Synthesis Of Transition-Metal-Based Composite Electrocatalysts And Their Applications In Overall Splitting Water

For the sustainable development of the economy,clean and renewable hydrogen energy has been paid increasing attention.At present,electrochemical water splitting is thought to be the most ideal method for hydrogen production in large quantities.The electrocatalyst with high efficiency and low cost is the premise of promoting the industrialization of electrochemical water splitting.For the development of hydrogen economy,transition metal-based composite electrocatalysts,which were constructed by combining with substracts or interface engineering strategy have been studied for their hydrogen evolution reaction（HER）or oxygen evolution reaction（OER）in an alkaline electrolyte in this paper.The specific research content is as follows:1.Two-dimensional nitrogen-doped carbon nanosheets（NCs）with large specific surface area were successfully prepared by a template method.Then,composite electrocatalyst combined with ultrafine Ru nanoparticles and NCs（Ru/NCs）was prepared using NCS as carriers.Here,NCs provide the localized site for the growth of Ru nanoparticles,preventing the agglomeration of particles and maximizing the exposure of active sites,which ultimately improve the catalytic activity and stability of Ru/NCs.The prepared Ru/NCs catalyst was characterized by XRD,TEM,XPS,BET and so on.Electrochemical test results show that 20%Ru/NCs has remarkable HER catalytic performance and good stability in 1 M KOH solution.20%Ru/NCs delivered an overpotential of as low as 13 m V at the current density of 10 m A cm^-2,which is superior to benchmark Pt/C catalyst（Overpotential of 17 m V）.2.ZIF 67/NF nanoarray materials were prepared by co-precipitation method on NF substrate.Then,a novel Ce O₂/Ni Co P/NF electrocatalyst with intimate oxide-phosphide interface was successfully prepared by a low temperature phosphating and further hydrothermal reaction,with ZIF 67/NF as a precursor.The interfacial structure is not only beneficial to increase the active sites but also accelerate charge transfer,which may be beneficial to regulate the electronic structure and adsorption energy.As OER electriccatalyst,the overpotential of the optimal1.4-Ce O₂/Ni Co P/NF is as low as 249 m V at the current density of 10 m A cm^-2,which is significant improved compared with one-component electriccatalyst of Ni Co P/NF.3.Ni/WO_x/NF electrocatalyst with porous nanosheet arrays structure was successfully prepared by twice hydrothermal method and a subsequent hydrogen reduction step.Abundant interfaces between Ni and WO_xenables the fast charge transfer and positive synergistic effect,which collectively improve the catalytic performance of Ni/WO_x/NF.Furthermore,the porous structure allows further contact of the electrode material with electrolyte and accelerates the releasing of gas bubbles from electrode surface.Hence,both HER and OER performance of the Ni/WO_x/NF catalyst were significantly enhanced.The optimal Ni/WO_x/NF delivers a low overpotentials of 42 m V for HER and 296 m V for OER and a low cell working voltage of 1.52 V for the overall water splitting,respectively,in 1M KOH at 10 m A cm^-2.