Bulk-phase and surface dual-defective engineering enabled Ti-based nanotubes photoanode for highly efficient photoelectrochemical water splitting

Photoelectrochemical (PEC) water splitting employing Ti-based nanostructures represents a promising strategy for achieving solar-to-hydrogen (STH) conversion. Nevertheless, the process is largely hindered by intrinsic sluggish kinetics of the oxygen evolution reaction (OER) process. In this work, we fabricate a high-efficiency Vo/TiNbO photoanode by anodizing the specifically designed Ti–Nb alloys followed by one-step electrochemical reduction. It's worth noting that bulk-phase and surface dual-defective engineering involved in Ti-based nanotubes could be utilized as effective micro-reaction platform for augmented PEC water splitting. Microstructure analysis demonstrates that bulk-phase doping and surface oxygen defects lead to a negative shift of valence-conductive band edges, which increases electrical conductivity and optical absorption. An impressive STH conversion efficiency of the co-doped system could reach 1.12 %, which is 4.6 times of pristine system. Density functional theory (DFT) calculation further confirms that the synergistic dual-defective effects play a vital role in boosting OER process. With the optimization of coordination electron configuration, determining rate step (DRS) energy barrier and adsorption energy of key intermediates decrease. We hope that the rational amalgamation of bulk-phase elements doping with surface oxygen defects introduced in this work may provide insights into developing high-performance nanostructured photoanodes for driving solar water splitting.