The carbon deposition process on NiFe catalyst in CO methanation: A combined DFT and KMC study

Carbon deposition often occurs in CO methanation on NiFe catalyst, resulting in the deactivation of the catalyst, which is an urgent problem to be solved in industrial production. In this work, the carbon deposition process on the surface of NiFe catalyst was systematically investigated by the combination of Density Functional Theory (DFT) and Kinetic Monte Carlo (KMC). The results of DFT calculations show that for C1 similar to C9, the most stable adsorption configurations are carbon chains while for C10 and C11, the carbon rings are the most stable. Besides, in the reaction network of carbon deposition, the formation of C2 is the key reaction with high activation energy. KMC simulation shows that temperature can significantly affect the occurrence of carbon deposition and C2 will accumulate and react to form larger carbon species instead of decomposing. In addition, the growth rate of carbon chains is faster than that of carbon rings, and carbon species mainly react with C1 and C2 to form longer carbon chains. Therefore, the anti-carbon deposition performance of the catalyst can be improved by increasing the activation energy of carbon-carbon coupling and inhibiting the formation of C2.