Study On Oxygen Reduction/precipitation Performance Of Carbon-supported Iron-cobalt Alloy Catalys

The constant advancement of human society has propelled the demand for energy,leading to the search for renewable and sustainable energy sources to replace fossil fuels.The establishment of a low-carbon economy and the reduction of environmental pollution have become universal goals in the contemporary era.Electrochemical conversion technologies,such as rechargeable metal-air batteries,have garnered significant attention in recent times due to their noteworthy advantages,which include high specific energy(1370 Wh/kg),inexpensive,safety,and environmentally friendly.In addition,undesirable interference with conflicting redox properties(OER and ORR)between redox pairs typically leads to accelerated decay of catalytic activity of metal-air cells under repeated charge/discharge cycles,therefore,there is an urgent need to promote the advancement of electrochemical energy storage.Currently,precious metal-based catalysts are the dominant electrocatalysts in the world today,but commercially available precious metals are limited by the scarcity and instability of the alkaline solution used in zinc air batteries.Therefore,the development of non-precious metal electrocatalysts with ORR and OER activity would be the most efficient and cost-effective solution for rechargeable zinc-air batteries.The objective of this paper is to prepare highly efficient ORR/OER bifunctional catalysts for energy storage and conversion systems.Low-cost carbon materials and transition metal alloys with excellent stability under alkaline electrolyte solution,such as FeCo alloy,are targeted and analyzed for their physical and chemical properties using Xray diffraction(XRD),nitrogen absorption/desorption,and scanning electron microscopy.Moreover,rotating circular and rotating annular disc electrode tests are employed to examine the ORR and OER electrocatalytic performance and reaction mechanisms of the catalysts.In this paper,FeCo alloy anchored on nitrogen-doped porous carbon-nanosheets(FeCo/NUCSs)are used as bifunctional electrocatalysts.Using FeCo-PBA derived from Co/N co-doped ultrathin carbon sheets(Co/NUCSs)as precursors,the FeCo/NUCSs composites with core-shell structure and high ORR/OER bifunctional electrocatalytic activity are obtained via a self-growth strategy.The FeCo/NUCSs demonstrated notable ORR half-wave potential(E1/2=0.89 V)and high OER activity(overpotential of 300 mV at Ej=10 mA cm-2),lead to a ΔE(Ej=10(OER)-E1/2(ORR))of 0.64 V.FeCo/NUCSs were used as cathode materials for assembling zinc air batteries(ZABs),which shows an open circuit voltage(OCV)of 1.51 V,specific capacity of 791.86 mAh g-1,and good durability of 102 hours during charge/discharge cycles.For ORR,the key to the active site is the formation of Fe-Nx/Co-Nx;secondly,under the influence of N doping,the transfer of negative charges from the CoFe alloy-based core to the PBA-derived carbon skeleton and NUCS can be enhanced.For OER,in situ X-ray diffraction showed that highly reactive FeOOH/CoOOH material was produced on FeCo alloy as the main active site for OER.In addition,nitrogen-doped carbon-coated Co/CoO.7Fe0.3 heterojunction porous carbon spheres have been synthesized using a two-step method to produce Co/Co0.7Fe0.3PCS as bifunctional ORR/OER electrocatalysts in this work.The Co/Co0.7Fe0.3-PCS catalyst displays a high oxygen reduction peak of 0.903 V for ORR and remarkable OER performance with an overpotential of 1.536 V at 10 mA cm-2.Rechargeable Zinc-air batteries(ZABs)assembled with Co/Co0.7Fe0.3-PCS as cathode material show OCV of 1.51 V and excellent cycle stability of 280 hours(943 charge/discharge cycles).The synergistic coupling effect between Co0.7Fe0.3 alloy and metallic Co monomers and the electronic interactions at the heterogeneous interface significantly accelerate the electron transfer and conductivity,which favor the catalytic stability and high OER/ORR performance(ΔE=0.634 V).In addition,the graphitized carbon network facilitates the mass transfer process during the reaction.In this paper,carbon-based composite electricity catalytic materials based on cobaltiron alloy are constructed,and the good bifunctional electrocatalytic activity unveils the prospect of such catalysts in electrocatalysis field,which guides the further design of cobalt-iron alloy-based electrocatalysts.