Cu2O/CuO functionalization of TiO2 nanotubes for enhanced Photoelectrochemical hydrogen generation

Developing efficient and stable photoelectrodes for solar-driven hydrogen generation remains a major challenge. Here, Ti-xCu (0–8 wt%) alloys were synthesized and anodized to form Cu 2 O/CuO-functionalized TiO 2 nanotube arrays. Structural and spectroscopic analyses confirmed the coexistence of Cu + and Cu 2+ species, which establish a mixed p-n heterojunction with TiO 2 . Among the prepared samples, Ti 6Cu exhibited the highest photoelectrochemical (PEC) activity, delivering a photocurrent density of 4.28 mA/cm 2 at 1.23 V vs. RHE, which is approximately 18 times higher than that of pristine TiO 2 nanotubes. Electrochemical impedance spectroscopy (EIS) indicated reduced charge-transfer resistance and improved carrier separation. Complementary DFT + U calculations revealed that Cu-oxide modification substantially lowers the hydrogen adsorption free energy, enabling more favorable H₂ evolution kinetics. The synergistic interaction of Cu 2 O and CuO enhances directional charge migration while suppressing recombination, yielding a noble-metal-free photoelectrode with superior PEC performance. These findings highlight Cu-oxide-modified TiO 2 nanotubes as a promising platform for scalable and cost-effective solar hydrogen production.