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

Abstract

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 adsorption and activation NO₃⁻, 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.