The Growth And Electrocatalytic Performances Of Bimetallic Phosphide And Sulfide

Because of the excessive consumption of fossil fuels and the aggravation of environmental problems,people need to develop clean and renewable energy which can replace fossil fuels.As a sustainable energy source,hydrogen energy has the characteristics of high energy density and zero emissions,and has great potential to replace fossil fuels in the future.Electrochemical water splitting is an effective way to produce hydrogen,which is gradually studied in depth.Electrochemical water splitting used in the electrolyzer mainly includes oxygen evolution reaction(OER)at cathode and hydrogen evolution reaction(HER)at cathode.In the process,because of the large overpotential,it is necessary to use efficient catalyst to promote the reaction kinetics of the electrode surface,so as to improve the efficiency of hydrogen production.The development of electrode materials with excellent catalytic performance is an important research topic,which has attracted wide attention from scientific researchers in recent years.Although noble metal catalysts such as Pt and Ru have excellent electrocatalytic activity,these noble metals have limited their industrial application prospects due to their low natural reserves,high cost and poor stability.Therefore,it is very important to develop electrode materials with abundant,cheap and high catalytic activity for the realization of sustainable hydrogen production process.Transition metal phosphides and sulfides are widely applied in the field of electrocatalysis due to their excellent electrical conductivity,corrosion resistance and good stability.In this paper,based on bimetallic catalyst materials were optimized which from the aspects of high catalytic activity,good stability and low preparation cost,their electrochemical HER and OER performance were studied.At the same time,the main mechanism of the improved catalytic performance was revealed.The specific research contents are as follows:(1)The Ni-Cu bimetallic(NiCu/P)catalyst was synthesized on foam nickel by hydrothermal and low-temperature phosphating technology.SEM results show that Ni-Cu phosphide catalyst is branched structure.This special branched structure contains a large number of grain boundaries,which is conducive to the rapid diffusion of electrolyte into electrode materials,and provides more active sites for HER.In addition,there is a strong synergistic effect between bimetallic phosphides,which optimizes the electronic structure and improves the conductivity of the material.The experimental results show that the prepared NiCu/P has better HER performance than the single metal phosphide(nickel phosphide,copper phosphide).The NiCu/P electrocatalysts exhibited a low overpotential of 99 mV at a current density of 10m A/cm~2,and a small Tafel slope of 76 mV/dec for the HER.This work provides a new way to develop other bimetallic phosphides instead of precious metals as catalysts for hydrogen evolution.(2)The cobalt manganese bimetallic sulfide electrocatalyst for oxygen evolution was synthesized on the surface of nickel foam by electrodeposition.SEM observation showed that the morphology of the samples was interlaced nanosheets.By adjusting the Mn/Co atomic molar ratio,it was found that the sample Mn CoS-2with the Mn/CO atomic molar ratio of 2/13 showed the best electrocatalytic activity for oxygen evolution.The Mn Co S-2 catalyst can produce a current density of 50mA/cm~2only at 302 m V,with a Tafel slope of 87 mV/dec.At the same time,MnCo S-2 catalyst has good circulation stability.When the current density is 50m A/cm~2,the voltage required is not significantly improved for 24 hours of continuous oxygen production.Comparing the LSV curves before and after the 24 hour test,it was found that the voltage of 100 m A/cm~2increased by only=18.1 m V.The catalyst exhibits excellent catalytic activity and stability,which is attributed to the fact that nano-sheets with rough surface expose a large number of active sites.On the other hand,the introduction of the second metal can adjust the electronic structure and improve the conductivity of the catalyst,resulting in enhanced electrochemical activity.