Interfacial Metal Nanocluster Conduits Direct Charge Transfer for Record Unassisted Solar Water Splitting

Photoelectrochemical (PEC) water splitting offers one of the most promising solutions for sustainable solar-to-chemical fuel conversion. However, sluggish charge migration across the photoelectrode interface fundamentally limits the PEC efficiency. Herein, we design and engineer an atomic-scale interfacial charge conduit by inserting metal nanoclusters between the cocatalyst and semiconductor. The distinct work-function differences among the cocatalyst, metal nanoclusters, and semiconductor induce interfacial band bending, enabling the selective, directional transport of photogenerated carriers from the semiconductor to the cocatalyst. Particularly, bismuth (Bi) nanoclusters synthesized through a universal laser-induced <i>in situ</i> growth strategy on 29 distinct bismuth-based semiconductors induce the formation of metal/semiconductor Schottky junctions and directionally steer electron migration into the semiconductor conduction band while effectively suppressing electron-hole recombination. Benefiting from the Bi nanoclusters and CoFe cocatalyst, the large-area (3 × 3 cm²) earth-abundant CoFe/Bi/BiVO₄ photoanode achieves a photocurrent of 26 mA at 1.1 V versus RHE, maintaining stable performance for 600 h. For practical application, an all-oxide-semiconductor tandem PEC device combining a CoFe/Bi/BiVO₄ photoanode and a Pt/TiO₂/Ga₂O₃/Cu₂O/CuO photocathode records an unassisted 4.8% solar-to-hydrogen conversion efficiency under AM 1.5G light illumination for 70 h. This work demonstrates the atomic-scale engineering of interfacial charge conduits for high-efficiency solar energy conversion.