Roles of Copper in Nitrate Reduction at Copper-Modified Ru/C Catalysts
Jiaqi Chen, Xuxu Ye, Da Zhou, Yanxia Chen
Abstract
Electrochemical reduction is a potential solution to eliminate nitrate in wastewater; however, the poor activity and product selectivity of traditional electrocatalysts impede its large-scale application. Herein, we report a new catalyst of Cu-modified Ru nanoparticles (Cu-modified Ru/C NPs) prepared by underpotential deposition (UPD) of Cu atoms onto Ru NPs, which shows good nitrate reduction kinetics and NH 3 selectivity. To unravel the enhancing mechanism, the impact of Cu coverage on nitrate reduction and the formation of possible products/intermediates as well as the competition of side products H 2 have been investigated systematically by tracking the reverse oxidation of such species using rotation ring disk electrode (RRDE) combined with cyclic voltammetry. Our results reveal that the Cu-modified Ru/C NPs perform NH 3 yield of 23.7 μmol h –1 cm –2 and 95% Faradaic efficiency, which is better than Ru/C NPs (6.0 μmol h –1 cm –2 with Faradaic efficiency of 66%); This enhancement of modified Cu atoms toward nitrate reduction results from synergetic effects: (i) Cu blocks the hydrogen evolution reaction (HER) sites on Ru surface; (ii) Cu accelerates the rate of nitrate reduction to nitrite; (iii) the enhanced nitrite reduction activity of Cu sites on Ru substrate is probably a result of changes in electronic structure of Cu.