Role of solvation model on the stability of oxygenates on Pt(111): A comparison between microsolvation, extended bilayer, and extended metal/water interface

Abstract

The activity of catalysts is mainly dictated by the adsorption strength of reaction intermediates at their surfaces. For electrocatalysts in solution, the adsorption strength is not only determined by the intrinsic properties of catalysts and reactants, but also by the solvation energy of reaction intermediates, which is difficult to capture with theoretical methods. Here, we report the impact of different explicit solvation approaches in estimating the stability of oxygenates on the (111) surface of platinum, widely used in oxygen electrocatalysis. We simulate the adsorption of OH, O, and OOH intermediates, relevant for oxygen reduction and oxygen evolution reactions, on Pt(111) with different solvation environments. We apply the static water bilayer model, typically adopted to calculate solvation energies on Pt(111) in computational studies. We then study the trend of solvation energies under different microsolvation environments, by adsorbing the intermediates in presence of an increasing number of water molecules. Last, we use a dynamic approach based on ab‐initio molecular dynamics (AIMD) to account for dynamic effects. Our results indicate that the stabilities of oxygenates approach those of the water bilayer when the number of molecules increases from zero to three, but the free energies are affected in a not trivial way by the morphology and size of the water cluster, due to the increased complexity and configurational space. Moreover, static methods imply overcorrected free energies. The adoption of a molecular dynamics approach, based on single‐run AIMD simulation of the Pt(111)/H2O interface, allows retrieval estimates close to the experimental observation, including dynamic effects, and is highly transferrable. These results suggest that i) when using a microsolvation scheme, it is recommended to include a few water molecules, up to three to resemble the picture of the static bilayer model; ii) dynamic effects are important and can be included with a single‐run AIMD scheme.

Role of Water Solvation on the Key Intermediates Catalyzing Oxygen Evolution on RuO2

“…The second static solvation model is based on the microsolvation approach recently proposed by Calle-Vallejo et al The basic idea is to approximate the entire solvation environment with a local one made by a few water molecules around the chemical intermediate. In this case, one must consider that small aggregates of water molecules can be characterized by several nearly isoenergetic local minima. − An optimum number of three molecules was found to nearly resemble the energy stabilization induced by an extended water bilayer. , Using this approach, the calculated free energies are 3.94 and 3.02 eV for −OOH and −OO–H, respectively, as shown in Figure S5. This result confirms that a microsolvation environment allows one to mimic the behavior of an extended water bilayer in stabilizing oxygenates.…”

“…40−42 An optimum number of three molecules was found to nearly resemble the energy stabilization induced by an extended water bilayer. 27,43 Using this approach, the calculated free energies are 3.94 and 3.02 eV for −OOH and −OO−H, respectively, as shown in Figure S5. This result confirms that a microsolvation environment allows one to mimic the behavior of an extended water bilayer in stabilizing oxygenates.…”

Hydrogen and oxygen evolution reactions on single atom catalysts stabilized by a covalent organic framework

“…Of course, other effects can be relevant in modeling the reaction, in particular pH-dependence and solvation effects should be considered to provide quantitative predictions. 57–65 Nevertheless, the purpose of this work is to assess the overall ability of SACs stabilized at COF to catalyze HER and OER and to analyze the similarities or differences that TM atoms embedded in COFs present compared to other supporting matrices with similar local structure, such as N-doped graphene or carbon nitride. In this respect, models that do not include solvation effects can provide a first assessment.…”

Evaluating Adsorbate–Solvent Interactions: Are Dispersion Corrections Necessary?

“…Electrocatalytic reactions are largely influenced by the interactions between adsorbates, substrates, solvents, and electrolytes. − Despite its importance, the investigation of solvent–adsorbate and solvent–substrate effects in electrocatalysis is still in its infancy, especially for aqueous solutions and surfaces with defects. − To describe solvent–adsorbate interactions, one can resort to implicit solvent, microsolvation, and explicit solvent methods. The way the solvent is described varies from one family of methods to the next and so do the accuracy and the computational expenses.…”