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.