Optimization of semiconductor–electrolyte interfacial phenomena for stable and efficient photoelectrochemical water oxidation behavior of Bi2Mo2O9–Bi2MoO6 heterojunction

Abstract

Bismuth molybdates are considered the essential photocatalysts due to their mesoporous structure, low energy gap, suitable ion conductions, acousto-optics, photo-conduction, and sensing properties. The present report describes a cost-effective route for developing stable and efficient photocatalysts for optical to chemical energy conversion and environmental purification. In this work, we have developed nano-structured mixed bismuth molybdates with different thicknesses in the presence of TX-100 as the surfactant through drop-cast route taking bismuth nitrate and ammonium molybdate as the precursors. Final products were subsequently dried and annealed in air at 600 °C for 3 h. The semiconductors’ photoelectrochemical performance was measured under periodic illumination in the presence of Na2SO4 (0.1 M) solution and (0.1 M) Na2SO3 with 0.1 M Na2SO4 for water and sacrificial oxidation, respectively. These materials exhibit noticeable photocatalytic activity even after successive runs, indicating stable behavior. The materials are composed of Bi2Mo2O9–Bi2MoO6 heterostructures and the film with optimized thickness yields a photocurrent of 220 µA/cm2 at 1.3 V. This value is exceptionally higher in magnitude than the literature reports employing conventionally prepared bismuth molybdates (1.8 µA/cm2). Electrochemical impedance and photocurrent action spectra support a noticeable photon to current conversion efficiencies of the materials under illumination.