High-ammonia selective metal-organic framework-derived Co-doped Fe/FeO catalysts for electrochemical nitrate reduction.

Ammonia (NH) is an ideal carbon-free power source in the future sustainable hydrogen economy for growing energy demand. The electrochemical nitrate reduction reaction (NORR) is a promising approach for nitrate removal and NH production at ambient conditions, but efficient electrocatalysts are lacking. Here, we present a metal-organic framework (MOF)-derived cobalt-doped Fe@FeO (Co-Fe@FeO) NORR catalyst for electrochemical energy production. This catalyst has a nitrate removal capacity of 100.8 mg N g h and an ammonium selectivity of 99.0 ± 0.1%, which was the highest among all reported research. In addition, NH was produced at a rate of 1,505.9 μg h cm, and the maximum faradaic efficiency was 85.2 ± 0.6%. Experimental and computational results reveal that the high performance of Co-Fe@FeO results from cobalt doping, which tunes the Fe d-band center, enabling the adsorption energies for intermediates to be modulated and suppressing hydrogen production. Thus, this study provides a strategy in the design of electrocatalysts in electrochemical nitrate reduction.