N-doping FeNi@C(Nx) core-shell nanoparticles synthesized by arc plasma as a highly efficient bifunctional electrocatalyst for all-solid zinc-air batteries

Abstract

Applications of zinc-air batteries (ZABs) are generally hampered by limited efficiency and poor stability of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) at the air cathode. The key to solving the problem is the highly efficient bifunctional electrocatalyst. Herein, the bifunctional electrocatalyst of nitrogen-doping carbon-coated FeNi (FeNi@C(Nx)) core-shell nanostructures was fabricated by one-step physical vapor evaporation technology of DC arc plasma and subsequent -nitrogen treatment. The energy state in the synthesis of FeNi@C precursor was monitored by a real-time optical emission spectroscopy (OES) measurement. The obtained FeNi@C(N15) nanoparticles was proved to be an excellent electrocatalyst for both ORR and OER processes, the OER overpotential is 326 mV which is better than that of RuO2 (405 mV) and the ORR catalytic reaction is close to the typical 4e− process. It is indicated that all-solid Zn-air battery assembled with this FeNi@C(N15) electrocatalyst provides a high open circuit voltage of 1.394 V, and a high peak power density of 59.7 mW cm−2. The synergistic effect between the bimetallic FeNi core and the N-doped carbon shell is responsible for the bifunctional activities, and such a core-shell nanostructure can prevent the catalyst from corrosion in working. This study provides a new approach for the design and preparation of transition metal alloys nanostructures encapsulated into the carbon-shell with quantitative nitrogen-doping, such a core-shell structured nanocapsule has excellent potential as the electrochemical bifunctional catalyst in some renewable energy devices.