Quantitative correlation between cyclic voltammetry and electrochemical impedance spectroscopy models on TiO2 film electrodes

Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) are widely used to characterize semiconductor electrodes, yet their quantitative equivalence is not often established. Here, we introduce a model framework that clarifies when CV and EIS probe the same physical processes and when they diverge on TiO 2 film photoelectrodes with controlled thickness and morphology. EIS measurements are registered at different potentials, covering the whole CV window, and show a progressive evolution. In the general case, outside the charge-accumulation regime, the low-frequency limit of EIS converges quantitatively with a density-of-states-based CV description, demonstrating that both techniques capture identical electronic responses. At more cathodic potentials, systematic deviations arise: EIS yields larger capacitances and lower Faradaic resistances than CV. These discrepancies possibly originate from the different timescales of the techniques, as the longer polarization of EIS may activate slow electrochemical processes that are kinetically inaccessible during CV. The divergence between CV and EIS therefore suggests an onset for different charge transport regimes. In this way, the proposed framework provides a predictive diagnostic tool for TiO 2 film electrodes, supporting a consistent interpretation and cross-validation of classical CV and EIS data.