Synthesis And Electrocatalysis Performance Of Transition Metal(Ni,Co,Fe,Mo) Based Nanocomposites

In recent years,due to the excessive consumption of fossil fuels and the gradual deterioration of the environment,more attention has been paied to the development of renewable clean energy and energy storage equipment.As a new type of clean energy,hydrogen was favored by people for its clean and sustainable carbon-free energy society.Among many hydrogen production methods,electrolytic water technology stands out for its advantages of simple equipment,abundant raw materials and energy-saving.Up to now,although platinum,ruthenium and other precious metal based electrocatalysts show excellent catalytic performance,their low storage and high price limit the large-scale use of this technology.Therefore,the development of cheap,reasonable and efficient electrocatalysts is still a research hotspot.In this paper,the preparation and properties of transition metal-based nanocomposites are investigated,with emphasis on the preparation process and their application to the overall water splitting.This paper consists of the following three parts:1.A facile sacrificial template method to synthesize hierarchical Ni-Co-P hollow nanobricks with oriented nanosheets for efficient electrocatalytic water splitting.We have developed a rapid microwave-assisted method to prepare uniform Ag₂WO₄ solid nanobricks as the templates for the first time.The NiCo precursor nanosheets were prepared via oil bath reflux.Ultimately,electrocatalytic materials of Ni-Co-P hollow nanobricks?HNBs?structure were obtained by calcining,acid-base etching and phosphating,which displayed excellent catalytic performance compared with the NiCoP catalyst without template.For the hydrogen and oxygen evolution reactions with the Ni-Co-P HNBs in alkaline medium,the low overpotentials of 107mV and 270 mV are observed,respectively,and the required cell voltage towards overall water splitting is only as low as 1.62 V for the driving current density of 10mA cm^-22.The electrocatalyst of polymetallic 2D nanosheets on the surface of Ni foam was prepared via hydrothermal and solvent thermal reaction.Meanwhile,it was tested for OER,HER and water splitting.The oxidability of Fe³⁺in this section was used to prepare NiFe₂O₄-Ni?OH?₂nanosheets on the surface of Ni foam.And the electrocatalyst has excellent oxygen evolution reaction in alkaline medium with overpotential of 208 mV at the current density of 10 mA cm^-2,and Tafer shop of 57.9 mV dec^-1.Furthermore,the Ni-Fe-Mo-S 2D nanosheets was prepared though solvent thermal reaction with Ammonium tetrathiomolybdate,which shown outstanding hydrogen evolution reaction in 1 M KOH with overpotential of 129 mV at the current density of-10 mA cm^-2,and Tafer shop of 113.1 mV dec^-1.Ultimately,electrocatalysts of NiFe₂O₄-Ni?OH?₂ and Ni-Fe-Mo-S ware seen as anode and cathode in the cell respectively,and the required cell voltage towards overall water splitting is only as low as 1.58 V at the driving current density of 10 mA cm^-2.3.Synthesis of Ni_1-xFe_xSe₂ nanoparticles supported on N-doped carbon nanotube for highly efficient oxygen evolution reaction.In this section,we designed and synthesized a novel nanostructure of Ni_1-xFe_xSe₂ nanocubes on N-doped carbon nanotube.In the first step,the composite of metal nickel and N-doped carbon nanotube was obtained through nickel ion catalysing tripolycyanamide.Ni_1-x-x Fe_xSe₂/N-CNT was obtained through the reaction with K₃Fe?CN?₆ at room temperature in 1 M H₂SO₄,followed by selenylation.The as-prepared Ni_1-xFe_xSe₂/NCNT showed excellent catalytic performance and stability of oxygen evolution reaction.