Gradually changing the fraction of clusters and nanoparticles in Au13/WO3-derived photocatalysts for H2O2 synthesis

Abstract

Atomically-precise ligand-protected gold (Au) clusters have emerged as a promising co-catalyst in a wide range of reactions. It is known that the Au cocatalyst size plays a defining role in photocatalytic performance. However, Au size effects have not been fully established for the size transition from clusters (<2.2 nm) to nanoparticles (>2.2 nm) in photocatalytic hydrogen peroxide (H₂O₂) synthesis. Using the [Au₁₃(dppe)₅Cl₂]Cl₃ cluster (Au₁₃ for convenience) as a cocatalyst deposited onto WO₃, we investigated the effects of Au size and the fraction of clusters and nanoparticles on the photocatalytic activity in H₂O₂ synthesis by gradually changing the calcination temperature. Increasing the calcination temperature gradually increases the Au size and the fraction of aggregated species (nanoparticles). Uncalcined Au₁₃/WO₃ (all cluster species) is photocatalytically inactive. The Au₁₃/WO₃-derived photocatalysts only exhibit photoactivity in H₂O₂ production after calcination with increasing activity as the Au size and the fraction of nanoparticles increase. The high activity of calcined Au₁₃/WO₃ is attributed to the formation of a strong metal–support interaction that promotes charge separation and transfer, together with the formation of larger Au particles. Calcined Au₁₃/WO₃ (all nanoparticles) at 200 °C exhibits the highest H₂O₂ production yield (2.1 mM) and rate (21 mM g⁻¹ h⁻¹) with an apparent quantum yield of 1.27% under violet (∼405 nm) light irradiation. This work unravels the effects of Au cocatalyst size, the fraction of clusters and nanoparticles, and calcination temperature on the activity of Au₁₃/WO₃-derived photocatalysts in H₂O₂ synthesis.