Ice-Templated Synthesis of Atomic Cluster Cocatalyst with Regulable Coordination Number for Enhanced Photocatalytic Hydrogen Evolution

Supported metal catalysts have been exploited in various applications. Among them, cocatalyst supported on photocatalyst is essential for activation of photocatalysis. However, cocatalyst decoration in a controllable fashion to promote intrinsic activity remains challenging. Herein, a versatile method is developed for cocatalyst synthesis using an ice-templating (ICT) strategy, resulting in size control from single-atom (SA), and atomic clusters (AC) to nanoparticles (NP). Importantly, the coordination numbers (CN) of decorated AC cocatalysts are highly controllable, and this ICT method applies to various metals and photocatalytic substrates. Taking narrow-band gap Ga-doped La₅Ti₂Cu_0.9Ag_0.1O₇S₅ (LTCA) photocatalyst as an example, supported Ru AC/LTCA catalysts with regulable Ru CNs have been prepared, delivering significantly enhanced activities compared to Ru SA and Ru NPs supported on LTCA. Specifically, Ru_{(CN = 3.4)} AC/LTCA with an average CN of Ru─Ru bond measured to be ≈3.4 exhibits excellent photocatalytic H₂ evolution rate (578 µmol h⁻¹) under visible light irradiation. Density functional theory calculation reveals that the modeled Ru_{(CN = 3)} atomic cluster cocatalyst possesses favorable electronic properties and available active sites for the H₂ evolution reaction.