Non-Noble-Metal Catalyst and Zn/Graphene Film for Low-Cost and Ultra-Long-Durability Solid-State Zn-Air Batteries in Harsh Electrolytes

Abstract

Exploration and development of cost-effective, ultra-long durability, and high-performing non-noble-metal catalysts for the oxygen reduction reaction (ORR) to replace Pt-based catalysts for electrochemical energy conversion devices is still of great challenge. Although several types of non-noble-metal catalysts (N-doped graphene, transition metal nanoparticles, single atomic metal-nitrogen-carbon, etc.) are claimed to have comparable or overwhelming catalytic performances compared with commercial Pt/C, their long-durability, especially in harsh electrolytes, are still unsatisfactory for practical applications. Herein, the classical Fe3C-NG catalysts are synthesized and investigated to understand the catalytic and degradation behaviors in Zn-Air batteries. Experimental analysis and theoretical calculations reveal that the Mott–Schottky heterojunction formed by Fe3C quantum dots (QDs) and N-doped graphene carbon (Fe3C-NG) boosts the ORR, since the Fe3C quantum dots provide rapid electron transfer to the valence band of NG. Molecular dynamic simulation suggests that the graphene structure in NG is relatively stable in extremely corrosive electrolyte, which avoids the corrosion of Fe3C quantum dots. In combination of the Zn/graphene composite film and solid-state electrolyte, the optimized Zn-air battery with Fe3C-NG catalyst delivers a high open circuit voltage of 1.506 V, high energy density of 706.4 Wh kg–1, and long-term stability for 1000 h.