Photoelectrochemical Hydrogen Production Using TiO2/Mn-CdS Photoanode with ZnS Passivation and CoPi as Hole Transfer Relay

Abstract

To improve photoelectrochemical water splitting efficiency, it is crucial to simultaneously enhance light absorption, surface stability, and interfacial charge transfer. This work reports the rational design and fabrication of a multi-functional TiO2/Mn-CdS/ZnS/CoPi photoanode that integrates these critical aspects. TiO2 acts as a robust and conductive mesoporous film that absorbs UV light, while Mn-doped CdS broadens the absorption spectrum into the visible region owing to its narrower bandgap and suitable band alignment. To address the photocorrosion typically associated with CdS, a ZnS passivation is applied, offering chemical stability without impeding charge flow. Finally, cobalt phosphate is introduced as a surface catalyst to accelerate the oxygen evolution reaction, enhancing interfacial hole transfer and reducing the overpotential. This hierarchical architecture promotes synergistic interaction between each component, enabling efficient charge separation and transport. As a result, the TiO2/Mn-CdS/ZnS/CoPi photoanode achieves an enhanced photocurrent density under illumination. These results highlight the effectiveness of integrating light-harvesting, protective, and catalytic components to achieve high-performance and stable operation in PEC water splitting.