Preparation And Hydrogen Evolution Reaction Performance Of Transition Metal Ni,Co And Mo Compounds Electrodes

Electrolysis is an electrochemical process that uses electricity as a driving force to decompose water into hydrogen and oxygen.Transition metal catalyst has high catalytic activity at the same time cheap and easily accessible,superior stability.Therefore the transition metal catalyst has attracted the attention of researchers,being a very promising non-platinum hydrogen evolution reaction catalyst.Based on carbon cloth and nickel foam,the cathode material for electrolysis water was prepared through high temperature solid-state method,solvothermal method,direct growth method and chemical reduction method,and so on.The physical characterization means,such as scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,X-ray diffraction（XRD）,X-Ray Photoelectron Spectroscopy（XPS）and the electrochemical test methods,such as cyclic voltammetry（CV）,linear sweep voltammetry（LSV）,chronoamperometry（CA）and electrochemical impedance spectroscopy（EIS）are employed to characterize the physical structure and electrochemical property of the electrodes.Mo₂C catalyst was prepared by high-temperature solid-phase method using ammonium heptamolybdate and walnut shell powder.With a 5%naphthol solution as binder,a certain amount of Mo2C and a mixed solution of naphthol solution,anhydrous alcohol and deionized water in a certain ratio are uniformly mixed by simple mechanical stirring.The mixture was smeared onto a carbon cloth by a simple“slurry and coating”method as the electrocatalyst for HER.Electrochemical tests show that the blank carbon cloth is basically no hydrogen evolution ability.While the Mo2C/CC exhibits excellent HER performance,requiring only140 mV of overpotential for a current of 10 mA·cm^-2.After a large number of cyclic tests,the performance attenuation is maintained within 10%and the performance of the E-t and i-t curves was almost unchanged after 10 hours of testing.Stability tests show that the electrode has outstanding electrochemical stability.The Ni-Co-NiCo2O4/NF electrode based on nickel foam is prepared by grown directly at low temperature of 90℃,calcined at 350℃and finally reduced in 0.1 mol·dm^-3 NaBH₄solution,with 3D network structure.The edge of Ni-Co-NiCo2O4 nanosheet is surrounded by a layer of metallic nickel-cobalt nanoparticles,which is a typical core-shell structure.This metallic shell enhances the electrical conductivity of the electrode and alleviates the inherent defects of poor conductivity of the oxide.Electrochemical tests showed that the blank nickel foam possesses a certain degree of hydrogen evolution performance in alkaline environment.After the Ni-Co-NiCo2O4 nanosheets with core-shell structure grown on the nickel foam,the performance of HER has been greatly improved,the required overpotential is about 125 mV when the current reaches 10 mA·cm^-2,corresponding slope is 77 mV·dec^-1.After a long period of stability testing,the performance decay was maintained at around 10%,indicating that the electrode has good electrochemical stability.Foam nickel supported CoMoO₄/NF cathode electrode is prepared by solvothermal method and calcination at high temperature.The atomic ratio of molybdenum source and cobalt source has a great influence on the product species.Only when the atomic ratio is 1:1,can we get pure CoMoO4.The CoMoO4/NF electrode with a three-dimensional（3D）network structure demonstrates excellent HER performance in alkaline environments with overpotentials of 68 mV and 97 mV at currents of 10 mA·cm^-2 and 20 mA·cm^-2,respectively,with a slope of 80 mV·dec^-1.After 1000 and 3000 cycles CV test,the performance degradation maintaines at about 10%,and the performance of E-t and i-t curves after 10 hours has almost no attenuation.It is proved that CoMoO4/NF electrode shows excellent electrochemical stability.