Studies On The Synthesis Of Dual Transition Metal Catalysts And Their Electrocatalytic Performances For Oxygen Reduction & Oxygen Evolution Reactions

Recently,facing the increasingly aggravated energy crisis and environment pollution,developing low-cost and environment-friendly renewable energy conversion and storage devices has been regarded as a focusing issue in modern society.Non-noble metal catalysts have attracted extensive attention due to their low cost,excellent performance and stability,and are considered as the most potential catalysts for oxygen reduction and oxygen evolution electrocatalysts.However,the low number of active sites of single transition metal-doped electrocatalysts and their unsatisfied activities lead to many difficulties for researchers in synthesizing catalysts and improving the activities of catalysts.As a result,it is of great importance to design and prepare multimetallic electrocatalysts with high content of active sites and to explore the composition of catalytic active sites of metal ions.This thesis aims at exploring the synthesis strategy of dual transition metal-doped electrocatalysts and catalytic performences,using the rotating disk electrode technology,combined with physical characterization methods.Dual transition metal-doped oxygen reduction(FeCo)and oxygen evolution(FeNi)catalysts were successfully prepared.The catalytic activity regularity of the dual transition metal-doped catalysts was investigated for oxygen reduction reaction(ORR)and oxygen precipitation reaction(OER),and the main results are as follows:(1)The obtained FeCo-N/C-800 has been proved to exhibit not only a high-performance electrocatalytic performance towards ORR in 0.1 M KOH solution,but also superior long-term durability and methanol-tolerance to commercial Pt/C.The synergetic interaction of the multiple ORR active sites,hierarchical mesoporous structure(bimodal pores system),suitable N-doping level and the highly conductive carbon matrix can be responsible to the excellent ORR performance.(2)The synergistic electronic interaction between initially active Ni and the properly doped Fe endows the Fe-Ni/N(1/2)catalyst with superior electrocatalytic performance for OER with desired stability in alkaline medium.Additionally,such highly defective N-doped mesoporous carbon matrix embedded Fe/Ni alloy particles provides large specific surface area to expose more active sites and possess excellent electronic conductivity,which facilitate the electron transfer and further promote the OER catalytic kinetics.Meanwhile,the superior electrocatalytic activity can also be attributed to the introduction of the active O radical(hydroxyl groups)along with Fe-doping in the surface electronic structure,improving the ability of adsorbing intermediates in the OER process.In this thesis,the reasonable strategies for preparing dual transition metal doped carbonbased materials are explored,and electrocatalytic performances of the two materials for ORR and OER under alkaline conditions are studied,respectively.To a certain extent,our work can provide ideas for the synthesis of non-noble metal catalysts involved in the application of fuel cells and metal-air batteries,and may promote the development of materials related to energy conversion devices.