Low-Spin W^III-Triggered Triplet Spin-Polarized Electron Delocalization of Tungsten Oxide for Photocatalytic Reduction of Uranium

Solar-light-driven photocatalysis is a green and efficient technology to immobilize high-toxic and radioactive uranium (U). However, a great challenge is to develop photocatalysts with simultaneous elevated conduction band (CB) potential and rapid charge carrier separation rate. Herein, spin-state engineering in d⁰ WO₃ through (110) facet-confined oxygen vacancies (OVs) is proposed. Anchoring OVs at the symmetry-broken (110) facets induces low-spin W^III (d³) generation, delocalizing CB electrons and elevating CB by -0.86 V versus NHE due to higher electron occupancy in π antibonding orbitals. Density functional theory (DFT) calculations combined with femtosecond transient absorption spectroscopy (fs-TAS) reveal that triplet (T)-dominated spin-polarized electron delocalization significantly disrupts the charge carrier recombination pathway. Experiments and theoretical calculations confirm the enhanced interfacial charge transfer via O bridging between W 5d and U 5f provides a W 5d → U 5f directional electron transfer channel. Thus, the developed (110)-WO_2.35 achieves high photocatalytic activity for U(VI) removal from water under simulated solar light, with a reduction efficiency of 98.0% (C₀ = 10 mg L^-1) and a reaction rate constant (k₁) of 0.022 min^-1, which is 4.1 times higher than the conventional WO₃. This work pioneers atomic-scale spin-orbital synergy in d⁰ photocatalysis, offering a novel strategy for radionuclide remediation.