Architecting an ‘electron highway’: cobalt-doped tubular carbon nitride for superior photocatalytic PMS activation

The persistent presence of tetracycline (TC) in aquatic environments demands advanced oxidation processes capable of efficiently degrading this micropollutant. Although peroxymonosulfate (PMS)-based catalysis shows promise in this regard, its practical efficiency is limited by sluggish activation kinetics and rapid charge recombination, necessitating the development of high-performance catalysts. Herein, we present a strategically engineered cobalt-doped tubular carbon nitride (Co-TCN) that integrates morphological control with atomic-level doping to achieve enhanced photocatalytic PMS activation. The unique tubular architecture of TCN improves light harvesting and facilitates mass transfer, while atomically dispersed cobalt species, confirmed by XAS and XPS, act as efficient electron traps and active sites for PMS activation. This synergistic design yields a catalyst with an increased specific surface area, significantly suppressed charge recombination, and accelerated electron transfer. Under visible light, the optimized 1.1%Co-TCN/PMS system achieved a TC degradation rate constant of 15.87 × 10−2 (mg L−1)−1·min−1, which was 15.6-fold higher than that of PMS alone and demonstrates remarkable performance across various antibiotics. Mechanistic investigations reveal a catalytic cycle involving Co2+/Co3+ redox pairs, generating both radical species (SO4˙−, ˙OH, ˙O2−) and non-radical species (1O2). Furthermore, toxicity assessment confirmed the effective detoxification of TC during the degradation process. This work establishes a novel strategy for designing cost-effective, non-precious-metal–based photocatalysts through concurrent structural and electronic modulation, offering a promising approach for sustainable water treatment.