Fe2+/Fe3+ Cycling for Coupling Self-Powered Hydrogen Evolution and Preparation of Electrode Catalysts

A novel Zn-Fe flow battery featuring an Fe3+ reduction reaction (Fe3+RR)-coupled zinc oxidation, and an Fe2+ oxidation reaction (Fe2+OR)-coupled hydrogen evolution reaction (HER) system as well, was established. This battery is capable of driving two Fe2+OR-coupled HER systems in series based on the above Fe2+/Fe3+ cycling, for efficient self-powered hydrogen evolution. Meanwhile, this Fe2+/Fe3+ cycling enables the preparation of a multifunctional catalyst, Pt-3@SXNS (siloxene nanosheet), by the Fe2+OR-promoted dispersion of Pt nanoparticles on SXNS; alternatively, this support could be obtained by Fe3+RR-assisted exfoliation using Fe3+ from the anolyte of Fe2+OR-coupled HER. The Pt-3@SXNS catalyst exhibits excellent catalytic activities toward Fe3+RR in the Zn-Fe flow battery, HER, and Fe2+OR in the electrolyzer, which is attributed to the strong electronic interaction between Pt and Si. This work offers a new strategy for energy storage and low-cost hydrogen production from acidic wastewater.