Preparation method and application of foamed nickel-loaded nickel-molybdenum-based heterostructure photo-thermal catalyst

Abstract

The invention discloses a preparation method and application of a foamed nickel loaded nickel-molybdenum-based heterostructure photo-thermal catalyst. The preparation method comprises the following steps: immersing foamed nickel into a precursor solution containing a nickel source and a molybdenum source, carrying out a hydrothermal reaction, and growing a NiMo-based nano material on the foamed nickel; carrying out electro-deposition in an electrolyte containing a nickel source and a copper source by taking the foamed nickel after the NiMo-based nano-material is grown as a working electrode so as to grow a NiCu alloy nano-material on the NiMo-based nano-material; wherein a heterogeneous interface structure is formed between the NiMo-based nano-material and the NiCu alloy nano-material, and electron transfer between two phases of the heterogeneous interface structure is induced, so that the electronic structure of the catalyst is regulated and controlled, and the catalyst has extremely high electrocatalytic activity and stability on a water electrolysis hydrogen evolution reaction. Meanwhile, the catalyst can be used in an electrolytic bath-TE device (a photo-thermal auxiliary water electrolysis device), and the voltage of the whole water decomposition tank can be effectively reduced.

Description

Technical Field

[0001] The present invention relates to the field of non-precious metal water electrolysis catalysts; more specifically, it relates to a preparation method of a nickel foam-loaded nickel-molybdenum-based heterostructure photothermal catalyst and its application in photothermal-assisted water electrolysis to produce hydrogen. Background Art

[0002] Due to the scarcity of energy and the environmental crisis, it is urgent to develop green, clean and sustainable energy. Hydrogen, as a new type of energy, has the characteristics of high energy density, clean and high efficiency. Electrolysis of water to produce hydrogen has been widely studied as a recent hot topic because of its high efficiency in hydrogen production and the products are H2 and O2, which can be recycled to save resources. Among the currently known catalysts, Pt and Ru-based catalysts are considered to have the highest HER and OER catalytic activities, respectively. However, their high cost, low stability and poor stability make them difficult to commercialize on a large scale. Therefore, it is necessary to vigorously develop cost-effective non-precious metal catalysts.

[0003] Phosphides, sulfides and nitrides of transition metals (such as Fe, Co, Cu, Mo, Ni) have been widely reported as HER catalysts to replace precious metals. Among them, oxides and sulfides of transition metals have become a promising electrocatalytic material due to their eco-friendliness, abundant resources and fairly strong catalytic properties. Although transition metal oxides are very stable, they are usually catalytically inert to alkaline HER reactions due to their slow kinetics. The catalytic performance of transition metal oxide and sulfide catalysts can be optimized by constructing heterostructures, maximizing the exposure of active sites under harsh electrochemical conditions, improving conductivity and optimizing electronic structure. In addition, research on hydrogen production by electrolysis of water using renewable energy such as solar energy has attracted much attention. By integrating electrocatalytic materials with photothermal effects with thermoelectric devices, this method can significantly reduce the energy consumption in the process of hydrogen production by electrolysis of water. Summary of the invention

[0004] The present invention aims to further develop the existing technology to provide a method for preparing a nickel foam-loaded nickel-molybdenum-based heterostructure photothermal catalyst and its application in photothermal-assisted water electrolysis to produce hydrogen.

[0005] The first aspect of the present invention provides a method for preparing a nickel foam-supported nickel-molybdenum-based heterostructure photothermal catalyst, comprising the following steps:

[0006] The nickel foam (NF) is immersed in a precursor solution containing a nickel source and a molybdenum source to perform a hydrothermal reaction, and a NiMo-based nanomaterial is grown on the nickel foam;

[0007] Using the nickel foam after growing the NiMo-based nanomaterial as a working electrode, electrodeposition is performed in an electrolyte containing a nickel source and a copper source to grow a NiCu alloy nanomaterial on the NiMo-based nanomaterial;

[0008] Wherein, a heterogeneous interface structure is formed between the NiMo-based nanomaterial and the NiCu alloy nanomaterial.

[0009] Furthermore, the NiMo-based nanomaterial is a nickel-molybdenum-based oxide, specifically NiMoO4.

[0010] Furthermore, the temperature of the hydrothermal reaction is 120-200° C., and the time is 3-8 hours.

