Towards Environment Friendly Hydrothermally Synthesized Li+, Rb+, In3+ Intercalated Phosphotungstate (PW12O40) Thin Films

In the present investigation, a one-step hydrothermal approach is proposed to synthesize Li+, Rb+, and In(3+)intercalated PW12O40 (PTA) thin films. The photoelectrochemical performance of the deposited Li3PW12O40 (Li-PTA), Rb3PW12O40 (Rb-PTA), and In3PW12O40 (In-PTA) photocathodes were investigated using a two-electrode cell configuration of FTO/Li3PW12O40/(0.1 M I-/I3-)(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 In3+. 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+, In3+, P5+, W6+, and O2- 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 In3+ ions. This work offers a one-step hydrothermal approach that is a prominent way to develop Li+, Rb+, and In3+ ions intercalated PTA, i.e., Li3PW12O40, Rb3PW12O40, and In3PW12O40 photocathodes for competent solar energy harvesting.

Automated summary

A one-step hydrothermal approach was used to synthesize Li+, Rb+, and In3+ intercalated PTA thin films. The Li-PTA, Rb-PTA, and In-PTA photocathodes showed good photoelectrochemical performance in a two-electrode cell configuration. The incorporation of Rb+ into the PTA Keggin structure resulted in an increase in crystallite size and a change in surface morphology.