Accelerating Small Electron Polaron Dissociation and Hole Transfer at Solid–Liquid Interface for Enhanced Heterogeneous Photoreaction

In a photocatalysis process, quick charge recombination induced by small electron polarons in a photocatalyst and sluggish kinetics of hole transfer at the solid-liquid interface have greatly limited photocatalytic efficiency. Herein, we demonstrate hydrated transition metal ions as mediators that can simultaneously accelerate small electron polaron dissociation (via metal ion reduction) and hole transfer (through high-valence metal production) at the solid-liquid interface for improved photocatalytic pollutant degradation. Fe³⁺, by virtue of its excellent redox ability as a homogeneous mediator, enables the BiVO₄ photocatalyst to achieve drastically increased photocatalytic degradation performance, up to 684 times that without Fe³⁺. The enhanced performance results from Fe(IV) species production (via Fe³⁺ oxidation) induced by dissociation of small electron polarons (via Fe³⁺ reduction), featuring an extremely low kinetic barrier (5.4 kJ mol^-1) for oxygen atom transfer thanks to the donor-acceptor orbital interaction between Fe(IV) and organic pollutants. This work constructs a high-efficiency artificial photosynthetic system through synergistically eliminating electron localization and breaking hole transfer limitation at the solid-liquid interface for constructing high-efficiency artificial photosynthetic systems.