Photoelectrochemical Methods for Flat Band Potential Estimation: Case Studies of ZnO Nanorods and TiO₂ Compact Films

Semiconductor materials play a major role in the use of solar energy. ZnO and TiO₂-based nanomaterials have been broadly used in photocatalytic applications, such as water splitting and environmental remediation. In order to determine the thermodynamic feasibility in a specific application, it’s important to determine the electronic band structure of these materials. This determination of the energetics in the semiconductor can be conducted from different approaches, usually by first determining the bandgap and conduction band edge. The bandgap determination is made through well-defined and standardized processes, unlike the conduction band, where the discrepancy is found between the values reported by different authors under the same conditions. In this article a comparison is made between the Mott-Schottky, photocurrent onset potential, and open-circuit potential (OCP) methods, as techniques of determining the flat band potential, taking as case studies the two semiconductor materials mentioned above. This comparison is followed by a discussion of the difficulties that may arise during experimentation and the possible difference between the values reported by each method.