Towards Environment Friendly Hydrothermally Synthesized Li(+), Rb(+), In(3+) Intercalated Phosphotungstate (PW(12)O(40)) Thin Films

In the present investigation, a one-step hydrothermal approach is proposed to synthesize Li(+), Rb(+), and In(3+)intercalated PW(12)O(40) (PTA) thin films. The photoelectrochemical performance of the deposited Li(3)PW(12)O(40) (Li−PTA), Rb(3)PW(12)O(40) (Rb−PTA), and In(3)PW(12)O(40) (In−PTA) photocathodes were investigated using a two-electrode cell configuration of FTO/Li(3)PW(12)O(40)/(0.1 M I(−)/I(3−))(aq.)/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(3+). 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(3+), P(5+), W(6+), and O(2−) valence states. Furthermore, the J-V 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(3+) ions. This work offers a one-step hydrothermal approach that is a prominent way to develop Li(+), Rb(+), and In(3+) ions intercalated PTA, i.e., Li(3)PW(12)O(40,) Rb(3)PW(12)O(40), and In(3)PW(12)O(40) photocathodes for competent solar energy harvesting.