Synthesis And Water Splitting Electrocatalytic Performance Study Of ZIF-67 Derivative

The energy crisis brought by the rapid development of society makes people realize the importance of renewable energy.Hydrogen energy stands out among the most promising renewable sources of energy.Existing systems for producing hydrogen commercially cause a lot of non-renewable energy loss and environmental pollution.Hydrogen production from water splitting is expected to become an important part of future hydrogen energy systems.In order to reduce the energy consumption required for water splitting,it is necessary to introduce catalysts.Most of the existing catalysts are precious metal catalysts,such as Pt/C catalysts for hydrogen evolution reactions,and catalysts Ru O₂ and Ir O₂ used for oxygen evolution reactions.The scarcity of reserves,high price and other factors limit the possibility of its large-scale application.The development of catalysts with abundant raw material reserves and low prices is an important direction for the development of water splitting.In this paper,based on ZIF-67metal-organic framework material,the effect of ZIF-67 derivatives in water splitting is studied by changing the morphology of the material and increasing the active sites of the material.The main conclusions of the paper are as follows:（1）ZIF-67 precursor is synthesized from cobalt nitrate hexahydrate and dimethylimidazole.The effects of the ratio of raw materials,reaction time,p H of solution and pyrolysis temperature on the structure and properties of the materials are studied.The results show that the addition of ammonia water can shorten the reaction time and particle size,and the Co/NC material obtained from the pyrolysis of ZIF-67 at 800℃has good catalytic performance for hydrogen evolution:the required overpotential is 135 m V at the current density of 10 m A/cm2（η10）.（2）During the synthesis of ZIF-67,Fe-ZIF-67 material is prepared by adding ferric nitrate.The introduction of Fe atoms increases the number of active sites and changes the electron arrangement of Co atoms,thereby reducing the hydrogen adsorption capacity of the material and improving the catalytic activity of the material.When the molar ratio of Co to Fe is 2:1,the obtained catalyst has the best catalytic performance.Under alkaline conditions,the overpotential required for hydrogen evolution reaction and oxygen evolution reaction（η10）is136 m V and 282 m V,respectively,and the voltage required for water spliting is 1.619 V.（3）In order to improve the catalytic performance of ZIF-67 derivatives under acidic conditions,Mo-ZIF-67 is synthesized by one-step method from sodium molybdate dihydrate as raw material.After pyrolysis,a series of Mo₂C@Co/NC materials were obtained.The results show that the proper introduction of Mo element can improve the hydrogen evolution performance of the materials,and the materials have excellent HER catalytic activity in both acidic and alkaline environments,with overpotentials of 147 m V and 82 m V,respectively.