Synergistic photocatalysis for naphthalene (NAP) removal in seawater by S-scheme heterojunction Bi2S3/CeVO4: Mechanistic investigation and degradation pathways

The construction of S-scheme heterostructure is a prospective strategy to remove polycyclic aromatic hydrocarbons (PAHs) from simulated seawater. In this study, a novel Bi2S3/CeVO4 S-scheme heterojunction photocatalyst was prepared by solvent thermal method. The successful construction of S-scheme heterostructure is beneficial to the separation and migration of photogenerated carriers, thus achieving excellent redox capacity and efficient production of free radicals, which is conducive to promoting the photocatalyst to transform pollutants into H2O, CO2. In pure water, the optimized Bi2S3/CeVO4 heterojunction (Bi/Ce-30) achieved a high degradation efficiency (97.39 %) for naphthalene (NAP). In simulated seawater, the degradation efficiency of NAP still reaches 87.20 % (k = 0.01653 min−1), which is 7.58 folds higher than pure CeVO4. Furthermore, the effect (such as solution pH, pollutant concentration, etc.) on the photocatalytic performance of Bi2S3/CeVO4 heterojunction was investigated. The possible photocatalytic degradation processes of NAP were qualitatively analyzed using 3D fluorescence spectroscopy and HPLC-MS to reveal the major degradation pathways. In addition, toxicity assessment software was used to demonstrate the gradual decrease in toxicity of the intermediate products. Furthermore, we elucidated the possible photocatalytic mechanism of Bi2S3/CeVO4 S-scheme heterojunction for the degradation of NAP. This work provides new insights into the realization of S-scheme heterojunction for removing polycyclic aromatic hydrocarbons from natural seawater.