Dual-ligand Cu-based MOFs for electrocatalytic reduction of NO3–

Abstract

Electrocatalytic nitrate reduction reaction (ENRR) to recyclable NH3 or environmental-friendly N2 is a sustainable technology. In this study, we prepared three dual ligand Cu-based metal organic framework (Cu@MOFs) for efficient ENRR. The batch ENRR test revealed that Cu-bip-BTC exhibited the best performance in terms of NH3-N selectivity (61.64%), NH3-N yield (12.09 ×103 µgCu·h–1 mg–1) and faradaic efficiency for NH3 (80.97%) at −0.58 V vs. RHE. The ligands and coordination of Cu@MOFs affect the electronic structure of Cu and the adsorption performance of NO3–, leading to differences in the performance of the electrocatalytic reduction of nitrate. The quenching experiment of tert-butanol (TBA) demonstrates that NO3– is directly reduced by electrons on Cu@MOFs at −0.58 V, and in-situ spectrometric analysis identified the intermediates and pathways of ENRR. Cu-bip-BTC has the highest NH3-N selectivity due to its faster kinetic reaction rate, stronger inhibition of the hydrogen evolution reaction, and higher NO3– adsorption energy. In addition, ENRR combined with breakpoint chlorination reactions suggests that achieving nitrogen elimination is feasible, and this study provides a strategy for the application of dual-ligand Cu-based MOFs in ENRR.