Research On Gradient Deposition Technology Based On Bipolar Electrochemistry

Electrodeposition technology based on bipolar electrochemical effects has become an effective method for preparing characteristic electrodeposited layers in recent years.In this paper,a copper-based gradient nickel electrodeposition layer and a sponge sponge copper-based gradient nickel electrodeposition layer were prepared by bipolar electrodeposition technique.Combined with the excellent conductivity of copper and the hydrogen evolution catalytic property of nickel,it can be used as an alkaline electrolytic water hydrogen evolution cathode material.Scanning electron microscopy(SEM)and energy dispersive spectroscopy(EDS)were used to detect the morphology and composition of the film layer.The open circuit potential method of the electrochemical workstation was used to measure the overpotential of the substrate/solution interface.The electrochemical noise method and wavelet analysis were used to investigate the driving voltage.The effect on the nucleation of the electrodeposited layer;the cathodic polarization curve method was used to test the catalytic performance of the electrode.The experimental results show that the copper/solution interface overpotential changes with the space of the sample;due to the filling of solution,the partial pressure of sponge copper decreases in bipolar electrodeposition system,so the measured interface overpotential of sponge copper/solution is lower than that of copper/solution.The SEM results show that the structure of the metal nickel electrodeposited layer changes in a gradient.When the driving voltage is 5V,the surface of the copper-based nickel electrodeposited layer exhibits a stacked layer-flat stripe-agglomerate granular gradient structure;and when the driving voltage is 11V,the surface thereof is a rough gully-flower layer-protrusion pleated gradient structure;The positions of the sponge copper-based nickel electrodeposited layer in turn present a flower cluster-spherical stack-dispersion layered gradient structure.The EDS line scan results of the copper-based nickel electrodeposited layer and the EDS surface scan results of the sponge-copper-based nickel electrodeposited layer indicate that there is a composition gradient in the metal nickel electrodeposited layer.The results of noise signal analysis show that the bipolar electrodeposition process is controlled by electrochemical polarization,and the nucleation process is dominant,that is,increasing the driving voltage is beneficial to the nucleation of Ni.The copper-based gradient nickel electrodeposited layer and the sponge copper-based gradient nickel electrodeposited layer all exhibited the optimal hydrogen evolution catalytic effect.The process condition was 11V driving voltage and deposition for 5 min.Copper-based gradient nickel electrodeposition layer(sponge copper-based gradient nickel electrodeposition layer)prepared by bipolar electrodeposition technology is used as a cathode material in hydrogen production from alkaline electrolyzed water.Its catalytic performance is compared with that of metallic nickel(sponge metal nickel).The improvement is also superior to the copper-based nickel electrodeposited layer(sponge copper-based nickel electrodeposited layer)prepared by a conventional electrodeposition method.The Tafel slope results show that the combination of the low resistivity of sponge copper and the low hydrogen evolution overpotential of nickel in the deposited layer is indeed more conducive to the improvement of hydrogen evolution performance.The gradient structure is more conducive to the effective combination of hydrogen ions and electrons to make hydrogen ions on the surface of the electrode.Adsorption has been improved.