Simultaneous Desalination and COD Degradation Enabled by the ZnMoS₃@ZIF-8/BVO Heterojunction Photoanode

Converting wastewater or saltwater into clean, safe, and fresh water offers a solution to the pressing global issues of water scarcity and pollution. In this work, a novel ZnMoS₃@ZIF-8/BVO composite was fabricated by successfully anchoring ZnMoS₃ nanoparticles onto a metal-organic framework (MOF) structure. With light as the driving force, the photocurrent density reached 6.01 mA/cm² (under zero bias). The salt removal rate achieved as high as 104.99 μg/(cm²·min), reducing the concentration of high-salinity water from 4276 to 72 ppm. Simultaneously, the photocatalytic degradation of chemical oxygen demand (COD) was achieved, with a degradation efficiency of 91.07%. The resulting photoelectrode synergistically enhances photoelectrochemical desalination and COD degradation, attributable to its high photoelectric conversion efficiency and optimized photocatalytic redox kinetics. This degradation performance is attributed to the synergistic effect of multiple reactive species, among which ^•OH and ^•O₂^- played a dominant role. The mechanisms of photoelectric conversion and photocatalytic degradation of the ZnMoS₃@ZIF-8/BVO photoanode in the electrochemical desalination system were investigated by SI-XPS and EPR. Furthermore, the reaction pathways of photocatalytic degradation were analyzed by ESI-MS and ATR-FTIR. This study not only concurrently accomplished the desalination of high-salinity water and the degradation of organic pollutants but also provided an efficient and feasible technical solution to solve the problems of the freshwater resource's shortage and water pollution.