Nitrite-Mediated Pulsed Electrocatalytic Nitrate Reduction to Ammonia over Co@Cu NW with Dual Active Sites
Rundong Zhao, Qiuyu Yan, Ling Lu, Lihong Yu, Chen Huang, Tian Yan, Le Liu, Jingyu Xi
Abstract
As a potential alternative to the Haber–Bosch process for ammonia (NH 3 ) synthesis, the electrocatalytic nitrate reduction reaction (NO 3 RR) has attracted extensive attention. The electrocatalytic conversion of NO 3 – to NH 3 involves a complex 8e – reaction with various byproducts. By decomposing the overall reaction into a 2e – process from NO 3 – to NO 2 – and a 6e – process from NO 2 – to NH 3, the two-step reaction can be strategically optimized to achieve efficient tandem catalysis. This work developed a NO 2 – -mediated pulsed electrocatalytic NO 3 RR by Co@Cu nanowire (NW) with dual active sites of the Co phase and Cu phase. The Cu phase rapidly accumulates NO 2 – at low potentials, while the Co phase efficiently converts NO 2 – to NH 3 at high potentials, completing a time-separated tandem catalytic reaction. Ultimately, the Co@Cu NW achieved a maximum NH 3 yield rate of 5148.6 μg·h –1 ·cm –2 and a maximum Faraday efficiency of 88.6% under pulsed potentials of −0.2 and −0.7 V versus the reversible hydrogen electrode in an electrolyte of 0.5 M SO 4 2– and 0.1 M NO 3 – . Furthermore, in situ reflection absorption imaging and in situ total internal reflection imaging revealed that the pulsed strategy effectively enhances the utilization of NO 2 – and suppresses competitive hydrogen evolution reaction, thereby improving NO 3 RR performance.