KOH solution. -2 This is much higher than the 1.1 V (vs. RHE) in 1 M KOH and 0.5 M Glucose electrolytes. In addition, the current density is 100 mA cm -2The potential of GOR is 515mV lower than that of OER. The biggest difference between the two curves is that OER has a small peak. This small peak is due to the conversion of divalent nickel in NiCe(OH)n / NF to trivalent nickel, which is a valence change peak of the catalyst itself. In order to study whether the substrate and intermediates have an effect on the circulation system, the LSV curves of NiCe(OH)n / NF, Ni(OH)n / NF and NF substrates in 1M KOH and 0.5M Glucose electrolytes are compared (see Figure 4 From Figure (c), we can see that the GOR kinetics with NiCe(OH)n is more active, and no small peaks appear in the three curves, indicating that glucose promotes the circulation between Ni(OH)2 and NiOOH.

[0055] The present invention evaluates the electrochemical performance of the catalyst in the cathode hydrogen evolution half-reaction. The CoP / NF prepared in Example 1 is used as the main research object, and the Ni2P / NF prepared in Comparative Example 2 and the NF substrate prepared in Comparative Example 3 are used as comparative samples. Figure 5 From the LSV curves in Figure (a), it can be seen that CoP / NF has a lower HER overpotential compared with Ni2P / NF and NF substrate. Figure 5 The EIS graph in Figure (b) shows that the Rct of CoP / NF is significantly lower than that of the comparison sample (Ni2P / NF, NF substrate) catalyst, indicating that CoP / NF can promote electron transfer at the electrocatalytic interface. Figure 5 As shown in Figure (c), CoP / NF at 50 mA cm -2 The durability test results for 20 hours under the same conditions showed that its electrocatalytic performance has excellent durability.

[0056] Since the electrolytes of the anode and cathode are different, the present invention selects an H-type electrolytic cell separated by a cation exchange membrane to perform electrochemical tests on the HER / / GOR cycle system. The CoP / NF prepared in Example 1 is used as the cathode electrode material, and the NiCe(OH)n / NF prepared in Example 1 is used as the anode electrode material for the cycle reaction. The anode may undergo the following Figure 7 In the cyclic reaction shown in Figure (a), glucose produces glucaric acid, which has higher value. Figure 7 The LSV curve in (b) shows that the coupling of HER and GOR cycles results in a significant improvement in cell voltage compared to conventional water electrolysis.

[0057]

Product Analysis

[0058] To calculate the Faradaic efficiency (FE) of HER, the generated H2 is collected using the water displacement method, which is calculated using the following formula: Where Z2 is the number of electrons required to produce H2 molecules, and F is the Faraday constant (96485C·m -1 ), Q2 is the total charge consumed during HER, V m It represents the standard molar volume of a gas at 25°C (24.5 L / mol). Figure 8 The carbon NMR spectra before and after the reaction. Fig. 9 Figure (a) shows the conversion rate of glucose and the yield of glucaric acid. Fig. 9 Figure (b) is the Faraday efficiency diagram of HER. Fig. 9 Figure (c) shows the HER / / GOR at [1.3V (vs. RHE)] (10mA·cm -2 ) 24h stability test chart.

[0059] By comparing the electrolyte before and after the reaction 13 C NMR spectrum showed that glucose was selectively oxidized to glucaric acid with a small amount of glucose residue. Figure 8 It can be seen that in addition to glucaric acid, the product also contains a portion of monogluconic acid and a small amount of carbonate. The present invention believes that this is the result of glucose being oxidized to glucaric acid and then further oxidized to carbon dioxide. The conversion efficiency of glucose is as high as 95%, while the yield of glucaric acid is 70% (e.g. Fig. 9 The conversion efficiency of glucaric acid did not reach 90%, which may be due to the fact that the byproduct glucaric acid was not further converted. Regarding the hydrogen production problem, the present invention tested the Faraday efficiency of the cathode hydrogen evolution reaction, and the results showed that the Faraday efficiency was close to 100% (see Fig. 9 After 24h stability test (see Fig. 9(c) in the figure), the total current is in a stable state, which indicates that the constructed coupled reaction system has excellent catalytic stability and durability.

