A method for preparing a cobalt-copper-based electrolytic water catalyst having a porous structure

Abstract

The application discloses a preparation method of a cobalt-copper-based electrolytic water catalyst with a porous structure, and mainly comprises the following steps: dissolving copper nitrate trihydrate, cobalt nitrate hexahydrate and isonicotinic acid in a mixed solution of N, N-dimethylacetamide, methanol and water to prepare a CuCo bimetallic precursor; and annealing the precursor in a tube furnace to obtain a CuCo2O4 / CuO / Cu2P7 composite material. The material has the advantages of cheap raw materials, simple preparation method, low reaction energy consumption and good industrial application prospect. The catalyst can be used as a high-efficiency bifunctional electrocatalyst for electrocatalytic HER, OER and electrolytic water, and has high electrocatalytic activity and good stability. In particular, in the OER, the catalytic activity is much higher than that of RuO2.

Description

Technical Field

[0001] This invention belongs to the technical field of water electrolysis catalysts, specifically relating to a method for preparing a cobalt-copper based water electrolysis catalyst with a porous structure. Background Technology

[0002] Hydrogen, with its high energy density, wide range of applications, and green, pollution-free nature, is considered an ideal clean energy source for the 21st century. Among various hydrogen production technologies, water electrolysis is a particularly convenient and efficient method. It involves two half-reactions: the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). The OER, a reaction involving the transfer of four electrons, is slow in kinetics and is a major bottleneck in water electrolysis. The use of catalysts can improve reaction kinetics and energy conversion efficiency, while reducing economic costs. Currently, oxides of Pt, Ir, and Ru are the most efficient electrocatalysts for the HER and OER, respectively. However, these precious metal catalysts are not only expensive but also scarce, significantly limiting their commercial application. Therefore, to reduce the complexity and cost of the entire water electrolysis system, it is necessary to provide an electrocatalyst that is highly active, stable, easy to prepare, and low in cost. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing a cobalt-copper-based electrolytic water catalyst that is highly active, stable, simple to prepare, and low in cost.

[0004] The preparation method of the cobalt-copper based water electrolysis catalyst of the present invention includes the following steps: 1) A mixed solution is formed by ultrasonically dissolving copper salt, cobalt salt, and isonicotinic acid ligand in an organic solvent. The mixed solution is then reacted at 120-180℃ for 6-30 h. After cooling to room temperature, the precipitate is collected by centrifugation at 8000 rpm for 2-5 min, washed three times with ethanol and water respectively, and then dried in an oven at 60℃ for 10-24 h to obtain precursor A. The organic solvent is at least two of methanol, N,N-dimethylformamide, N,N-dimethylformamide, and ethanol. The copper salt is at least one of copper nitrate, copper chloride, and copper acetate. The cobalt salt is at least one of cobalt nitrate, cobalt chloride, cobalt acetate, and cobalt acetylacetonate. The molar ratio of copper salt to cobalt salt is 1:1 to 1:4, and the molar ratio of copper salt to isonicotinic acid is 1:1 to 1:4.

[0005] 2) Place precursor A in a magnetic boat and heat it to 350~750℃ in a tube furnace under Ar protection for 1~3 hours to obtain precursor B; 3) Precursor B and phosphate salt were annealed at 250-350℃ for 1-3 hours under Ar protection to obtain a cobalt-copper based water electrolysis catalyst with a porous structure. The phosphate salt was sodium hypophosphite, and the mass ratio of phosphate salt to precursor B was 8-12:1.

