Investigation Of Transition-Metal Phosphides/Nitrides Electrocatalysts For Hydrogen Evolution/Oxidation Reaction

In recent years,China has attached great importance to the development of the hydrogen energy industry.In the hydrogen energy economy,hydrogen-oxygen fuel cells and electrolysis of water to produce hydrogen are technologies that realize the mutual conversion of chemical energy and electric energy,which can bring us a clean and sustainable energy cycle system.Recently,alkaline anion exchange membrane fuel cells（AEMFC）and hydrogen production from water electrolysis have developed rapidly.Based on the major breakthrough of alkaline non-precious metal catalysts for oxygen reduction reaction,compared with proton exchange membrane fuel cells,AEMFC can theoretically realize the use of non-precious metal catalysts for both anode and cathode,which will greatly reduce the high production cost of fuel cells.At present,the realization of high-performance AEMFC requires the use of platinum group noble metals on the anode side.In order to fully realize the economic advantages of AEMFC,non-noble metal electrocatalysts for hydrogen oxidation reaction（HOR）in alkaline media need to be developed urgently.Hydrogen adsorption energy is an important descriptor of hydrogen evolution reaction（HER）and HOR,and the optimal hydrogen adsorption energy is a necessary condition for high activity.Based on the extensive research of non-precious metal electrocatalysts for HER,transition metal phosphides（TMPs）and transition metal nitrides（TMNs）were selected for alkaline HOR performance evaluation and optimization.The specific work is as follows:1.The hybrid material of Co₂P and Co P is synthesized by hydrothermal method and phosphating reaction through heat treatment.By controlling the degree of phosphating,the mixing ratio of the two phases of cobalt phosphide is adjusted to realize the comprehensive optimization of hydrogen binding energy and conductivity.And the performance of cobalt phosphide in alkaline HOR catalysis was evaluated.2.The above-mentioned cobalt phosphide hybrid material is modified by molybdenum element through the secondary hydrothermal.The influence of the addition of molybdenum on the activity of HER and HOR was also discussed.It was found that the enhancement of HER activity benefited from the enlarged electrochemical active area after modification,while the intrinsic performance did not change significantly.However,molybdenum modulates the hydroxide binding energy of phosphides,thus enhancing the intrinsic activity of phosphides in HOR catalysis.However,the addition of molybdenum adjusts the hydroxide binding energy of cobalt phosphide,which improves the intrinsic activity of phosphide in HOR catalysis.3.Based on the reported excellent HOR activity of nickel nitride,Ni Mo O₄ precursor was prepared by hydrothermal method.Subsequently,Ni/Ni_0.2Mo_0.8N heterogeneous materials were prepared through thermal nitridation reaction.Here,the in-situ reduced metal Ni is lattice-matched with Ni_0.2Mo_0.8Nat the heterogeneous interface,resulting in the generation of lattice stress.The enlarged lattice spacing can adjust the excessive hydrogen binding energy of nickel.Therefore,like Ni_0.2Mo_0.8N,nickel also acts as an active center in the material.Thanks to the dual active center system,the Ni/Ni_0.2Mo_0.8N heterogeneous material exhibits excellent HOR activity and resistance to electrochemical oxidation.