High coverage adsorption and co-adsorption of CO and H₂ on Ru(0001) from DFT and thermodynamics

Abstract

The adsorption and co-adsorption of CO and H2 at different coverages on p(4 × 4) Ru(0001) have been computed using periodic density functional theory (GGA-RPBE) and atomistic thermodynamics. Only molecular CO adsorption is possible and the saturation coverage is 0.75 ML (nCO = 12) with CO molecules co-adsorbed at different sites and has a hexagonal adsorption pattern as found by low energy electron diffraction. Only dissociative H2 adsorption is possible and the saturation coverage is 1 ML (nH = 16) with H atoms at face-centered cubic sites. The computed CO and H2 desorption patterns and temperatures agree reasonably with the experiments under ultrahigh vacuum conditions. For CO and H2 co-adsorption (nCO + mH2; n = 1-6 and m = 7, 6, 5, 5, 3, 1), CO pre-coverage affects H adsorption strongly, and each pre-adsorbed CO molecule blocks 2H adsorption sites and H2 does not adsorb on the surface with CO pre-coverage larger than 0.44 ML (nCO = 7); all these are in full agreement with the experiments under ultrahigh vacuum conditions. Our results provide the basis for exploring the mechanisms of catalytic conversion of synthesis gas.

Coverage and Stability of NHx Terminated Cobalt and Ruthenium Surfaces: a First Principles Investigation

“…The contribution of vibrations to the solid surface is negligible and can be substituted by the results from DFT. 52 The gas phase term can be calculated by the equation (2):…”

Scalable approach to high coverages on oxides via iterative training of a machine‐learning algorithm

“…[19][20][21][22][23] For example, the ordered structures of CO on Co (0001), Ru(0001) and Pt (111) surfaces can be tuned by lateral interactions under different coverages. [24][25][26] In addition, the NO adsorption has been studied with both experiment and theoretical techniques on the TiO 2 (110) surface, the results found that N 2 O molecules as reduction product desorbed at 250 K. [27] The formation of N 2 O was observed to increase with NO coverage at 110 K, indicating that coverage effects play a role. [28] Theoretical calculations also demonstrated that the halfmonolayer coverage of NO on the TiO 2 (110) is in agreement with the experimental results.…”

“…Surface phase diagrams are widely used to study the most stable surface composition as a function of reaction conditions. [25,26,31] For the low-coverage surface configurations of metals, full DFT calculations are relatively computationally inexpensive and are commonly used to identify the stability of a species on the surface. In addition, linear scaling relations driven by the d-band model have been established for adsorbates at low-coverage on metal surfaces, where the slope of the scaling relations follows simple bond counting principles.…”

Adsorption and Dissociation of CO2 on Ru(0001)

“…While metallic ruthenium is known to catalyze the reverse water gas shift reaction, its interaction with CO 2 has not, to our knowledge, been the subject of investigation. 5−8 The chemisorption and reaction of CO 2 on metal oxides, including RuO 2 , and metallic alloys, including Ru, are well-studied processes. 1,3 Moreover, the adsorption of CO 2 on other single-crystal metal surfaces has been extensively studied.…”