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 O2 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 O2 and H2O2 molecules, we determined the most stable adsorption configurations. Finally, we calculated the energy barrier for O2 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.