The Challenge of CO Hydrogenation to Methanol: Fundamental Limitations Imposed by Linear Scaling Relations

Recent developments in computational catalysis have allowed the routine reduction of the dimensionality of complex reaction networks to a few descriptors based on linear scaling relations. Despite this convenient benefit, linear scaling relations fundamentally limit the activity and selectivity of a given class of materials towards a given reaction. Here, we show an example by offering a novel description of the fundamental limits on the activity of CO hydrogenation to methanol; a reaction that offers a sustainable route to obtaining value-added chemicals from syngas. First, we show that there is a strong linear correlation between the formation energy of CO* (where * denotes an adsorbed species) and those of the transition states of a number of elementary steps along the methanol synthesis pathway on these surfaces. Using microkinetic modeling, we cast this information into activity volcano plots with the formation energies of a given transition state and CO* as independent descriptors. This analysis reveals the fundamental limits on activity imposed by the aforementioned linear scaling relations, and invites a vigorous search for novel materials that escape these linear scaling relations as a necessary condition for achieving improved activity towards methanol from CO hydrogenation. Specifically, we point out the transition states H–CO* and CH₃O–H* as key transition states to be stabilized independently of CO* for improved activity and selectivity towards methanol synthesis.