Cu Atomic Subnanoclusters on TiO2 for Photocatalytic Hydrogen Evolution.

Subnanocluster (SNC) cocatalysts are considered to be promising cocatalysts for photocatalytic hydrogen evolution reaction (HER) due to their rich surface-active sites and high atom utilization efficiency. Herein, a reductant-mediated in situ growth of the atomic clusters procedure is developed to synthesize SNC-Cu serving as advanced cocatalysts on TiO₂ nanoparticles for HER. The optimized SNC-Cu/TiO₂ catalyst, with 1.8 wt % metal mass loading, exhibits a remarkable hydrogen evolution rate of 6832 μmol g^–1 h^–1, which is ca. 25-fold that of bare TiO₂ (273 μmol g^–1 h^–1 and comparable to that of 1 wt % Pt-modified TiO₂ (7754 μmol g^–1 h^–1). Meanwhile, decent photostability and recyclability are also certified via a 20 h durability test. Comprehensive electron microscopy and spectroscopy characterizations unveil that the outstanding performance of SNC-Cu/TiO₂ can be attributed to accelerated charge separation/transfer and suppressed photoinduced electron–hole recombination. Furthermore, in situ X-ray photoelectron spectroscopy and first-principle calculations reveal that the electron-localized SNC-Cu, with its abundant surface sites, facilitates *H adsorption and desorption, thus enhancing the HER activity significantly. This work highlights the promising potential of constructing noble-metal-free SNCs in semiconductors for photocatalytic HER. [ABSTRACT FROM AUTHOR]