Ammonia decomposition on LaV(O,N) 3-δ surfaces: toward a mechanistic understanding

Abstract

Ammonia, as a carbon-free hydrogen carrier, provides an efficient pathway for hydrogen transport, storage and utilisation in the green energy transition. To recover hydrogen from ammonia, perovskite-structured oxynitrides show promise as noble metal-free catalysts for ammonia decomposition, offering both encouraging catalytic performance and highly tuneable electronic properties. However, understanding of the critical catalytic pathways of these materials remains unresolved, with the nature of the active sites for ammonia decomposition on perovskite oxynitrides unclear. In this work, LaV(O,N)3-δ oxynitrides with varying nitrogen contents were synthesised and found to exhibit good catalytic activity. Machine learning interatomic potential (MLIP) simulations were employed to investigate the underlying mechanisms, revealing that anion vacancies play a critical role as active sites for ammonia decomposition. Furthermore, near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) measurements were performed, showing the continuous surface nitridation processes occurring on the LaV(O,N)3-δ oxynitride. These results provide new insights into the reaction mechanisms of ammonia decomposition and underscore the innovative potential of perovskite oxynitrides as a pioneering class of noble metal-free catalysts, paving the way for sustainable hydrogen production through efficient ammonia decomposition.