Design And Electrochemical Performance Of High-efficiency Ni-Fe LDH Electrocatalysts

Facing the increasingly serious ecological environment and energy crisis,people are looking for new and more sustainable renewable energy sources.Hydrogen（H₂）is a clean and renewable energy source,its high energy density and harmless products generated by combustion make it attractive as the best alternative energy source for traditional fossil fuels.Compared with the use of expensive steam reforming method,the use of water splitting is more economical and efficient to produce H₂.The process of water splitting includes oxygen evolution reaction（OER）at the anode and hydrogen evolution reaction（HER）at the cathode.However,the fourelectron transfer process involved in OER causes a slow kinetic process with high over-potential,which becomes a bottleneck restricting the water splitting.Therefore,there is an urgent need to develop electrocatalyst with higher catalytic activity for OER.At present,iridium oxide and ruthenium oxide are the best OER catalysts.However,their low reserves and the high price,making them difficult to use on a widespread industrial application.Owing to its unique layered structure,high-efficiency OER catalytic performance and stability,and abundance and cheap cost,nickel-iron layered double hydroxide（Ni-Fe LDH）based electrocatalysts have received extensive attention in the fields of electrocatalysis for OER.In this study,we chose MIL-88 A as the iron precursor to produce Ni-Fe LDH with hollow structure or even a hierarchical structure through the hydrothermal method,and the corresponding electrochemical performances were studied.The main research contents are as follows:（1）The synthesis of Ni-Fe LDH is by determining MIL-88 A as the iron precursor,and then selecting different nickel salts for hydrothermal reaction.By adjusting the reaction time and temperature,Ni-Fe LDH with a hollow structure was obtained.The increase of the specific surface area helps to shorten the ion transport distance during the reaction,electrocatalytic evaluation shows that the Ni-Fe LDH exhibited an excellent OER performance.（2）Through one-step hydrothermal synthesis,the surface of MIL-88A is coated with a layer of ZIF-67,and then select the appropriate nickel salt for another hydrothermal reaction.By adjusting the reaction time and temperature,hollow structured NiFeCo LDHs were obtained.The complex hierarchical structure helps to improve space utilization,expose more active sites,and further improve OER catalytic performance.