Selective Electroreduction of Nitrates to Ammonia by Enhanced Byproduct Conversion over a Tandem CuCo-NC Catalyst

The electrochemical reduction of nitrate (NO3–, NO3RR) and nitrite (NO2–, NO2RR) enables sustainable, carbon-neutral, and decentralized routes to produce ammonia (NH3). Copper-based materials are promising electrocatalysts for NO3– conversion; however, their performance in selective conversion to NH3 is still poor. Herein, we present a Cu–Co tandem catalyst inspired by the conversion of NO3–-to-NH3 in nature, which can easily remove NO2– via the collaboration of two active centers. A mechanistic study has elucidated the tandem catalytic process, where direct electron transfer coupled with H+ bonding plays a dominant role in the NO3–-to-NO2– conversion at the Cu site, followed by the further reduction of NO2– to NH3 at the Co site. The Cu3Co1-NC electrode delivers a NO3– removal efficiency of 80% at −0.58 V vs reversible hydrogen electrode, with a NH3 yield rate of 490 μg·h–1·cm–2 and an FE of 77%. More importantly, the as-prepared Cu3Co1-NC electrode maintains comparable activity and stability for complex NO3RR systems with coexisting substrates, which is promising for sustainable ammonia synthesis and its application.