Disentangling Chemical Interaction and Electric Fields at Electrochemical Interfaces
Year: 2024
Type: article
Abstract: The specific binding of solution components to a catalytic surface and the interfacial electric field are critical to electrocatalysis, but the two factors are entangled. Distinguishing whether adsorbate binding to the surface is governed by through-bond charge transfer that is modulated by a field or through-space electrostatic effects is essential for rational catalyst design. Here, we probed the binding of thiocyanate (SCN – ) to Au and Pd as a function of applied potential (ϕ app ) using surface-enhanced infrared absorption spectroscopy (SEIRAS). The IR data showed distinct shifts of the CN stretching wavenumbers (ν̃ CN ) with ϕ app for S- versus N-bound SCN – and on Au versus Pd. These ν̃ CN shifts with ϕ app are the result of different extents of through-space electric field (Stark) effects and through-bond chemical binding effects. The presence of two binding modes of SCN – on the metal surfaces provided two separate interfacial probes, which enabled estimating the contributions of the two effects to the overall ν̃ CN versus ϕ app slopes quantitatively. Competitive adsorption experiments using SCN – and different halides (Cl –, Br –, and I – ) support our conclusions. While the through-bond effect for S-bound SCN – is more pronounced on Pd than on Au, that of N-bound SCN – is similar. Our data also suggest a similar electric field change with ϕ app on Pd and Au. This work offers a method to differentiate key contributors to interfacial chemistry in an external electric field and provides important groundwork for the development of future electrocatalysts.
Authors: Tzu-Chin Chang Chien, Murielle F. Delley
Institution: University of Basel
Language: English
Field: Energy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W4405883922