Plasmonic Au-Loaded Hierarchical Hollow Porous TiO2 Spheres: Synergistic Catalysts for Nitroaromatic Reduction.

Plasmonic Au nanoparticle (NP)-loaded hierarchical hollow porous TiO2 spheres are designed and synthesized with the purpose of enhancing the overall catalytic activity by introducing the Au plasmonic effect into the system, where Au NPs themselves are catalytically active. The constructed nanohybrid exhibits both high activity in 4-nitrophenol reduction, compared to all of the previously reported Au-based catalysts, and high selectivity. The synergy of the inherent catalytic property of Au NPs and the plasmonic effect (mainly via hot electron transfer) under irradiation is confirmed by a series of control experiments. The specifically designed, porous hollow structure also greatly contributes to the good catalytic activity because it provides a large surface area, facilitates reactant adsorption, and hinders charge recombination. In addition, theoretical calculations reveal that such a structure also leads to an increase in light absorption of about 21% in the range of 400-800 nm with respect to a uniform water-TiO2 background featuring the same filling factor. This work provides insight into the rational design of plasmon-enhanced catalysts that will show their versatility in various electro-/photocatalysis.