In situ Sr2+ ions diffusion synthesis SrTiO3-δ quantum dots on TiO2-δ nanorods with efficient interfacial electron transfer for deeply NO oxidation removal

Abstract

The reduction and oxidation sites on the photocatalyst surface are spatially close at the nanoscale, resulting in a high recombination rate of internal charges and surface trapped charges, limiting the practical applications of photocatalysts. This work is a first study to provide a simple technique to introduce SrTiO3 quantum dots with a size of about 1.5 nm on the surface of TiO2 nanorods by Sr2+ ion diffusion. The formation of SrTiO3 quantum dots improve photogenerated electrons and holes transfer ability of TiO2 to the reduction and oxidation sites. Additionally, the in-situ growth scheme can further reduce the donor-acceptor distance and improve electronic coupling between SrTiO3 quantum dots and TiO2. The light-absorption and photocatalytic activity of SrTiO3/TiO2 composites are further improved by introducing surface oxygen vacancies to regulate the band gap with enhancing light absorption ability and separate photo-induced electron-hole pairs. Additionally, surface oxygen vacancies can improve the molecular adsorption activation ability by changing the surface electron configuration and increasing the dangling bonds on the catalyst surface. Density functional theory calculations (DFT) confirm the coupling effect of SrTiO3-δ quantum dots and oxygen vacancies which significantly improve the composite photocatalyst capability for the adsorption-activation of O2, H2O and NO as well as to reduce the energy required for the reaction process, thus causing the enhanced generation of active species. This work promotes the application of quantum dots and oxygen vacancies in the research domain of NO removal.