CH sub(4) dissociation on the perfect and defective MgO(0 0 1) supported Ni sub(4)

• Published in: Fuel (Guildford) 2014-05, Vol.123, p.285-292
• Main Authors: Liu, Hongyan, Teng, Botao, Fan, Maohong, Wang, Baojun, Zhang, Yulong, Harris, HGordon
• Format: Article
• Language: English
• ISSN: 0016-2361
• DOI: 10.1016/j.fuel.2014.01.087

A theoretical understanding of CH sub(4) dissociation on Ni-based catalysts is of great importance for the development of CH sub(4) reforming catalysts with high activity and carbon-deposition resistance. Based on comparisons of CH sub(4) dissociation on perfect and defective MgO supported Ni sub(4), as well as Ni(1 1 1), the effects of the strong interactions between Ni sub(4) and MgO on CH sub(4) dissociation are systematically investigated by density functional theory (DFT) calculations. Our results indicate that the interaction between Ni sub(4) and the defective MgO is stronger than for the perfect MgO. Consequently, the adsorptions of CH sub(x)(x = 0-4) are weaker than those on the perfect Ni sub(4)/MgO. Hirshfeld charge analysis shows that electrons are transferred from MgO to Ni sub(4), then to CH sub(x) adspecies; the stronger interactions between Ni sub(4) and MgO lead to less electronic transfer from Ni sub(4) to adspecies, which result in weaker adsorption of CH sub(x). Potential energy surface calculations of CH sub(4) dissociation indicate that there are lower energy barriers for the sequent dissociations of CH sub(4) arrow right CH sub(2) + 2H and an appropriate barrier of CH oxidation matching up with that of CH sub(2) further dissociation on the model catalyst of Ni sub(4) supported on defective MgO. This might be an elementary requirement for an excellent CH sub(4) reforming catalyst, and may shed light on experimental catalyst development.