[0011] Furthermore, the electrodeposition is a constant current density deposition, and the deposition current density is -0.1 to -0.3 A cm -2 , the deposition time is 500 to 800 s.

[0012] Furthermore, the molar concentration of the nickel source in the precursor solution is 0.01-0.1M, and the molar concentration of the molybdenum source is 0.005-0.05M.

[0013] Furthermore, the nickel source in the precursor solution is nickel nitrate, and the molybdenum source is ammonium molybdate.

[0014] Furthermore, the NiMo-based nanomaterial is nickel-molybdenum-based sulfide, and the precursor solution also contains thiourea with a molar concentration of 0.1 to 0.5M.

[0015] Furthermore, the molar concentration of the nickel source in the electrolyte is 0.01-0.1M, and the molar concentration of the copper source is 0.01-0.1M.

[0016] Furthermore, the nickel source in the electrolyte is nickel sulfate, and the copper source is copper sulfate.

[0017] Furthermore, the electrolyte also contains ammonium sulfate with a molar concentration of 0.01 to 0.05M.

[0018] The second aspect of the present invention discloses the application of the nickel foam loaded nickel-molybdenum-based heterostructure photothermal catalyst obtained by the aforementioned preparation method in photothermal-assisted water electrolysis to produce hydrogen.

[0019] The technical solution of the present invention has the following beneficial effects:

[0020] The present invention selects nickel foam as a substrate, firstly synthesizes NiMo-based oxide or sulfide nanomaterials on the nickel foam substrate by a hydrothermal method, and then grows NiCu alloy nanomaterials on the NiMo-based oxide or sulfide nanomaterials by an electrochemical deposition method, thereby constructing a heterogeneous interface between the two phases, which not only increases the catalyst active sites, but also regulates the electronic structure of the catalyst through charge transfer between the two phases, optimizes the intermediate adsorption energy, and thus promotes the electrocatalytic reaction.

[0021] Under alkaline conditions, NiMo-based oxides and sulfides have strong ability to adsorb oxygen-containing intermediates and exhibit excellent OER catalytic activity. v ) improves its hydrogen evolution performance. During the HER process, water is preferentially adsorbed on oxygen vacancies (O v ), and the H* species after hydrolysis is adsorbed on O v The activated O sites nearby promote the subsequent H2 generation reaction.

[0022] Furthermore, the catalyst of the present invention has super hydrophilicity and excellent photothermal performance, and can be used in an electrolyzer-TE device (photothermal-assisted water electrolysis hydrogen production device) to effectively reduce the overall water splitting cell voltage.

[0023] In order to more clearly illustrate the purpose, technical solutions and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is the XRD pattern of NiCu / NiMoO4 in the catalyst of Example 1;

[0025] Figure 2 In the figure: a is the Ni 2p XPS spectra of the NiCu / NF catalysts of Example 1 and Comparative Example 2, and b is the Cu 2p XPS spectra of the two; c is the Mo3d XPS spectra of the NiMoO4 / NF catalysts of Example 1 and Comparative Example 1, and d is the O1s XPS spectra of the two;

[0026] Figure 3 Middle: a is a SEM image of the catalyst of Comparative Example 1, b is a SEM image of the catalyst of Comparative Example 2, and c is a SEM image of the catalyst of Example 1;

[0027] Figure 4 Middle: ac are TEM images of the catalyst of Example 1;

[0028] Figure 5 In the figure: a is a comparison diagram of the HER linear sweep voltammetry (LSV) curves of Example 1, Comparative Examples 1 and 2 and commercial Pt / C catalysts, b is a comparison diagram of their Tafel slopes, c is a comparison diagram of their double-layer capacitances for evaluating the electrochemical surface area (ECSA), and d is a HER chronovoltage curve (CP) diagram of the catalyst of Example 1;

[0029] Figure 6In the figure: a is a comparison of the OER linear sweep voltammetry (LSV) curves of Example 1, Comparative Examples 1 and 2, and the commercial RuO2 catalyst, b is a comparison of their Tafel slopes, c is a comparison of their double-layer capacitances for evaluating the electrochemical surface area (ECSA), and d is a diagram of the OER chronovoltage curve (CP) of the catalyst of Example 1;

