Revealing Significant Electronic Effects on the Oxygen Reduction Reaction with Iron Porphyrins
Haonan Qin, Jiafan Kong, Xinyang Peng, Zhimeng Wang, Xialiang Li, Haitao Lei, Wei Zhang, Rui Cao
Abstract
Abstract Understanding electronic effects on catalysis from a mechanism point of view is of fundamental significance but is also challenging. We herein report on electronic effects on the oxygen reduction reaction (ORR) with Fe porphyrins. By using Fe III tetraphenylporphyrin ( TPP‐Fe ) and Fe III tetra(pentafluorophenyl)porphyrin ( TPFP‐Fe ), we showed their different electrochemical and chemical behaviors for ORR. Mechanism studies revealed that the Fe III ‐superoxo species of TPP‐Fe can undergo smooth protonation with trifluoroacetic acid (TFA) but the electron‐deficient Fe III ‐superoxo species of TPFP‐Fe cannot be protonated with TFA. The Fe III ‐superoxo reactivity difference between TPP‐Fe and TPFP‐Fe is the origin of their different catalytic ORR behaviors.