Dual-site engineering of N vacancies and K single-atoms in C3N4

Abstract

Graphitic carbon nitride (C3N4) is a promising photocatalyst due to its suitable band gap and polymer properties, but its efficiency is limited by the poor separation of photoinduced electron/hole (e–/h+) pairs. To address this issue, we propose creating N vacancies within the layers and bridging K single-atoms between the C3N4 layers through the self-assembly of potassium citrate and melamine–urea monomers. The introduction of N vacancies disrupts the symmetry of C3N4, promoting electron transfer along the delocalized π-conjugated network, while the presence of K atoms provides channels for electron transfer between the layers by forming N[sbnd]K[sbnd]N bridges, thereby leading to significant enhancement in the separation and transfer of e–/h+ pairs across spatial dimension. As expected, the co-modified C3N4, with N vacancies and K single-atoms (designated as CN-K-VN), exhibits excellent photocatalytic performance, with reaction rate constant of 9.69 × 10−2 min−1 (7.39 × 10−2 min−1 in real water environment) for tetracycline, achieving 80% degradation of tetracycline within 20 min. The reaction mechanism, as well as the toxicity of the degradation intermediates, is deeply discussed. This study provides a strategy to enhance the spatial separation of electrons for photocatalyst, highlighting its significance role in photocatalysis.