Preparation Of NiFe-based Composite Nanoarrays And Their Electrocatalytic Oxygen Evolution Properties

Demand for energy growing quick along with the continuous development of modern society.But currently,non-renewable fossil fuels with severe pollution are still the most important energy source for human beings.Therefore,development of clean and renewable green energy is of great urgent.Electrochemical water splitting technology can effectively convert"abandoned energy"in sustainable resource such as solar and wind into hydrogen energy,which is of high combustion heat value and benefit for environmental protection,providing an effective solution for energy crisis.However,the slow reaction kinetics of electrolyzed water decomposition,especially the half-reaction of oxygen evolution involved in the four-electron transfer process with high energy barrier and junction resistance resulting in a higher overpotential and increase energy consumption.Therefore,in order to obtain further practical application of electrolyzed water technology,it is urgent to develop corresponding catalysts to reduce overpotential and improve catalytic efficiency.Currently,noble metal catalysts such as ruthenium-based or iridium-based catalysts are mostly used for electrolyzed water reactions.However,due to their high prices and scarce quantities,their practical applications have been greatly restricted.Therefore,research on corresponding non-noble metal-based catalysts is the key to large-scale application of electrolyzed water technology.In this paper,nickel-iron-based transition metal compounds are chosen as the main research objects.Two types of nickel-iron-based composite nanosheets arrays have been synthesized with carbon fiber cloth as substrate,and then a series of characterization of their morphology,phase and composite and analysis of the regulation of the electronic structure have been conducted.The electrocatalytic oxygen evolution reaction activity of the samples was also studied,and the specific contents are as follows:（1）Electrodeposition method was used to deposit the FeOOH nanosheets on carbon fiber cloth as substrate,then,a layer of Ni-BDC was coated on the FeOOH nanosheets by hydrothermal method,resulting in the formation of FeOOH@Ni-BDC/CFC composite nanosheets.The composite sample still holds the hierarchical nanosheet structure.This structure effectively increases the contact area between catalyst and electrolyte and can obviously improves the mass transfer efficiency.The introduction of the electron-withdrawing group in Ni-BDC reduces the electron density of Fe cations and enhances its electrocatalytic activity.Compared with pristine FeOOH and Ni-BDC,the composite sample shows excellent oxygen evolution activity with an overpotential of only 270 mV at a current density of 10 m A cm^-2.Regarding the long-term stability of the catalyst,the composite samples remained stable in the chronopotential test for more than 20 h and the cyclic voltammetry test for 2000 cycles.At the same time,the morphology and physical properties of the samples did not show obvious change before and after the reaction.（2）Fe-doped Ni（OH）2 nanosheet array grown on carbon fiber cloth substrate was partially converted into Ni-BDC through an in-situ partial conversion strategy,resulting in the as-synthesized Fe-Ni（OH）2@Ni-BDC/CFC composite nanosheet array.The electronic state of the transition metal cations in the catalyst can be regulated by Fe doping and partial conversion process,which makes them holding higher oxidation state and improves the electrocatalytic performance.Compared to untransformed and fully transformed samples,the composite sample showed superiority to the oxygen evolution reaction in a series of electrochemical properties including the LSV curve,Tafel slope,and electrochemical impedance.