A surface treatment method of a non-noble metal electrocatalyst growth substrate

Abstract

This invention discloses a surface treatment method for a non-precious metal electrocatalyst growth substrate, relating to the field of new energy technology for hydrogen production through water electrolysis. The specific method includes the following steps: ultrasonically cleaning and drying the growth substrate in a mixed solution of ethanol and deionized water to obtain a pretreated growth substrate; etching the pretreated growth substrate with an acid solution, followed by cleaning and drying to obtain an etched growth substrate; starting an ultraviolet ozone cleaner, and after the ultraviolet source has pre-stabilized, activating the etched growth substrate to obtain a surface-treated growth substrate; the growth substrate can be any one of foamed nickel, foamed cobalt, foamed nickel-iron, or foamed copper. This invention uses an acid etching + ultraviolet ozone activation method to form micron-sized cracks and nickel oxide on the surface of foamed nickel, resulting in a highly efficient foamed nickel electrocatalyst that exhibits good catalytic activity under high current density conditions in industrial applications and remains stable over a long period without significant performance degradation.

Description

Technical Field

[0001] This invention relates to the field of new energy technology for hydrogen production by water electrolysis, specifically a surface treatment method for a non-precious metal electrocatalyst growth substrate. Background Technology

[0002] Amidst the global economic boom, the demand for fossil fuels continues to rise; however, the ensuing environmental degradation and climate crisis pose a serious threat to the sustainable development of human society. Replacing traditional fossil fuels with green and renewable energy is an important area that humanity should invest heavily in. Hydrogen energy, due to its high energy density and zero carbon emissions, is considered a highly promising clean energy carrier. However, as a secondary energy source, it must be produced from other primary energy sources. Currently, most hydrogen comes from fossil fuels, and the production process involves large amounts of carbon emissions, causing serious environmental pollution. In contrast, water electrolysis for hydrogen production has advantages such as flexible operation, zero pollution, and relatively mature technology. The water electrolysis process involves two half-reactions: the hydrogen evolution reaction at the cathode and the oxygen evolution reaction at the anode. Among them, the oxygen evolution reaction at the anode involves a four-electron / four-proton cooperative transfer process, which is kineticly slow and requires a high overpotential, thus becoming a bottleneck restricting the overall water splitting efficiency. In traditional water electrolysis devices, noble metal oxides such as RuO2 and IrO2 are widely used as electrocatalysts for the oxygen evolution reaction. However, these precious metal catalysts are scarce and expensive, severely limiting their widespread application in large-scale industrial applications. Therefore, developing low-cost, highly active non-precious metal electrocatalysts for the oxygen evolution reaction is one of the core challenges in realizing the commercialization of water electrolysis for hydrogen production.

[0003] Nickel foam, as a three-dimensional porous material, is widely used as a substrate material for water electrolysis catalysts due to its low cost, excellent conductivity, good chemical stability, and high mechanical strength. However, commercially available nickel foam typically has a smooth and flat surface, exhibiting hydrophobic properties, which cannot meet the mass transfer requirements under high current densities. Furthermore, it has low intrinsic catalytic activity and poor electrocatalytic oxygen evolution reaction (OER) performance. To overcome these shortcomings, surface modification methods are commonly used in existing technologies to improve its surface roughness and hydrophilicity. For example, existing literature reports a high-temperature calcination method for surface modification of nickel foam: under an inert atmosphere, nickel foam is heat-treated at 750°C for 5 hours to form a uniform micro-wrinkle and groove structure on its surface. The modified catalyst, after electrochemical activation, exhibits good OER activity. However, this method has inherent drawbacks such as high energy consumption, complex processes, long production cycles, demanding equipment requirements, and high costs, making it difficult to meet the needs of large-scale industrial production.

