Synchrotron Infrared Radiation for Electrochemical External Reflection Spectroscopy: A Case Study Using Ferrocyanide

Abstract

Synchrotron infrared radiation has been successfully coupled through an infrared (IR) microscope to a thin-cavity external reflectance cell to study the diffusion controlled redox of a ferrocyanide solution. Excellent signal-to-noise ratios were achieved even at aperture settings close to the diffraction limit. Comparisons of noise levels as a function of aperture size demonstrate that this can be attributed to the high brilliance of synchrotron radiation relative to a conventional thermal source. Time resolved spectroscopic studies of diffusion controlled redox behavior have been measured and compared to purely electrochemical responses of the thin-cavity cell. Marked differences between the two measurements have been explained by analyzing diffusion in both the axial (linear) and radial dimensions. Whereas both terms contribute to the measured current and charge, only species that originate in the volume element above the electrode and diffuse in the direction perpendicular to the electrode surface are interrogated by IR radiation. Implications for the use of ultramicroelectrodes and synchrotron IR (SIR) to study electrochemical processes in the submillisecond time domain are discussed.

In Situ Electrocatalytic Infrared Spectroscopy for Dynamic Reactions

“…As a consequence, in situ EIRS microscopy has been developed in synchrotron radiation sources worldwide. For example, Burgess et al conducted a series of systematic studies on the redox of ferrocyanide using in situ EIRS microscopy at the Mid-IR beamline of the Canadian Light Source (CLS). − Vincent et al studied the redox of flavin mononucleotide by employing in situ EIRS microscopy on the MIRIAM beamline at the Diamond Light source . It is worth nothing that users of our beamline (infrared spectroscopy and microscopy at the National Synchrotron Radiation Laboratory) also reported various work using IR microscopy methodology developed by our beamline.…”

Attenuated Total Reflection Fourier Transform Infrared (ATR FT-IR) Spectromicroscopy Using Synchrotron Radiation and Micromachined Silicon Wafers for Microfluidic Applications

“…Infrared spectromicroscopy (IR-SM) provides spatially resolved vibrational characterization of materials and has become an established tool in numerous fields including histopathology, 1 characterization of biological cells and tissues, 2,3 and spectroelectrochemistry. [4][5][6][7] One of the major challenges and limitations in conventional IR-SM for microfluidic applications is the large attenuation of IR power due to solvent absorption. Path lengths of approximately < 50 mm are required to prevent broad solvent absorption features from reducing the transmitted IR intensity below useful levels.…”

Femtomole Infrared Spectroscopy at the Electrified Metal–Solution Interface

“…Synchrotron sources of IR offer excellent spatial resolution and have been used, for example, to analyze reaction profiles with high temporal and spatial resolution. , Proof of principle external reflection studies by Rosendahl et al demonstrate that synchrotron infrared (SIR) radiation provides enough brilliance to perform IR-microspectroscopy studies of 50 μm diameter gold electrodes. Generally, the external reflection approach does not afford the surface sensitivity needed to detect monolayer quantities of adsorbed species although Ash and co-workers used external reflectance SIR to study biological flavin cofactors bound on large effective surface area carbon supports .…”