[0006] Synthesis mechanism of the present invention: Using cobalt nitrate hexahydrate as the cobalt source, copper nitrate trihydrate as the copper source, and isonicotinic acid as the ligand, these three components were dissolved in a mixed solution of N,N-dimethylacetamide, methanol, and water. The solution was then placed in a high-pressure reactor for a solvothermal reaction to form coordination polymer A. The obtained A was then heat-treated at 350–750 °C for 1–2 h under an Ar atmosphere with a heating rate of 2.0 °C / min, followed by natural cooling to obtain precursor B. Finally, using sodium hypophosphite (NaH₂PO₂·H₂O) as the phosphorus source, precursor B was heated at 250–350 °C for 1–2 h under an Ar atmosphere with a heating rate of 2.0 °C / min for a low-temperature phosphating treatment. NaH₂PO₂ decomposes at 250 °C, and the resulting PH₃ gas, under Ar protection, reacts with metal ions (Cu) on the surface of the calcined material. 2+ A chemical reaction occurs, producing metal phosphides. The composition, structure, and catalytic performance of the catalyst can be controlled by adjusting the ratio of cobalt and copper sources and ligands, the heat treatment temperature and reaction time, and the amount of phosphate salt (NaH2PO2·H2O). For example, increasing the reaction temperature can improve the degree of graphitization of the material, thereby increasing its electrical conductivity.

[0007] The aforementioned cobalt-copper based water electrolysis catalyst exhibits excellent water electrolysis performance in alkaline electrolytes, at 10 mA / cm². 2 At current densities, the overpotential of HER can be as low as 133mV, the overpotential of OER can be as low as 250mV, the decomposition voltage of water electrolysis can be as low as 1.48V, and it has good cycle stability.

[0008] In summary, the present invention has the following advantages: 1. This invention optimizes the electronic structure of a heterogeneous catalyst and improves its activity by constructing a multiphase catalyst. Furthermore, the three-dimensional framework material of this invention possesses characteristics such as high specific surface area, porous structure, multiple metal centers, and tunable composition. The porous structure increases the active area of ​​the nanomaterial, enabling effective contact with the electrolyte and thus enhancing electrocatalytic activity. 2. The porous catalyst prepared by this invention has long-term stability and higher bifunctional catalytic performance, which reduces the cost of hydrogen production and is expected to be widely used in the field of water electrolysis. Attached Figure Description

[0009] Figure 1 Transmission electron microscopy (SEM) image of CuCo2O4 / CuO / Cu2P7 prepared for an embodiment of the present invention.

[0010] Figure 2 High-resolution transmission electron microscopy (TEM) image of CuCo2O4 / CuO / Cu2P7 prepared in an embodiment of the present invention.

[0011] Figure 3 The X-ray diffraction (XRD) pattern of CuCo2O4 / CuO / Cu2P7 prepared in the embodiments of the present invention.

[0012] Figure 4 Linear sweep polarization (LSV) performance curves of CuCo2O4 / CuO / Cu2P7 and commercial RuO2 prepared for embodiments of the present invention.

[0013] Figure 5 This is the N2 adsorption-desorption isotherm of the catalyst prepared in the embodiments of the present invention.

[0014] Figure 6 This is a pore size distribution diagram of the catalyst prepared in the embodiments of the present invention.

[0015] Figure 7 LSV curve of HER catalyzed by CuCo2O4 / CuO / Cu2P7 prepared in an embodiment of the present invention in 1.0 MkOH.

[0016] Figure 8 The LSV curve of CuCo2O4 / CuO / Cu2P7 prepared in an embodiment of the present invention for catalyzing OER in 1.0 MkOH.

[0017] Figure 9 The LSV curves of CuCo2O4 / CuO / Cu2P7 prepared as an example of the present invention are obtained by catalytic electrolysis of water in 1.0 MkOH.

[0018] Figure 10 The above describes the voltage-time curve of CuCo2O4 / CuO / Cu2P7 prepared in an embodiment of the present invention for catalytic water electrolysis in 1.0 MkOH. Detailed Implementation

[0019] The present invention will be further explained and described below with reference to specific embodiments. Example

[0020] Preparation of CuCo2O4 / CuO / Cu2P7 First, 36.2 mg Cu(NO3)2·3H2O, 131.0 mg Co(NO3)2·6H2O, and 36.0 mg isonic acid were weighed and ultrasonically mixed in 30 mL of a mixed solution of N,N-dimethylacetamide, methanol, and water. The resulting solution was then heated to 160 °C in an oven for 24 h. After centrifugation, the precipitate was collected, washed three times with water and ethanol solutions respectively, and dried in an oven at 60 °C. The obtained material was heated to 450 °C in an Ar atmosphere tube furnace at a heating rate of 2 °C / min and held for 2 h. After natural cooling, CuCo2O4 / CuO was obtained.