[0030] Figure 7a This is a comparison chart of the LSV of complete water splitting of Example 1 and commercial catalysts. Figure 7b The Faraday efficiency (FE) diagram of the catalyst of Example 1 is obtained by calculating the hydrogen production efficiency test system. Figure 7c is a graph of the total water splitting chronopotentiometry (CP) curve of the catalyst of Example 1;

[0031] Figure 8a is a comparison chart of the UV-visible-near infrared absorption spectra of the catalysts of Example 1, Comparative Examples 1 and 2, Figure 8b is the surface temperature of the catalysts of Example 1, Comparative Examples 1 and 2 and NF (nickel foam) monitored in air, Figure 8c is the temperature change of the catalysts and NFs of Example 1, Comparative Examples 1 and 2 in 1M KOH solution;

[0032] Fig. 9 In the figure: a is the overall water splitting performance of the catalyst of Example 1 under light and no light conditions tested in an electrolyzer without a thermoelectric device; b is the overall water splitting performance of the catalyst of Example 1 under light and no light conditions tested in an electrolyzer with a thermoelectric device; c is the overall water splitting performance of the catalyst of Example 1 at a current density of 50 mA cm -2 The stability test diagram below;

[0033] Fig.10 is a comparison chart of oxygen vacancy contents of the catalysts of Example 1 and Comparative Example 1;

[0034] Fig.11 is a comparison diagram of the hydrophilic contact angles of the catalyst in Example 1 and pure nickel foam;

[0035] Fig.12 is the XRD pattern of NiCu / NiMoS in the catalyst of Example 2;

[0036] Fig.13 In the figure: a is the Ni2p XPS spectra of the NiCu / NiMoS / NF catalysts of Example 2 and Comparative Example 4, and b is the Cu 2p XPS spectra of the two; c is the Mo 3d XPS spectra of the NiMoS / NF catalysts of Example 2 and Comparative Example 3, and d is the S2p XPS spectra of the two;

[0037] Fig.14is the SEM image of the catalyst of Comparative Example 4;

[0038] Fig.15 is a SEM image of the catalyst of Example 2;

[0039] Fig.16 In the figure: a is a comparison diagram of the HER linear sweep voltammetry (LSV) curves of the catalysts of Example 2, Comparative Example 3 and Comparative Example 4, b is a comparison diagram of their impedance, c is a comparison diagram of their double-layer capacitance, and d is a HER chronovoltage curve (CP) diagram of the catalyst of Example 2;

[0040] Fig.17 In the figure: a is a comparison chart of the UV-Vis-NIR absorption spectra of the catalysts of Example 2, Comparative Example 3 and Comparative Example 4, b is the surface temperature of the catalysts of Example 2, Comparative Example 3 and Comparative Example 4 monitored in air, c is the full water splitting performance of the catalyst of Example 2 under light and no light conditions tested in an electrolyzer using a thermoelectric device, d is the full water splitting performance of the catalyst of Example 2 under light and no light conditions tested in an electrolyzer not using a thermoelectric device. DETAILED DESCRIPTION

[0041] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other variations or replacements made on this basis. Therefore, other possible implementation methods that may be known to those skilled in the art based on the embodiments described in this application all belong to the protection scope of the present invention.

[0042] Example 1: Preparation of NiCu / NiMoO4 / NF catalyst

[0043] (1) The nickel foam (1 cm*2 cm) was ultrasonically cleaned in acetone, 6.0 M hydrochloric acid solution and deionized water for 30 minutes, and then dried to obtain a clean nickel foam substrate. The thickness of the nickel foam was 1.6 mm and the pore size was 110 ppi.

[0044] (2) First, 300 mg of nickel nitrate hexahydrate and 200 mg of ammonium molybdate tetrahydrate were dispersed in 25 mL of deionized water (the molar concentration of nickel nitrate was 0.04 M, and the molar concentration of ammonium molybdate was 0.0065 M), and uniformly dispersed them by ultrasonication at room temperature for 300 s, and then the uniformly dissolved solution was transferred to a Teflon high-pressure reactor.

[0045] ⑶ Place the cleaned nickel foam horizontally at the bottom of the Teflon high-pressure reactor liner, then place the reactor in a forced air drying oven, set the temperature to 150°C, and keep it warm for 5 hours.

[0046] (4) The product obtained after the reaction was washed three times with deionized water and anhydrous ethanol in sequence, and then placed in a vacuum drying oven at 60° C. for 6 h to obtain a NiMoO4 / NF precursor.

