Decoupling pH dependence of flat band potential in aqueous dye-sensitized electrodes

Yongze Yu, Kevin A. Click, Szu Chia Chien, Jiaonan Sun, Allison Curtze, Li Chiang Lin, Yiying Wu

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


When a semiconductor is in contact with an electrolyte, its flat band potential (EFB) is an important quantity for determining band edge positions in photoelectrochemistry. Oxide semiconductors generally have a EFB shift of-59 mV in aqueous solutions when the pH is increased by 1 unit as a consequence of surface deprotonation. Many of the most desirable redox reactions, such as the reduction of CO2 to HCOOH, or water to H2, also show the same dependence on pH due to the involvement of protons. Therefore, pH cannot be used to tune the relative energy alignment between the electrode and the electrolytes. Here, we demonstrate via Mott-Schottky measurement that sensitized NiO with a membrane-inspired design of dye molecule (BH4) can decouple the pH dependence of EFB. The EFB of BH4-sensitized NiO films shows very little to zero change as a function of pH, whereas less hydrophobic dye (P1)-sensitized NiO and the bare NiO follow the Nernst shift with respect to pH.

Original languageEnglish
Pages (from-to)8681-8687
Number of pages7
JournalJournal of Physical Chemistry C
Issue number14
StatePublished - 11 Apr 2019


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