Preparation And Electrochemical Catalytic Performance For Hydrogen Evolution Reaction Of Cobalt And Its Compounds/Carbon Nanomaterials Composites

Hydrogen,as one of the most ideal energy carriers,is regarded as a promising alternative to fossil fuels in the future due to its high energy but carbon-free content.Until now,water electrolysis is one of the most mature technology to produce hydrogen fuels,but its high-energy consumption and high cost constrain the practical widespread application of this technique.So we have to develope advanced electrocatalyst for hydrogen evolution reaction(HER)with high efficiency and low cost.In this study,carbon nanomaterials with catalytic activity for the HER were prepared through modifying graphene and multi-walled carbon nanotubes(MWCNTs)with heteroatoms(such as N,S,etc.)doping.And then,these modified carbon materials were used as support when composited with Co or Co9S8 nanoparticles to synthesize inexpensive and efficient non-noble-metal electrocatalysts for the HER,whose electrocatalytic activity were studied in detail.The main research results are summarized as follows:(1)We successfully fabricated a binary composite by embedding Co nanoparticles in nitrogen doped graphene matrix(Co@NG)through a facile and controllable one-step pyrolysis method.This facile one-step pyrolysis method not only achieved the N doping to graphite oxide(GO),but also converted Co2+ to Co nanoparticles with good catalytic activity for HER.The research result shows that the prepared binary composite displays good catalytic performance and stability for the HER.The HER overpotential is 126 mV when the current densities reach 10 mA cm-2.Also,it demonstrates good stability reflected from the negligible activity decrease after 1000 consecutive cycles and negligible attenuation in current density of chronoamperometric curve for 10 hours,which prove that the composite has excellent catalytic stability.(2)A kind of three-dimensional(3D)nitrogen doped unzipped carbon nano tubes gel supports Co nanoparticles binary composite was synthesized through solvothermal method and thermal treatment.Solvothermal method not only can achieve the reduction and N-doping of oxidized unzipped carbon nanotube but also create a 3D gel-like structure,which can provide the composite with larger specific surface area to achieve more active sites.The research result shows that the prepared binary composite displays good catalytic performance and stability for HER.The HER overpotential is 113 mV when the current densities reach 10 mA cm-2.Also,it demonstrates good stability reflected from the negligible activity decrease after 1000 consecutive cycles and negligible attenuation in current density of chronoamperometric curve for 10 hours.(3)In this work,we successfully fabricated a 3D hierarchical ternary composite by embedding Co9S8 nanoparticles in a nitrogen and sulfur co-doped graphene-unzipped carbon nanotube matrix(Co9S8/NSG-UCNTs)through a facile and controllable one-step pyrolysis method.This facile one-step pyrolysis method not only achieved the N and S co-doping to graphite oxide(GO)and O-UCNTs,but also converted Co2+ to Co9S8 with good catalytic activity for HER.The as prepared 3D ternary composite displays superior catalytic performance and good stability for HER,The HER overpotential is 65 mV when the current densities reach 10 mA cm-2,and the exchange current density reaches 0.503 mA cm-2.Also,it demonstrates good stability reflected from the negligible activity decrease after 1000 consecutive cycles and negligible attenuation in current density of chronoamperometric curve for 10 hours.