The Contradicting Influences of Silica and Titania Supports on the Properties of Au⁰ Nanoparticles as Catalysts for Reductions by Borohydride

This study investigates the significant impact of metal–support interactions on catalytic reaction mechanisms at the interface of oxide-supported metal nanoparticles. The distinct and contrasting effects of SiO₂ and TiO₂ supports on reaction dynamics using NaBD₄ were studied and focused on the relative yields of [HD]/[H₂] and [D₂]/[H₂]. The findings show a consistent increase in HD yields with rising [BD₄⁻] concentrations. Notably, the sequence of HD yield enhancement follows the order of TiO₂-Au⁰-NPs < Au⁰-NPs < SiO₂-Au⁰-NPs. Conversely, the rate of H₂ evolution during BH₄^- hydrolysis exhibits an inverse trend, with TiO₂-Au⁰-NPs outperforming the others, followed by Au⁰-NPs and SiO₂-Au⁰-NPs, demonstrating the opposing effects exerted by the TiO₂ and SiO₂ supports on the catalytic processes. Further, the catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) confirms the catalytic mechanism, with TiO₂-Au⁰-NPs demonstrating superior activity. The catalytic activity observed aligns with the order of TiO₂-Au⁰-NPs > Au⁰-NPs > SiO₂-Au⁰-NPs, suggesting that SiO₂ donates electrons to Au⁰-NPs, while TiO₂ withdraws them. It is of interest to note that two very different processes, that clearly proceed via different mechanisms, are affected similarly by the supports. This study reveals that the choice of support material influences catalytic activity, impacting overall yield and efficiency. These findings underscore the importance of selecting appropriate support materials for tailored catalytic outcomes.