Cobalt Porphyrin with a Fine-Tuned Molecular Pocket Bottleneck for Improved Oxygen Reduction Reaction

Highly active and selective four-electron oxygen reduction reaction (ORR) is required in energy conversion. Difficulties to get the activity-selectivity trade-off challenge the development of high-performance ORR catalysts. Herein, we report Co porphyrin 1 with fine-tuned molecular pocket bottleneck for active and selective four-electron electrocatalytic ORR. By using the αααα atropisomer to create a molecular pocket above the porphyrin plane and by tailoring pocket bottleneck steric effects, we designed Co porphyrin 1, which electrocatalyzes ORR in 0.10 M KOH solutions with E1/2 = 870 mV vs RHE and n = 3.50. This performance is noteworthy among mononuclear Co porphyrin catalysts.