Electrochemical Hydrogen Evolution Performence And Nitrate Reduction Of Nickel Phosphide/Modified Graphite Oxide Hybrids

As an high efficient,pollution-free and renewable clean energy,hydrogen is an idea alternative to fossil fuels.Also,water electrolysis is considered as a sustainable and environmental friendly method for hydrogen production,which has been widely used and developed.Among the hydrogen evolution materials,nickel phosphide（Ni₂P）has attracted tremendous attention due to its simple preparation process,low cost and high catalytic activity.However,its small specific area leads to a small number of exposed active sites,thereby limiting its application in electrochemical hydrogen evolution reaction（HER）.As a consequence,the exploitation of suitable carriers to improve its conductivity in pursuit of enhancement in HER performance has been imperative.In this research,two kinds of composites（Ni₂P/NRGO and Ni₂P/BRGO）were fabricated by a hydrothermal synthesis process and used nitrogen-doped graphite oxide and boron-doped graphite oxide as carriers.The crystallinity and compositions of the aforementioned composites were characterized,and electrochemical hydrogen evolution performances of them were evaluated.It’s shown that the hybrids has a better hydrogen evolution performance than pure nickel phosphide,which can be attributed to the high conductivity and bigger specific surface area of doped reduced graphite oxide.Among the nitrogen-doped composites,Ni₂P/NRGO-0.17 has the best hydrogen evolution performance with a lower initial potential of 78 mV,a smaller tafel slope of 57 mV/dec and a larger exchange current density of 4.8×10^-66 A/cm²;while,of all the boron-doped hybrids,Ni₂P/BRGO-0.25 has a lower initial potential（58 mV）,a smaller tafel slope（54 mV/dec）and the largest number of active sites（8.02×10-9 mol/cm²）,thus showing the outstanding electrocatalytic performance.Meanwhile,both of them has a better stability in acidic medium.In addition,the nitrate reduction by use of HER process was investigated,and the effect of hydrogen evolution reaction was assessed.It can be concluded that when the initial concentration of nitrate nitrogen is 22.6 mg/L,the applied current is 50 mA and the magnetic stirring speed is medium,the maximum removal efficiency of nitrate is up to52%within two hours.Therefore,this research will pave a new path for the application of HER and the eutrophication disposal caused by nitrogen sources.