Photocatalytic oxidation of high concentration NO over SnS₂/g-C₃N₄: A mechanistic study

This study aims to enhance the photocatalytic performance of 2D/2D heterojunctions for NO removal from marine vessel effluents. SnS₂/g-C₃N₄ composites were successfully constructed via a facile solvothermal method, demonstrating a significant improvement in photocatalytic NO removal under visible light irradiation. For high-flux simulated flue gas, the composite with 10% SnS₂ (denoted as SNCN-10) showed exceptional NO removal efficiency, reaching up to 66.8%, along with excellent reusability over five consecutive cycles. Detailed band structure and density of states (DOS) calculations confirmed the formation of a characteristic heterojunction. Spin-trapping ESR spectroscopy identified ·O₂ ⁻ as the key reactive species driving NO oxidation. Additionally, in situ DRIFT spectroscopy revealed that SNCN-10 facilitated the conversion of NO to nitrate through intermediate species, including bridging nitrite and cis-nitrite (N₂O₂ ²⁻). Kinetic studies further indicated that NO oxidation followed the Langmuir-Hinshelwood (L-H) mechanism. Based on density functional theory (DFT) calculations of free energy changes, a comprehensive reaction pathway for NO oxidation was proposed. These findings provide valuable insights for the development of efficient photocatalytic strategies for NO removal.