Pyrolysis-free cobalt porphyrin coordination polymer as electrocatalyst for Zn-air batteries and water splitting

The development of high-performance and stable trifunctional electrocatalysts for oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) plays key role in the practical application of renewable energy systems. Herein, we report a pyrolysis-free synthesis of a Co-N-C based porphyrin cobalt coordination polymer electrocatalyst by using 5,10,15, 20-tetrad-[4'-(terpyridinyl) phenyl] porphyrin and cobalt bivalent ions. The polymer exhibits pronounced trifunctionality at a low ORR onset potential of 0.87 V vs. RHE, and an overpotentials of 378 and 210 mV at 10 mA cm-2 for the OER and HER with substantial stability in alkaline media. In the constructed aqueous Zn-air battery, it displays satisfied specific capacity of 723 mAh g-1 and appreciable stability for 85 h. Density functional theory computations reveal that TTBPP-Co exhibits excellent donor-acceptor characteristics with HOMO-LUMO band gap of 1.87 eV. This work provides a new design of metal porphyrin coordination polymers as efficient trifunctional electrocatalysts for clean energy applications.