Cobalt single-atoms anchored on porphyrinic triazine-based frameworks as bifunctional electrocatalysts for oxygen reduction and hydrogen evolution reactions

Designing and fabrication of highly active single-atom catalysts (SACs) with maximized atomic efficiency is highly desirable but still remains a great challenge. Herein, highly active and stable cobalt single-atoms with a Co-N-4 moiety were uniformly anchored on a porous porphyrinic triazine-based framework (CoSAs/PTF) by a simple ionothermal method. Due to the abundant single-atom Co-N-4 species, the hierarchical porous structure and the good conductivity, the resultant catalyst is highly active for the electrocatalytic oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER). For the ORR, a more positive half-wave potential of 0.808 V (vs. RHE) was achieved, compared with commercial benchmark Pt/C (0.806 V). Furthermore, a small onset potential of 21 mV and a low Tafel slope of 50 mV per decade were obtained for the HER. The porphyrin-like structure was found to stabilize the CoSAs effectively, thus leading to long-term durability and a remarkable methanol-tolerant behavior. This bifunctional single-atom catalyst might be a promising candidate to replace Pt-based electrocatalysts in electrolysers and fuel cells.