TiO₂ nanorod/nanotube interface reconstruction and synergistic role of oxygen vacancies and gold in H–Au–TiO₂ NR/NT for photoelectrochemical bacterial inactivation and water splitting

Photoelectrochemical (PEC) water splitting by semiconductor photoanodes is limited by sluggish water oxidation kinetics coupled with serious charge recombinations. In this paper, an effective strategy of TiO₂ nanorod/nanotube nanostructured interface reconstruction, oxygen vacancies and surface modification were employed for stability and efficient charge transport in the photoanodes. Successive anodization and hydrothermal routes were adopted for the TiO₂ NR/NT photoanodes interface reconstruction, followed by Au nanoparticles/clusters (Au NP) loading and hydrogen treatment. This resulted in H–Au–TiO₂ NR/NT photoanodes. A three-dimensional structure of TiO₂ NR on TiO₂ NT/Ti foil nanotubes achieved the highest photocurrent density (1.42 mA cm⁻² at 0.3 V vs. Ag/AgCl). The optimal oxygen vacancies and Au NP loading on TiO₂ NR/NT exhibited 1.62 mA cm⁻² photocurrent density at 0.3 V vs. Ag/AgCl in H–Au–TiO₂ NR/NT photoelectrode, which is eight times higher than the TiO₂ NT/Ti foil. TRPL analyses confirm the hydrogen treatments to TiO₂ exhibited the emission lifetime (46 ns) in the H–Au–TiO₂ NR/NT photoanodes due to newly formed lower Ti³⁺-related trapped electron states and Au NP. The optimum H–Au (4)–TiO₂ NR/NT photoanodes achieved 95% photoelectrochemical (PEC) bacterial inactivation and effective PEC water splitting with (278 and 135.4) μmol of hydrogen and oxygen generation, respectively. In this study, oxygen vacancies combined with gold particles and interface reconstruction provide an innovative way to design effective photoelectrodes.