Spatial confinement and electron transfer moderating Mo-N bond strength for superior ammonia decomposition catalysis

Abstract Advanced catalysts for ammonia (NH3) decomposition reaction hold great promise in the area of renewable energy. In this work, highly dispersed molybdenum nitride (MoN/Mo2N) nanocrystals anchored on in-situ assembled two-dimensional (2D) mesoporous silica/reduced graphene oxide (rGO) hybrid nanosheets (MoN/SBA-15/rGO and Mo2N/SBA-15/rGO) were designed and synthesized as active and stable catalysts for COx-free H2 generation via NH3 decomposition. Benefiting from well-defined molybdenum nitride nanocrystals and moderate Mo N band strength, the nanohybrids exhibited superior catalytic property, especially Mo2N/SBA-15/rGO with the highest NH3 decomposition rate of 30.58 mmol g−1cat min−1 among any Mo-based catalysts reported to date. Density functional theory (DFT) calculations revealed that the superior catalytic activity for Mo2N compared to MoN stemmed from a large reduction of kinetic energy barriers of dehydrogenation and nitrogen desorption. Moreover, the introduction of rGO can effectively weaken the associative desorption of adsorbed N atoms and thus improve NH3 decomposition activity. This study highlights the importance of designing spatially confined metal nitrides for enhancing energy catalysis.