Simultaneous determination of interfacial and kinetic currents at the WSe/sub 2//acetonitrile

The knowledge of the interfacial energetics (band edge potentials, doping density, and formal reduction potential) of a semiconductor electrode immersed in a solution containing a redox couple is crucial to the interpretation of electron-transfer rates. The techniques used for the acquisition of impedance data simultaneous with current-potential measurements at both n- and p-type WSe/sub 2/ electrodes with doping densities spanning 3 orders of magnitude are described. The band edges were found to be energetically stable in the presence of different redox couples at differing concentrations. Evidence is presented to support the technique of simultaneous interfacial energetic determinations and to defend the validity of carefully executed impedance determinations of interfacial energetics. Simultaneous current-potential and impedance-potential data are reported for decamethylferrocene/sup +,0/ and ferrocene/sup +,0/ at an n-WSe/sub 2/ electrode with a doping density of 2.8 /times/ 10/sup 17/ cm/sup /minus/3/. The behavior of these two outer-sphere redox couples is dramatically different with respect to the shape of the current-potential curves and the dependence of the current on the concentration of solution species. The exchange current densities are compared to theoretical predictions.