Construction of Ho2O3-modified TiO2 nanotube array photoanodes for efficient photoelectrochemical water splitting

Photoelectrochemical water splitting is considered one of the key pathways for efficiently converting solar energy into hydrogen energy. This study employed electrochemical anodization to fabricate ordered TiO2 nanotube arrays (TNTAs), followed by in situ loading of Ho2O3 nanoparticles onto their surfaces via impregnation-annealing, forming Ho2O3/TNTAs nanocomposite photoanodes. The 4f state of Ho3+ introduces localized energy levels within the TiO2 band gap. It hybridizes with Ti 3d and O 2p orbitals, thereby achieving bandgap tuning, promoting rapid migration of photogenerated electrons at the heterojunction interface, and suppressing e–/h+ recombination. The optimized Ho2O3/TNTAs photoanode achieves a photocurrent density of 1.73 mA/cm2, significantly higher than that of pure TNTAs. During a 3-hour photocatalytic hydrogen production experiment under constant bias, the cumulative hydrogen yield of Ho2O3/TNTAs reaches 61.37 μmol/(cm2·h), approximately 6.19 times that of TNTAs. In summary, Ho2O3-modified TiO2 nanotube arrays demonstrate outstanding photocatalytic conversion and hydrogen evolution performance in photocatalytic water splitting for hydrogen production, providing a viable strategy for constructing efficient Photoelectrochemical (PEC) photoanodes based on rare-earth oxide-modified TiO2.