Defective UiO‐66 toward boosted electrochemical nitrogen reduction to ammonia

Abstract

Electrochemical nitrogen reduction reaction (NRR) to ammonia is considered as one of the most promising green techniques, which is an alternative to traditional Haber-Bosch method. However, ammonia yield rate and Faradic efficiency is still limited currently, and thus efficient catalysts are still highly required. Herein, defective UiO-66 has been developed as highly active NRR catalyst by using acetic acid (HAc) or formic acid (FA) as defect modulators. Both the resultant defective UiO-66-HAc and UiO-66-FA include truncated cubic nanoparticles with the smaller sizes as compared with UiO-66 without acid modulator that consists of the larger sized octahedral nanoparticles. More importantly, both of them have more defects than UiO-66, which involve losing terephthalic linkers. The more linker-lost defects can expose the more Zr6 nodes as active sites, increase electrochemical specific surface areas, improve the adsorption strength of N2 and the N-related intermediates during NRR to NH3, enlarge the specific surface areas and pore volumes (or porosity) and thus increase the amounts of adsorbed N2. As a result, the defective UiO-66-HAc with the most abundant lost linkers (or exposed Zr6 nodes) achieves the optimal catalytic performance of NRR to NH3. This work fully shows that the defective metal-organic frameworks are promising catalysts for NRR to NH3.