[0004] Therefore, there is an urgent need to develop a simple, energy-efficient, low-cost, and easily scalable method for modifying the surface of nickel foam to prepare high-performance catalysts suitable for the oxygen evolution reaction at high current densities in industrial applications. Summary of the Invention

[0005] The purpose of this invention is to provide a surface treatment method for a non-precious metal electrocatalyst growth substrate to solve the problems mentioned in the background art.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A surface treatment method for a non-precious metal electrocatalyst growth substrate includes the following steps: Step 1: Place a growth substrate in a mixed solution of ethanol and deionized water for ultrasonic cleaning and drying to obtain a pretreated growth substrate; Step 2: Take the pretreated growth substrate and etch it with acid solution. After the etching is completed, repeat Step 1 to clean it and dry it to obtain the etched growth substrate. Step 3: Start the UV ozone cleaner. After the UV source is pre-stabilized, place the etched growth substrate in the UV source for activation to obtain the surface-treated growth substrate.

[0007] Preferably, the growth substrate is any one of foamed nickel, foamed cobalt, foamed nickel iron, and foamed copper; More preferably, the nickel foam undergoes surface treatment, specifically including the following steps: Step 1: Place the nickel foam in a mixed solution of ethanol and deionized water for ultrasonic cleaning and drying to obtain pretreated nickel foam; Step 2: Take the pretreated nickel foam and etch it with acid solution. After the etching is completed, repeat Step 1 to clean it and dry it to obtain the etched nickel foam. Step 3: Start the UV ozone cleaner. After the UV source is pre-stabilized, put in the etched nickel foam for activation to obtain surface-treated nickel foam.

[0008] Preferably, the volume ratio of ethanol to deionized water in step 1 is 1:1; Preferably, the ultrasound time in step 1 is 30-40 minutes; Preferably, in step 2, the acid etching solution is either sulfuric acid or hydrochloric acid. More preferably, the process parameters for acid etching in step 2 are as follows: the etching solution is hydrochloric acid solution, the volume concentration of the hydrochloric acid solution is 1-5 mol / L, the etching temperature is 30-70℃, the stirring speed is 350-400 rpm, and the etching time is 1-3 h. Preferably, the UV source pre-stabilization in step 3 includes the following process parameters: UV irradiance of 28000-32000 μW / cm². 2The distance between the UV source and the sample cleaning tray should be 25-30 mm, and the pre-stabilization time should be 15-20 min. Preferably, the activation time in step 3 is 10-180 min; Preferably, the etched nickel foam surface has a micron-sized crack structure; and nickel oxide is formed on the surface-treated nickel foam surface. Compared with the prior art, the beneficial effects achieved by the present invention are: This invention provides a surface treatment method for non-precious metal electrocatalyst growth substrates, comprising pretreatment cleaning, acid etching, and ultraviolet-ozone activation. Specifically targeting nickel foam, one type of non-precious metal electrocatalyst growth substrate, pretreatment cleaning is performed first, followed by acid etching. By controlling the etching temperature, etching time, and etching solution concentration, the crack width is regulated, effectively increasing the specific surface area of ​​the nickel foam, exposing more active sites, and improving hydrophilicity. Finally, ultraviolet-ozone surface activation forms active nickel oxide (NiO) on the surface of the nickel foam. X This improves the electrocatalytic performance of nickel foam; the performance improvement is more significant at high current densities; the process of this invention is simple, time-saving, and does not require high-temperature treatment, thus achieving energy saving and cost reduction, and is suitable for large-scale production. Attached Figure Description

[0009] Figure 1 These are SEM images; where a and b are SEM images of NF without acid etching, c and d are SEM images of ENF-2h, and e and f are SEM images of UV-ENF-2h. Figure 2 The results are the hydrophilicity test results of the catalyst surface, where a is the contact angle of NF without acid etching treatment, and b is the contact angle of UV-ENF-2h catalyst; Figure 3 LSV curves of the hydrogen evolution reaction (OER) of catalysts UV-ENF-2h, ENF-2h, ENF-1h, ​​and NF in 1M KOH; Figure 4 The bar chart shows the overpotential of catalysts UV-ENF-2h, ENF-2h, ENF-1h, ​​and NF in 1M KOH. Figure 5 Impedance plots of OER for catalysts UV-ENF-2h, ENF-2h, ENF-1h, ​​and NF in 1M KOH; Figure 6 The figure shows the CV curve of the catalyst in 1M KOH, where a represents UV-ENF-2h, b represents ENF-2h, c represents ENF-1h, ​​and d represents NF. Figure 7The double-layer capacitance diagrams of catalysts UV-ENF-2h, ENF-2h, ENF-1h, ​​and NF in 1M KOH are shown. Figure 8 The OER polarization curves of the catalyst UV-ENF-2h before and after 3000 CV cycles are shown. Detailed Implementation

