Cobalt-doped ZnS Supported On Carbon Sheets As An Integrated Electrocatalyst For Efficient Hydrogen Evolution

Due to the rapid development of the global economy and the growing population base,energy sustainability is critical to human life and social development.Hydrogen is valued as a clean,storable and renewable green energy source.Electrochemical water splitting is a green,sustainable way to produce hydrogen,but this process requires efficient electrocatalysts to reduce hydrogen evolution overpotentials and improve hydrogen evolution efficiency.At present,Pt and Pt-based precious metal materials are considered to be the most effective hydrogen evolution electrocatalysts.However,due to the low abundance,high cost and short-term durability,the large-scale application of Pt is hindered.Therefore,the development of a low-cost,stable and efficient non-precious metal electrocatalyst is significant in the field of hydrogen evolution reaction.Metal sulfides have become a hot material that can replace Pt-based catalysts due to their high electrocatalytic activity,low cost,and high earth reserves.ZnS has a large application potential in the field of catalysis because of its easy preparation,abundant reserves and unique photoelectric effect.However,the bonding energy of Zn-H*on the surface is so weak that H atoms cannot be stably absorbed on the surface of ZnS,which decreases the reaction rate and thus restricts its potential in electrolytic water splitting.Co atom doping can adjust the electronic properties and surface structure of ZnS,and further improve the application of ZnS in the field of electrocatalytic hydrogen evolution.In this paper,we adjust the electronic properties and surface structure of ZnS by doping Co atom with ZnS.And we further control its morphology and structure.Then,we test and analyze their electrocatalytic hydrogen evolution performance.This paper mainly studies from the following aspects:?1?Different vulcanization methods were used to investigate the effect on the crystallinity and particle size of ZnS.Using cobalt nitrate and zinc nitrate as raw materials,L-cysteine and glucose were used as carbon sources,L-cysteine and thiourea as sulfur sources,and NaCl as template.The cobalt-doped ZnS was prepared by thermal decomposition and desulfurization in high purity N₂ conditions.The morphology and structure of the prepared hydrogen evolution catalyst were characterized by means of XRD and SEM.The effects of different vulcanization methods on the electrocatalytic hydrogen evolution of cobalt-doped ZnS were investigated by electrocatalytic hydrogen evolution experiments.The results show that when L-cysteine is used as the sulfur source and carbon source,and the cobalt-doped ZnS catalyst synthesized by one-step pyrolysis has high crystallinity and better performance for hydrogen evolution.?2?Adjusting the ratio of the template to explore its effect on the morphology and structure of the electrocatalysts.The one-step vulcanization method was used to change the template ratio under the same conditions,and the obtained samples were characterized by morphology and electrocatalytic performance.The results show that when the mass ratio of template to L-cysteine is 20,the size of ZnS particles is the smallest,and a large number of active sites are exposed,which has better electrocatalytic performance.?3?Exploring the effect of the ratio of cobalt to zinc on the structure and electrocatalytic properties of electrocatalysts in cobalt-doped ZnS.Under the same conditions,the molar ratio of cobalt to zinc atoms was changed,and the synthesized samples were characterized by a series of experiments and electrocatalytic hydrogen evolution test.The results show that when the Co/Zn molar ratio is 10,it has a lower overpotential and a smaller Tafel slope.The current density is 10 mA cm^–2,and the overpotential of Co/Zn?1/10?-S-C is 260 mV.After scanning for 22 hours at 260 mV,the current density is almost no attenuation,indicating it has good stability.