Boosting Cobalt Porphyrin for Selective Nitrate Electroreduction

Abstract

ABSTRACT The electrocatalytic reduction of nitrate (NO 3 − ) to ammonia (NH 3 ) offers a sustainable pathway for NH 3 synthesis. Metal porphyrins are promising electrocatalysts for the NO 3 − reduction reactions (NO 3 RR) due to their tunable molecular structures, yet effective strategies for enhancing their performance are still lacking. Herein, we develop an efficient composite electrocatalyst based on cobalt tetraphenylporphyrin (CoTPP) for electrochemical NH 3 synthesis by mitigating hydroxide (OH − ) interference and optimizing active hydrogen supply. CoTPP is identified as a superior catalyst with a strong affinity for NO 3 − adsorption, and neutral condition is adopted to suppress the competitive OH − adsorption. Poly(benzodifurandione) (PBFDO) is further introduced as an active hydrogen support cocatalyst. The optimized composite catalyst of CoTPP+carbon nanotube (CNT)+PBFDO shows high Faradaic efficiencies (FEs) of NH 3 near 100% across a broad potential range, and a high NH 3 yield rate (5.3 mg h −1 cm −2 ) is achieved, increasing by fivefold when compared to the catalyst without PBFDO. This work provides mechanistic insights into enhancing the activity of molecular electrocatalysts for the conversion of NO 3 − to NH 3 .