Preparation Of Ni-based SnO₂ Composite Electrode By Electrodeposition Method And Research On Their Performances For Hydrogen Evolution

As a new clean and renewable energy source,hydrogen energy is an ideal substitute for fossil fuels.Hydrogen production from electrolytic water has received a lot of attention from researchers for its efficient and sustainable advantages.Platinum group metals have the best hydrogen precipitation properties,but the scarcity and cost of platinum limit its large-scale application.Nickel has good hydrogen precipitation properties in alkaline solutions and is an ideal material to replace platinum group metals,but its hydrogen precipitation properties need to be improved.In this paper,several nickel-based composite electrode materials were prepared to improve the hydrogen precipitation performance of nickel-based composite electrodes by optimizing the composition of the plating solution and process conditions and introducing the complex particles.The main studies are as follows:The effects of the composition of nickel plating solution and electrodeposition process parameters on the performance of nickel electrodes were studied,and nickel electrodes were prepared by electrodeposition technique with purple copper as the substrate.The results showed that the nickel electrode plating was most finely crystallized when the concentration of Ni（NH₂SO₃）₂·4H₂O was 350 g·L^-1,Ni Cl₂·6H₂O was 10 g·L^-1,NH₄Cl was 30 g·L^-1,the current density was 3.0 A·dm^-2,the p H was 3.8,the plating solution temperature was 35℃,and the deposition time was 30 min.The nickel electrode has the best hydrogen precipitation overpotential of 500 m V at a polarization density of 10 m A·cm^-2,a Tafel slope b value of 120m V·dec^-1,and an exchange current density of 0.673 u A·cm^-2with the best hydrogen precipitation performance and corrosion resistance.The SnO₂composite particles were prepared by hydrothermal synthesis,the Ni/SnO₂composite electrodes were synthesized.The effects of particle size and concentration of SnO2composite particles on the hydrogen precipitation performance of Ni/SnO₂composite electrodes were systematically investigated.It was found that the addition of SnO₂composite particles in the plating solution affects the surface morphology of Ni/SnO₂composite electrodes.The addition of SnO₂composite particles refines the crystallization of the plating layer,increases the specific surface area of the plating layer,and changes the nickel particle growth orientation from the（200）crystal plane to the（111）crystal plane,which effectively improves the hydrogen precipitation performance of the composite electrode.At the same time,the presence of hydroxyl groups on the surface of SnO₂composite particles can promote the decomposition of water,which is conducive to the formation of H_adsin the hydrogen precipitation reaction and accelerate the rate of hydrogen precipitation reaction on the surface of the composite electrode.On this basis,the effects of different particle sizes of SnO₂composite particles（50,200,500 nm）on the performance of Ni/SnO₂composite electrodes were investigated.The results show that the composite electrode prepared with a SnO₂particle size of 200 nm has the lowest hydrogen precipitation overpotential and charge transfer resistance,and has the best hydrogen precipitation performance.The potential decay of Ni/SnO₂-200 composite electrode for hydrogen precipitation stability test was only 34 m V,which showed good stability.The electrodeposition reaction makes it easier for small-sized SnO₂composite particles to be deposited into the layer,resulting in a higher SnO₂content in the layer,a decrease in the conductivity of the composite electrode,and a decrease in its hydrogen precipitation activity.The deposition of large-size SnO₂composite particles into the plating layer is relatively difficult,and the SnO₂content in the plating layer is low,not reaching the optimal loading for the highest hydrogen precipitation performance of the composite plating layer,and the hydrogen precipitation performance is poor.The Ni/SnO₂composite electrode prepared at a concentration of 3 g·L^-1of SnO₂composite particles in the plating solution has the best hydrogen precipitation performance.The concentration of SnO₂composite particles is too low,resulting in coarse crystallization of the composite layer,less specific surface area of the layer