Choose Your Dopant─Ultrananotitania Directing Photocatalytic Electron Destination

Anatase titania photocatalysts are the subject of thousands of papers annually. Since the photoefficiency is low, doping TiO₂ photocatalysts with various elements is a widely employed technique to enhance performance. However, studies involving different catalyst sizes, morphologies, or dopants often yield varied or even contradictory conclusions. Herein, we report a versatile platform based on ultranano, <2 nm, particles, that minimizes defects, produces uniform morphology, and enables systematic investigation of dopant control of product formation. Charge-carrier destination is determined by the redox couple in the oxide matrix; a couple that is measured by diffuse reflectance spectroscopy. Versatility is demonstrated via doping with all fourth-period transition elements (except Sc). For oxidation reactions, two distinct reaction pathways are identified; the balance between the pathways is regulated by the reduction potential of the dopant in the matrix. The prospect for directing charge transfer significantly expands potential applications for titania.