The Electrochemical Performance And Mechanism Investigation Of Metal-Organic-Framework Derived Transition Metal Catalyst

The growing demand for energy,along with environmental pollution caused by the depletion of fossil fuels,have largely stimulated intense research on energy conversion and storage devices.Bifunctional electrocatalysis for oxygen evolution reaction?OER?and oxygen reduction reaction?ORR?constitutes the bottleneck of various sustainable energy devices and systems like rechargeable metal-air batteries and fuel cell.Although alloys of precious metals could provide the possibility to improve the catalytic activities towards the ORR and OER simultaneously,the high cost and instability of these catalysts caused by the scarcity and unpromising durability have prevented their widespread application.Therefore,the development of low-cost and durable electrocatalysts with high performance for ORR and OER is a fundamental step toward the practical application of renewable electrochemical energy technologies.As highly ordered three-dimensional framework structure materials,MOFs with an ultrahigh surface area,diverse composition and controllable porous structure have drawn particular interest over the past decades.By varying the metal ions/clusters and organic linkers,researchers can assemble and create different functional MOFs via coordination bonds.Meanwhile,transition metal and nitrogen co-doped carbon?M/N-C?have emerged as a promising new type efficient oxygen electrocatalysts.In addition,transition metal sulfides,oxides and hydroxides also have good catalytic properties.Therefore,a series of low-cost and high-performance catalysts with transition metal as the main active material were prepared by using MOFs as precursor,and the catalytic mechanism of OER/ORR and its practical application in batteries were explored.The main contents and conclusions of this paper are as follows.?1?We provide a two-steps hydrothermal fabrication to obtain the NiS₂/Fe for OER.The material characterization and electrochemistry test results suggest that the Fe was successfully doped into NiS₂ and formed the unique structure to create more active sites.The as-obtained NiS₂/Fe shows promising OER activity with potential of 1.48 V at current density of 10mA/cm² and a high durability?retention of 96.85%after 36000 minutes?in 1.0 M KOH.The tafel slope is only 45.66 mV/dec and the smaller electrochemical impedances value?16.27??indicates that the fast electron and mass transfer,which definitely contributes to enhance the catalytic performance.In short,the NiS₂/Fe Nanosphere was a promising non-noble metal catalyst for OER.?2?By using FeZIF-8/CoS as precursor,a highly efficient and stable noble metal-free electrocatalyst was synthesized by pyrolysis in argon.We synthesized an efficiently activity and durable electrocatalyst without noble metal.Benefiting from the unique sea urchin architecture and the effect of transition metals?Co,Fe?,the catalyst possesses abundant active sites,huge specific surface area and enhanced electron transfer.The catalyst exhibits excellent ORR(E_1/2=0.88 V,vs.RHE)and OER(E₁₀=1.46 V,vs.RHE)catalytic activity,simultaneously a high specifc capacity of 504 mA h/g for Zn-air battery.