How Interplay between UV and Visible Activation Dictates Charge Transfer in Nanoengineered Gold Nanoparticle Interfaces at Rutile TiO₂ Polymorphism: Photocatalysis with Contrasting Results

Abstract

The TiO2 polymorph at the phase interface undergoes charge equilibration when clubbed with Au nanoparticles, which in turn influences its band alignment by shifting the Fermi level under selective UV and visible irradiation. The migration of charges to the catalyst surface and their separation plays a crucial role in maximizing the efficiency of a photocatalyst. However, the formation of multiple junctions and the presence of photogenerated charge carriers can sometimes act as a sink, negatively impacting photocatalysis. Here in, the plasmonic Au nanoparticles embedded in the rutile phase of TiO2, polytypes display two opposing tendencies in photocatalysis in response to UV and visible irradiation. A convincing explanation for this may be due to photonic alignment of band edges between the anatase and rutile interphase of TiO2 and the Au nanoparticles. The rationale behind these unusual behaviors under different irradiation sources discussed here can highlight the mechanistic route in understanding the charge transfer properties of Au on TiO2 polytypes.