Gold-Enriched titania nanotubes via layered film anodization: Optimized annealing for photoelectrochemical efficiency

• Semitransparent Au-TiO 2 nanotubes via anodization + air/H 2 calcination. • Air-annealed samples achieved 2.7 mA/cm 2 at + 1.0 V (OER) • H 2 -annealed samples exhibited 640 µA/cm 2 at + 0.47 V (photoactivity) • IPCE up to 7.9 % for hydrogenated electrode outperforming bare TiO 2 (5.9 %) We present semitransparent electrodes fabricated by anodizing a thin film formed from alternating layers of sputtered titanium and co-sputtered titanium-gold, with varying Au content in each sample, resulting in formation of aligned oxide nanotubes. As-anodized materials were annealed under two distinct conditions: air and hydrogen atmosphere. Raman spectra obtained for prepared materials confirm the presence of anatase phase, while UV–vis spectra also reveal that the absorption band is shifted towards visible range beyond 400 nm. Furthermore, a reduction in energy band-gap is observed in comparison to bare titania materials for both annealing conditions. Air-annealed samples demonstrate improved anodic current densities, particularly favoring oxygen evolution reactions up to 2.7 mA cm −2 at + 1.0 V vs. Ag/AgCl/0.1 M KCl for sample with 2.35 at.% Au content. In contrast, among hydrogen-annealed materials, sample with 0.96 at.% Au content exhibits the highest photoactivity, achieving a photocurrent density of 640 µA cm −2 at + 0.5 V vs. Ag/AgCl/0.1 M KCl, substantially greater than that of bare titania reference material. Moreover, incident photon-to-electron conversion efficiency for this sample reaches approximately 7.9 %, compared to a peak value of 5.9 % for hydrogenated bare titania. These results highlight the potential of semitransparent electrode materials for advanced photoelectrochemical applications.