Ti2N nitride MXene evokes the Mars-van Krevelen mechanism to achieve high selectivity for nitrogen reduction reaction

Abstract We address the low selectivity problem faced by the electrochemical nitrogen (N 2 ) reduction reaction (NRR) to ammonia (NH 3 ) by exploiting the Mars-van Krevelen (MvK) mechanism on two-dimensional (2D) Ti 2 N nitride MXene. NRR technology is a viable alternative to reducing the energy and greenhouse gas emission footprint from NH 3 production. Most NRR catalysts operate by using an associative or dissociative mechanism, during which the NRR competes with the hydrogen evolution reaction (HER), resulting in low selectivity. The MvK mechanism reduces this competition by eliminating the adsorption and dissociation processes at the sites for NH 3 synthesis. We show that the new class of 2D materials, nitride MXenes, evoke the MvK mechanism to achieve the highest Faradaic efficiency (FE) towards NH 3 reported for any pristine transition metal-based catalyst—19.85% with a yield of 11.33 μg/cm 2 /hr at an applied potential of − 250 mV versus RHE. These results can be expanded to a broad class of systems evoking the MvK mechanism and constitute the foundation of NRR technology based on MXenes.