Solar-Driven Cu(II)–Cu(III) Redox Cycle on Decahedral BiVO4 for Scalable Water Purification

Abstract Conventional Fenton-like reactions rely on external oxidants to generate reactive oxygen species (ROS, e.g., high-valent metal-oxo species (HVMS)), a practice that is inherently unsustainable for water purification. Here, we propose a solar-driven Cu(II)–Cu(III) redox cycle that differs from the traditional view that HVMS generation originates from peroxide-mediated pathways. By tuning the anisotropic built-in field of decahedral BiVO4, photogenerated holes accumulate selectively on its {110} family, enabling hole-driven hydrated Cu(II) oxidation instead of water. This facilitates an oxygen atom transfer (OAT) from adjacent Bi–OH sites to the H-bonded Cu(II) center, stabilizing the Cu(III)-oxo center by forming the Bi–O–Cu(III)–O structure (Cu(III)). Meanwhile, electron-driven dissolved oxygen reduction maintains charge balance. The photosynthetic Cu(III) mediates antibiotic degradation with a rate constant of 0.174 min–1, representing a ∼16-fold enhancement in the degradation rate constant compared to traditional photocatalysis. Crucially, the solar BiVO4 sheet/Cu(II) system sustains consistent up to ∼85% moxifloxacin degradation efficiency in each cycle over 35 days. No total Cu was detected in the effluent of cycling experiments after pH adjustment (∼7.5). These findings provide a new solution to the long-standing challenge of achieving peroxide-free HVMS synthesis and scalable water purification.