Isolated/interacting Au islands on TiO2 NTs for the switching photocatalytic/photoelectrocatalytic degradation of refractory organic pollutants in wastewater

Abstract

A three-dimensional surface catalyst with isolated/interacting Au islands loaded on TiO₂ nanotubes (Au/TiO₂ NTs) was prepared for the switching photocatalytic/photoelectrocatalytic (PC/PEC) degradation of refractory organic wastewater, and shows prominent catalytic activity and favorable stability. The Au islands act as “electronic reservoirs” for prolonging the lifetime of photo-generated electron–hole pairs. The fundamental structures and morphologies of the Au/TiO₂ NTs were determined by XRD, SEM, EDS, XPS and ICP-AES, and the optical properties were estimated by UV-vis DRS and photocurrent response curves. The PC/PEC switching of the Au/TiO₂ NTs was measured by the degradation of nitrobenzene solution as a refractory pollutant in water, and the results showed that the optimum Au loading for photocatalysis and photoelectrocatalysis could be easily switched to have an optimal degradation rate. We creatively proposed that the interaction between the Au nanoparticles affects the catalytic performance of the catalyst, by using isolated/interacting Au islands to regulate and enhance the PC/PEC properties of the TiO₂ NTs. The synergistic effect between the nano-tubular organized TiO₂ and the isolated/interacting Au islands promotes the separation and transfer of charges induced by Au plasma which was characterized by photocurrent responses, thus enabling the catalyst to have a commercial and stable photocatalysis/photoelectrocatalysis effect to a large extent.