Towards Environment Friendly Hydrothermally Synthesized Li, Rb, In Intercalated Phosphotungstate (PWO) Thin Films.

In the present investigation, a one-step hydrothermal approach is proposed to synthesize Li, Rb, and Inintercalated PWO (PTA) thin films. The photoelectrochemical performance of the deposited LiPWO (Li-PTA), RbPWO (Rb-PTA), and InPWO (In-PTA) photocathodes were investigated using a two-electrode cell configuration of FTO/LiPWO/(0.1 M I/I)/Graphite. The energy band gaps of 2.24, 2.11, and 2.13 eV were observed for the Li-PTA, Rb-PTA, and In-PTA films, respectively, as a function of Li, Rb, and In. The evolution of the spinal cubic crystal structure with increased crystallite size was observed for Rb intercalation within the PTA Keggin structure, which was confirmed by X-ray diffraction (XRD). Scanning electron microscopy (SEM) revealed a modification in the surface morphology from a rod-like structure to a densely packed, uniform, and interconnected microsphere to small and large-sized microspheres for Li-PTA, Rb-PTA, and In-PTA, respectively. Compositional studies confirmed that the composing elements of Li, Rb, In, P, W, and O ions are well in accordance with their arrangement for Li, Rb, In, P, W, and O valence states. Furthermore, the performance of the deposited photocathode shows power conversion efficiencies (PCE) of 1.25%, 3.03%, and 1.62%, as a function of the incorporation of Li, Rb, and In ions. This work offers a one-step hydrothermal approach that is a prominent way to develop Li, Rb, and In ions intercalated PTA, i.e., LiPWO RbPWO, and InPWO photocathodes for competent solar energy harvesting.