Conjugated Cobalt Porphyrin Polymer for Highly Active and Selective Electrocatalytic Nitrite Reduction to Ammonia

Abstract Electrocatalytic nitrite (NO 2 − ) reduction (NO 2 RR) to ammonia (NH 3 ) is a promising green technology for producing NH 3 with high efficiency. Cobalt macrocyclic complexes have attracted great interest because of their ability to selectively convert NO 2 − to NH 3 , but suffer from low NH 3 yields. Herein, cobalt porphyrin conjugated polymer on carbon nanotubes (CoPCOP@CNT) is reported to display exceptional NO 2 RR performance with a large NH 3 yield of 133.39 mg h −1 mg CoP −1 at −1.0 V and high Faradaic efficiency (FE) of 98.0% at −0.8 V. Utilizing CoPCOP@CNT as the catalyst cathode, the Zn‐NO 2 − battery exhibits remarkable power density (5.34 mW cm −2 ), open‐circuit voltage (≈1.45 V), FE (94.6%), and NH 3 yield (29.15 mg h −1 mg CoP −1 ). The active intermediates and reaction pathways of CoPCOP in NO 2 RR process are revealed by differential electrochemical mass spectroscopy and theory calculations. This work highlights the potential of electrocatalysts based on metal porphyrins for the conversion of nitrogenous pollutant into NH 3 .