Mechanism of CO2 reduction by H2 on Ru(0001) and general selectivity descriptors for late-transition metal catalysts

[Display omitted] •CO2 reduction by H2 on Ru studied with DFT calculations and microkinetic modeling.•CO∗ is common intermediate for competing CH4 and CO production pathways.•CHO* identified as initial hydrogenated intermediate leading to CH4 production.•Rate limiting steps for CO and CH4 production are CO* desorption and CHO* dissociation.•O∗ adsorption energy is an effective descriptor of selectivity between CO and CH4. The mechanism of CO2 reduction by H2 at atmospheric pressure was investigated on Ru(0001) by coupling density functional theory (DFT) calculations with mean-field microkinetic modeling. The initial CO2 hydrogenation step leading to CH4 production was shown to occur through CO2 dissociation and subsequent hydrogenation of CO∗ to CHO∗. The dissociation of CHO∗ to form CH∗ and O∗ was identified as the rate limiting step for CH4 formation, while the rate limiting step for CO production through the reverse water gas shift reaction was identified as CO∗ desorption. Based on a scaling relations analysis of competing CHO∗ dissociation and CO∗ desorption, O∗ adsorption energy was found to be an effective descriptor of differences in selectivity between CO and CH4 production previously observed on late-transition metal catalysts. These mechanistic insights provide critical information to guide the design of catalysts with tunable selectivity for CO2 reduction by H2 at atmospheric pressure.