Generalized Mott–Schottky Analysis of Photoelectrodes

Mott–Schottky
analysis is a widely used technique for characterizing
photoelectrodes that are critical to photoelectrochemical energy conversion.
However, its validity depends on strict assumptions that are often
overlooked, leading to potential inaccuracies in the interpretation
of experimental data. In this study, we present an extended theoretical
framework that overcomes the limitations of conventional Mott–Schottky
analysis. This improved approach accounts for nonlinearities commonly
observed in experimental data by considering the influence of the
electrostatic potential in the Helmholtz layer. Reanalysis of literature
data using this enhanced model demonstrates significant revisions
in key parameters, including reductions in donor density by up to
a factor of 5 and flat-band potential shifts of 0.1 V, while achieving
a better fit to experimental observations. Importantly, the modified
equation is consistent with a linear-conventional Mott–Schottky
analysis for materials with low doping density. These refinements
underscore the need for adopting this generalized Mott–Schottky
analysis in the electrochemical characterization of energy materials.