[0021] 10 mg of CuCo2O4 / CuO and 100 mg of NaH2PO2·H2O were placed at opposite ends of the same magnetic boat, and then placed in a tube furnace and annealed in Ar at 300 °C for 2 h to obtain CuCo2O4 / CuO loaded with Cu2P7. After cooling, CuCo2O4 / CuO / Cu2P7 was obtained.

[0022] Structural characterization of CuCo2O4 / CuO / Cu2P7 Figure 1 The image shows a scanning electron microscope (SEM) image of CuCo2O4 / CuO / Cu2P7 prepared in Example 1. As can be seen from the image, the surface of CuCo2O4 / CuO / Cu2P7 is rough and porous.

[0023] Figure 2 The image shows a transmission electron microscope (TEM) image of CuCo2O4 / CuO / Cu2P7 prepared in Example 1, which further illustrates the porous structure of CuCo2O4 / CuO / Cu2P7.

[0024] Figure 3 The image shows a high-resolution transmission electron microscope (TEM) image of CuCo2O4 / CuO / Cu2P7 prepared in Example 1. The image shows the presence of CuCo2O4, CuO, and Cu2P7.

[0025] Figure 4 The image shows the X-ray diffraction (XRD) pattern of CuCo2O4 / CuO / Cu2P7 prepared in Example 1. The image further demonstrates that the composite material consists of three phases: CuCo2O4, CuO, and Cu2P7.

[0026] Figure 5 The N2 adsorption-desorption isotherm of the catalyst prepared in Example 1 of this invention shows that the obtained sample exhibits a typical type IV isotherm and has an H3 type hysteresis loop, indicating that the sample has a multi-level pore structure.

[0027] Figure 6 This is a pore size distribution diagram of the catalyst prepared in Example 1 of the present invention. As can be seen from the figure, the pore size distribution of the obtained sample is wide, mainly concentrated in 2-40 nm, which further proves the rich mesoporous structure of the catalyst.

[0028] Catalytic performance evaluation of CuCo2O4 / CuO / Cu2P7 Test Method: Weigh 5.0 mg of the prepared catalyst and add it to 1 mL of a mixture of anhydrous ethanol and water. Then add 20 μL of Nafion (5 wt%) solution and sonicate for 30 min. Take 6 μL of the suspension and coat it onto a 3 mm glassy carbon electrode as the working electrode. Use a carbon rod as the counter electrode, an Ag / AgCl electrode as the reference electrode, and 1.0 MkOH as the electrolyte. Perform HER and OER tests in a three-electrode system. For the water electrolysis performance test, a two-electrode system is used. Drop the prepared suspension onto two thoroughly cleaned 1 cm electrodes. 2 On the nickel foam, the catalyst loading was 1 mg / cm³. 2 The cathode and anode were fabricated and tested in a 1.0 M KOH solution. Stability testing was conducted at a current density of 10 mA / cm². 2 The following method is used to test the potential-time curve.

[0029] Figure 7 The figure shows the LSV curve of CuCo2O4 / CuO / Cu2P7 prepared in Example 1 catalyzing HER in 1.0 MkOH. Since the theoretical voltage of the HER reaction is 0 V and the overpotential η = |E| - 0, it can be seen from the figure that at a current density of 10 mA•cm -2 At this point, the corresponding voltage E = -0.133V, and the calculated overpotential is only 133mV, indicating that the catalyst has excellent HER catalytic activity.

