C₃N₄ with engineered three coordinated (N3_C) nitrogen vacancy boosts the production of ¹O₂ for Efficient and stable NO photo-oxidation

The introduction of nitrogen vacancy to C₃N₄ holds promise in the photocatalytic behavior improvement. Yet, minimal literatures on reaction and stability mechanisms are presently available in the NO-oxidation reaction of C₃N₄. Here C₃N₄ with three coordinated (N3_C) nitrogen vacancy was prepared by directly calcining the mixture of azodicarbonamide and melamine. Unlike previously reported C₃N₄ that exhibits an obvious deactivation beyond 30 min (>10% loss of reactivity after one cycle) and high in-situ formed NO₂ concentration (>100 ppb), the C₃N₄ with three coordinated (N3_C) nitrogen vacancy exerts increased NO-oxidation performance (40.3%, ~2.28 times higher than that of pristine C₃N₄ with a NO-removal rate of 17.7%) and suppressed in-situ produced NO₂ (36.3 ppb, decreased by 76.6 ppb compared to pure C₃N₄) as well excellent stability (<2% loss of activity after a 5 h cycling test). DFT calculations reveal that, intermediates (NO₂) and end-products (NO₂⁻ and NO3⁻) can weakly adsorp on the surface of C₃N₄ with three coordinated (N3_C) nitrogen vacancy, thus rendering a well maintained activity. Based on the time-dependent ESR measurements, the ¹O₂ generation, which achieving from the O₂ activation process, can compensate for the consumption of major reactive species and thus support the remarkable reusability. Therefore, this study provides a potential and sustainable route for the steady and efficient NO-oxidation. Copyright © 2020 Elsevier B.V. All rights reserved.