Kinetic Simulations of CO2 Hydrogenation to Ethanol on Pd2Cu (110)

Abstract

Conversion of CO₂ to ethanol is a potential method for carbon capture and utilization. Among various catalysts for this reaction, Pd₂Cu is found to have high activity and selectivity. In this paper, we investigated the reaction mechanism using mean-field microkinetic modeling (MF-MKM) and kinetic Monte Carlo (kMC) simulations. To overcome the stiffness problem caused by the significant difference in time scales of different events in kMC simulation, we employed the ads-kMC algorithm proposed in our previous work, in which the adsorption/desorption/reaction rate constants were reduced under certain requirements and the diffusion process was treated by redistributing surface species each time an event occurs. Both methods show similar surface coverage, i.e., the surface is fully covered by H and CO and exhibits high selectivity for ethanol. This study also compares the effect of species diffusion rates on the kMC simulations. The results show that the diffusion rate changes the reaction mechanism and coverage, and under slow diffusion case the kMC predicted selectivity is higher than that under fast diffusion. The present study sheds light on the mechanism of CO₂ hydrogenation to ethanol on Pd₂Cu catalyst, deepens the understanding of kMC and MF-MKM simulations, and examines the influence of species diffusion on reaction kinetics.