Ethanol Synthesis from Syngas on Transition Metal-Doped Rh(111) Surfaces: A Density Functional Kinetic Monte Carlo Study

Abstract

Advances in methodology, software and power of supercomputers make computational approaches, specifically, density functional theory (DFT), capable of providing qualitative, and in many cases quantitative, insights into catalysis. In this article we adopted a multiscale modeling paradigm in combination of DFT calculations and kinetic Monte Carlo (KMC) methods to provide better understanding of the promoting effect of doping metals (Fe, Mo, Mn) in ethanol synthesis from syngas on Rh(111). Our calculations show that metal-doping and the position of doped metals can have significant effects on the yield and selectivity of ethanol synthesis on Rh(111). Depending on the reaction conditions, Mo and Mn may stay either on the surface or in the subsurface region, while Fe prefers to stay at the surface and participate in the reaction directly. In term of the overall yield and ethanol yield, Mo–Rh(111) with Mo at the surface layer exhibits the highest activity, followed by Mn–Rh(111) with Mn at the subsurface > Fe–Rh(111) > Mo–Rh(111) with Mo at the subsurface, Mn–Rh(111) with Mn at the surface and Rh(111) in a decreasing sequence. In term of the ethanol selectivity, Fe–Rh(111) displays the highest to ethanol, followed by Mo–Rh(111) with Mo at the surface layer, Mn–Rh(111) with Mn at the subsurface > Mo–Rh(111) with Mo at the subsurface, Mn–Rh(111) with Mn at the surface and Rh(111) in a decreasing sequence. As long as Mo stays at the surface layer, Mo is the only dopant we studied here, being able to enhance both yield and selectivity of ethanol synthesis from syngas on Rh(111). Our results suggest that the design of alloy catalyst should be very careful and controlling the position of dopants is essential to the overall catalytic performance.