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 N2 is an environmental-friendly strategy to close the anthropogenic nitrogen-based cycle. This work reported a metal-organic framework-derived electrocatalyst with earth-abundant bimetallic sites, showing quantitative (~97.9% conversion) and selective (~99.3%) nitrate-to-N2 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 N2 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*).