The Research On Cobalt-based Sulfides Derived From Metal-Organic Frameworks As Bifunctional Oxygen Electrocatalysis

Zinc-air batteries have becomed a hot spot in current research due to their high energy density,good safety,rich resources and low cost.Among them,the high-activity oxygen electrocatalyst is an important problem that the zinc-air battery needs to solve.In this paper,a new type of bifunctional catalyst with high catalytic activity is prepared by hydrothermal sulfidation.Firstly,use ZIF-67 as the precursor for vulcanization,and then dopamine coating.The zinc source is introduced in the coating process,and then heat treatment is performed to obtain a new composite catalyst Zn_0.76Co_0.24S-Co₉S₈/HCNT.The ORR half-wave potential of the catalyst reaches 0.83 V under alkaline conditions,while the overpotential of OER at 10 mA cm^-2is 330 mV,and the Tafel slopes of ORR and OER are 56 mV dec^-1and 143 mV dec^-1,respectively.At the same time,the effects of vulcanization temperature,vulcanization time and heat treatment temperature on the catalyst were explored.The study found that the corresponding conditions are optimal when the curing temperature is 180℃,the ORR half-wave potential reaches 0.83 V under alkaline conditions,and the overpotential of OER at 10 mA cm^-2is 330mV;When the hydrothermal time is 6 h,the catalyst has the best performance.The ORR half-wave potential reaches 0.83 V under alkaline conditions,while the overpotential of OER at 10 mA cm^-2is 330 mV;when the heat treatment temperature is950℃,the corresponding catalyst has a higher degree of graphitization.Compared with other heat treatment temperatures,the catalyst exhibits excellent catalytic performance under the corresponding conditions of 950℃.ZIF-8 is used as the core to prepare ZIF-8@ZIF-67 composite structure.After heat treatment,Co/NHCNT is generated,and then Co/NHCNT is hydrothermally vulcanized to prepare CoS₂/NHCNT catalyst.The catalyst exhibits excellent ORR and OER catalysis active.The ORR half-wave potential reaches 0.86 V under alkaline conditions,while the overpotential of OER at 10 mA cm^-2is 350 mV.The Tafel slopes of ORR and OER are 60 mV dec^-1and 167 mV dec^-1,respectively.By changing the process parameters,the effects of heat treatment temperature,vulcanization ratio and vulcanization time on the performance of the catalyst were explored.The study found that:when the heat treatment temperature is 950℃,the degree of graphitization is higher,and the active material of cobalt disulfide generated by sulfurization shows excellent catalytic performance.The ORR half-wave potential reaches 0.86 V under alkaline conditions,while the overpotential of OER at 10 mA cm^-2is 350 mV;When the sulfurization ratio is 1:2 to produce pure cobalt disulfide,the corresponding catalyst is the best.The ORR half-wave potential of the catalyst reaches 0.86 V under alkaline conditions,while the overpotential of OER at 10 mA cm^-2is 350 mV;When the vulcanization time is 12 h,cobalt disulfide is formed after vulcanization,and the catalyst exhibits excellent performance.The ORR half-wave potential reaches 0.86 V under alkaline conditions,while the overpotential of OER at 10 mA cm^-2is 350 mV.