Activity Trends and Mechanisms in Peroxymonosulfate-Assisted Catalytic Production of Singlet Oxygen over Atomic Metal-N-C Catalysts.

We synthesized a series of carbon-supported atomic metal-N-C catalysts (M-SACs: M=Mn, Fe, Co, Ni, Cu) with similar structural and physicochemical properties to uncover their catalytic activity trends and mechanisms. The peroxymonosulfate (PMS) catalytic activity trends are Fe-SAC>Co-SAC>Mn-SAC>Ni-SAC>Cu-SAC, and Fe-SAC displays the best single-site kinetic value (1.65×105  min-1  mol-1 ) compared to the other metal-N-C species. First-principles calculations indicate that the most reasonable reaction pathway for 1 O2 production is PMS→OH*→O*→1 O2 ; M-SACs that exhibit moderate and near-average Gibbs free energies in each reaction step have a better catalytic activity, which is the key for the outstanding performance of Fe-SACs. This study gives the atomic-scale understanding of fundamental catalytic trends and mechanisms of PMS-assisted reactive oxygen species production via M-SACs, thus providing guidance for developing M-SACs for catalytic organic pollutant degradation.