Abstract
A thorough framework for how to interpret and predict the steady-state voltammetric responses of semiconductor ultramicroelectrodes (SUMEs) has been compiled. Through consideration of the Marcus–Gerischer treatment for heterogeneous charge transfer and the interplay between the fractions of the applied potential that drop across the space-charge region, the solution, and their interface in depletion and accumulation conditions, the complex potential dependences of the majority carrier densities, n s, and the rate constant for electron transfer from the conduction band edge, k et, are identified. Incorporation of these terms in the conventional fitting procedures of steady-state voltammetry at inlaid disk electrodes affords determination of the full J–E responses of n-type SUMEs in a variety of experimental permutations. Working curves are presented to illustrate how the specific values of the conduction band edge potential, the reorganization energy for charge transfer, the standard potential of the redox species, and the doping density control the form of the voltammetric responses of a pristine semiconductor/electrolyte interface. Further working curves are provided to highlight the expected influence of surface states on the steady-state voltammetry of SUMEs. An example of how to analyze experimental data without the use of “non-ideality” factors is shown, illustrating that it is possible to extract validated estimates of heterogeneous charge-transfer constants and the defect character of the semiconductor/electrolyte interface. In total, this work provides a clear guide for utilizing simple, raw voltammetric data from SUMEs to study semiconductor/electrolyte contacts of interest.