Recent Advances in in‐situ Infrared Spectroscopy and Applications in Single‐Crystal Electrochemistry and Electrocatalysis

In Situ Confocal Raman Microscopy of Redox Polymer Films on Bulk Electrode Supports

A spectroelectrochemical cell is described that enables confocal Raman microscopy studies of electrode-supported films. The confocal probe volume (∼1 μm³) was treated as a fixed-volume reservoir for the observation of potential-induced changes in chemical composition at microscopic locations within an ∼20 μm thickness layer of a redox polymer cast onto a 3 mm diameter carbon disk electrode. Using a Raman system with high collection efficiency and wavelength reproducibility, spectral subtraction achieved excellent rejection of background interferences, opening opportunities for measuring within micrometer-scale thickness redox films on widely available, low-cost, and conventional carbon disk electrodes. The cell performance and spectral difference technique are demonstrated in experiments that detect transformations of redox-active molecules exchanged into electrode-supported ionomer membranes. The in situ measurements were sensitive to changes in the film oxidation state and swelling/deswelling of the polymer framework in response to the uptake and discharge of charge-compensating electrolyte ions. The studies lay a foundation for confocal Raman microscopy as a quantitative in situ probe of processes within electrode-immobilized redox polymers under development for a range of applications, including electrosynthesis, energy conversion, and chemical sensing.

Surface Sensitive Infrared Spectroelectrochemistry using Palladium Electrodeposited on ITO-Modified Internal Reflection Elements

Palladium nanoparticles have been electrodeposited on the surfaces of conductive indium tin oxide (ITO) modified silicon internal reflection elements. The resulting films are shown to be excellent platforms for attenuated...

Surface enhanced infrared spectroelectrochemistry using a microband electrode

The successful use of a microband electrode printed on a silicon internal reflection element to perform time resolved infrared spectroscopy is described. Decreasing the critical dimension of the microband electrode to several hundred micrometers provides a sub-microsecond time constant in a Kretschmann configured spectroelectrochemical cell. The high brilliance of synchrotron sourced infrared radiation has been combined with a specially designed horizontal attenuated total reflectance (ATR) microscope to focus the infrared beam on the microband electrode. The first use of a sub-microsecond time constant working electrode for ATR surface enhanced infrared absorption spectroscopy (ATR-SEIRAS) is reported. Measurements show that the advantage afforded by the high brilliance of the synchrotron source is at least partially offset by increased noise from the experimental floor. The test system was the potential induced desorption of an adsorbed monolayer of 4-methoxypyridine (MOP) as measured using step-scan interferometry. Based on diffusion considerations alone, the expected time scale of the process was less than 10 microseconds but was experimentally measured to be three orders of magnitude slower. A defect-mediated dissolution of the condensed film is speculated to be the underlying cause of the unexpected slow kinetics.