Preparation And Electrocatalytic Water Reduction Of Carbon Nanotube Sponge Electrode Decorated With Metal Phosphide

With the increasing energy consumption and environmental pollution,developing renewable,and clean energy attract people's attention widely.Electrochemical water reduction could convert the redundant electric energy to hydrogen energy which develops rapidly recently.Three-dimensional(3D)porous carbon nanotube sponge is a promising electrode platform on account of its special nanostructure,excellent electrical and mechanical properties,would optimize the composite electrocatalyst's nanostructure,specific surface area and electron transportation rate between the substrate and electrocatalyst,therefore,improving the efficiency of electrocatalytic water splitting.In this dissertation,enhancing the catalytic performance is the main goal.We directly grow the transition metal phosphide onto the carbon nanotube sponge via electrochemical deposition to obtain the 3D porous nickel phosphide/carbon nanotube sponge hybrid electrodes,and investigate the relationship between the electrodeposition parameters and electrocatalyst's morphology,and performance.Then,its electrcatalytic performance in electrolyte of different pH values are studied carefully.Carbon nanotube sponges are synthesized by chemical vapor deposition(CVD),and prepared as electrodes support after hydrophilic treatment.Then,the amorphous nickel phosphide/carbon nanotube sponge hybrid electrodes are prepared by cyclic voltammetry deposition,and adjust the cyclic times to control the electrocatalyst's morphology and size,meanwhile,optimize the electrocatalytic performance.During electrodeposition,the nickel phosphide directly deposited onto carbon nanotube sponge enhance the contact between nickel and carbon nanotube sponge,thus the electron transport rate through the electrocatalyst and substrate.The hybrid sponge electrdes exhibit superior electrocatalytic activity for sustained hydrogen evolution in acidic,neutral,and basic media.Specially,the hybrid electrodes generate cathodic currents of 10 and 100 mA·cm-2 at overpotentials of 105 and 226 mV,respectively,in a 1 M phosphate buffer solution(pH = 6.5);and exhibit a stable current density with continuous hydrogen generating for over 110 h without obvious decay.One-step synthesis ternary electrocatalyst nickel cobalt phosphide/carbon nanotube sponge hybrid electrodes via cyclic voltammetry deposition,and regulate the rate and concentration of nickel and cobalt precursor in electrolyte to adjust the structure and the amount of nickel and cobalt in nickel cobalt phosphide.In neutral media,the ternary catalyst could generate cathodic current of 10 mA·cm-2 at the overpotential of 93 mV.The nickel cobalt phosphide/carbon nanotube sponge hybrid electrodes show the bifunctional performance of electrocatalytic hydrogen evolution and oxygen evolution in base media,which could generate current density of 10 mA cm-2 at the overpotentials of 73 mV for hydrogen evolution and 288 mV for oxygen evolution,respectively.