Preparation Of Ni-Cu-X@NF Porous Electrode By Electrodeposition And Hydrogen Evolution Properties

The use of traditional fossil energy has caused human society to face severe environmental problems.As a kind of new energy,hydrogen energy has the advantages of clean and pollution-free,high energy density(140 MJ·kg^-1)and easy storage and transportation.At present,the preparation of green hydrogen in industry is mainly through electrolysis technology.However,due to the high overpotential of hydrogen evolution at the cathode in the electrolysis process,the hydrogen production efficiency is low and the energy consumption is large.Therefore,the research and preparation of new cathode materials with high catalytic activity and low hydrogen evolution overpotential is crucial for realizing large-scale electrolytic hydrogen production.In this paper,three kinds of porous electrode materials,Ni-Cu@NF,Ni-Mo-Cu@NF and Ni-Mo-Cu-W@NF,were prepared by DC electrodeposition using nickel foam（NF）as the base material.The optimal preparation parameters were determined based on orthogonal and single factor experiments.The morphology,crystallinity and composition of the prepared porous electrode materials were characterized.The catalytic hydrogen evolution（HER）performance of the prepared electrode materials was also investigated.The results show:（1）The optimal process parameters for the preparation of Ni-Cu@NF porous electrodes are:nickel sulfate is 100 g·L^-1,sodium citrate is 120 g·L^-1,copper sulfate is15 g·L^-1,current density is 100 m A·cm^-2,temperature is 35°C and p H is 9.The surface of the Ni-Cu@NF electrode is a large spherical cauliflower structure formed by tightly packed small spherical particles.XRD test results show that the electrode has a crystalline structure,and the surface grain size is 76.2 nm.The hydrogen evolution overpotentialη100 of the Ni-Cu@NF electrode is reduced by 186 m V compared with that of the NF electrode.The Tafel slopes of NF and Ni-Cu@NF electrodes are 171.69m V·dec^-1 and 138.32 m V·dec^-1,respectively.According to the AC impedance spectrum,the control steps of the above two electrodes in the hydrogen evolution reaction are mixed control of electrochemical and diffusion.The charge transfer resistance R_ct of the two electrodes is 29.45Ω·cm² and 22.5Ω·cm²,respectively.According to the results of hydrogen evolution overpotential,Tafel slope and charge transfer resistance,it can be seen that the HER performance of Ni-Cu@NF electrode is better than that of NF electrode.（2）The optimal process parameters for preparing Ni-Mo-Cu@NF porous electrodes are:nickel sulfate 100 g·L^-1,sodium citrate 120 g·L^-1,sodium molybdate 50g·L^-1,copper sulfate is 10 g·L^-1,current density is 80 m A·cm^-2,temperature is 45°C and p H is 9.The surface of the Ni-Mo-Cu@NF electrode is a closely packed spheroid structure.XRD test results show that the electrode has a crystalline structure,and the surface grain size is 43.4 nm.The hydrogen evolution overpotentialη100 of Ni-Mo-Cu@NF electrode is reduced by 259.69 m V compared with NF electrode.The Tafel slopes of the ternary electrodes are 117.84 m V·dec^-1,respectively.According to the AC impedance spectrum,the control steps of the electrode during the hydrogen evolution reaction are mixed control of electrochemical and diffusion.The charge transfer resistance R_ct of the electrode was 12.5Ω·cm².According to the results of hydrogen evolution overpotential,Tafel slope and charge transfer resistance,it can be seen that the HER performance of Ni-Mo-Cu@NF electrode is better than that of Ni-Cu@NF electrode.（3）The optimal process parameters for the preparation of Ni-Mo-Cu-W@NF porous electrodes are:nickel sulfate is 100 g·L^-1,sodium citrate is 120 g·L^-1,sodium molybdate is 50 g·L^-1,copper sulfate is 10 g·L^-1,sodium tungstate is 60 g·L^-1,current density is 80 m A·cm^-2,temperature is 35°C and p H is 9.The surface of the Ni-Mo-Cu-W@NF electrode is a small spheroid structure formed by close packing,the grooves on the electrode surface disappear,and the particles are finer.XRD test results show that the electrode has a crystalline structure,and the surface grain size is 41.5 nm.The grain size of the quaternary electrode is the smallest,indicating that the grains are finer and can provide a larger specific surface area.The hydrogen evolution overpotentialη100 of the Ni-Mo-Cu-W@NF electrode is reduced by 278.72 m V compared with that of the NF electrode.The Tafel slope of the quaternary electrode is115.69 m V·dec^-1.According to the AC impedance spectrum,the control steps of the electrode during the hydrogen evolution reaction are mixed control of electrochemical and diffusion.The charge transfer resistance R_ct of the electrode was 4.71Ω·cm².According to the hydrogen evolution overpotential,Tafel slope and charge transfer resistance results,the Ni-Mo-Cu-W@NF electrode has the best HER performance.