How electrolyte properties and applied potential impact pathways and performance in electrochemical nitrate reduction

Applied Catalysis B: Environmental, vol. 398, pp. 127017

Abstract

Electrochemical nitrate reduction reaction (NO 3 RR) is a promising route for the valorization of nitrate pollutants into ammonia; however, while extensive efforts have focused on catalyst development, the influence of electrolyte properties on NO 3 RR performance has been largely overlooked and remains poorly understood. Here, we show that the electrolyte alone contributes significantly and systematically to the reaction, independent of catalyst identity. To identify the electrocatalytic trends driven by the electrolyte, key parameters —including pH, nitrate concentration, and co-existing cations— were investigated through rationally designed electrochemical experiments performed across multiple metals (Cu, Ag, Pd, Au, Bi, Mo, and Ti), enabling differentiation of catalyst-specific behavior from electrolyte-driven effects. We find that pH and co-existing cations are critical, as they modulate interfacial proton availability, nitrate adsorption, intermediate stabilization, and controlled protonation toward ammonia formation. The effect of nitrate concentration depends on these two parameters as well as the applied potential. Importantly, our study highlights a commonly neglected aspect: alkali metal cations are not simple spectators but act as critical electrostatic field mediators in NO 3 RR. This work provides guidance for engineering electrolytes for nitrate-to-ammonia electrocatalytic systems and calls for redefining alkali metal cations as a key tuning parameter.

Authors 6

1. Ana Daniela Azúa-Humara Aachen Institute of Physical Chemistry

   Forschungszentrum Jülich · RWTH Aachen University

   Affiliation as printed

   Institute of Energy Technologies, Fundamental Electrochemistry (IET-1), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany

   Institute of Physical Chemistry, RWTH Aachen University, 52074 Aachen, Germany

2. Christina Oeß

   Forschungszentrum Jülich

   Affiliation as printed

   Institute of Energy Technologies, Fundamental Electrochemistry (IET-1), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany

3. Anna K. Mechler Aachen Electrochemical Reaction Engineering

   Forschungszentrum Jülich · Jülich Aachen Research Alliance · RWTH Aachen University

   Affiliation as printed

   Electrochemical Reaction Engineering (AVT.ERT), RWTH Aachen University, 52074 Germany

   Institute of Energy Technologies, Electrochemical Process Engineering (IET-4), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany

   JARA-ENERGY, 52425 Jülich, Germany

4. Hermann Tempel

   Forschungszentrum Jülich

   Affiliation as printed

   Institute of Energy Technologies, Fundamental Electrochemistry (IET-1), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany

5. Rüdiger‐A. Eichel Aachen Faculty of Mechanical Engineering Institute of Physical Chemistry

   Forschungszentrum Jülich · RWTH Aachen University

   Affiliation as printed

   Faculty of Mechanical Engineering, RWTH Aachen University, 52062 Germany

   Institute of Energy Technologies, Fundamental Electrochemistry (IET-1), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany

   Institute of Physical Chemistry, RWTH Aachen University, 52074 Aachen, Germany

6. Ana Laura Luna corresponding

   Forschungszentrum Jülich

   Affiliation as printed

   Institute of Energy Technologies, Fundamental Electrochemistry (IET-1), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany