Challenging GC-DFT: Adsorption of pyridine on Au(111) as a model for non-Nernstian effects at electrified interfaces
Year: 2026
Type: article
Abstract: Electrified interfaces are ubiquitous in heterogeneous electrocatalysis. To achieve an atomistic description of their reactivity, grand-canonical density functional theory (GC-DFT) has become one of the most popular and convenient approaches. Moreover, GC-DFT is almost unavoidable to capture non-Nernstian effects. However, the accuracy of the widely used implicit solvation models that are usually used in combination with GC-DFT is limited for metal/water interfaces. We have developed a quantum mechanics (QM)/molecular mechanics (MM) approach, applied separately to the surface and the solvent, respectively, to model the solvent in a more realistic way and maintaining an acceptable computational costs. First, GC-DFT with an implicit solvent is employed to optimize the geometry and determine the atomic charges. This information is then transferred to the MM part, where solvent molecules and electrolyte ions are explicitly added. Following molecular dynamics for the solvent and electrolyte, the average charge distribution is extracted and combined with GC-DFT to retrieve the electrochemical potential. In this work, the hybrid QM/MM scheme with electrostatic embedding is assessed against an experimental model system: the potential-dependent re-orientation of pyridine adsorbed on Au(111). Three adsorption modes of pyridine to Au surface have been reported experimentally: parallel adsorption of the aromatic ring, tilted and perpendicular adsorption via lone-pair electrons of the nitrogen atom. In contrast to implicit solvents, the transition potential is predicted in better agreement with experiment when explicitly taking the solvent into account. While trends are found to be robust across a panel of methods (solvent models and density functional approximations), our benchmarking study demonstrates that both the precise nature of the solvent treatment and the choice of the density functional approximation significantly impacts the reorientation potential and the adsorption energy. Hence, quantitative agreement between computation and experiment for the transition potential, potential-dependent coverage and adsorption energy has not been achieved. This illustrates that the subtle competition between pyridine and water adsorption makes pyridine adsorption on Au(111) a very challenging model system. • Modelling of non-Nernstian effects for pyridine on Au(111). • DFT functional has minor influence on insight compared to the solvent model. • Testing QM/MM-based electrostatic embedding for GC-DFT. • Assessing competition between pyridine and H 2 O on Au(111).
Source: Electrochimica Acta
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,790
OpenAlex ID: W7123728768