Surface N-, NH-, and H-Promoted NH ₃ Decomposition over MoN(001): A First-Principles Investigation

A comprehensive understanding of the formation and reactions of surface N-containing species is vital for the development of efficient Mo nitride-based catalysts for H2 production by the NH3 decomposition reaction (ADR) to tackle the challenges in industrial applications of H2. We estimated the stability of potential Mo nitride phases and found that MoN in P63/mmc symmetry is the hexagonal MoN phase relevant to experiments. All possible ADR pathways over MoN(001) were investigated theoretically. We showed that the stepwise pathway would be the dominant pathway as the scission of N–H bonds is more plausible than competing alternatives. We also showed that the coadsorbed surface species (such as N, NH, and H) downshift the surface d-band, leading to reduction of both the surface N–Mo interaction and the barriers for the rate-determining N2 formation (to 1.62 eV), thereby facilitating the overall ADR process. The findings may benefit the development of efficient catalysts for ADR.