Tandem photocatalysis of nitrate to nitrogen on Cu@CN/TiOx S-scheme heterojunction

The persistent challenge of nitrate (NO 3 – ) pollution in water systems, profoundly impacting ecosystems and human health, demands effective remediation strategies. Here, we present an innovative S-scheme Cu@CN/TiO x heterojunction for high-efficiency photocatalytic denitrification (PCDN). Evaluation of its performance demonstrates exceptional NO 3 – removal efficiency (99.5%) and remarkable N 2 selectivity (95.5%), with 13.7 and 4.1 times higher rate constants of NO 3 – removal than the individual Cu@CN and TiO x components. Notably, this catalyst exhibits impressive stability across multiple cycles, maintaining consistent high conversion rates and selectivity. Mechanistic insights unveiled a tandem reaction pathway where Cu@CN selectively reduced NO 3 – to NO 2 – , followed by the TiO x -mediated CO 2 • – generation, enabling highly selective NO 2 – to N 2 conversion. This unique catalytic system, featuring spatially separated redox-active sites, presents a promising avenue for efficient, selective, and stable denitrification processes, offering significant potential in addressing water pollution challenges and advancing tandem catalytic systems.