Boosting Hot Electron-Driven Photocatalysis through Anisotropic Plasmonic Nanoparticles with Hot Spots in Au-TiO2 Nanoarchitectures

Ana Sousa-Castillo, Miguel Comesaña-Hermo, Benito Rodríguez-González, Moisés Pérez-Lorenzo, Zhiming Wang, Xiang-Tian Kong, Alexander O. Govorov, and Miguel A. Correa-Duarte

J. Phys. Chem. C 2016, 120, 11690‒11699

The use of plasmonic metal nanoparticles as photosensitizers has undergone a strong development in the last few years given their ability to increase the activity of semiconductors into the visible and near infrared regions. The present work reports an experimental and theoretical study on the critical influence that shape anisotropy of gold nanoparticles exerts on the photocatalytic performance of Au-TiO2 nanoarchitectures. The obtained results show that for a given amount of metallic material, Au nanostars endow titania with a strongly-enhanced catalytic efficiency compared to that found in the presence of Au nanospheres or nanorods. This is ascribed to the ability of nanostars to locally create extremely large electromagnetic field enhancements around their spikes, which ensures an increased population of hot electrons close to the interface between the metal and the semiconductor. Therefore, these nanostructures exhibit a novel regime of photocatalytic activity that could be described as plasmonic hot-spot photocatalysis. Numerical simulations confirm that the hot electron injection is a feasible mechanism behind the photosensitization process and that the nanostars should have the strongest photochemical response. These results pave the way for a more rational design of the plasmonic component in the search for high-performance photocatalytic nanoreactors operating under visible and NIR light.