Preparation Of Transition Metal Hydroxide And Sulfide Electrodes And Their Application In Electrocatalytic Water Splitting

Electrocatalytic water splitting for hydrogen production process is simple and the product purity is high.It is considered to be the ideal hydrogen production technology in the future.The catalyst can effectively solve the problem of high cost of hydrogen production due to high overvoltage caused by electrode polarization.Transition metal catalysts have been widely concerned as electrocatalytic catalysts for water splitting due to their low price and high catalytic potential.A series of transition metal catalytic electrodes were prepared and their catalytic properties of HER/OER were explored.In this paper,a series of Ni-Fe/Ti oxygen evolution electrodes without binders were prepared by electrodeposition on titanium mesh substrate by Amperometic i-t Curve.Nickel-iron hydroxide nanoparticles tightly wrapped titanium mesh.The electrode catalytic activity first increased and then decreased with the increase of Ni content in the precipitated solution.WIhen the molar ratio of Ni/Fe is 9:1,the electrode shows the best OER catalytic activity.In 0.1 mol L-1 KOH,the overpotential of Ni9Fel/Ti electrode at the current density of 50 mA cm-2 is 280 mV,and the corresponding Tafel slope was 29.6 mV·dec-1.The synergistic effect of Ni-Fe bimetal enhanced the catalytic activity of electrode.A series of Ni9FelS/Ti electrodes were prepared by solid phase sulfuration of Ni9Fel/Ti electrode.The catalyst particles were agglomerated with the crystal structure of NiS2 and NiSO4(H2O)6.The sulfidation greatly improved the catalytic activity of hydrogen evolution of the electrode.The influence of sulfidation temperature and thiurea content on the catalytic activity of hydrogen evolution of the electrode was investigated.In 0.1 mol·L-1 KOH,at the current density of 50 mA·cm-2,the overpotential of Ni9FelS0.25/Ti electrode is 269 mV,and the corresponding Tafel slope was 121.5 mV·dec-1.Ni9Fel/Ti and Ni9Fe1S0.25/Ti were used as anodes and cathodes respectively for overall water splitting.The current density of 50 mA·cm-2 was achieved at a voltage of 1.69 V.A series of polymetallic sulfide(M-Mo)S2/NF electrodes(M=V,Co,Ni,V/Ni,V/Co,Co/Ni)were synthesized by hydrothermal method.The influence of metal ion ratio on catalytic activity of hydrogen evolution was investigated.In series of bimetallic sulfides,at 1 mol·L-1 KOH solution,when M(V,Co,Ni):Mo=0.5:9.5,the overpotential of the electrodes was close to 103 mV at the current density of 50 mA·cm-2;In 0.5 mol·L-1 H2SO4 solution,when M(V,Co,Ni):Mo=1:9,the electrode overpotential is close to 177 mV.The synergistic action between metals can promote the catalytic activity of electrodes.Ternary metal sulfides also had good hydrogen evolution catalytic performance.The V10Ni10Mo80S/NF electrode had the best HER catalytic activity at 1 mol·L-1 KOH solution,with an overpotential of 102 mV.The catalytic activity of hydrogen evolution of V5Ni5Mo90S/NF electrode in 0.5 mol·L-1 H2SO4 solution was the best,with an overpotential of 169 mV,which was 28 mV lower than Mo-S/NF.Due to the interaction of metal ions,the catalytic performance of polymetallic sulfide electrode for hydrogen evolution is improved,and the electrode shows good electrocatalytic stability.