Single-atom catalysts based on one-dimensional metal porphyrin chains toward oxygen reduction reactions

Single-atom catalysts has emerged as a groundbreaking concept in catalysis, where individual metal atoms are anchored on supports such as carbon-based materials, oxides, or nitrides, serving as isolated active sites for catalytic reactions. In the present study, we theoretically explore the geometries, bonding properties, electronic structures, and potential catalytic performances of the recently synthesized one-dimensional (1D) M-porphyrin chains, in which the M-N₄-C motif acts as the active site for oxygen reduction reactions (ORRs). Three configurations of 1D M-porphyrin chains (M = Ni, Zn) were investigated, including (a) M-porphyrin ribbon, (b) butadiyne-linked M-porphyrin, and (c) M-porphyrin-fused graphene nanoribbons. The calculation results reveal that all those 1D M-porphyrin chains are semiconductors. Energy decomposition analysis combined with natural orbital for chemical valence (EDA-NOCV) shows that the metal-ligand interaction in Ni-porphyrin is stronger than that in Zn-porphyrin. Compared to Zn-porphyrin chains, Ni-porphyrin chains exhibit stronger adsorption and superior electron transfer capabilities, which is attributed to enhanced orbital hybridization between the Ni 3d atomic orbitals and adsorbed oxygen 2p orbitals. The catalytic reaction pathways of these chains are similar for all those SACs and depend slightly on linker types, highlighting the importance of the local environment of the M-N₄-C coordination framework. These findings provide valuable insights into the design of SACs with tailored properties, offering significant potential for applications in energy conversion and environmental catalysis.