A single-atom Fe–N₂ embedded in nitrogen-doped porous carbon as a bifunctional photocatalyst for efficient removal of marine petroleum pollutants

Petroleum and its refined products enter the marine environment during the extraction process, causing serious pollution. Herein, a bifunctional Fe–N₂ single-atom embedded in nitrogen-doped porous carbon photocatalyst (FC) was fabricated for the efficient removal of marine petroleum pollutants. The combination of highly dispersed Fe–N₂ active sites, large surface area, high porosity, and good conductivity results in excellent photocatalytic activities. The FC catalyst exhibited a 96.7% degradation rate in the oxidative removal of bisphenol A (BPA) and a 63.4% reduction of Cr(Ⅵ) within 1 ​h, whereas the reaction equilibrium rate constants of 0.0132 ​min⁻¹ and 0.0505 ​min⁻¹ were reached, respectively. FC with good stability and reusability could reach 88.3% and 53.5% removal rate of BPA and Cr(Ⅵ) after 5 cycles. Radical quenching experiments and electron spin resonance (ESR) confirmed that ·OH and e⁻ were the most driving active species for photo-oxidation and reduction, respectively. Besides, the FC catalyst was applied to an actual seawater system and the simulation results showed a good removal rate (82.7% of BPA and 50.9% of Cr(Ⅵ) within 1 ​h). The BPA oxidation pathway in the system was proposed and the toxicity of each intermediate was accessed. This work offers a new way to construct single-atom functionalized carbon-based catalysts for marine pollution control.