[0047] ⑸ NiMoO4 / NF precursor was used as the working electrode, carbon rod and Ag / AgCl were used as the counter electrode and reference electrode respectively. 100 mL of electrolyte containing 1050 mg nickel sulfate hexahydrate, 600 mg copper sulfate pentahydrate, and 350 mg ammonium sulfate was prepared (the molar concentration of nickel sulfate was 0.04 M, the molar concentration of copper sulfate was 0.024 M, and the molar concentration of ammonium sulfate was 0.026 M). In the three-electrode system, -0.2 A cm -2 The catalyst was deposited under constant current for 650 s to obtain NiCu / NiMoO4 / NF catalyst.

[0048] Example 2: Preparation of NiCu / NiMoS / NF catalyst

[0049] (1) The nickel foam (1 cm*2 cm) was ultrasonically cleaned in acetone, 6.0 M hydrochloric acid solution and deionized water for 30 minutes, and then dried to obtain a clean nickel foam substrate. The thickness of the nickel foam was 1.6 mm and the pore size was 110 ppi.

[0050] (2) First, disperse 260 mg of nickel nitrate hexahydrate, 640 mg of ammonium molybdate tetrahydrate and 400 mg of thiourea in 25 mL of deionized water (the molar concentration of nickel nitrate is 0.03 M, the molar concentration of ammonium molybdate is 0.019 M, and the molar concentration of thiourea is 0.2 M), and disperse them uniformly by ultrasonication at room temperature for 300 s, and then transfer the uniformly dissolved solution to a Teflon high-pressure reactor.

[0051] ⑶ Place the cleaned nickel foam horizontally at the bottom of the Teflon high-pressure reactor liner, then place the reactor in a forced air drying oven, set the temperature to 120°C, and keep it warm for 8 hours.

[0052] (4) The product obtained after the reaction was washed three times with deionized water and anhydrous ethanol in sequence, and then placed in a vacuum drying oven at 60° C. for 6 h to obtain a NiMoS / NF precursor.

[0053] ⑸ NiMoS / NF precursor was used as the working electrode, carbon rod and Ag / AgCl were used as the counter electrode and reference electrode respectively. 100 mL of electrolyte containing 1050 mg nickel sulfate hexahydrate, 600 mg copper sulfate pentahydrate, and 350 mg ammonium sulfate was prepared. In the three-electrode system, -0.2 A cm -2 The deposition was carried out at a constant current density of 600s to finally obtain NiCu / NiMoS / NF catalyst.

[0054] Comparative Example 1: Preparation of NiMoO4 / NF Catalyst

[0055] The difference between Comparative Example 1 and Example 1 is that step (5) in the preparation steps of Example 1 is omitted, that is, NiCu alloy is not deposited.

[0056] Comparative Example 2: Preparation of NiCu / NF-650s catalyst

[0057] The difference between Comparative Example 2 and Example 1 is that steps (2) to (4) in the preparation process of Example 1 are omitted, that is, NiCu alloy is directly deposited on the clean nickel foam.

[0058] Comparative Example 3: Preparation of NiMoS / NF Catalyst

[0059] The difference between Comparative Example 3 and Example 2 is that step (5) in the preparation steps of Example 2 is omitted, that is, NiCu alloy is not deposited.

[0060] Comparative Example 4: Preparation of NiCu / NF-600s catalyst

[0061] The difference between Comparative Example 4 and Example 2 is that steps (2) to (4) in the preparation steps of Example 2 are omitted, that is, NiCu alloy is directly deposited on the clean nickel foam.

[0062] Morphology, size and phase analysis of examples and comparative examples

[0063] Figure 1 The X-ray diffraction (XRD) spectrum of the catalyst of Example 1 includes peaks corresponding to NiMoO4 (PDF#13-0128) and NiMoO4 (PDF#31-0902), indicating the formation of the NiMoO4 phase. At the same time, the peaks of Ni (PDF#87-0712) and Cu (PDF#99-0034) are offset to varying degrees, indicating the formation of the NiCu alloy phase. This proves the successful preparation of the NiCu / NiMoO4 / NF catalyst in Example 1.

