Enabling Bidirectional Electron Supply by Interlayer-Loaded Co3(PO4)2 on Layered g-C3N4 to Enhance Co2+ Regeneration for Boosted Peroxymonosulfate Activation

Abstract

The slow Co2+ regeneration and low photogenerated electron utilization efficiency in conventional surface-loaded composite systems severely limit the practical application of Co-based peroxymonosulfate activation for organic pollution degradation. Herein, cobalt phosphate (Co3(PO4)2) is anchored in the interlayers of layer-stacked g-C3N4 to realize the unique bidirectional electron supply. Experimental and theoretical investigations reveal that the interlayer-loaded structure enables Co3(PO4)2 to simultaneously accept photogenerated electrons from adjacent layers of layer-stacked g-C3N4, doubling electron supply channels and reducing electron recombination loss. Simultaneously, Co is positioned closer to the bottom of the conduction band of layer-stacked g-C3N4, enhancing its ability to accept photogenerated electrons, thus significantly accelerating the Co2+/Co3+ redox cycle. The optimal catalyst achieves 100% chloroquine phosphate degradation within 15 min (k = 0.35 min–1, 2.5 times higher than that of the surface-loaded control sample) with ultralow Co leaching (0.49 μg/L after 100 h of operation). This study clarifies the enhancement mechanism of interlayer spatial structure on electron supply efficiency, providing a novel strategy for designing high-efficiency Co-based peroxymonosulfate activation catalysts from the perspective of spatial structure regulation.