Remarkably improved photocatalytic hydrogen evolution performance of crystalline TiO2 nanobelts hydrogenated at atmospheric pressure with the assistance of hydrogen spillover

Abstract

The unusual photocatalytic performance of hydrogenated black TiO₂ has aroused worldwide interest. However, hydrogenation of well-crystallized TiO₂ is always thought to be difficult even under rigorous conditions. In the present work, crystalline TiO₂ nanobelts were successfully hydrogenated at atmospheric pressure and middle temperature (340–700 °C) in diluted H₂ (8 vol% H₂/N₂) with the assistance of the hydrogen spillover effect by loading Pt nanoparticles onto the surface. The as-hydrogenated TiO₂ (denoted as Pt-Belt) exhibited 6–10 times higher hydrogen evolution rates than that of untreated ones. Compared with pristine TiO₂, the Inverse Fast Fourier Transform (IFFT) on the HRTEM image clearly revealed the formation of a surface disordered shell on Pt-Belt. Moreover, density functional theory (DFT) calculations also have shown that the loading of Pt nanoclusters promotes the formation of surface oxygen vacancies efficiently. The positron annihilation spectroscopy, EPR and EXAFS results indicated that the bulk phase defects in Pt-Belt decreased while the surface defects increased. It is noteworthy that the formation of surface defects and the decrease of bulk phase defects occurred simultaneously, especially at higher hydrogenation temperature. As a result, the transfer and separation of e⁻–h⁺ pairs were greatly promoted. All the characterization results accounted well for the greatly improved catalytic performance of hydrogenated black TiO₂.