The Cobalt-nickel-based Hydroxide Catalyst Is Prepared By Electrodeposition Method For The Hydrogen Reaction Of Water Desorption

Hydrogen has been deemed as a potential energy carrier to meet our need for future fuel application due to its high energy density and cleanliness.It is necessary to develop superior efficient,low-cost and environmentally friendly electrocatalysts for hydrogen evolution reaction(HER).First-row transition metal such as cobalt,nickel and copper have been investigated extensively as electrocatalysts due to their high activity,low cost,simple preparation,and good stability and continues efforts have been undertake to optimize the catalysts activity.In order to improve the electrochemical performance of Co-based catalyst for HER,cauliflower-like cobalt nickel hydroxide(CoNi-OH)composites were fabricated on the 3D nickel foam(NF)by electrodeposition method.The effects of NiCl2 concentration in electrolyte on the overpotential of CoNi/NF electrodes in 1.0 M KOH solution for hydrogen evolution reaction were investigated when CoCl2 concentration in electrolyte was 0.2 M.The chemical compositions of the CoNi-OH composites were characterized by XPS and Raman spectrum.These collective data suggest that cobalt-nickel hydroxide composite is obtained.The structure of the CoNi-OH was investigated by XRD and high-resolution TEM,no characteristic diffraction peaks and lattice fringes were observed in the picture and it suggest that the as-deposited CoNi-OH composite is amorphous in nature.The HER activity of Cu(0)-CoNi-OH/NF electrode was studied using linear sweep voltammetry(LSV)at a scan rate of 2 mV s-1 in 1.0 M KOH with 95%iR compensation.To reach a benchmark HER current density of 10 mA cm-2,CoNi-OH/NF electrode only requires an overpotential of 94 mV,which is much lower than of Co(OH)2/NF electrode(185.5 mV)and Ni(OH)2/NF electrode(189 mV).The enhanced electrochemical performances are due to the synergistic metal ion-metal ion interactions.Chronopotentiometric curve of CoNi-OH/NF is tested in 1.0 M KOH and it shows exceeding stability and durability.The overpotential required to deliver 100 mA cm-2 is about 260 mV and only?11 mV during the course of electrolysis.The CoNi-OH catalyst is comparable or smaller than recently reported non-noble-metal-based HER electrocatalysts.The physicochemical characterizations and electrochemical measurements were further carried out to explore the advantageous effect of Ni2+ doping.The enhanced HER activities of CoNi/NF catalyst are mainly attributed to unique 3D nanoporous structure,high active surface areas(about 14 times higher than the bare NF),low charge-transfer resistance and the synergistic effect of nickel and cobalt in the nickel cobalt hydroxides.We also investigated the OER performance of CoNi-OH/NF electrode in 1.0 M KOH.It produced an anode current density of 10 mA cm-2 at a overpotential of 334 mV,Overall water-splitting was measured in a two-electrode system,CoNi-OH/NF electrode shows excellent activity,with 10 mA cm-2 water-splitting current reached by applying just 1.68 V.Nowadays,the enhancement of catalytic performance of cobalt-nickel-based catalysts for the HER is still challenging.The applications of copper(Cu)and Cu-based nanoparticles have generated a great deal of interest in recent years,especially in the field of catalysis.In this work,the doping effect of transition metal(Cu)for improvement electrocatalytic activity of cobalt nickel hydroxide composite for HER was studied systematically.Three-dimensional nano-composite composed of metallic copper and amorphous cobalt nickel hydroxide(Cu(0)-CoNi-OH)was deposited on nickel foam(NF)via a cyclic voltammetry method.A typical potentiodynamic deposition curve and the surface morphology of Cu(0)-CoNi-OH/NF composites with the different cycle number were systematic studied.An obvious reduction peak at-0.25 V only appeared in the first cycle voltammogram cycle and there is no obvious reduction peak in the control electrolyte containing only 0.2 M CoCl2 and 0.1 M NiCl2,indicating the reduction peak observed at-0.25V is due to the reduction of Cu2+ to metal Cu in the first cycle.However,after 1 CV cycle,many spherical particles with an average diameter of 50-200 nm were deposited on NF surface.The Cu particles were demonstrated by energy-dispersive X-ray spectroscope(EDX)and it can be known that the reduction process of copper occurs mainly in the first lap of cyclic voltammograms.The chemical composition and structure of Cu(0)-CoNi-OH/NF was characterized by XRD?XPS and TEM,it confirms that the oxidation state of Cu in Cu(0)-CoNi-OH/NF is zero.The like core-shell structure of Cu(0)-CoNi-OH/NF can be proved combining with the surface morphology of Cu(0)-CoNi-OH/NF composites with different cycle numbers.The Cu(0)-CoNi-OH/NF electrode exhibits efficient electrocatalytic activity for HER.A benchmark HER current density at 10 mA cm-2 is achieved at overpotential of 47 mV in 1.0 M KOH.The electrode exhibits extraordinary stability and fast kinetics with a Tafel slope 48 mV dec-1.The excellent activity is attributed to the metal/hydroxide interfaces and the enhanced electrochemical activity surface area.