Efficient and selective electrochemical reduction of nitrate to N2 by relay catalytic effects of Fe-Ni bimetallic sites on MOF-derived structure

Selective electrocatalytic conversion of NO3- to N-2 is an environmental-friendly strategy to close the anthropogenic nitrogen-based cycle. This work reported a metal-organic framework-derived electrocatalyst with earthabundant bimetallic sites, showing quantitative (similar to 97.9% conversion) and selective (similar to 99.3%) nitrate-to-N-2 transformation. More importantly, both post-catalysis concentrations of NO3- and NO2- meet the drinking water limit requirements, set by World Health Organization. The reaction intermediates and mechanistic pathways in electrocatalytic reduction of NO3- to N-2 are elucidated by a variety of in-situ experimental studies and DFT calculations. The enhanced and selective electrocatalytic performances are ascribed to the relay catalytic effects of the neighboring Fe-Ni catalytic sites residing in the porous carbon electrocatalysts, which are structurally determined by X-ray absorption spectroscopy (XAS) as well as calculated structural model, with Fe sites decreasing the reaction barrier for NO3- conversion and Ni centers facilitating the adsorption and activation of reaction intermediates (NO2-, NO* and N2O*).

Automated summary

Selective electrocatalytic conversion of NO3- to N-2 using metal-organic framework-derived electrocatalyst was achieved with high efficiency, meeting drinking water standards. The study elucidated reaction intermediates and mechanistic pathways, highlighting the crucial role of neighboring Fe-Ni catalytic sites in enhancing and selectively catalyzing the reaction.