All-electrochemical fabrication of -Fe₂O₃nanotube array/Cu₂O composites toward visible-light-responsive photocatalysis

Composites of anodized hematite (-Fe2O3) nanotube (FNT) arrays and Cu2O nanoparticles (CNPs) were fabricated using all-electrochemical processes. Two-step anodized iron foils with ethylene-glycol-based electrolyte containing ammonium fluoride show hematite-rich phase after post-annealing in oxygen atmosphere. P-type CNPs with an average diameter of 200 nm were deposited uniformly onto the FNT surface by pulse electrodeposition. The enhancement of hydroxyl radical formation in water for the FNT/CNP composite under visible light (VIS) irradiation was verified by photoluminescence technique using terephthalic acid, suggesting that co-catalyst CNPs on FNT arrays may promote photo-generated hole-electron separation and successive water oxidation on FNT surfaces. Furthermore, hydrogen generation from gas phase photocatalytic decomposition of water/methanol mixture over FNT/CNP was clearly confirmed under VIS irradiation, while H2 was not detected with only FNT and only CNP. This study indicates that electrodeposited CNPs can work as noble-metal-free co-catalysts for VIS responsive photocatalysis based on anodized FNT arrays.