[0064] Figure 2 It is the XPS spectrum of the catalysts of Example 1, Comparative Examples 1 and 2. Among them, Figure 2 a shows the Ni 2p XPS spectrum, the peaks at 856.43 eV and 874.51 eV correspond to 2p3 / 2 and 2p1 / 2, corresponding to Ni 2+ ;Ni 0 Peaks appeared at 852.74 eV and 869.78 eV. Figure 2 b XPS spectrum of Cu 2p, the two peaks at 933.02 eV and 953.9 eV belong to Cu 0 , while the two peaks at 935.52eV and 955.65eV belong to Cu2+ . Figure 2 c shows the Mo 3d XPS spectrum, where the two peaks correspond to Mo 5+ (232.15eV) and Mo 6+ (233.55eV). Figure 2 d shows the O1s XPS spectrum, in which the three peaks are attributed to hydroxyl (OH), oxygen vacancies, and lattice oxygen (MO). Figure 2 The test results show that NiCu / NiMoO4 heterostructure was in situ grown on the surface of nickel foam by hydrothermal-electrochemical deposition.

[0065] Figure 3 ac are field emission scanning electron microscope (FE-SEM) images of the catalysts of Comparative Examples 1 and 2 and Example 1, respectively. Figure 3 a shows the rod-shaped NiMoO4 nanomaterial grown on nickel foam in Comparative Example 1, Figure 3 b shows the needle-shaped NiCu alloy nanomaterial in Comparative Example 2, Figure 3 c shows the growth state of the NiCu alloy nanomaterial of Example 1 on the NiMoO4 nanorods.

[0066] Figure 4 ac are transmission electron microscope (TEM) images of the catalyst of Example 1, Figure 4 The high-resolution transmission electron microscopy (HRTEM) image of b shows two different lattice fringes, where the lattice fringes with a spacing of 0.21 nm correspond to the (111) crystal plane of NiCu, and the lattice fringes with a spacing of 0.371 nm correspond to the (021) crystal plane of NiMoO4. The figure also shows that the two phases of NiCu and NiMoO4 form a heterogeneous interface structure.

[0067] Fig.12 is the X-ray diffraction (XRD) pattern of the catalyst of Example 2, including the patterns corresponding to Ni 2.5 6S 6.7 The peaks of Ni (PDF#39-0481) and Cu (PDF#99-0034) were also shown, indicating the formation of NiMoS phase. Meanwhile, the peaks of Ni (PDF#87-0712) and Cu (PDF#99-0034) were offset to different degrees, indicating the formation of NiCu alloy phase. The successful preparation of NiCu / NiMoS / NF catalyst in Example 2 was confirmed.

[0068] Fig.13 It is the XPS spectrum of the catalysts of Example 2, Comparative Examples 3 and 4. Among them, Fig.13 a shows the Ni 2p XPS spectrum, the peaks at 856.10 eV and 873.71 eV correspond to the 2p 3 / 2 and 2p 1 / 2, corresponding to Ni 2+ , Ni 0 Peaks appear at 852.90 eV and 870.10 eV. Fig.13 The two peaks at 933.11 eV and 953.21 eV in the XPS spectrum of Cu 2p in b belong to Cu 0 , while the two peaks at 935.09eV and 954.81eV belong to Cu 2+ . Fig.13 c shows the Mo 3d XPS spectrum, where the two peaks correspond to Mo 5+ (231.85eV), Mo 6+ (232.76eV). Fig.13 d shows the S2p XPS spectrum, in which the three peaks are attributed to the 2p 3 / 2 and 2p 1 / 2 track. Fig.13 The test results show that NiCu / NiMoS heterostructure was in situ grown on the surface of nickel foam by hydrothermal-electrochemical deposition.

[0069] Fig.14 This is a field emission scanning electron microscope (FE-SEM) image of the catalyst of Comparative Example 3, from which it can be seen that bulk NiMoS grown on nickel foam in Comparative Example 3. Fig.15 3 is a field emission scanning electron microscope (FE-SEM) image of the catalyst of Example 2, from which it can be seen that the heterostructure NiCu / NiMoS grown on the nickel foam in Example 2.

[0070] Electrocatalytic performance test of examples and comparative examples

[0071] The three-electrode system test conditions are as follows: the test is conducted in a 1 mol / L KOH solution saturated with N2; the reference electrode is an Ag / AgCl electrode, and the counter electrode is a carbon rod / Pt sheet electrode.

[0072] The conditions for the complete water splitting test were as follows: the test was conducted in a 1 mol / L KOH solution saturated with N2; wherein the reference electrode and the counter electrode were both the catalysts prepared in Example 1 or 2.

