Structure-sensitive scaling relations among carbon-containing species and their possible impact on CO2 electroreduction

Abstract

The arduous modelling of reactions at heterogeneous catalysts is greatly simplified when adsorption-energy scaling relations between intermediates exist. The offset of these linear relations is structure-independent when the slope is unity and otherwise depends on the coordination number of the active sites. Here we examine the adsorption of *C, *CH, *CH2, *CH3 and *COH on five different surface sites of nine transition metals to establish their structure-sensitive scaling relations. Interestingly, we show that the scaling relations of *C (valency 4) and C-containing species with valency 3 (*CH, *COH) have peculiar structure-independent offsets. These offsets stem from the analogous bonding of those adsorbates to the adsorption sites, in spite of their dissimilar valency. We show how this result implies that reaction pathways in catalysis involving *C, *CH and *COH, for instance CO2 electroreduction to CH4, will usually have sizable thermodynamic limits imposed to their optimization.