The need to reduce atmospheric CO₂ concentrations has necessitated the growth of technologies for CO₂ capture and conversion. Electrocatalysis plays a key role in reducing CO₂ under milder conditions in a controlled environment. A silver nanoparticle/ordered ligand interlayer (NOLI) system in an aqueous electrolyte has been shown to demonstrate CO₂ reduction to CO in a specific range of negative electric potentials. The silver-ligand interaction results in four possible binding configurations, corresponding to the number of oxygen atoms of the ligand attached to the Ag surface: non-dentate, monodentate, bidentate, and tridentate configurations with 0, 1, 2, and 3 oxygens attached, respectively. Understanding the bias-induced ligand behavior on silver surface during the formation of NOLI is the key towards understanding its performance with the objective of enhancing it further. In this work, we use computational modeling via density functional theory to investigate the bias-driven structural evolution of the NOLI system, evaluate the effect of electric potential on it, and provide an understanding of the atomistic phenomena that drive these structural changes. We find that while the monodentate configuration is the most thermodynamically stable state, the bidentate structure is the kinetically favorable one. These configurations were found to be highly sensitive to the presence of solvent water molecules in the region between the ligand and the surface, indicating that we require some degree of explicit solvent modeling to represent the phenomena at the atomistic scale. In fact, the explicit presence of water acting in tandem with fewer oxygen attachment favored by the Ag surface result in the lower dentate configurations being more favorable at more negative potentials, making the non-dentate structure the most stable at the most negative potentials. Moreover, the extended pocket formed between the surface and the ligand from complete detachment of the ligand in the non-dentate structure, in combination with the presence of easily movable water molecules in that pocket result in this configuration providing the highest CO selectivity for electrocatalysis. This work highlights the importance of solvent effects in electrocatalysis and demonstrates its intricate relationship with structure and energetics.

Peidong Yang

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