Preparation And Electrocatalytic Properties Of Transition Metal Chalcogenide Carbon-Based Composites

The problems of energy crisis and environmental pollution have been serious increasingly in recent years.The development of new energy resources is imperative.Fuel cell is considered as one of the ways to alleviate the energy crisis.It can directly convert the chemical energy of fuel into the electric energy with high energy conversion efficiency and small environmental pollution.However,oxygen reduction reaction(ORR)occurs at the cathode during discharge with a slow kinetic process,which affects the performance and life of the devices and the traditional commercial catalysts that platinum(Pt)and its nanomaterials face the problems of high price,poor stability,low durability and so on,which hindered the widespread commercialization of fuel cells.Therefore,it is of great significance to develop environmentally friendly,inexpensive and efficient catalysts.This paper focus on the synthesis of new fuel cell electrocatalysts and the study of electrocatalytic performance,provides theoretical support and new ideas for the further research of new electrocatalysts The main contents are as follows:(1)Structural transformation from the thermally stable orthorhombic CoSe2(o-CoSe2)to metastable monoclinic(m-Co3Se4)was succeeded by adding Cu(II)ions to the precursor.The resulting Cu-14-Co3Se4/GC catalyst show remarkable enhancement in hydrogen/oxygen electrocatalysis comparing with the sample CoSe2/GC before structural transformation.This is the first time to realize a Co3Se4 based remarkable tri-functional electrocatalyst for ORR,OER,and HER in the same working electrolyte which the lowest value among all the Co3Se4-based catalysts reported in literature.Density functional theory(DFT)calculations demonstrated the higher intrinsic electrocatalytic activity of m-Co3Se4 than o-CoSe2.The results in present work not only highlight the importance of structural engineering in tailoring electrocatalytic activities,but also open up a novel route for the synthesis of transition metal chalcogenides based electrocatalysts(2)Cobalt thiourea resin grown with the Zeolitic Imidazolate Frameworks template was treated at high temperature with sealed in NaCl crystal.During the calcining process,nitrogen and sulfur co-doped carbon nanosheets(Co9S8/NSC)loaded with Co9S8 nanoparticles are formed along the crystal interface.The ORR test shows the performance closed to that of commercial Pt/C and the stability superior to that of Pt/C.The synergistic effect of Co9S8 and the 2D carbon nanosheets doped with N and S is crucial to the realization of the high ORR activity of the sample.This work providing a new idea for the preparation of cheap and efficient electrocatalyst.