Cobalt Tritolylcarboxy Porphyrin-Carbon Black Composite Bifunctional Electrocatalyst for Nitrate and Carbon Dioxide Electroreduction to Ammonia and Formic/Acetic Acid

Abstract Electrochemical nitrate reduction reaction (NO3RR) and carbon dioxide reduction reactions (CO2RR) can serve as environmental remediation tools for pollution control and thus support a circular economy for sustainability. The electrochemical process relies heavily on electrode materials; thus, developing highly active and efficient electrocatalysts for these reactions in a green and cost-effective way is essential. In this study, we examined cobalt porphyrins with different modifications for electrochemical NO3RR and CO2RR to independently produce ammonia and acetic acid/formic acid. The carboxylic acid group-substituted cobalt tetrakis(p-tolyl) porphyrin showed a high Faradaic efficiency of 94% for ammonia, 33.8% for CH3COOH, and 21.1% for HCOOH at various potentials in a neutral pH (∼7) electrolyte. Computational results suggest enhanced binding of key NO3RR and CO2RR intermediates to the −COOH group-substituted cobalt porphyrin during electrocatalysis.