Understanding the lattice nitrogen stability and deactivation pathways of cubic CrN nanoparticles in the electrochemical nitrogen reduction reaction

Abstract

Transition metal nitrides (TMNs) are predicted to be highly promising electrocatalysts for nitrogen reduction reaction (NRR) by theoretical calculations. TMNs follow a special Mars–van Krevelen (MvK) mechanism during NRR, involving surface lattice nitrogen exchange and regeneration. It is hence essential to identify the source of nitrogen, especially taken the stability of lattice nitrogen into consideration. Herein, we investigated the deactivation process of a benchmark CrN nanoparticles catalyst (CrN NPs) with phase-pure cubic rocksalt (RS) structure for electrochemical NRR. The current work identifies two possible deactivation pathways for CrN: i) potential-induced structural collapse of catalyst including both lattice N leaching and metal dissolution; ii) ammonia poisoning due to accumulation and strong chemical bonding of produced ammonia on CrN surface. This work provides new perspectives for understanding the structural evolution of nitrogen-containing electrocatalysts for NRR research.