Synthesis And Electrocatalytic Hydrogen Evolution Of Mo/W/Co Compounds

Strong dependence on fossil fuels has made our economy susceptible to price spikes and at the same time overuse of fossil fuels also aggravates air pollution and global warming.Thus,development of clean,renewable energy sources alternative to fossil fuels is extremely urgent.Among diverse technology,hydrogen is a propitious candidate for future energy supply as it possesses higher combustion efficiency,abundant resources,no pollution,and relatively inexpensive cost etc.In this regard,water electrolysis is one of the most promising,attractive and simplest approaches for the production of hydrogen due to its higher electrolytic efficiency,considerable product purity,no pollution etc.However,the main bottleneck in the widespread usage of hydrogen is the high energy consumption caused by the overpotential of hydrogen evolution reaction(HER).Therefore,it still remains as daunting task in front of the scientific community to seek efficient,novel,highly active electrocatalysts is required for hydrogen evolution reaction.Herein,we have developed a series of effective HER catalysts with inexpensive materials by simple and facile methods.The research contents and the results of this paper were obtained as follows:(1)We synthesized molybdenum carbide and tungsten carbide by using ammonium molybdate(ammonium tungstate)and melamine as precursor materials via a one-step temperature-control program.Results showed that both Mo2C and WXC had good HER performance in alkaline electrolyte.In 1 M KOH solution,Mo2C and W,C required overpotential of 104 and 152 mV to reach current densities of 10 mA cm-2,respectively.And then we discussed the effect of material ratio and treatment temperature on the performance of HER.(2)In addition,we have prepared cobalt phosphide by using CoCl2·6H2O as Co source and NaH2PO2 as phosphorus source.Furthermore,we combined different proportion of Co(OH)2 with nitrogen doped graphene(NG)and exploded graphene(EG)followed by phosphatization reaction to get CoP/NG and CoP/EG,respectively.Results showed that the nanowire-CoP required 184 and 226 mV to obtain current densities of 10 and 20 mA cm-2 in 1 M KOH solution,respectively.Interestingly,when NG combined with CoP with appropriate ratio(6:1)have shown remarkable higher HER activity than CoP and CoP/EG with small overpotential of 122 and 145 mV were enough to reach current densities of 10 and 20 IA cm-2,(3)We have also demonstrated the effect of reduction temperature towards HER activity of Co nanocrystal/Co foil with the starting material of Co foil,which was firstly oxidized in air and then reducted in 5%H2/Ar atmosphere at different temperature.Results showed that Co nanocrystal/Co foil achieved optimal HER performance when reduction temperature is 500?,which required 124 and 181 mV to obtain current densities of 10 and 20 mA cm-2 in 1 M KOH solution.However,this catalyst has shown poor stability in alkaline medium,which needs some improvements in future.