[0073] Figure 5 a is a comparison of the HER linear sweep voltammetry (LSV) curves of Example 1, Comparative Examples 1 and 2, and commercial Pt / C catalysts, wherein NiCu / NiMoO4 / NF is at 10 mA cm -2 and 100mA cm -2 The HER overpotentials at different current densities are 18mV and 154mV, respectively, and the catalytic activity is significantly better than that of NiMoO4 / NF, NiCu / NF and commercial Pt / C. Figure 5b is the Tafel comparison diagram, NiCu / NiMoO4 / NF has the lowest Tafel slope (34mV dec -1 ), which indicates that NiCu / NiMoO4 / NF has faster reaction kinetics; Figure 5 c is the double layer capacitance (C dl ) comparison chart for evaluating the electrochemical surface area (ECSA) of NiCu / NiMoO4 / NF dl 37mF cm -2 , indicating that it can provide more active sites in the HER process. Figure 5 d is the chronovoltage curve (CP) of NiCu / NiMoO4 / NF at 50 mA cm -2 The catalytic activity of NiCu / NiMoO4 / NF was almost not attenuated after continuous operation for more than 100 hours at a current density of 1.5 %. Figure 5 Overall, the test results show that NiCu / NiMoO4 / NF has better HER catalytic performance than comparative examples 1 and 2 and commercial Pt / C catalyst.

[0074] Figure 6 a is a comparison of the OER linear sweep voltammetry (LSV) curves of Example 1, Comparative Examples 1 and 2, and commercial RuO2 catalyst. It can be seen that NiCu / NiMoO4 / NF shows the lowest overpotential, which is at 10 mA cm -2 The OER overpotential is 248 mV at 100 mA cm -2 The OER overpotential is 330 mV, and the OER performance is significantly better than that of NiMoO4 / NF and commercial RuO2 catalysts. Figure 6 b is a comparison of Tafel slopes. NiCu / NiMoO4 / NF exhibits the lowest Tafel slope (27mV dec -1 ), which indicates that NiCu / NiMoO4 / NF has faster reaction kinetics; Figure 6 c is the double layer capacitance (C) used to estimate the electrochemically active surface area (ECSA) dl ) comparison chart, in which the C of NiCu / NiMoO4 / NF dl 40mF cm -2 , indicating that it can provide abundant active sites in the OER process. Figure 6 d is the chronovoltage curve (CP) of the NiCu / NiMoO4 / NF catalyst of Example 1, at 50 mA cm -2 The catalytic activity of NiCu / NiMoO4 / NF hardly decayed after continuous operation for more than 100 hours at a current density of 1.54 W / m2 / cm2.

[0075] Figure 7aThis is a comparison of the LSV of the complete water splitting of NiCu / NiMoO4 / NF and commercial catalysts in Example 1. NiCu / NiMoO4 / NF only needs 1.503V and 1.638V voltages to reach 10mA cm -2 and 50mAcm -2 The current density is much higher than that of commercial catalysts. Figure 7b The Faraday efficiency (FE) of NiCu / NiMoO4 / NF was calculated by testing the hydrogen production efficiency test system. The calculated FE of the NiCu / NiMoO4 / NF catalyst was close to 100%, indicating its excellent catalytic activity. Figure 7c The chronovoltage curve (CP) of the NiCu / NiMoO4 / NF catalyst of Example 1 is shown at 50 mA cm -2 The catalytic activity of NiCu / NiMoO4 / NF hardly decayed after continuous operation for more than 100 hours at a current density of 1.547 W / cm2.

[0076] Fig.16 a is a comparison of the HER linear sweep voltammetry (LSV) curves of the catalysts of Example 2, Comparative Examples 3 and 4, wherein NiCu / NiMoS / NF has significantly enhanced HER activity and shows the lowest overpotential; at 10 mA cm -2 The HER overpotential of NiCu / NiMoS / NF is 32 mV, and its catalytic activity is significantly better than that of NiMoS / NF and NiCu / NF. Fig.16 b is the EIS comparison diagram, NiCu / NiMoS / NF exhibits the lowest electrochemical impedance, which indicates that NiCu / NiMoS / NF has a faster charge transfer rate; Fig.16 c is the double layer capacitance (C dl ) comparison chart for evaluating the electrochemical surface area (ECSA), C of NiCu / NiMoS / NF dl 36mFcm -2 , indicating that it can provide more active sites in the HER process; Fig.16 d is the chronovoltage curve (CP) of the NiCu / NiMoS / NF catalyst of Example 2, at 50 mA cm -2 The catalytic activity of NiCu / NiMoS / NF hardly decayed after continuous operation for more than 100 hours at a current density of 1.547 W / m2.

