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

Developing a high-efficiency trifunctional catalyst with superior electrochemical properties for stable Zn-air batteries and large-current-density H-2 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.