Optimizing intermediate adsorption and active hydrogen supply on multi-sites Ru,B co-doped Co3O4 for enhanced nitrate electroreduction to ammonia

Electrocatalytic nitrate reduction reaction (NO3-RR) is a highly attractive route for both nitrate-containing wastewater treatment and sustainable ammonia (NH3) synthesis. However, the efficiency of NO3-RR is still too low to meet the requirements for practical applications. Here we report a facile dual doping strategy to construct a multi-sites Ru,B co-doped Co3O4/CNT catalyst, which exhibits an attractive NH3 yield rate of 178.1 mg h(-1) mg(cat)(-1) and a high NH3 Faradic efficiency of 97.1 % at 0.1 V vs. RHE, far superior to the Co3O4/CNT (20.1 mg h(-1) mg(cat)(1) and 52.6 %) and most of the reported catalysts under similar conditions. Experiments and density functional theory calculations reveal that the co-doping of Ru and B into Co3O4 can generate multiple active sites, in which the Ru-Co bridge site facilitates the NO3 adsorption and activation, the Co atom near B atom boosts the *NO protonation to form *NOH, and meanwhile Ru-B dopants promote H2O dissociation to supply abundant *H for intermediates hydrogenation. The cooperation of different active sites promotes the NO3-RR. This work offers an opportunity to design more efficient NO3 RR electrocatalysts with potential for practical application.