Boosting photocatalytic hydrogen evolution via regulating Pt chemical states

As a cocatalyst, chemical states of Pt have significant effects on hydrogen evolution activity of photocatalysts, but the effects have not been elucidated. Herein, we report an effective strategy to greatly improve hydrogen production via regulating the chemical states of Pt. A highly efficient C3N4 photocatalyst with high Pt0 proportion (denoted as 1.0%-Pt/CN-BH-H) is successfully prepared. Under visible-light condition (lambda >= 420 nm), 1.0%-Pt/ CN-BH-H (Pt0 proportion is 60.1%) affords -2.316 mmol h-1 g-1 of hydrogen, approximately four-fold higher than that obtained by a photodeposited sample 1.0%-Pt/CN-P (Pt0 proportion is 8.2%, -0.605 mmol h-1 g-1 of hydrogen). Atmospheric treatment increases the amount of Pt0 species by causing electrons transfer from N element to Pt2+ in 1.0%-Pt/CN-BH-H, as proved by in situ experimental investigation and DFT calculations. Mass formation of the Pt0 species facilitates charge separation. In addition, Pt0 has a lower hydrogen adsorption energy than that of Pt2+; therefore, photocatalysts containing Pt0 show an improved hydrogen-evolution performance.