Synthesis And Electro-catalysis Properties Research Of Transition Metal Phosphide

In twenty-first century,the energy crisis and environmental destruction are the two major problems of development of human.Because of the rapid consumption of fossil fuels,the contradiction between energy supply becomes increasingly acute.Hydrogen energy has many advantages,such as abundant reserves,high calorific value of combustion,pollution-free products and so on.It is one of the ideal alternative energy sources at present.Compared with other hydrogen production methods,electrolysis of water has obvious advantages in current practical application and future development.Noble metal catalysts restrict the development of hydrogen production from electrolysis of water because of their rare sources and high price.Transition metal phosphides?TMPs?,as a new type of electrolytic water catalyst,have attracted extensive attention due to their excellent catalytic activity and abundant reserves.Low-dimensional catalysts such as nanoparticles tend to agglomerate under the action of electric current,resulting in the reduction of catalytic activity.In this paper,transition metal phosphides with high catalytic activity were prepared by doping elements and constructing nanostructures using low-temperature phosphorization.The microstructures,compositions and applications in catalysis of hydrogen evolution for electrolysis of water of the prepared catalytic materials were tested and analyzed.?1?We have prepared a binary NiCo phosphide with hierarchical architecture via a facile hydrothermal method,followed by oxidation and phosphorization.The special hierarchical architecture was constructed by controlling the content of NH₄F and the reaction time of hydrothermal process.In the hydrothermal reaction process,the micro-morphology of the precursor is controlled by changing the reaction time and the content of ammonium fluoride,which results in a single structure's transformation into a three-dimensional hierarchical structure with a larger specific surface area.By changing the initial molar ratio of metal salts in hydrothermal process,the optimum proportion of nickel-cobalt metal salts was explored.The results of electrochemical performance test showed that NiCoP HA/CC exhibited good catalytic activity for hydrogen evolution in acidic and alkaline media.In 0.5 M H₂SO₄,the overpotential required for NiCoP HA/CC to reach 10 mA cm^-2 current density is only 74 mV,and the corresponding Tafel slope and electrochemical impedance values for?=100 mV are 77.2 mV dec^-1 and 4.2 Ohm,respectively.In 1.0 M KOH,the overpotential required for NiCoP HA/CC to reach 10 mA cm^-2 current density is only 89 mV,and the corresponding Tafel slope and electrochemical impedance value for?=100 mV are99.8 mV dec^-1 and 5.7 Ohm,respectively.?2?Cobalt salt was added into silk by impregnation method,and then the silk carbon fiber based cobalt phosphide nanoparticles?Co₂P/SCC?were obtained by low-temperature phosphorization and carbonization.By changing the mass fraction of cobalt in the impregnation process,the surface morphology of the catalyst material was regulated,and the size of cobalt phosphide nanoparticles was suitable and uniformly distributed,which greatly shortened the electron transfer path and enhanced the conductivity of the material.The results of electrochemical performance test showed that Co₂P/SCC exhibited good catalytic activity in hydrogen evolution reaction and oxygen evolution reaction.In the hydrogen evolution reaction,the overpotential required for Co₂P/SCC to reach 10 mA cm^-2 current density is only 146mV and the corresponding Tafel slope is 123.0 mV dec^-1.In oxygen evolution reaction,the overpotential required for Co₂P/SCC to reach 10 mA cm^-2 current density is only358 mV,and the corresponding Tafel slope is 155.5 mV dec^-1.At the same time,Co₂P/SCC has good stability in both acidic and alkaline media.