Mechanism of high PEC performance of B-doped TiO2 nanotube arrays: Highly reactive surface defects and lattice stress

Abstract

The role of the boron (B) doping induced defect state in the PEC process is still unclear though B doped TiO2 nanotube arrays (TNAs) via anodic oxidation has commonly used to improve the photocatalytic decomposition of water by TNAs. Therefore, this work aims to establish the underlying reasons for the high PEC reactivity and stability maintained by the B doping induced defective states. Special attention is paid to the differences in carrier behavior and surface reactivity in the PEC process between the B doped induced and NaBH4 treatment induced defective states. DFT calculations show that B doping can effectively reduce the generation energy of Ti3+/Vo (oxygen vacancies) pairs and enhance the adsorption energy of defects on the surface of TiO2 (101) for H2O and ·OH. Moreover, due to the presence of B atoms, the surface defects of TiO2 can maintain high adsorption of H2O and ·OH, without being deactivated by the healing of oxygen vacancies, which ensures the stability and activity of the catalyst. Meanwhile, the lattice stress induced by B doping forms the internal electric field, which ensures the efficient separation of carriers in the bulk phase and avoids the negative effect of bulk phase defects on carrier separation.