First‐Principles Modeling of the Adsorption Mechanism of Carboxylic and Phosphonic Acids onto Pristine and Defective Delafossite CuAlO₂ Surfaces

Abstract

In order to provide atomistic insights on the mechanism and stability of dye grafting to delafossite surfaces, the authors study, using density‐functional theory calculations in vacuo and in implicit solvent, the adsorption of carboxylic and phosphonic anchoring groups onto stoichiometric and defective slabs exposing the most stable (012) termination. A remarkable increase of the adsorption energies is found on the reduced surfaces when the vacancy is on the top surface layer, in proximity to the molecule. While on the pristine substrate, the monodentate anchoring is the most stable one, and on the reduced interface, a strong bidentate bridging anchoring mode is favored, after the transfer of the hydroxyl proton to the oxygen surface atom adjacent to the copper vacancy. Identification of a largely stable bidentate coordination suggests a possible long‐term device stability, as well as a larger efficiency of the interfacial hole injection, indicating that may be a good alternative to NiO in p‐type photocathodes.

Selenorhodamine-Sensitized CuAlO2 Photocathodes That Reduce Protons to Hydrogen under Visible Illumination

“…The most significant result from these desorption experiments, with respect to selecting a system for photochemical studies, is that 3-SeP persisted on the surface of CuAlO 2 during prolonged immersion in acetonitrile. This result is consistent with recent computational studies by Fatihi et al, who reported that calculated adsorption energies for methylphosphonic acid were 18-to-33% greater than for benzoic acid, on both the pristine (012) surface of CuAlO 2 and a (012) surface with Cu(I) vacancies. The greater adsorption energy of the phosphonic acid, relative to the carboxylic acid, would give rise to an increased activation energy for desorption, which is consistent with our experimental data revealing that 3-SeP is more inert than 1-Se-1 on CuAlO 2 .…”