Electrochemical Performance of Pt-Modified Mn3O4 Electrodes for Chlorine Evolution

Electrochemical chlorine production is of considerable industrial importance in areas such as water treatment, chemical manufacturing, and disinfection. However, conventional precious metal-based dimensionally stable anodes (DSAs), such as RuO2- and IrO2-based systems, are limited by high cost and resource constraints, motivating the development of low-cost alternative catalysts. In this study, Mn3O4 electrodes with controllable defect characteristics were fabricated by electrochemical deposition under various processing conditions. The effects of defect modulation and surface modification on the structural, electronic, and electrochemical properties of the electrodes were systematically evaluated. X-ray diffraction analysis confirmed that all deposited films retained a stable tetragonal Mn3O4 crystal structure, indicating that the deposition parameters primarily influenced defect states rather than the bulk phase. Mott–Schottky measurements revealed that the Mn3O4 electrodes exhibited p-type semiconducting behavior, with charge carrier densities on the order of 1014 cm−3, suggesting that oxygen vacancy-related defect states may contribute to the observed electronic properties of the electrodes. To further enhance anodic performance, Pt was introduced onto the Mn3O4 surface via sputtering, resulting in significantly improved charge transfer characteristics. Electrochemical measurements demonstrated that the best performing Pt/Mn3O4 electrodes delivered a current density exceeding 100 mA cm−2 at an applied potential of 1.5 V versus Ag/AgCl. More importantly, defect-enriched Pt/Mn3O4 electrodes exhibited markedly enhanced chlorine evolution activity, with the chlorine production rate increasing from approximately 14 µmol cm−2 to 29 µmol cm−2, corresponding to an enhancement of about 2.07-fold. Faradaic efficiency analysis further showed that sample (g) and sample (n) achieved chlorine evolution efficiencies of 59.2% and 74.6%, respectively, indicating a higher tendency toward chlorine evolution for the Pt-modified electrodes under the tested conditions. These findings suggest that the synergistic combination of defect engineering and surface modification effectively modulates the electronic structure of Mn3O4, providing a viable strategy for improving chlorine evolution performance.