Investigation of a Free-Standing Boron-Doped Diamond Grid Electrode for Fundamental Spectroelectrochemistry

Spectroelectrochemistry (SEC) is a technique for studying redox properties and characterizing electrochemical and optical properties of electrodes, including diffusion coefficient (D) and heterogeneous electron transfer rate constant (k). SEC measurements require an optically transparent electrode (OTE), traditionally composed of metal or metal oxide films atop transparent substrates (one-electroactive side) or the use of a metallic mesh (two-electroactive sides). Robust electrode materials like boron-doped diamond (BDD) could expand the environments in which SEC can be performed. In this work, a grid is laser-cut into a free standing BDD electrode (G-BDD) for fundamental SEC measurements, such as chronoabsorptometry for the determination of D and k. The chronoabsorptometry equation, which relates absorbance to D, was modified in 1971 by the Murray group to account for electrodes with two electroactive sides. This necessitates a multiplication factor of two. To accurately determine the electrochemical properties of the G-BDD electrode a third dimension must be considered due to the development of diffusion layers on either side and inside the grid holes. This suggests a multiplication factor greater than two would better represent the system. Furthermore in 1981 Hawkridge and Blount reported on a spectroelectrochemical method for the determination of k that is independent of the surface area of the working electrode. The redox couple of ferricyanide(II) (Fe(CN)6^4-/3-) was used to compare the redox properties obtained from cyclic voltammetry and chronoabsorptometry. The redox properties of the G-BDD were compared with electrodes with one- (indium tin oxide coated glass slides) and two- (platinum grid) electroactive dimensions. This work expands on the applicability of BDD as an electrode material and broadens the general applicability of SEC.