[0077] Photothermal performance test of embodiments and comparative examples

[0078] The nickel foam-loaded nickel-molybdenum-based heterostructure photothermal catalyst disclosed in the present invention can be used as a hydrogen evolution electrode and / or an oxygen evolution electrode in, for example, a photothermal-assisted water electrolysis device disclosed in Chinese invention patent No. CN202210279172.1.

[0079] Figure 8a The UV-visible-near infrared absorption spectra of the catalysts of Example 1, Comparative Examples 1 and 2 show that compared with Comparative Examples 1 and 2, the catalyst of Example 1 has significantly enhanced absorption capacity in the wavelength range of 200-2000nm, especially can effectively absorb near-infrared light. This enhanced absorption capacity is due to the surface plasmon resonance (SPR) absorption of NiCu alloy on the one hand, and on the other hand, it can be attributed to the formation of NiCu / NiMoO4 heterostructure, which promotes the effective separation of photogenerated electrons and holes at the heterogeneous interface. In air environment, Figure 8b As shown in FIG. 1 , the maximum temperature of Example 1 at 12 min is 72.3°C, and the peak temperatures of Comparative Examples 1, 2 and bare NF are 68.8°C, 60.6°C and 49.9°C, respectively. In addition, under the same light intensity, the photothermal performance curves of Example 1 and Comparative Examples 1 and 2 in 1M KOH are as follows: Figure 8c As shown, when Example 1 is used, the maximum temperature of the electrolyte (53.5°C @ 90min) exceeds that of the comparative example, which confirms the superior photothermal performance of Example 1.

[0080] The overall water splitting performance of the catalyst of Example 1 was tested in an electrolyzer-TE device (photothermal assisted water electrolysis hydrogen production device). Fig. 9 a is the test result of the catalyst in Example 1 as hydrogen evolution electrode and oxygen evolution electrode without using thermoelectric (TE) device, under the light intensity of 200 mW cm -2 , current density is 50mAcm -2 When the light is on, the full water bath voltage of the electrolytic cell is measured to be 1.61 V, which is lower than the voltage when no light is added (1.65 V). Fig. 9 b The overall water decomposition performance of the thermoelectric device with the catalyst of Example 1 as the hydrogen evolution electrode and the oxygen evolution electrode was studied when there was a temperature difference of 25°C between the electrolyzer and its bottom water cooling plate and the current density was 50 mA cm -2 The full-water cell voltage of the electrolyzer was measured to be 0.96 V when the electrolyzer-TE device was illuminated and the current density was 50 mA cm -2 The results of the 10h stability test are as follows Fig. 9 As shown in c, no obvious decay was observed.

[0081] Fig.17a shows the UV-visible-near infrared absorption spectra of the catalysts of Example 2, Comparative Examples 3 and 4. It can be seen that Example 2 has a good absorption capacity in the wavelength range of 200-2000nm. Fig.17 As shown in Figure b, the maximum temperature of Example 2 is 71.4°C at 12 min, and the peak temperatures of Comparative Examples 3, 4 and bare NF are 68.8°C, 58.5°C and 48.6°C, respectively. Fig.17 c The overall water decomposition performance of the case where the catalyst of Example 2 is set as the hydrogen evolution electrode on the thermoelectric device is studied. When there is a temperature difference of 25°C between the electrolytic cell and its bottom water cooling plate and the current density is 50 mA cm -2 At this time, the full water bath voltage of the electrolytic cell was measured to be 0.84V. Fig.17 d The photothermal effect on the overall water decomposition reaction was studied when the catalyst in Example 2 was used as the hydrogen evolution electrode without using a thermoelectric (TE) module. -2 , current density is 50mAcm -2 When the light is on, the full water bath voltage of the electrolytic cell is measured to be 1.61 V, which is lower than the voltage when no light is added (1.83 V).

