Difference between Conduction Band Minimum and Flat-Band Potential in Mott–Schottky Analysis of Anatase TiO2

Abstract

Mott–Schottky analysis is widely used to estimate the band structures of semiconductors, including anatase TiO2, a representative photocatalyst. However, the conduction band minimum (CBM) derived from the flat-band potential (Vfb) in Mott–Schottky analysis often differs from the results obtained using other methods, such as ultraviolet photoelectron spectroscopy. Although this discrepancy has been attributed to environmental variations at the semiconductor–electrolyte interface, the underlying mechanisms remain unclear. This study elucidates the difference between the CBM and Vfb in anatase TiO2 by demonstrating the carrier distribution to higher energy levels. This mechanism is logically deduced from the reported optical spectra and subsequently confirmed by the observed energy distribution of the electrons stored in photocatalytic TiO2 suspensions. These findings highlight the need for careful interpretation when estimating the CBM from the Vfb using Mott–Schottky analysis, particularly for indirect-bandgap semiconductors.