Theoretical study coupling DFT calculations and kMC simulation of CO methanation on Ni(111) and Ni3Fe(111)

Abstract

Obtaining synthetic natural gas from coal is an effective way to alleviate the contradiction between supply and demand of natural gas, realize clean and efficient utilization of coal, and promote the development of energy transformation. Syngas methanation is the core technology of coal-to-natural gas conversion, in which an efficient catalyst is the key. As one of the most promising methanation catalytic systems, Ni-based catalysts have attracted extensive attention in academia and industry. In this work, the mechanism of CO methanation on the surface of Ni and Ni₃Fe(111) was first studied with DFT calculations, and the results were compared with previous research results. It was found that the surface activity of Ni(111) and Ni₃Fe(111) is very low, while Ni(211) and Ni₃Fe(211) have significantly higher activity. The (211) surface is more conducive to CH₄ generation than the (111) surface. The microkinetics of CO methanation over Ni and Ni₃Fe catalysts was studied using the kMC method. The comparison between (111) and (211) surfaces further indicated that, under reaction-dependent conditions, the (111) surface was not the main catalytic activity surface, but the (211) surface could be used as an effective catalytic activity surface. It is also found that the CH₄ conversion frequency at Ni₃Fe(211)-AA is equivalent to that at Ni(211), while the CH₄ conversion frequency at Ni₃Fe(211)-AB is about one order of magnitude higher than that at Ni(211), indicating that Ni₃Fe(211)-AB has high activity.