[0082] Oxygen vacancy content test of examples and comparative examples

[0083] like Figure 2 As shown in d, the three peaks in the O1s XPS spectrum of NiCu / NiMoO4 / NF are attributed to hydroxyl groups (OH), oxygen vacancies (O v ) and lattice oxygen (MO), and the oxygen vacancy intensity in NiCu / NiMoO4 / NF catalyst is higher than that in NiMoO4 / NF catalyst. In order to further confirm the existence of oxygen vacancies, electron paramagnetic resonance (EPR) technology was used to characterize the NiCu / NiMoO4 / NF and NiMoO 4 / NF conducted the test.

[0084] Fig.10 In the graph, at g = 2.003, a strong signal corresponding to oxygen vacancies appears in both NiCu / NiMoO4 / NF and NiMoO4 / NF catalysts. Importantly, the EPR signal of NiCu / NiMoO4 / NF is stronger than that of NiMoO4 / NF, indicating that there are more abundant oxygen vacancies in NiCu / NiMoO4 / NF, which is consistent with the XPS results. Abundant oxygen vacancies can enhance the conductivity of electrocatalysts, facilitate the adsorption and dissociation of water and other reaction intermediates, optimize the binding strength of reaction intermediates, and improve the electrocatalytic performance of NiCu / NiMoO4 / NF.

[0085] Hydrophilicity Test of Examples and Comparative Examples

[0086] Fig.11The surface properties of the electrocatalyst were revealed by measuring the contact angles of NiCu / NiMoO4 / NF and nickel foam (NF) substrate at the solid-liquid and solid-gas interfaces. Among them, the contact angle of nickel foam (NF) is 115.63°, indicating that nickel foam is a hydrophobic material. The contact angle of NiCu / NiMoO4 / NF is 0°, indicating that the NiCu / NiMoO4 / NF electrocatalyst has superhydrophilicity, which is conducive to the contact between the solution and the material surface, thereby accelerating its reaction kinetics and further improving the electrocatalytic efficiency.

[0087] Although the present invention is described above through specific embodiments, it should be understood that any equivalent improvements made by ordinary technicians in this field without departing from the scope of the present invention should be covered by the protection scope of the present invention.

Claims

1. A method for preparing a nickel foam-supported nickel-molybdenum-based heterostructure photothermal catalyst, comprising the following steps: Immersing the nickel foam in a precursor solution containing a nickel source and a molybdenum source for a hydrothermal reaction, and growing a NiMo-based nanomaterial on the nickel foam; Using the nickel foam after growing the NiMo-based nanomaterial as a working electrode, electrodeposition is performed in an electrolyte containing a nickel source and a copper source to grow a NiCu alloy nanomaterial on the NiMo-based nanomaterial; in, A heterogeneous interface structure is formed between the NiMo-based nanomaterial and the NiCu alloy nanomaterial.

2. The preparation method according to claim 1; wherein The NiMo-based nanomaterial is a nickel-molybdenum-based oxide.

3. The preparation method according to claim 1; wherein The temperature of the hydrothermal reaction is 120-200° C., and the time is 3-8 hours.

4. The preparation method according to claim 1; wherein The electrodeposition is a constant current density deposition, and the deposition current density is -0.1 to -0.3Acm -2 , the deposition time is 500 to 800 s.

5. The preparation method according to claim 1; wherein The molar concentration of the nickel source in the precursor solution is 0.01-0.1M, and the molar concentration of the molybdenum source is 0.005-0.05M.

6. The preparation method according to claim 5, wherein the nickel source is nickel nitrate, and the molybdenum source is ammonium molybdate.

7. The preparation method according to claim 5; wherein The NiMo-based nanomaterial is nickel-molybdenum-based sulfide, and the precursor solution also contains thiourea with a molar concentration of 0.1-0.5M.

8. The preparation method according to claim 1; wherein The molar concentration of the nickel source in the electrolyte is 0.01-0.1M, and the molar concentration of the copper source is 0.01-0.1M.

9. The preparation method according to claim 8; wherein The nickel source is nickel sulfate, the copper source is copper sulfate, and the electrolyte further contains ammonium sulfate with a molar concentration of 0.01-0.05M.

10. Use of the nickel foam-supported nickel-molybdenum-based heterostructure photothermal catalyst obtained by the preparation method according to any one of claims 1 to 9 in photothermal-assisted water electrolysis to produce hydrogen.

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