[0060] In summary: The present invention prepares NiCe(OH)n / NF, an electrode material rich in catalytic active sites, by a hydrothermal and electrolytic conversion method, and utilizes the cycle between Ni(OH)2 / NiOOH to reduce the potential required for water electrolysis to reduce energy consumption, and the potential is reduced by about 515mV. At the same time, by adding the sacrificial agent organic molecule glucose, it is oxidized to a more valuable organic substance, glucaric acid, thereby obtaining a value-added product, killing two birds with one stone. The present invention selects transition metal cobalt phosphide (CoP / NF) as the cathode hydrogen evolution material, prepares the precursor material by a hydrothermal method, and then phosphates the material by a thermal phosphating method. This material is used for hydrogen evolution reaction, and the hydrogen evolution overpotential only needs 127mV to reach 100mA·cm -2 , and its Faraday efficiency is close to 100%. The present invention combines the excellent performance CoP / NF with NiCe(OH)n / NF to make a coupled electrolysis system. A method for reducing the anode potential in a cyclic manner is provided, and a new cyclic coupled high-efficiency hydrogen production system is constructed. The introduction of cerium promotes the further reaction of glucose in the anode to obtain high-value glucaric acid. The entire coupling system greatly reduces the cell voltage required for hydrogen production by electrolysis of water, and only 1.4V (vs.RHE) is required to reach 50mA·cm -2 of current density.

[0061] The above description is only a detailed description of the preferred embodiments and principles of the present invention. For ordinary technicians in this field, according to the ideas provided by the present invention, there will be changes in the specific implementation methods, and these changes should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing highly active NiCe(OH)n / NF, characterized in that: The following steps are involved: (S.1) dissolving nickel acetate tetrahydrate, cerium acetate tetrahydrate, ammonium fluoride and urea in deionized water under stirring, then transferring the mixture into a reaction kettle and adding nickel foam to carry out a hydrothermal reaction. After the reaction is completed, the nickel foam coated with nickel cerium hydroxide is taken out, washed, dried and subjected to potential scanning by cyclic voltammetry to obtain an anode material NiCe(OH)n / NF of nickel foam coated with nickel cerium hydroxide; (S.2) adding cobalt nitrate hexahydrate, sodium p-hydroxybenzenesulfonate dihydrate, urea and ammonium fluoride into deionized water and stirring to obtain a precursor solution, which is then transferred into a reactor and nickel foam is added to perform a hydrothermal reaction. After the reaction is completed, the solution is taken out and washed and dried to obtain a cobalt-phosphorus compound precursor Co(OH)n / NF. The cobalt-phosphorus compound precursor Co(OH)n / NF and sodium hypophosphite are then calcined. After the reaction is complete, the solution is cooled to room temperature to obtain a cathode material CoP / NF loaded with nickel foam containing a cobalt-phosphorus compound. (S.3) Using Hg / HgO as a reference electrode, the NiCe(OH)n / NF anode material obtained in step (S.1) and the CoP / NF cathode material obtained in step (S.2) are assembled into a coupling system in an alkaline electrolyte solution to obtain a highly active NiCe(OH)n / NF cyclic coupled hydrogen production system.

2. The method for preparing a highly active NiCe(OH)n / NF according to claim 1, characterized in that: The molar ratio of nickel acetate tetrahydrate, cerium acetate tetrahydrate, ammonium fluoride and urea in step (S.1) is 0.5-1.5:0.05-0.15:3-5:15-18.

3. The method for preparing a highly active NiCe(OH)n / NF according to claim 1, characterized in that: The reaction temperature of the hydrothermal reaction in step (S.1) is 60 to 140° C., and the reaction time is 6 to 14 hours.

4. The method for preparing a highly active NiCe(OH)n / NF according to claim 1, characterized in that: The scanning speed of the potential scanning process in step (S.1) is 5 to 20 mV / s, the potential interval is (0.3 to 0.6) V (vs. Hg / HgO), and the number of scanning cycles is 10 to 50 cycles.

5. The method for preparing a highly active NiCe(OH)n / NF according to claim 1, characterized in that: The molar ratio of cobalt nitrate hexahydrate, sodium p-hydroxybenzenesulfonate dihydrate, urea and ammonium fluoride in step (S.2) is 0.6-3.6:0.2-1.2:15-18:3-5.

6. The method for preparing a highly active NiCe(OH)n / NF according to claim 1, characterized in that: The reaction temperature of the hydrothermal reaction in step (S.2) is 90-110° C., and the reaction time is 2-8 hours.

7. The method for preparing a highly active NiCe(OH)n / NF according to claim 1, characterized in that: The mass ratio of the cobalt-phosphorus compound precursor Co(OH)n / NF to sodium hypophosphite in step (S.2) is 1-5:2-10.

8. The method for preparing a highly active NiCe(OH)n / NF according to claim 1, characterized in that: The calcination temperature in the step (S.2) is 280-350°C, and the calcination time is 2-4 hours.

9. The method for preparing a highly active NiCe(OH)n / NF according to claim 1, characterized in that: The alkaline electrolyte solution in step (S.3) is any one or more combinations of potassium hydroxide solution, sodium hydroxide solution, and alkaline glucose solution.

10. Application of the preparation method of high-activity NiCe(OH)n / NF as claimed in any one of claims 1 to 9 in the electro-oxidation of glucose-assisted cycle-coupled efficient hydrogen production.

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