Mechanistic insights into chemical reduction of CO2 by reverse water-gas shift reaction on Ru(0001) surface: The water promotion effect

In this work, we systematically illustrate CO2 reduction by H-2 on the Ru(0001) surface using periodic DFT calculations with micro-kinetic modeling to explore adsorbate-substrate, adsorbate-solvent, solvent-substrate interactions as well as reaction mechanisms. The effects of adsorbate-substrate interactions, water-mediated protonation kinetics, thermodynamics, and transient potential sweeps on reaction rate and selectivity are also studied. We propose three simple thermodynamic descriptors (CO + O, HCOO, and COOH) that represent the effectiveness of CO selectivity on Ru catalysts. More importantly, we explore the role of water solvation on the CO2 conversion by assessing the H-shuttled (O-H bond formation) and water solvated (C-H bond formation) with various solvation models. To examine the solvation effect, a 6H(2)O/Ru(0001) water bilayer model is constructed by optimizing six H2O molecules close to the Ru surface, and multiple H-bonds are observed as local-minimum solvation structures among water molecules. Finally, the efficiency of the ruthenium catalyst is expressed by turnover frequencies (TOFs). We hope that these insights will deliver useful guidelines for designing more efficient, earth-abundant electrocatalysts in the future.

Automated summary

In this study, the CO2 reduction on the Ru(0001) surface using H-2 is systematically investigated through DFT calculations and micro-kinetic modeling. The effects of adsorbate-substrate interactions, water solvation, and thermodynamics on reaction rate and selectivity are analyzed. Thermodynamic descriptors are proposed to represent the effectiveness of CO selectivity on Ru catalysts. The solvation effect is examined using a water bilayer model, and the efficiency of the ruthenium catalyst is expressed by turnover frequencies (TOFs).