Improved Electrocatalytic Water Splitting Reaction on CeO2(111) by Strain Engineering: A DFT+U Study

Ceria is a promising cathode material in solid oxide electrolysis cells (SOECs) because ceria can become a mixed electronic and ionic conductor through doping, which enables a high surface area for electrocatalysis. Here, we systemically investigate the effect of strain on the electrocatalytic water splitting reaction (WSR) for renewable hydrogen production on CeO2(111) by using density functional theory corrected for on-site Coulomb interactions (DFT+U). We find that tensile strain stabilizes the reduced states of ceria such as oxygen vacancies and surface hydroxyls, while compressive strain destabilizes the reduced states. These trends are explained by a downshift of the Ce 4f orbital energy under tensile strain and agree with the larger size of the Ce3+ ion in comparison to the Ce4+ ion. Our results show that hydroxyl decomposition into H2 has the highest activation energy along the WSR pathway (Ea) and that the free energy of hydroxyl formation (ΔGH) prior to hydroxyl decomposition can act as a thermo...