[0010] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0011] It should be noted that there are no special restrictions on the manufacturers from which the raw materials involved in this invention can be purchased; Example 1: This example provides a surface treatment method for nickel foam, specifically including the following steps: Step 1: The nickel foam was ultrasonically cleaned in a mixture of 50 mL ethanol and 50 mL deionized water for 30 min, and then dried in a vacuum oven at 60 °C for 12 h to obtain the pretreated nickel foam; the size of the nickel foam was 2.5 × 6 cm. 2 The thickness is 1.7 mm, the average pore size is 0.1 mm, and the porosity is 97.2%. Step 2: Place the pretreated nickel foam into 50 mL of 3 mol / L hydrochloric acid solution and stir for 2 h at 400 rpm and 60 °C to perform acid etching. After the etching is completed, repeat Step 1 to clean and dry to obtain nickel foam with micron-crack structure. Step 3: Start the SC-UV-I ultraviolet ozone cleaner, which generates 30000μW / cm² through the mercury vapor grid lamp. 2 The ultraviolet radiation was applied, with the distance between the ultraviolet source and the sample cleaning tray set to 30 mm. The ultraviolet source was irradiated for 15 min to generate O3. Micron-cracked nickel foam was placed in the tray for activation for 60 min to obtain micron-cracked nickel foam with nickel oxide loaded on the surface; that is, the catalyst UV-ENF-2h.

[0012] Comparative Example 1: As a control experiment for Example 1, the difference is that step 3, UV-ozone activation, was not performed; specifically, the following steps were included: Step 1: The nickel foam was ultrasonically cleaned in a mixture of 50 mL ethanol and 50 mL deionized water for 30 min, and then dried in a vacuum oven at 60 °C for 12 h to obtain the pretreated nickel foam; the size of the nickel foam was 2.5 × 6 cm. 2 The thickness is 1.7 mm, the average pore size is 0.1 mm, and the porosity is 97.2%. Step 2: Place the pretreated nickel foam into 50 mL of 3 mol / L hydrochloric acid solution and stir for 2 h at 400 rpm and 60 °C for acid etching. After the etching is completed, repeat Step 1 for cleaning and drying to obtain nickel foam with micron-crack structure; that is, catalyst ENF-2h.

[0013] Comparative Example 2: As a control experiment for Example 1, the difference is that the acid etching time was adjusted to 1 hour, and the UV-ozone activation in step 3 was not performed; specifically, the following steps were included: Step 1: The nickel foam was ultrasonically cleaned in a mixture of 50 mL ethanol and 50 mL deionized water for 30 min, and then dried in a vacuum oven at 60 °C for 12 h to obtain the pretreated nickel foam; the size of the nickel foam was 2.5 × 6 cm. 2 The thickness is 1.7 mm, the average pore size is 0.1 mm, and the porosity is 97.2%. Step 2: Place the pretreated nickel foam into 50 mL of 3 mol / L hydrochloric acid solution and stir for 1 h at 400 rpm and 60 °C for acid etching. After the etching is completed, repeat Step 1 for cleaning and drying to obtain nickel foam with micron-crack structure; that is, catalyst ENF-1h.

