C3N4 with engineered three coordinated (N3C) 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%, similar to 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 O-1(2) generation, which achieving from the O-2 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.