Computational insight into the mechanism of O2 to H2O2 reduction on amino-groups-containing g-C3N4

First-principles DFT calculations were conducted to investigate the mechanism of O-2 to H2O2 reduction on both amino-group-containing (g-C3N4-NH2) and defect-free g-C3N4. The theoretical results obtained were directly compared with the experimental findings reported by Li et al. [Appl. Catal., B 190, 26-35, (2016)]. It was found that the defective system with one amino and one imine group is more stable than that with two amino groups. By studying different adsorption structures using O-2 and H2O2 molecules, we determined the most stable adsorption configurations. Finally, we calculated the energy barrier for O-2 reduction for both the systems. We found that the oxygen reduction process proceeds via two different mechanisms on g-C3N4-NH2 and g-C3N4, which was in agreement with the experimental results. Our results indicate that the energy barrier for oxygen reduction for the defective system is higher than that for a defect-free system; hence, we determined and discussed other factors that may impact the observed reaction rates. The influence of carbon vacancy defects combined with hydrogen saturation on electronic properties was also investigated.