Cooperative Effects Drive Water Oxidation Catalysis in Cobalt Electrocatalysts through the Destabilization of Intermediates.

A barrier to understanding the factors driving catalysis in the oxygen evolution reaction (OER) is understanding multiple overlapping redox transitions in the OER catalysts. The complexity of these transitions obscure the relationship between the coverage of adsorbates and OER kinetics, leading to an experimental challenge in measuring activity descriptors, such as binding energies, as well as adsorbate interactions, which may destabilize intermediates and modulate their binding energies. Herein, we utilize a newly designed optical spectroelectrochemistry system to measure these phenomena in order to contrast the behavior of two electrocatalysts, cobalt oxyhydroxide (CoOOH) and cobalt-iron hexacyanoferrate (cobalt-iron Prussian blue, CoFe-PB).

Phenol as a Tethering Group to Gold Surfaces: Stark Response and Comparison to Benzenethiol.

Understanding the adsorption of organic molecules on metals is important in numerous areas of surface science, including electrocatalysis, electrosynthesis, and biosensing. While thiols are commonly used to tether organic molecules on metals, it is desirable to broaden the range of anchoring groups. In this study, we use a combined spectroelectrochemical and computational approach to demonstrate the adsorption of 4-cyanophenols (CPs) on polycrystalline gold.

Direct Determination of Plasmon Enhancement Factor and Penetration Depths in Surface Enhanced IR Absorption Spectroscopy.

Surface Enhanced Infrared Absorption Spectroscopy (SEIRAS) is a powerful tool for studying a wide range of surface and electrochemical phenomena. For most electrochemical experiments the evanescent field of an IR beam partially penetrates through a thin metal electrode deposited on top of an attenuated total reflection (ATR) crystal to interact with molecules of interest. Despite its success, a major problem that complicates quantitative interpretation of the spectra from this method is the ambiguity of the enhancement factor due to plasmon effects in metals.

Controlling Water Delivery to an Electrochemical Interface with Surfactants.

Most electrochemical reactions require delivery of protons, often from water, to surface-adsorbed species. However, water also acts as a competitor to many such processes by directly reacting with the electrode, which necessitates using water in small amounts. Controlling the water content and structure near the surface is an important frontier in directing the reactivity and selectivity of electrochemical reactions.

Adiabatic Frequency Conversion Using a Time-Varying Epsilon-Near-Zero Metasurface.

A time-dependent change in the refractive index of a material leads to a change in the frequency of an optical beam passing through that medium. Here, we experimentally demonstrate that this effect-known as adiabatic frequency conversion (AFC)-can be significantly enhanced by a nonlinear epsilon-near-zero-based (ENZ-based) plasmonic metasurface. Specifically, by using a 63-nm-thick metasurface, we demonstrate a large, tunable, and broadband frequency shift of up to ∼11.

Interfacial Polarization and Ionic Structure at the Ionic Liquid-Metal Interface Studied by Vibrational Spectroscopy and Molecular Dynamics Simulations.

Ionic liquids (ILs) have both fundamental and practical value in interfacial science and electrochemistry. However, understanding their behavior near a surface is challenging because of strong Coulomb interactions and large and irregular ionic sizes, which affect both their structure and energetics. To understand this problem, we present a combined experimental and computational study using a vibrational probe molecule, 4-mercaptobenzonitrile, inserted at the junction between a metal and a variety of ILs.

Strong Propensity of Ionic Liquids in Their Aqueous Solutions for an Organic-Modified Metal Surface.

Understanding ionic structure and electrostatic environments near a surface has both fundamental and practical value. In electrochemistry, especially when room temperature ionic liquids (ILs) are involved, the complex ionic structure near the interface is expected to crucially influence reactions. Here we report evidence that even in dilute aqueous solutions of several ILs, the ions aggregate near the surface in ways that are qualitatively different from simple electrolytes.