Hydrothermal synthesis of tungsten oxide photo/electrocatalysts: precursor-driven morphological tailoring and electrochemical performance for hydrogen evolution and oxygen reduction reaction application.

A hydrothermal approach was adopted to synthesize tungsten oxide (WO) nanocatalysts with tailored morphology, using oxalic acid (HCO) and hydrochloric acid (HCl) as precursors. This precursor-driven method yielded two distinct WO catalysts with unique structural and functional properties, viz. rod-shaped WO-ox and nanoflower-shaped WO-h. Characterization by FESEM and XRD revealed variations in morphology and crystallite size, contributing to their specialized catalytic applications. UV-Vis spectroscopy confirmed strong UV absorption by WO-ox at 283.57 nm with an optical band gap of 2.86 eV, making it ideal for photocatalytic activities. Electrochemical analysis demonstrated that WO-ox effectively drives the hydrogen evolution reaction (HER), while WO-h is more suitable for the oxygen reduction reaction (ORR), an essential process in microbial fuel cells (MFCs). In practical applications, WO-ox achieved an 83.9% degradation efficiency of methylene blue (MB) within 3 h, validating its high photocatalytic efficacy for wastewater treatment. Meanwhile, WO-h, utilized as a cathode catalyst in MFCs, significantly enhanced system performance, elevating chemical oxygen demand (COD) removal efficiency to 78.7% and improving coulombic efficiency by 3%. These findings underscore the potential of precursor-driven hydrothermal synthesis for optimizing WO catalysts tailored for energy and environmental applications, specifically in hydrogen production and sustainable wastewater treatment systems.