| Rechargeable Zn-Air batteries are expected to be extremely efficient energy storage and conversion devices due to their superior theoretical energy density,low cost,safety and environment friendliness.Among them,the key to improve the energy conversion efficiency of battery is to ensure the high efficiency of electron conduction of cathode catalyst during oxygen evolution reaction(OER)and oxygen reduction reaction(ORR).Noble metal-based catalysts(Pt/C,RuO2,IrO2)have some problems,such as high cost and lack of bifunctionality,which hinder their practical application.Therefore,it is necessary to construct a dual-function non-noble metal electrocatalyst to reasonably improve the performance of Zn-air batteries.Antiperovskite(ABX3)material is often designed as an efficient electrocatalyst due to its advantages of low cost,high activity and controllable components.Among them,antiperovskite carbide shows strong conductivity and good durability.Therefore,in this paper,the catalytic activity of antiperovskite carbide ZnCNi3 was studied by means of material nano-crystallization,nitrogen doping ratio regulation and X site component regulation,aiming to develop and confirm the application potential of antiperovskite carbide in the field of bifunctional oxygen electrocatalysis.The specific research work is divided into the following two parts:(1)Firstly,antiperovskite ZnCNi3 nanoparticles were synthesized by high temperature calcination technology,and then ZnCNi3 antiperovskite/carbon nanofibers(ZnCNi3/CNFs)were prepared by combing electrostatic spinning technology.ZnCNi3/CNFs relies on carbon fiber substrate to improve the dispersion of ZnCNi3 nanoparticles,so that ZnCNi3 nanoparticles are more evenly loaded on carbon nanofibers.The strong coordination between N and metal elements was further regulated by adjusting the ratio of metal to melamine and the calcination time in situ preparation,which enhance the electron transfer in OER and ORR.The results showed that 1:3:3-9 h ZnCNi3/CNFs exhibited a half wave potential of 0.75 V in ORR and an overpotential of 352 mV in OER.It was tested as a cathode catalyst for self-assembled Zn-air batteries,and the 1:3:3-9 h ZnCNi3/CNFs performed a power density of 83.9 mW cm-2 and a stable voltage gap in constant-current charge/discharge tests.(2)The X site of antiperovskite carbide was optimized based on the advantage of flexible structure and adjustable components of antiperovskite.A series of X site Ni-doped antiperovskites ZnCCe3-xNix/CNFs(x=0,0.3,0.9,1.5,2.1,2.7 and 3)were prepared by electrospinning and high-temperature calcination techniques.While retaining the antiperovskite crystal structure,Ni was introduced to replace Ce.The X-site bimetal filled with high bonding energy Ce4+and high conductivity Ni2+,Ni0 improved the electron transport of the catalyst in the OER/ORR reaction process and enhanced the stability of the catalyst in alkaline solution.The adjustment of X bimetallic components changes the surface element proportion and electronic structure,and promotes the redox reaction.The results showed that ZnCCe2.7Ni0.3/CNFs had the best bifunctional performance when x=0.3,and the potential difference between OER and ORR was 0.82 V,using it as a cathode catalyst of Znair batteries,the power density can reach 117.99 mW cm-2 and the stable running time can reach 300 h. |
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