[0014] Comparative Example 3: As a control experiment for Example 1, the difference is that only the pretreatment cleaning step of step 1 is retained; specifically, it includes the following steps: Nickel foam was ultrasonically cleaned in a mixture of 50 mL ethanol and 50 mL deionized water for 30 min, and then dried in a vacuum oven at 60 °C for 12 h to obtain pretreated nickel foam, i.e., catalyst NF; the size of the nickel foam was 2.5 × 6 cm. 2 It has a thickness of 1.7 mm, an average pore size of 0.1 mm, and a porosity of 97.2%.

[0015] Testing 1. The surface morphology of catalysts UV-ENF-2h, ENF-2h, and NF was observed by scanning electron microscopy; 2. Contact angle test: The contact angles of the catalysts UV-ENF-2h and NF were measured using an SDC-200SH contact angle tester; 3. Electrochemical Testing: Testing was conducted using a three-electrode system on a CS310M potentiometer. The Hg / HgO electrode and graphite rod were used as the reference and counter electrodes, respectively, with 1M KOH as the electrolyte. The catalysts prepared in Example 1 and Comparative Examples 1-3 were used as the working electrodes, with an immersion area of ​​1×1 cm² in the electrolyte. 2 ; 3.1 Electrochemical hydrogen evolution performance: Activation was performed using cyclic voltammetry, followed by linear sweep voltammetry testing at a scan rate of 2 mV / s; the frequency range was set to 10. 5 -10 -2 The electrochemical impedance of the catalyst was measured at Hz and a voltage amplitude of 5.0 mV. 3.2 Cyclic voltammetry curves: CV curves at different scan rates (20-100 mV / s) in the non-Radida potential range of 0.1-0.20 V vs. Ref; 3.3 Stability test: The stability of the UV-ENF-2h catalyst was tested by cyclic voltammetry at a scan rate of 100 mV / s, a potential range of 1-2.1 V vs. Ref, and 3000 cycles.

[0016] Conclusion: The morphology of the catalysts prepared in Example 1 and Comparative Examples 1 and 3 was observed by scanning electron microscopy, and the results are as follows: Figure 1 As shown, the surfaces of the un-etched catalysts NF (a, b) are relatively smooth and flat. However, after acid etching, the surface of the nickel foam is reconstructed, becoming rough and porous, and a large number of micron-sized cracks are generated. These cracks are uniformly distributed at the grain boundaries, with a width of about 1-3 μm, which may be due to the preferential etching of the grain boundaries by acid. After ultraviolet-ozone treatment, nickel oxide nanosheets are formed on the surface of the nickel foam. The results of the contact angle test are as follows: Figure 2 As shown, a is the contact angle of the catalyst NF without acid etching, which is 129°, exhibiting hydrophobicity; b is the contact angle of the micron-cracked nickel foam UV-ENF-2h after etching, which is 0°, exhibiting a superhydrophilic structure. This indicates that the hydrophilicity of the catalyst is significantly improved after acid etching. The hydrogen evolution performance was tested using electrochemical methods, and the results are as follows: Figure 3 , 4 As shown, where, Figure 3 The linear voltammetry curves were obtained based on the LSV curves for each catalyst at a current density of 10 mA·cm⁻¹. -2 100mA·cm -2 and 500mA·cm -2 The overpotential for catalytic water splitting is shown in the bar chart below. Figure 4 As shown, the catalyst UV-ENF-2h at 10 mA·cm -2 100mA·cm -2 and 500mA·cm -2 The catalyst exhibits the lowest oxygen evolution reaction overpotential at the current density, with required overpotentials of 296mV, 370mV, and 398mV respectively. The overpotentials are lower than those of other catalysts, indicating that the UV-ENF-2h catalyst has excellent performance in catalyzing oxygen evolution in water electrolysis. The results were obtained through electrochemical impedance spectroscopy. Figure 5 As shown, the semicircular arc reflects the magnitude of the charge transfer resistance. The smaller the semicircular arc, the better the electrode activity. The semicircular arc of the catalyst UV-ENF-2h is the smallest, indicating that UV-ENF-2h has lower resistance and stronger catalytic kinetics. The results obtained through cyclic voltammetry scanning are as follows: Figure 6 , 7 As shown, a graph is plotted with half of the difference in current density (Δj) at different scan rates on the ordinate and the scan rate on the abscissa. Figure 6 The slope of the fitted line is C. dl Then, the electrochemically active surface area (ECSA) value is estimated, and the double-layer capacitance diagram of the catalyst is shown in the figure. Figure 7 As shown, UV-ENF-2h has the largest slope, indicating that UV-ENF-2h has a higher C content. dl It has the largest active area and more catalytic active sites than the untreated catalyst NF. The stability test results are as follows: Figure 8 As shown, this demonstrates that the catalyst UV-ENF-2h possesses the ability to operate stably for extended periods.

