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Abstract Nitrate is a ubiquitous aqueous pollutant from agricultural and industrial activities. At the same time, conversion of nitrate to ammonia provides an attractive solution for the coupled environmental and energy challenge underlying the nitrogen cycle, by valorizing a pollutant to a carbon-free energy carrier and essential chemical feedstock. Mass transport limitations are a key obstacle to the efficient conversion of nitrate to ammonia from water streams, due to the dilute concentration of nitrate. Here, we develop bifunctional electrodes that couple a nitrate-selective redox-electrosorbent (polyaniline) with an electrocatalyst (cobalt oxide) for nitrate to ammonium conversion. We demonstrate the synergistic reactive separation of nitrate through solely electrochemical control. Electrochemically-reversible nitrate uptake greater than 70 mg/g can be achieved, with electronic structure calculations and spectroscopic measurements providing insight into the underlying role of hydrogen bonding for nitrate selectivity. Using agricultural tile drainage water containing dilute nitrate (0.27 mM), we demonstrate that the bifunctional electrode can achieve a 8-fold up-concentration of nitrate, a 24-fold enhancement of ammonium production rate (108.1 ug h −1  cm −2 ), and a >10-fold enhancement in energy efficiency when compared to direct electrocatalysis in the dilute stream. Our study provides a generalized strategy for a fully electrified reaction-separation pathway for modular nitrate remediation and ammonia production. 

Abstract Strain engineering is an effective strategy in modulating activity of electrocatalysts, but the effect of strain on electrochemical stability of catalysts remains poorly understood. In this work, we combineab initiothermodynamics and molecular dynamics simulations to examine the role of compressive and tensile strain in the interplay between activity and stability of metal oxides considering RuOand IrOas exemplary catalysts. We reveal that although compressive strain leads to improved activity via the adsorbate‐evolving mechanism of the oxygen evolution reaction, even small strains should substantially destabilize these catalysts promoting dissolution of transition metals. In contrast, our results show that the metal oxides requiring tensile strain to promote their catalytic activity may also benefit from enhanced stability. Importantly, we also find that the detrimental effect of strain on electrochemical stability of atomically flat surfaces could be even greater than that of surface defects.