Optimization and comparative analysis of Cs ion intercalated H₃PMO₁₂O₄₀ photocathode: one-step hydrothermal strategy

The current study focused on fabrication of phosphomolybdic acid (H₃PMo₁₂O₄₀) (PMA) and cesium intercalated phosphomolybdic acid (Cs₃PMo₁₂O₄₀) (Cs-PMA) thin films via simplistic and low-cost hydrothermal reaction. We explored comparative analysis of PMA and Cs⁺ intercalated PMA for their optoelectronic and photoelectrochemical properties. UV–Visible absorption study demonstrates the decrement in band gap energy from 2.37 to 2.22 eV, forming a well-grown cubic crystal structure with alteration in the surface morphology. XPS analysis validates the presence of Cs, P, Mo, and O in its valence states of +1, +5, +6, and − 2, respectively. The p-type semiconducting nature of Cs₃PMo₁₂O₄₀ films was confirmed by thermoelectric measurement. The photoelectrochemical solar cell exhibited a conversion efficiency (η) of 0.21 and 0.82% for PMA and Cs-PMA photocathode, respectively. The photoelectrochemical performance of PMA and Cs-PMA photocathodes was thoroughly described using Nyquist plots and a circuit model of the electron impedance spectra. The enhancement in the conversion efficiency is attributed to compact nanospheres like microstructures with improved crystallinity as well as optimal band gap energy of Cs-PMA photocathode.