Abstract
The reverse sintering effect of Ni particles under thermal treatment has been observed in the Ni/γ-Mo2N catalysts. The ab initio molecular dynamic simulation has demonstrated the redispersion of metallic Ni particles into under-coordinated two-dimensional Ni clusters over γ-Mo2N is a thermodynamically favorable process. Utilizing pre-synthesized 4 nm Ni nanoparticles as the loaded particles, a Ni-4nm/γ-Mo2N model catalyst was synthesized and used to study the reverse sintering effect by the combination of multiple in-situ characterization methods, including in-situ quick XANES and EXAFS, ambient pressure XPS and environmental SE/STEM etc. The theoretical and experimental studies both confirmed the reverse sintering effect in the Ni-γ-Mo2N system is driven by the strong metal-support interaction between Ni and γ-Mo2N. The potential application of the reverse sintering effect in heterogeneous catalysis has been realized using the high temperature favored CO2 hydrogenation reaction. The under-coordinated two-dimensional layered Ni clusters on molybdenum nitride support generated from the Ni-4nm/γ-Mo2N has been demonstrated to be a thermally stable catalyst in 50 h stability test, and exhibits a remarkable catalytic selectivity reverse compared with traditional Ni based catalyst, leading to a chemo-specific CO2 hydrogenation to CO.
Reversing sintering effect of Ni particles on γ-Mo2N via strong metal support interaction