A BIFUNCTIONAL PHOTOELECTROCHEMICAL PLATFORM FOR CONCURRENT H2 EVOLUTION AND SULFATE OXIDATION USING MoSX AND WO3 ELECTRODES

Among recently explored electrocatalytic materials, molybdenum sulfide (MoSx) has emerged as a promising cathode material for electrochemical hydrogen production [1]. In particular, the edge sites of molybdenum disulfide (MoS2) are widely recognized as the active centers for the Volmer step of the H2 evolution reaction (HER) [2]. At the same time, the development of efficient and sustainable electrochemical systems capable of coupling hydrogen generation with production of strong oxidants has attracted increasing attention for both energy conversion and environmental applications. In this work, a bifunctional photoelectrochemical system was developed employing MoSx as the HER cathode and WO3 as the photoanode for the generation of reactive sulfur species. The MoSx electrode exhibited catalytic activity toward HER, while the WO3/FTO photoanode promoted anodic oxidation reactions leading to the formation of persulfate (S2O82-). MoSx electrodes were synthesized hydrothermally on Ti foil at 200–220 °C using ascorbic acid as a green reducing agent, at different synthesis durations. Meanwhile, WO3 films were hydrothermally deposited on FTO substrates at 160 °C. The electrochemical performance of the prepared MoSx electrodes was first evaluated in 0.1 M H2SO4 electrolyte by Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS), and Linear Sweep Voltammetry (LSV) (Fig. 1). Subsequently, the WO3 and MoSx electrodes were assembled into a two-electrode photoelectrochemical cell, serving as photoanode and cathode, respectively. During operation, the WO₃ photoanode was continuously illuminated to enhance the generation of S2O82-. Simultaneous H2 evolution at the cathode and persulfate formation at the anode were monitored under an applied bias of 1.4 V. The concentration of H2 measured by H2 sensor, while amount of generated S2O82- was determined by redox titration with FeCl2 and K2Cr2O7. Preliminary results demonstrate a synergistic coupling between cathodic HER and anodic sulfur oxidation, enabling the simultaneous production of hydrogen fuel and value-added sulfur oxidants. The influence of MoSx synthesis conditions and operational parameters, including electrolyte concentration, on product distribution and Faradaic efficiency was investigated. After 2 h of photoelectrochemical reaction, the concentration of generated H2 reached 40–60 µmol L-1, while the Faradaic efficiency toward S2O82- formation reached 35–60%. Overall, this work presents a novel integrated electrochemical approach for the coupled generation of H2 and reactive sulfur species, contributing to the development of sustainable solar-to-X technologies.