Synergistic surface-band engineering of Fe/CDs-g-C3N4: Balancing light absorption and redox capability for green and efficient photocatalysis of nitrobenzene

The study employed a synergistic surface-band engineering strategy to prepare a novel g-C 3 N 4 -based photocatalyst for the efficient and safe degradation of nitrobenzene (NB), a typical recalcitrant pollutant. Fe 0.010 /LCDs-TCN exhibited a higher density of active sites, a broader visible light absorption range, and a more effective separation and transfer of charge carriers. Importantly, Fe 0.010 /LCDs-TCN displayed a bandgap of 2.59 eV, with a valence band of + 2.04 eV and a conduction band of −0.55 eV. This narrowed bandgap, along with an optimized band potential, enabled the simultaneous generation of crucial active species ·OH and ·O₂⁻ from water and O₂. This mechanism skillfully balanced visible light absorption and redox capability. Regarding degradation performance, degradation rates reached up to 93 % for NB within 4 h, and 98 % for nitrophenols within only 60 min. Moreover, this system exhibited strong stability against pH variations and coexisting ions. The 5 cyclic experiments achieved high degradation efficiency of 74.3–94.7 %. The QSAR-based ECOSAR and Toxicity Estimation Software Tool (T.E.S.T.) confirmed a significant reduction in acute and chronic toxicity and mutagenicity of NB degradation system. This work offers a novel perspective on regulating g-C 3 N 4 by balancing light absorption and redox capability, providing a promising strategy for safe, efficient, and sustainable water purification technologies.