Diffusion layer imaging and the related electrochemistry studied by optical absorption spectroscopy

Due to the fundamental importance of mass transport to electrochemical processes, significant theoretical and experimental efforts have been expanded to study the shape and dynamics of concentration vs. distance profiles. Observing the shapes and behavior of concentration profiles, the thickness of which is usually thin at about 100 {dollar}mu{dollar}m, has become possible using the spatially resolved absorption spectroelectrochemical (SRAS) technique. By adapting a continuum light source (xenon arc lamp), the utilities and versatility of SRAS have been broadened greatly in studying electrochemical reactions and mass transport processes.; SRAS with a broad band source is used for multi-wavelength monitoring of electrochemical reaction products and diffusion processes. In the planar electrode case, SRAS is used to study the diffusion processes at transient as well as steady states with a single and a twin electrodes geometries. In the case of microcylindrical electrodes, SRAS is used to obtain cylindrical concentration profiles and to reveal unexpected mass transport effects in electrochemical studies. SRAS is expanded into a two-dimensional imaging system by using a CCD detector to obtain information of three-dimensional diffusion at microdisk electrodes and arrays, and to study the surface activities of electrochemical processes with electrogenerated chemiluminescence (ECL). As an example, SRAS is used to study homogeneous reactions between chlorpromazine cation radical (CPZ{dollar}cdotsp{lcub}+{rcub}{dollar}) and dopamine (DA) initiated electrochemically.