Hydrothermal Synthesis of Tungsten Oxide Photo/electrocatalysts: Precursor-Driven Morphological Tailoring and Electrochemical Performance for Hydrogen Evolution and Oxygen Reduction Reaction Application

This research examines the effective use of two specific precursor i.e Hydrochloric acid and Oxalic acid used in the synthesis of Tungsten oxide (WO ₃ ). Catalytic reactions including Oxygen Reduction Reaction (ORR) and Hydrogen Evolution Reaction (HER) was investigated with the synthesised material. The morphological as well as electrochemical characteristics were studied using Field Emission Scanning Electron Microscope (FESEM), X-ray Diffraction (XRD), Energy-Dispersive X-ray spectroscopy (EDX), UV spectroscopy along with electrochemical analysis. It is being found that the WO ₃ synthesised with oxalic acid (WO ₃ -ox) demonstrated in superior HER catalysis, whereas the other variant (WO ₃ with HCl (WO ₃ -h)) showed better ORR performance. An optical bandgap of 2.638 eV was obtained for WO ₃ -ox. Moreover, electrochemical analysis revealed an ORR peak at 0.52 V for WO ₃ -h, in acidic media of electrolyte. As a result of which the two electrocatalyst were utilised in two different applications. WO ₃ -ox was used for Methylene Blue (MB) degradation under the UV light and WO ₃ -h was incorporated as a cathode catalyst for electricity generation and wastewater treatment in Microbial Fuel Cell (MFC). A degradation efficiency of 83.9% was attained in a span of 3 hours. On the other hand, MFC showed superior electrical power density of 209.72 mW/m ² with catalyst as compared to bare carbon cloth electrode (139.78 mW/m ² ). The chemical oxygen demand (COD) removal efficiency, which acts as a measure of wastewater treatment was 1.47 folds higher with the MFC having the catalyst. Thus, by tailored modulation of synthesised material with different precursor can lead to optimization of its features for various applications like degradation of methylene blue and microbial fuel cell.