Electrochemical Stability of Thiolate Self-Assembled Monolayers on Au, Pt, and Cu

Abstract

Self-assembled monolayers (SAMs) of thiolates have increasingly been used for modification of metal surfaces in electrochemical applications including selective catalysis (e.g., CO 2 reduction, nitrogen reduction) and chemical sensing. Here, the stable electrochemical potential window of thiolate SAMs on Au, Pt, and Cu electrodes is systematically studied for a variety of thiols in aqueous electrolyte systems. For fixed tail-group functionality, the reductive stability of thiolate SAMs is found to follow the trend Au < Pt < Cu; this can be understood by considering the combined influences of the binding strength of sulfur and competitive adsorption of hydrogen. The oxidative stability of thiolate SAMs is found to follow the order: Cu < Pt < Au, consistent with each surface's propensity toward surface oxide formation. The stable reductive and oxidative potential limits are both found to vary linearly with pH, except for reduction above pH ∼10, which is independent of pH for most thiol compositions. The electrochemical stability across different functionalized thiols is then revealed to depend on many different factors including SAM defects (accessible surface metal atom sites decrease stability), intermolecular interactions (hydrophilic groups reduce the stability), and SAM thickness (stability increases with alkanethiol carbon chain length) as well as factors such as SAM-induced surface reconstruction and the ability to directly oxidize or reduce the non-sulfur part of the SAM molecule.

Layered Sn–Au Thin Films for Increased Electrochemical ATR-SEIRAS Enhancement

“…Thiolate stability under reducing conditions was not directly evaluated in this work. But, following previous reports in the literature, on Au-based electrocatalysts, decanethiols drop below 75% of a monolayer above the theoretical HER onset potential, while in the case of Sn-based electrocatalysts, decanethiols were proposed to desorb reductively around the SnO x reduction potential . As an attempt to compare penetration and propagation lengths, while considering a simplified set of equations (Supporting Information), we calculated a ratio of ∼1.41 for Sn/Au penetration depth (normal to the surface) and a ratio of ∼0.07 for Sn/Au lateral propagation depth (parallel to the surface).…”

Combining Renewable Electricity and Renewable Carbon: Understanding Reaction Mechanisms of Biomass-Derived Furanic Compounds for Design of Catalytic Nanomaterials

“…Further design strategies to alter rates and product selectivity can be considered. One example may be in creative engineering of the microenvironment of the active site through modification of catalysts using electrolyte engineering or organic ligands. , Beyond traditional alloys, the electronic structure of isolated atomic sites may even be tailored to target specific molecular orbitals of reactant molecules to achieve a desired selectivity . Additionally, catalyst deactivation prevents practical applications of many systems.…”

Electrochemical reduction of carbon dioxide to multicarbon (C2+) products: challenges and perspectives

“…In this regard, organic molecular functionalization-based surface modification has been achieved by different additives, such as N-containing compounds (amino acids, phenanthroline and the corresponding derivatives), S-containing compounds (alkanethiols) or Pcontaining compounds. [145][146][147] All the above-mentioned organic molecules can dramatically change the electronic structure of active metal sites, resulting in the optimization of *CO/*H coverage, hydrogen bond interactions and hydrophobic effects. Another effective approach is heteroatom doping for tailoring the spin state and electronic structure of active sites.…”