The Preparation Of ZIF-67 Derived Co-Based Dichalcogenides And Study On Their Electrocatalytic Performance

At present,the ever-growing depletion of limited fossil fuels and increasingly grave global environmental problems have resulted in an urgent search for clean,renewable,and alternative sources of energy.Hydrogen（H₂）is an eco-friendly and sustainable energy source,thus,it is deemed to be a future energy carrier to eliminate the constraints of the hydrocarbon economy.The water electrolysis device is considered a facile and efficient method for hydrogen production,which generates molecular hydrogen and oxygen through the cathodic hydrogen evolution reaction（HER）and the anodic oxygen evolution reaction（OER）,respectively.The OER process requires a four-electron transfer in alkaline media,thus it has a large overpotential,which is regarded as the most energy-intensive step in water splitting.Thus,the development of low-cost,high-performance and durable bifunctional electrocatalysts boosts the prospects of application of renewable energy conversion techniques.This study devoted to the synthesis of non-noble metal-based bifunctional electrocatalysts with zeolite imidazolate skeleton-67（zif-67）as a precursor,to explore the reaction mechanism and the influence of electrolyte.Details are listed as follows:we proposed a facile two-step approach comprising the pre-oxidation and sulfurization/selenylation process for the synthesis of Co³⁺-enriched Co(S_xSe_1–x)₂@C core-shell nanoparticles.the resulting Co(S_0.46Se_0.54)₂@C exhibits ultralow overpotential of 220 m V to achieve 10 m A cm^-2 in 0.1 M KOH,transcending the most reported non-noble metal-based electrocatalysts.Moreover,Co(S_0.46Se_0.54)₂@C possesses comparable HER activity.This work allows a new paradigm to strategically design non-noble metal-based bifunctional electrocatalysts with high efficiency and low-cost by the synergistic effect of the disulfide group elements.In order to further explore the specific reaction mechanism,we conducted a series of characterization tests.The co-introduced S and Se not only exposes more Co³⁺as active sites,but also induces structural defects.Furthermore,the influence of S/Se atomic ratio on OER and HER activity was investigated.Benefitting from the unique merits of Co³⁺enrichment,high surface area,excellent conductivity and abundant defects,Co(S_0.46Se_0.54)₂@C is considered to be a promising non-noble metal-based bifunctional electrocatalysts of OER and HER for energy conversion devices.