Cu/Co bimetallic conductive MOFs: Electronic modulation for enhanced nitrate reduction to ammonia

Abstract

Electrochemical reduction of nitrate to ammonia is an eco-friendly strategy to remove the nitrate pollution in waste effluents. Developing new-type electrocatalysts with high activity for NO3RR has attracted worldwide attention. Owing to the numerous active single-metal sites, electric conductivity and ordered in-plane porous structure, conductive metal–organic frameworks (cMOFs) are promising alternative to construct the next-generation NO3RR electrocatalysts. In this work, a bimetallic cMOF (CuxCoyHHTP) is proposed for efficient NO3– electroreduction to ammonia and the synergy effect between different types of single-metal sites is also revealed. As the result, the optimal Cu1Co1HHTP exhibits an outstanding electrocatalytic activity with a high NH3 yield rate of 299.9 μmol h−1 cm−2 and a large Faradic efficiency of 96.4%. Both theoretical and experimental results reveal that the Co sites can affect the electron structure of Cu sites in Cu1Co1HHTP slab and decrease the ΔG of potential determining step in NO3RR process. Moreover, the Co sites bring a higher selectivity to Cu active sites for reducing *NO2 to *NO, rather than the desorption of NO2–. The bimetallic c-MOFs strategy will innovate the design concept of next-generation catalyst, paving the way to investigate catalytic mechanism of single-metal-atom and open up their application prospects.