Nitrate electroreduction: volcanoes à la carte

The electrochemical nitrate reduction reaction (NO₃RR) is a promising strategy for sustainable ammonia production and nitrate remediation, but its complex reaction mechanism poses significant experimental and computational challenges. While simplified reaction pathways are frequently adopted in density functional theory studies for the sake of affordability, the impact of their approximations on the predicted catalytic trends remains largely unexplored. In this work, we investigate how different choices in the reaction coordinates, ranging from a complete pathway to progressively simplified pictures, affect the modelling of the NO₃RR to NO_(g) on transition-metal electrodes through free-energy diagrams and volcano plots at different applied potentials. We illustrate how some mechanistic simplifications substantially alter the predicted critical reaction steps and their magnitude, and reshape volcano plots, while others closely reproduce the original trends. These observations provide practical guidelines to refine computational high-throughput electrocatalyst screening workflows for the NO₃RR and other electrocatalytic reactions.