Preparation Of Cobalt Phosphide Nano-materials And Their Electrocatalytic Performance In Hydrogen Evolution Reaction

With the increasing depletion of fossil fuels and the increasing pollution of the environment,the development of new renewable energy has become a common consensus.As a kind of zero-emission energy,hydrogen is considered a potential energy carrier with high energy density and abundant resources.Water electrolysis is a promising way to produce hydrogen,but there is a shortcoming of high energy consumption,which requires high-efficiency electrocatalyst to lower the overpotential for the hydrogen evolution reaction(HER)in order to achieve the purpose of reducing energy consumption.Pt is known as the most efficient HER catalyst,but the scarcity and high cost limit its widespread use.Therefore,the development of high-efficiency,cost-effective HER electrocatalysts based on earth-abundant elements is highly desired.Based on the above ideas,two kinds of cobalt phosphide composites with different structures have been prepared by a facile one-step electrodeposition combined with in-situ potentiostatic activation or low-temperature phosphidation,and the characterization of the materials and the electrocatalytic performance test have been carried out.The results are as follows:(1)We first report a novel cobalt-phosphide(Co-P)hybrid with flake-like structure by a facile one-step electrodeposition combined with in-situ potentiostatic activation technique.Exotic microstructure transformation of Co-P hybrid from microspheres to nanosheets has been noted during the activation process,which can be attributed to the chemical sculpture by the reduction reaction at the cathode.Owning to the abundant exposed active sites emerged through chemical sculpture in the activation process,the increased HER performance was observed.The Co-P catalyst exhibits striking kinetic metrics with an overpotential of 85 mV(at 10 mA cm-2)and Tafel slope of 37 mV dec-1,performing among the best of all the HER catalysts in strong alkaline media.(2)Co(OH)2 precursor is prepared by one-step electrodeposition,followed by low-temperature phosphidation reaction in a tubular furnace.Finally,cobalt phosphide(CoP)nanosheets with a titanium(Ti)plate as substrate,named CoP/Ti,is obtained.XRD and XPS show that phosphorus element is successfully introduced into the precursor by phosphidation.CoP/Ti exhibits excellent electrocatalytic performance and excellent long-term stability in acidic medium.The overpotential at current density of 10 mA cm-2 is only 83 mV,and after 2000 cycles of cyclic voltammetry(CV),the activity is almost no degradation.Moreover,CoP/Ti requires such a low overpotential of 87 mV at a current density of 10 mA cm-2 under strong alkaline medium.