Light-induced surface defects in anodic TiO2 nanotubes as trapping centers for single Pt atoms, a co-catalyst for enhanced photocatalytic hydrogen evolution

Abstract

The utilization of metal co-catalysts in a single atom (SA) form has garnered significant attention due to their potential in maximizing atomic metal efficiency when developing high-performance photocatalysts for the hydrogen evolution reaction (HER). However, anchoring isolated atoms to the support without aggregation is challenging. Herein, we demonstrate that the amorphous nature of TiO₂ nanotubes enables the formation of air-stable light-induced surface Ti³⁺–V_O defects, facilitating reactive Pt SAs deposition through galvanic replacement reaction in diluted Pt-precursor solutions. In particular, the TNT/Pt SA sample that exhibited the highest photocatalytic H₂ generation activity has been obtained by immersing defective TNT arrays in a 1200 μM of H₂PtCl₆ solution for 30 seconds. Upon crystallization, these TiO₂ nanotubes with surface-anchored Pt SA and few-atom clusters (TNT/Pt1200) reached hydrogen production up to ∼6440 μl cm⁻² after 6 h. This corresponds to a hydrogen production rate of 47.8 μmol h⁻¹ cm⁻² for TNT/Pt1200, which is 126 times higher than for the unmodified TNT. Furthermore, our research indicates that titania nanotubes loaded with metal in a single atom and clusters form exhibit exceptional photoelectrochemical (PEC) activity toward water splitting. Thus, the approach presented in this work paves the way for designing advanced materials with outstanding photocatalytic and photoelectrochemical properties.