Preparation Of Metal Sulfide By Electrochemical Reduction Of Sulfur And Study For Hydrogen Evolution Properties

With the accelerated transformation of China's energy,people are committed to finding new and alternative clean energy.Compared with the intermittent renewable energy sources such as wind energy and tidal energy that have been used in practice,hydrogen energy has the advantages of easy storage and transportation.At the same time,it is also an important link in the“energy internet”,which has attracted wide attention from all over the world and has become the main investment direction of the global technology,industry and finance in the energy field.As the second most potential new clean energy alternative to traditional fossil energy,hydrogen is regarded as the ultimate energy source in the 21st century.In many methods for preparing hydrogen energy?such as from fossil energy,biogas,synthetic methanol,and industrial by-products?,the reaction of electrolyzed water to produce hydrogen stands out and can store unstable renewable energy such as wind energy and tidal energy.The hydrogen is closely linked with the semi-electrode HER,which is great significance for the preparation of hydrogen from electrolyzed water.In recent years,TMS materials have attracted many scholars'attention because of their abundant sources,low price,good electrical conductivity and high catalytic activity.They are considered to be promising alternatives to HER catalysts for noble metal Pt.In this paper,a new method for preparing TMS cathode materials was designed and the reaction mechanism was introduced in detail.The effects of types of transition metals on morphology of Co_zNi_yS_x@PPy/CFP composites and the HER performance in alkaline solution were studied.The HER performance of Ni₃S₂@PPy/CFP composites prepared at different voltages was studied.The research results are as follows:?1?Using a simple and novel controlled electrochemical UPED method,a certain voltage is applied to the S@PPy composite that was coated on CFP,so that the elemental sulfur is reduced to sulfur ions,and then the 3D cauliflower-like composite material Co_zNi_yS_x@PPy was finally obtained by the diffusion effect and self-assembly nucleation pathway reacting with different molar ratios of Co and Ni ions.?2?Through a series of experiments,we found that when the molar ratio of Co/Ni in the electrolyte of the prepared material is 0/6,the electrode is the best electrode,i.e.,Co_zNi_yS_x@PPy/CFP-6?A-6?showed excellent HER catalytic activity(with an overpotential of 185 mV?vs.RHE?at a current density of 10mA·cm^-2 and a small Tafel slope of 78.13 mV·dec^-1)in 1 M KOH solutions.More importantly,the composite Co_zNi_yS_x@PPy/CFP?A-6?has very good stability and its stable setting can be maintained for 100h or even longer.Through SEM,TEM,XRD,XPS,FT-IR and other characterizations,we found that the Co_zNi_yS_x@PPy/CFP-6?A-6?composite has such excellent performance probably due to the synergistic effect of Ni_xS_y mixed structure and low adsorption energy for hydrogen of Ni in volcanic curve.This work provides a novel approach to guide us in continuing to search for catalysts with excellent HER performance;we have also found that the structure of the composite can be controlled by controlling the ratio of cobalt and nickel.In general,this study provides a new research idea for the current search for electrolyzed water hydrogen evolution cathode materials,and the prepared Co_zNi_yS_x@PPy/CFP composite has potential application prospects in HER.?3?The electrodeposition method has great controllability and greatly enhances the precise control of the microstructure of the transition metal complex,so we have also adjusted some parameters in the UPED method to find the catalyst with the best performance.Ni_yS_x@PPy/CFP composites were prepared by applying different voltages to the S@PPy/CFP surface.Through electrochemical performance tests,we found that the Ni₃S₂@PPy/CFP composite prepared at-1.8 V has the best HER performance,i.e.,the overpotential at a current density of 10 mA·cm^-2 is 149 mV?vs.RHE?,which is small.The Tafel slope is 77.54 mV·dec^-1 and very high stability.Through SEM,TEM,XRD,XPS and other series of characterization,we found that-1.8 V may be more favorable for the growth of Ni₃S₂ crystal planes?122?and?330?.Thus,it has a higher HER performance;and the very high stability may be related to the amorphous carbon polypyrrole,which was coated on the periphery of the Ni₃S₂ crystal.Therefore,this part of the work has great application value for the later development of electrolytic hydrogen evolution cathode materials,which can promote the rapid development of hydrogen energy.