Recognition of water-dissociation effect toward lattice oxygen activation on single-atom Co catalyst in toluene oxidation

The presence of water can promote the catalytic activity of some heterogeneous catalysts by oxygen activation, but the mechanism remains unclear especially for transition metal single-atom catalysts (SACs), which is further complicated due to the difficult identification of active sites. In this study, we prepared single-atom Co supported on MnO2 and investigated the promotion mechanism of oxidation reaction with the existence of water. According to the results of various characteristic experiments and density functional theory (DFT) calculations, it was found that the single-atom Co forms the Co−O−Mn entity as the actual active site on Co1/MnO2 and the dissociation of water on the active site facilitates the activation of lattice oxygen of support, which are responsible for the activity promotion. The unique water effect of Co1/MnO2 was further confirmed by comparing the performance of CoOx-nanoparticles catalyst (CoOx/MnO2). This work provides new insight into the lattice oxygen activation mechanism of transition metal SACs.