Dependency of solvation effects on metal identity in surface reactions

Abstract

Solvent interactions with adsorbed moieties involved in surface reactions are often believed to be similar for different metal surfaces. However, solvents alter the electronic structures of surface atoms, which in turn affects their interaction with adsorbed moieties. To reveal the importance of metal identity on aqueous solvent effects in heterogeneous catalysis, we studied solvent effects on the activation free energies of the O–H and C–H bond cleavages of ethylene glycol over the (111) facet of six transition metals (Ni, Pd, Pt, Cu, Ag, Au) using an explicit solvation approach based on a hybrid quantum mechanical/molecular mechanical (QM/MM) description of the potential energy surface. A significant metal dependence on aqueous solvation effects was observed that suggests solvation effects must be studied in detail for every reaction system. The main reason for this dependence could be traced back to a different amount of charge-transfer between the adsorbed moieties and metals in the reactant and transition states for the different metal surfaces.

Liquid-Phase Effects on Adsorption Processes in Heterogeneous Catalysis

“…To numerically verify the proposed methodology for adsorption/desorption processes, the aqueous-phase effect on the free energy of activation (ΔΔ G liq ‡ = Δ G liq ‡ – Δ G gas ‡ ) of the O–H bond cleavage of ethylene glycol over a Cu(111) surface at 423 K is computed using two different approaches, the eSMS methodology for surface reactions 25 and the adsorption scheme proposed here. In our proposed adsorption scheme, the solvent effect on the activation barrier (ΔΔ G liq ‡ ) is given by eq 4 where ΔΔ G TS gas→liq and ΔΔ G Reactant gas→liq indicate the solvent effect on the adsorption of the transition state (TS) and reactant state (RS), respectively.…”

“…In addition, recent simulations suggest that solvation effects are not only a strong function of adsorbate but also of the nature of the catalyst surface (e.g., Pt vs Cu). 25 Solvation effects do not cancel out in a descriptor-based catalyst design strategy, and solvation effects need to be considered explicitly. Differences in 1 eV in adsorption free energy are just too large as they could be neglected in any descriptor-based catalyst design strategy.…”

“…In this regard, we previously developed a computationally affordable and reliable method for computing free-energy changes in the presence of solvents using a hybrid QM/MM approach with electrostatic embedding, named Explicit Solvation for Metal Surfaces (eSMS) 55 and applied it to several surface reactions over various transition-metal surfaces. 25 , 56 …”

Hydrogen Spillover‐Enhanced Heterogeneously Catalyzed Hydrodeoxygenation for Biomass Upgrading

“…In addition, Zare et al. investigated the relationship between the aqueous phase and these descriptors by means of three intuitive descriptors, namely charge transfer effects, hydrogen bonding, and the gas‐phase activation free‐energy barrier [63] . In brief, the aqueous phase effect arises mainly for the various charge transfer effects of the different metals and, secondly, correlates with the number of hydrogen bonds and the gas‐phase activation barriers of the different metals.…”

Nonaqueous Solvent Adsorption on Transition Metal Surfaces with Density Functional Theory: Interaction of N,N-Dimethylformamide (DMF), Tetrahydrofuran (THF), and Dimethyl Sulfoxide (DMSO) with Ag, Cu, Pt, Rh, and Re Surfaces

“…Theoretical work has also been carried out to help develop the fundamental understanding of metal–solvent interactions. There are many first-principles studies of aqueous solvent effects at transition metal interfaces using a variety of implicit and explicit solvent methods. − Previous studies on aqueous metal interfaces have shown the importance of competitive adsorption of solvent molecules, which is strongly dependent on metal and surface facets, and is typically only able to be captured using explicit-solvent approaches . Theoretical studies of the effects of nonaqueous solvents and their interfaces with metal surfaces have been carried out, − but are relatively less common than studies on aqueous systems, especially when considering the large number of nonaqueous solvents available.…”