Density Functional Theory Study of the Oxygen Reduction Reaction on Metalloporphyrins and Metallophthalocyanines

In this paper, density functional theory is applied to study the electrochemical reduction of oxygen on iron phthalocyanine (FePc), iron porphyrin (FeP), cobalt phthalocyanine (CoPc), and cobalt porphyrin (CoP). According to the calculation results, for the four metal macrocyclic complexes, O-2 will not directly be cleaved without the cooperation of hydrogen. In the reduction process, on FePc or FeP, H2O2 does not form as an intermediate, and O-2 is reduced to H2O, while on CoPc or CoP, O-2 is just reduced to H2O2. The reason why the oxygen reduction ability of FePc or FeP is higher than that of CoPc or CoP, respectively, is that the energy level of the highest-occupied 3d orbital of the former is higher than that of the later. The high energy level of the metal 3d orbital leads to the strong ability of oxygen reduction.