Preparation Of Modification Of Nickel/Nanocarbon Composite Electrode Materials And Their Electrocatalytic Performance

Hydrogen energy as an important part of new energy due to it is the one of the cleanest and environmentally friendly fuel nowadays.However,the great majority of hydrogen is manufactured from fossil fuel with environmental pollution industrially,instead of electrolyzing water,owing to the high energy consumption.Consequently,to ameliorate this problem,fabricating excellent performance electrocatalysts for hydrogen evolution reaction?HER?and oxygen evolution reaction?OER?to decrease the high overpotential is demanded.As is well known that Pt and Ru etc.precious metals display excellent catalytic activity used for electrolysis of water.However,with the scarcity of precious metals and increasing economic cost,the development of economical and efficient noble-metal-free catalysts for HER is significant for industrializing the cleanest fuel in the future.In the past research of HER catalysts,Ni and Ni-based compounds have been indicated as the one of the most proper electrode for HER on the cathode attribute to their high effective activity and low-cost characteristics.Nevertheless,more manufacturing methods should be employed to improve Ni-based catalysts activities which have excellent performance and long-term stability,owing to easy agglomeration of Ni nanoparticles leads to reduction of active sites and limits catalyst performance.This article focuses on the co-deposition of carbon nanotubes?CNTs?and nickel on the nickel foam?NF?substrate.Electrodeposition can adjust the shape and composition of the electrode by controlling the conditions.NF can be used as a three-dimensional porous structure electrodeposition substrate.Using hydroxylated carbon nanotubes and sulfonated carbon nanotubes as composite phases,electrodeposited Ni-OH-CNTs/NF and Ni-SO₃H-CNTs/NF composite electrode materials were prepared by TEM,XRD,XPS,SEM and EDS and other testing methods were used to analyze the micro-morphology and structural composition of the composite electrode materials.The effects of different composite concentrations and different deposition current densities on the composite electrode materials were analyzed by electrochemical performance tests.Traditional CNTs have insufficient active sites for anchoring metal ions owing to the high curvature of the CNTs surface and easily tend to curl.Ni-OH-CNTs/NF electrode prepared with hydroxylated carbon nanotubes as composite phase electrodeposited increases the specific surface area of the composite.The introduction of hydroxyl groups improves the hydrophilicity and dispersion of carbon nanotubes in solution,and enhances the interaction between Ni particles and CNTs.After experimental research,when the concentration of hydroxylated carbon nanotubes in the plating solution is 0.2 g/L and the deposition current density is 30 mA cm^-2,the nickel particles on the surface of the coating are uniformly dispersed and spherical,and the catalytic activity of the electrode reaches the best.At a current density of 100 mA cm^-2,the overpotential required for the hydrogen evolution reaction is 203 mV and the load transfer resistance is 3.314?.In order to continue to improve the catalytic hydrogen evolution performance of carbon nanotubes,hydroxylated carbon nanotubes were modified through two steps of bromination and sulfonation to obtain sulfonic acid-grafted carbon nanotubes.The modified carbon nanotubes have better dispersibility,and Ni-SO3H-CNTs/NF composite electrodes with high efficiency and stability were prepared by electrodeposition technology.The nickel particles on the plating layer are hill-shaped and grow three-dimensionally like branches.This structure significantly increased the specific surface area of the electrode and increased the number of active sites.Through experimental studies,it was determined that the optimal concentration of sulfonic carbon nanotubes in the nickel sulfate system plating solution was 0.6 g/L.The Ni-SO₃H-CNTs_0.6/NF composite electrode exhibits excellent hydrogen evolution performance in 1 M KOH solution.When the current density reaches 100 mA cm^-2,the overpotential required for the hydrogen evolution reaction is 112 mV.Under the alkaline conditions,it exceeds most non-noble metal catalysts.