Transition metal coordinated framework porphyrin for electrocatalytic oxygen reduction

Oxygen reduction reaction (ORR) constitutes the core process of many clean and sustainable energy systems including fuel cells and metal–air batteries. Developing high-performance and cost-efficiency ORR electrocatalysts is of great significance to the practical applications of the above-mentioned energy storage devices. Transition metal coordinated porphyrin electrocatalysts are highly considered as a promising substitution of noble-metal-based electrocatalyst because of their high ORR reactivity, where the ORR performances of the porphyrin-based electrocatalysts are highly dependent on the transition metal center. Herein a series of framework porphyrin electrocatalysts coordinated with different transition metal centers (M-POF, where M is Mn, Fe, Co, Ni, Cu, or Zn) was designed, synthesized, and evaluated in regards of electrocatalytic ORR performances. Among all, the Co-POF electrocatalyst exhibits the best ORR performances with the highest half-wave potential of 0.81 V vs. RHE and the lowest Tafel slope of 53 mV/dec. This contribution affords an optimized high-performance ORR electrocatalyst and provides instructions for further rational design of porphyrin-based ORR electrocatalysts for sustainable energy applications.