Electrocatalytic Dinitrogen Reduction to Ammonia Using Easily Reducible N‐Fused Cobalt Porphyrins

Abstract

Single‐site molecular electrocatalysts, especially those that perform catalytic conversion of N2 to NH3 under mild conditions, are highly desirable to derive fundamental structure‐activity relations and as potential alternatives to the current energy‐consuming Haber‐Bosch ammonia production process. Combining theoretical calculations with experimental evidence, it has been shown that easily reducible cobalt porphyrins catalyze the six‐electron, six‐proton reduction of dinitrogen to NH3 at neutral pH and under ambient conditions. Two easily reducible N‐fused cobalt porphyrins – CoNHF and CoNHF(Br)2 – reveal NRR activity with Faradic efficiencies between 6 ‐ 7.5% with ammonia yield rates of 300 ‐ 340 µmol g‐1 h‐1. Contrary to this, much harder‐to‐reduce N‐fused porphyrins – CoNHF(Ph)2 and CoNHF(PE)2 – reveal no NRR activity. The present study highlights the significance of tuning the redox and structural properties of single‐site NRR electrocatalysts for improved NRR activity under mild conditions.