Iron rust for efficient photocatalytic hydrogen evolution

Iron (Fe) corrosion typically results in significant damage to Fe-based devices and structures. However, the corrosion products can be repurposed as active materials in electrocatalytic and photocatalytic reactions. In this study, we have strategically induced oxygen corrosion in Fe foams to synthesize cost-effective Fe rust cocatalysts (Orthorhombic FeOOH) for enhancing the photocatalytic hydrogen evolution reaction (HER), exemplifying the concept of "turning waste into treasure". The corrosion dynamics of Fe foams reveal that the incorporation of sodium chloride (NaCl) as an electrolyte accelerates the oxygen corrosion process during the preparation of Fe rust. In a photocatalytic system sensitized by Eosin Y (EY) and driven by visible light, Fe rust derived from 14 h of oxygen corrosion on Fe Foams exhibits a remarkable initial hydrogen evolution rate of 55.8 micromol h^-1, which substantially exceeds the performance of pure EY. Additionally, an apparent quantum yield (AQY) of 22.9 % at 420 nm was recorded. The pronounced enhancement in photocatalytic activity can be attributed to the role of Fe rust in effectively inhibiting the bleaching of EY. This enhancement is strongly supported by the photoluminescence (PL) spectra and light-assisted current density-voltage (j-V) curves. Significantly, we have further refined and simplified the Stern-Volmer-Meng (SVM) curve, a model for assessing the reduction or oxidation quenching of photosensitizers, building upon our previous work.