and the number of hydrogen precipitation active sites,and poor hydrogen precipitation performance.The concentration is too high,resulting in an increase of SnO₂content in the composite electrode,which reduces the electrode conductivity and decreases the hydrogen precipitation activity.The electrochemical test results show that the Ni/SnO₂-3 composite electrode has a hydrogen precipitation overpotential of 426 m V,a Tafel slope of 187 m V·dec^-1,an exchange current density of 52.29u A·cm^-2and a good stability of hydrogen precipitation when the polarization current is 10m A·cm^-2.The corrosion resistance study shows that the Ni/SnO₂composite electrode has good corrosion resistance.The corrosion resistance study shows that the Ni/SnO₂composite electrode has good corrosion resistance.C-SnO₂materials were synthesized by high-temperature hydrolysis,and Ni/C-SnO₂composite electrodes were prepared by composite electrodeposition technique.The purpose of introducing carbon materials is to improve the conductivity of the composite electrode,reduce the charge transfer resistance on the surface of the composite electrode in the hydrogen precipitation reaction,and improve the hydrogen precipitation performance of the composite electrode.It was found that the deposition of C-SnO₂composite particles into the plated layer refines the electrocrystallization,increases the specific surface area of the composite electrode,and exposes more catalytically active sites.The selective growth orientation of nickel in the composite coating changed from the（200）crystal plane to the（111）crystal plane,and the hydrogen precipitation performance was improved.The electrochemical test results showed that the addition of C-SnO₂composite particles effectively reduced the hydrogen precipitation overpotential and charge transfer resistance of the composite electrode,increased the exchange current density of the hydrogen precipitation reaction,and accelerated the hydrogen precipitation reaction rate.The Ni/C-SnO₂-0.5composite electrode prepared at a concentration of 0.5 g·L^-1of C-SnO₂composite particles in the plating solution has the most excellent hydrogen precipitation performance.When the polarization current is 10 m A·cm^-2,the hydrogen precipitation overpotential is 304 m V,the Tafel slope is 136 m V·dec^-1,and the exchange current density is 57.44 u A·cm^-2with good hydrogen precipitation stability and corrosion resistance.CNTs-SnO₂materials were prepared by high-temperature hydrolysis,and Ni/CNTs-SnO₂composite electrodes were further synthesized.It was found that CNTs with better electrical conductivity and large specific surface area could reduce the charge transfer resistance of the composite electrode and accelerate the hydrogen precipitation reaction rate of the composite electrode.CNTs-SnO₂composite particles deposited into the plating refine the crystallization of the plating,and the selective growth orientation of nickel changes to（111）crystal plane.The（111）crystalline surface strength of the composite layer is significantly enhanced compared with that of the Ni/C-SnO₂composite layer,and the half-peak width value is also increased,which may exhibit the most excellent hydrogen precipitation performance in the hydrogen precipitation reaction.The electrochemical test results showed that the addition of CNTs-SnO₂reduced the hydrogen precipitation overpotential of the composite electrode and increased the exchange current density of the hydrogen precipitation reaction.The EIS test results showed that the Ni/CNTs-SnO₂composite electrode had the largest double-layer capacitance value,and the composite electrode had a large specific surface area with a larger number of hydrogen precipitation active sites,showing the best hydrogen precipitation activity.When the CNTs-SnO₂composite particles in the plating solution are 0.75 g·L^-1,the prepared Ni/CNTs-SnO₂composite electrode has the most excellent catalytic activity for hydrogen precipitation.When the polarization current is 10 m A·cm^-2,the hydrogen precipitation overpotentials of the composite electrode and the Pt electrode were 259 and 285 m V,the Tafel slopes were 119 and133 m V·dec^-1,and the exchange current densities were 66.12 and 73.36 u A·cm^-2,respectively.The Ni/CNTs-SnO₂-0.75 composite electrode has better hydrogen precipitation performance than the Pt electrode,and has good hydrogen precipitation stability.