Nitrite-Mediated Pulsed Electrocatalytic Nitrate Reduction to Ammonia over Co@Cu NW with Dual Active Sites

As a potential alternative to the Haber-Bosch process for ammonia (NH3) synthesis, the electrocatalytic nitrate reduction reaction (NO3RR) has attracted extensive attention. The electrocatalytic conversion of NO3 - to NH3 involves a complex 8e- reaction with various byproducts. By decomposing the overall reaction into a 2e- process from NO3 - to NO2 - and a 6e- process from NO2 - to NH3, the two-step reaction can be strategically optimized to achieve efficient tandem catalysis. This work developed a NO2 --mediated pulsed electrocatalytic NO3RR by Co@Cu nanowire (NW) with dual active sites of the Co phase and Cu phase. The Cu phase rapidly accumulates NO2 - at low potentials, while the Co phase efficiently converts NO2 - to NH3 at high potentials, completing a time-separated tandem catalytic reaction. Ultimately, the Co@Cu NW achieved a maximum NH3 yield rate of 5148.6 mu g<middle dot>h-1<middle dot>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 SO4 2- and 0.1 M NO3 -. Furthermore, in situ reflection absorption imaging and in situ total internal reflection imaging revealed that the pulsed strategy effectively enhances the utilization of NO2 - and suppresses competitive hydrogen evolution reaction, thereby improving NO3RR performance.