Potassium ferrite nanosheets with tin doping for enhanced large-current-density H2 production and ultra-long life rechargeable Zn–air batteries

Abstract

Developing a high-efficiency trifunctional catalyst with superior electrochemical properties for stable Zn–air batteries and large-current-density H₂ production is of great significance. Herein, we directly introduced Sn⁴⁺ into K₂Fe₄O₇ (KFO) and synthesized self-supported nickel foam (NF)-based Sn-KFO nanosheets. Experimental results show that Sn-KFO displayed enhanced oxygen evolution reaction (OER), oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) performances compared to pure KFO. In addition, the assembled liquid Zn–air battery (ZAB) using Sn-KFO directly serving as the air-cathode showed better electrochemical activity than that assembled using bare KFO. Wherein, Sn-KFO delivered a much narrower voltage-gap (0.817 V) for more than 1000 h of continuous charging discharging at a current density of 10 mA cm⁻² and without much morphology change and electrocatalytic property decline. Further theoretical data evidence that the enhanced electrocatalytic properties of Sn-KFO are mainly due to the introduced Sn⁴⁺, which served as the most active catalytic site during the OER and HER processes. Thus, the electrochemical properties of KFO can be efficiently enhanced through Sn⁴⁺ doping. This work not only provides an efficient trifunctional catalyst, but will also be the experimental and theoretical research foundation for other Sn⁴⁺ doped materials.