Three-way photocatalytic redox conversions: Removal of organic contaminant and Cr(VI) with concurrent H2 production achieved in aerated condition

초록

The simultaneous photocatalytic production of hydrogen (H2) and mineralization of organic contaminants is challenging due to the inherently distinct reaction requirements (anoxic vs. oxic condition). Here, we demonstrate that a hybrid Rh/SrTiO3 (RhST) photocatalyst achieves concurrent H2 production and organic contaminant mineralization in the presence of hexavalent chromium (Cr(VI)) under air-equilibrated condition. Without Cr(VI), 4-chlorophenol (4-CP) was completely degraded within 1 h, while H2 production was negligible. In contrast, the addition of Cr(VI) enabled simultaneous 4-CP degradation and H2 evolution even in oxygen-rich conditions. This unique photocatalytic behavior is attributed to an in-situ formed Cr2O3 overlayer on Rh nanoparticles on SrTiO3 via Cr(VI) reduction, which selectively allows proton permeation but blocks dissolved O2. Rotating ring-disk electrode measurements confirmed that the Cr2O3 overlayer effectively suppresses electron transfer to external electron acceptors, thereby minimizing O2 reduction. Photogenerated electrons in RhST are preferentially consumed for transforming Cr(VI) to Cr2O3 and reducing protons to H2, while the valence band holes directly oxidize 4-CP. This mechanism facilitates the three-way photocatalysis for simultaneous H2 production, Cr(VI) reduction, and 4-CP mineralization in an oxic environment. The core-shell structure of the in-situ formed Cr2O3 overlayer on Rh nanoparticles was confirmed by X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HR-TEM). This study represents a novel three-way photocatalytic redox system that enables simultaneous organic contaminant mineralization, Cr(VI) reduction, and H2 production under air-equilibrated conditions, offering a sustainable and practical solution for the fuel-recovering water treatment. © 2026 Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

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