[0030] Figure 8 The LSV curve of CuCo2O4 / CuO / Cu2P7 prepared in Example 1 catalyzing OER in 1.0 MkOH is shown. Since the theoretical voltage of the HER reaction is 1.23 V, and the overpotential η = |E| - 1.23, it can be seen from the figure that at a current density of 10 mA•cm⁻¹, the overpotential η = |E| - 1.23 V is significantly higher than that of the HER reaction. -2 At this time, the corresponding voltage E=1.48V, and the calculated overpotential is only 250mV, indicating that the catalyst has excellent catalytic OER activity, which is significantly better than that of commercial ruthenium dioxide catalyst (290mV).

[0031] Figure 9 The figure shows the LSV curve of CuCo2O4 / CuO / Cu2P7 prepared in Example 1 for catalytic water electrolysis in 1.0 MkOH. As can be seen from the figure, the prepared composite material exhibits high performance at 10 mA•cm⁻¹. -2 The overpotential is only 1.48V, indicating that the catalyst has excellent activity in catalytic water electrolysis.

[0032] Figure 10The figure shows the voltage-time curve of CuCo2O4 / CuO / Cu2P7 prepared in Example 1 for catalytic water electrolysis in 1.0 M KOH. As can be seen from the figure, this catalyst, at a fixed current density of 100 mA•cm⁻¹, exhibits good performance. -2 Under these conditions, a 28-hour stability test was conducted, and the voltage remained almost unchanged, indicating that the catalyst has excellent stability in catalytic water electrolysis.

Claims

1. A method for preparing a cobalt-copper based electrolytic water catalyst CuCo2O4 / CuO / Cu2P7 with a porous structure, characterized in that, Includes the following steps: 1) Dissolve copper salt, cobalt salt and isonicotinic acid ligand in a mixed solution of N,N-dimethylacetamide, methanol and water by ultrasonication. Then react the resulting solution at 120~180℃ for 6~30h. After the solution is cooled to room temperature, centrifuge to collect the precipitate, wash and dry it to obtain precursor A. 2) Place precursor A in a magnetic boat and heat it to 350~750℃ in a tube furnace under Ar protection for 1~3 hours to obtain precursor B; 3) Precursor B and phosphate salt were placed in an environment of 250~350℃ under Ar protection and annealed for 1~3h to obtain a cobalt copper-based water electrolysis catalyst CuCo2O4 / CuO / Cu2P7 with a porous structure.

2. The preparation method of the cobalt-copper based electrolytic water catalyst CuCo2O4 / CuO / Cu2P7 with a porous structure as described in claim 1, characterized in that, In step 1), the copper salt is at least one of copper nitrate, copper chloride, and copper acetate; the cobalt salt is at least one of cobalt nitrate, cobalt chloride, cobalt acetate, and cobalt acetylacetonate.

3. The preparation method of the cobalt-copper based electrolytic water catalyst CuCo2O4 / CuO / Cu2P7 with a porous structure as described in claim 1, characterized in that, In step 1), the molar ratio of copper salt to cobalt salt is 1:1 to 1:4, and the molar ratio of copper salt to isonicotinic acid is 1:1 to 1:

4.

4. The preparation method of the cobalt-copper based electrolytic water catalyst CuCo2O4 / CuO / Cu2P7 with a porous structure as described in claim 1, characterized in that, In step 1), the centrifugation speed is 8000 rpm; the centrifugation time is 2~5 min.

5. The preparation method of the cobalt-copper based electrolytic water catalyst CuCo2O4 / CuO / Cu2P7 with a porous structure as described in claim 1, characterized in that, In step 1), drying refers to hot drying at 60℃ for 10~24 hours.

6. The preparation method of the cobalt-copper based electrolytic water catalyst CuCo2O4 / CuO / Cu2P7 with a porous structure as described in claim 1, characterized in that, In step 3), the phosphate salt is sodium hypophosphite, and the mass ratio of the phosphate salt to precursor B is 8~12:1.

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