CdS Nanoparticle-Modified α-Fe₂O₃/TiO₂ Nanorod Array Photoanode for Efficient Photoelectrochemical Water Oxidation

In this work, we demonstrate a facile successive ionic layer adsorption and reaction process accompanied by hydrothermal method to synthesize CdS nanoparticle-modified α-Fe₂O₃/TiO₂ nanorod array for efficient photoelectrochemical (PEC) water oxidation. By integrating CdS/α-Fe₂O₃/TiO₂ ternary system, light absorption ability of the photoanode can be effectively improved with an obviously broadened optical-response to visible light region, greatly facilitates the separation of photogenerated carriers, giving rise to the enhancement of PEC water oxidation performance. Importantly, for the designed abnormal type-II heterostructure between Fe₂O₃/TiO₂, the conduction band position of Fe₂O₃ is higher than that of TiO₂, the photogenerated electrons from Fe₂O₃ will rapidly recombine with the photogenerated holes from TiO₂, thus leads to an efficient separation of photogenerated electrons from Fe₂O₃/holes from TiO₂ at the Fe₂O₃/TiO₂ interface, greatly improving the separation efficiency of photogenerated holes within Fe₂O₃ and enhances the photogenerated electron injection efficiency in TiO₂. Working as the photoanodes of PEC water oxidation, CdS/α-Fe₂O₃/TiO₂ heterostucture electrode exhibits improved photocurrent density of 0.62 mA cm^- 2 at 1.23 V vs. reversible hydrogen electrode (RHE) in alkaline electrolyte, with an obviously negatively shifted onset potential of 80 mV. This work provides promising methods to enhance the PEC water oxidation performance of the TiO₂-based heterostructure photoanodes.