Towards improved stability of transition metal nitrides in aqueous solutions

Abstract

Transition metal nitrides (TMNs), in some cases referred as metallic ceramics, have unique physical and chemical properties, thanks to their ceramic-metallic nature, and are considered an attractive alternative to noble metals for electrochemical processes. In particular, theoretical work predicts TMNs as promising electrocatalysts towards the nitrogen reduction reaction (NRR). However, recent experimental studies under realistic conditions, have shown the release of lattice nitride to ammonia in a noncatalytic process, suggesting inherent instability of these materials. TMNs stability can be increased by the incorporation of a second metal in the lattice, to form bimetallic systems. Herein, we present a robust approach to prepare nonprecious transition multi-metallic nitride nano-catalysts, followed by a comprehensive study on their stability. The stability of the as-prepared catalysts was tested in electrolytes relevant for electrocatalysis, showing a higher chemical resistance of the bimetallic catalysts over the monometallic ones. This study suggests a novel approach to matching electrolyte pH and catalyst to ensure chemical stability in the electrochemical environment.