3D-ordered porous CdS/AgI/ZnO nanostructures for high-performance photoelectrochemical water splitting.

3D-ordered porous CdS/AgI/ZnO nanostructures were designed to perform as high-performance photoelectrodes for photoelectrochemical (PEC) water-splitting applications. They rely on the advantages of an extremely large active surface area, high absorption capacity in the visible-light region, fast carrier separation and transportation caused by the intrinsic ladder-like band arrangement. These nanostructures were fabricated by employing a three-stage experiment in a sequence of hard mold-assisted electrochemical deposition, wet chemical method and deposition-precipitation. First, 3D-ordered ZnO nanostructures were electrochemically deposited using a polystyrene film as the sacrificed template. AgI nanoparticles were then decorated on the interfacial ZnO nanostructures by deposition-precipitation. Finally, these binary AgI/ZnO nanoporous networks were thoroughly wet-chemically coated with a CdS film to form a so-called 'ternary interfacial CdS/AgI/ZnO nanostructures'. The PEC water-splitting properties of the fabricated 3D nanostructures were systematically studied and compared. As a result, the highest efficiency of the fabricated 3D-ordered porous CdS/AgI/ZnO measured under the irradiation of solar simulation is about 5.2%, which is relatively 1.5, 3.5 and 11.3 times greater than that of the corresponding CdS/ZnO (3,4%), AgI/ZnO (1.5%) and pristine porous ZnO (0.46%) photoelectrodes, respectively. The significant improvement in the PEC activity is attributed to the enhanced charge separation and transport of ternary photoelectrodes caused by an unconventional ladder-like band arrangement formed between interfacial CdS-AgI-ZnO. Our study provides a promising strategy for developing such ternary photoelectrode generation that possesses higher stability and efficiency towards water-splitting processes.