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

The electrochemical reduction of nitrate (NO 3 –, NO 3 RR) and nitrite (NO 2 –, NO 2 RR) enables sustainable, carbon-neutral, and decentralized routes to produce ammonia (NH 3 ). Copper-based materials are promising electrocatalysts for NO 3 – conversion; however, their performance in selective conversion to NH 3 is still poor. Herein, we present a Cu–Co tandem catalyst inspired by the conversion of NO 3 – -to-NH 3 in nature, which can easily remove NO 2 – 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 NO 3 – -to-NO 2 – conversion at the Cu site, followed by the further reduction of NO 2 – to NH 3 at the Co site. The Cu 3 Co 1 -NC electrode delivers a NO 3 – removal efficiency of 80% at −0.58 V vs reversible hydrogen electrode, with a NH 3 yield rate of 490 μg·h –1 ·cm –2 and an FE of 77%. More importantly, the as-prepared Cu 3 Co 1 -NC electrode maintains comparable activity and stability for complex NO 3 RR systems with coexisting substrates, which is promising for sustainable ammonia synthesis and its application.