Formic acid adsorption on K2O(110): A density functional theory study

The deactivation of basic heterogeneous catalysts by free fatty acids (FFAs) remains a critical limitation in biodiesel production, particularly due to adsorption–induced surface degradation and the eventual loss of active species. In this work, Density Functional Theory (DFT) calculations are employed to investigate the adsorption of formic acid, as a model FFA, on the K 2 O(110) surface and its role in initiating catalyst degradation. Both molecular and dissociative adsorption configurations are identified, with the latter exhibiting strong chemisorption (E ads up to −3.85 eV). Dissociative adsorption leads to the formation of a surface hydroxyl group and a strongly bound formate species, accompanied by significant structural distortions. In particular, pronounced displacement of surface K + ions and severe weakening of K–O bonds are observed, reaching bond order reductions of up to 95%, consistent with substantial destabilization of the surface K–O framework. Electronic structure analysis, including projected density of states and Bader charge calculations, reveals charge transfer from the surface to the adsorbate and strong hybridization between molecular and surface states. These findings highlight the critical role of dissociative FFA adsorption in inducing localized structural and electronic modifications of the K 2 O surface. Overall, the observed bond weakening provides atomistic insight into the adsorption–induced structural and electronic modifications that destabilize the K 2 O surface at the atomic scale. These findings contribute to a mechanistic understanding of the initial stages of catalyst degradation and provide atomistic design principles for the development of more durable basic catalysts by highlighting the importance of strengthening surface metal–oxygen interactions while preserving adequate basicity for catalytic activity.