Synergistic Dual‐Channel Charge Separation in Cr‐TiO _2‐x for Solar H ₂ O ₂ Synthesis

ABSTRACT

Solar‐driven hydrogen peroxide (H ₂ O ₂ ) synthesis offers a sustainable alternative to the energy‐intensive anthraquinone process, yet its efficiency is fundamentally constrained by the inability to simultaneously harness photogenerated electrons and holes in a balanced, synergistic manner. Here we report a spatially separated yet electronically coupled dual‐active‐site photocatalyst, comprising atomic chromium (Cr) and oxygen vacancies (O _Vs ) anchored on ultrathin TiO ₂ nanosheets (Cr‐TiO _2‐x ), that enables the cooperative coupling of two‐electron water oxidation (2e ⁻ WOR) and oxygen reduction (2e ⁻ ORR) in a single photocatalytic framework. In situ x‐ray absorption/emission spectroscopy and excited‐state density functional theory calculations reveal that Cr single atoms selectively accumulate photogenerated holes to drive 2e ⁻ WOR, while O _V sites trap electrons to activate O ₂ for 2e ⁻ ORR. This self‐sustaining proton‐coupled electron transfer (PCET) loop not only suppresses charge recombination but also achieves a record H ₂ O ₂ production rate of 764.9 µmol g ⁻¹  h ⁻¹ in pure water without sacrificial agents, with a solar‐to‐chemical conversion efficiency of 1.23% and an apparent quantum yield of 11.5% at 420 nm. This work establishes a blueprint for the atomic‐level design of dual‐redox photocatalysts and provides direct spectroscopic evidence of excited‐state charge partitioning, opening new avenues for efficient solar‐fuel synthesis.