[0017] This invention employs an acid etching + ultraviolet ozone activation method to form micron-sized cracks and nickel oxides on the surface of nickel foam, thereby improving the surface roughness and hydrophilicity of nickel foam. At the same time, a highly efficient nickel foam electrocatalyst is obtained, which not only exhibits good catalytic activity under industrial high current density conditions, but also can work stably for a long time without significant performance degradation.

[0018] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A surface treatment method for a non-precious metal electrocatalyst growth substrate, characterized in that, Includes the following steps: Step 1: Place a growth substrate in a mixed solution of ethanol and deionized water for ultrasonic cleaning and drying to obtain a pretreated growth substrate; Step 2: Take the pretreated growth substrate and etch it with acid solution. After the etching is completed, repeat Step 1 to clean it and dry it to obtain the etched growth substrate. Step 3: Start the UV ozone cleaner. After the UV source is pre-stabilized, place the etched growth substrate in the UV source for activation to obtain the surface-treated growth substrate.

2. The surface treatment method for a non-noble metal electrocatalyst growth substrate according to claim 1, characterized in that, The growth substrate is any one of foamed nickel, foamed cobalt, foamed nickel iron, or foamed copper.

3. The surface treatment method for a non-noble metal electrocatalyst growth substrate according to claim 1, characterized in that, The growth substrate is nickel foam; the surface treatment of the nickel foam specifically includes the following steps: Step 1: Place the nickel foam in a mixed solution of ethanol and deionized water for ultrasonic cleaning and drying to obtain pretreated nickel foam; Step 2: Take the pretreated nickel foam and etch it with acid solution. After the etching is completed, repeat Step 1 to clean it and dry it to obtain the etched nickel foam. Step 3: Start the UV ozone cleaner. After the UV source is pre-stabilized, put in the etched nickel foam for activation to obtain surface-treated nickel foam.

4. The surface treatment method for a non-noble metal electrocatalyst growth substrate according to claim 3, characterized in that, In step 1, the volume ratio of ethanol to deionized water is 1:1; the ultrasonic time in step 1 is 10-60 min.

5. The surface treatment method for a non-noble metal electrocatalyst growth substrate according to claim 3, characterized in that, In step 2, the acid etching solution can be either sulfuric acid or hydrochloric acid.

6. The surface treatment method for a non-noble metal electrocatalyst growth substrate according to claim 3, characterized in that, The process parameters for acid etching in step 2 are as follows: the etching solution is hydrochloric acid solution, the volume concentration of the hydrochloric acid solution is 1-5 mol / L, the etching temperature is 30-70℃, the stirring speed is 350-400 rpm, and the etching time is 1-3 h.

7. The surface treatment method for a non-noble metal electrocatalyst growth substrate according to claim 3, characterized in that, The UV source pre-stabilization in step 3 includes the following process parameters: UV irradiance of 28000-32000 μW / cm². 2 The distance between the UV source and the sample cleaning tray is 25-30 mm, and the pre-stabilization time is 15-20 min.

8. The surface treatment method for a non-noble metal electrocatalyst growth substrate according to claim 3, characterized in that, The activation time in step 3 is 10-180 min.

9. The surface treatment method for a non-noble metal electrocatalyst growth substrate according to claim 3, characterized in that, The etched nickel foam surface has a micron-sized crack structure; the surface-treated nickel foam surface forms nickel oxide.

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