Study On The Performance And Mechanism Of NiCo-based Multifunctional Electrocatalyst

Most energy consumption in today's world arises from the burning of fossil fuels(such as oil,natural gas and coal),as well as global problems caused by the massive emission of combustion products.For example,the reduction of fuel consumption and the greenhouse effect have attracted a series of environmental issues.Our living environment is severely affected by the ozone hole,acid rain and smog.Replacing diminishing non-renewable fuels with hydrogen energy is one of the effective strategies to solve our dilemma,because hydrogen is considered as an efficient and clean fuel,it does not produce any pollutants during the further application.As a non-polluting and promising hydrogen energy conversion and storage system,the electrolyzed water device and the hydrogen-oxygen fuel cell can efficiently realize the mutual conversion of electrical energy and chemical energy.Among them,the hydrogen evolution reaction(HER)of the electrolyzed water device stores energy by generating high-purity hydrogen with renewable energy imput;the fuel cell converts the stored energy into electrical energy during the HOR reaction.However,the paired oxygen evolution reaction(OER)suffer from a low kinetics due to its nature four-electron transfer,which limits the further application of hydrogen energy.Currently,Ir/Ru oxide is the most effective OER catalyst.For HER and HOR,Pt-based catalysts show the best performance.But high cost and scarcity hinder their large-scale application.Therefore,we need to develop highly efficient alternative catalysts to achieve hydrogen economy,which has very important practical significance.In this paper,the research on double transition metal catalysts is the main line,and the exploration of catalysts with high catalytic performance is the main goal.We have prepared a series of catalysts by adjusting the ratio of Ni and Co and the processing temperature.We also studied its influence on the catalytic performance of HER,HOR,OER and water splitting.The main research results obtained are as follows:(1)Different NiCo-based catalytic materials were synthesized by templateless electrodeposition and low temperature nitridation.The effects of Ni,Co atomic ratio and nitridation temperature on determining the catalytic properties of the resulting electrocatalysts were systematically studied.The results show that the obtained electrocatalysts exhibit the best performance with a Ni/Co ratio of 3/7 and nitridated at 420?.(2)The best performance material(Ni/Co2N)has excellent HER/HOR performance.To produce a current density of-10 mA cm-2 in an alkaline solution,only an overpotential of 16.2 mV is required.Moreover,for the electrolyzed water device,at a current density of 10 mA cm-2,the Ni/Co2N interface catalysts require only an overall voltage of 1.57 V,which is superior to most developed electrocatalysts couple.(3)DFT calculation results clarify that electrons transfer from Ni to Co2N at the Ni/Co2N interface.At the optimal N and Co sites for the interface,the free energy of hydrogen adsorption is only-0.08 eV and-0.11 eV,closed to 0 eV.These reuslts further prove that our interface engineering has a significant help in improving the catalytic performance.