Decoupling pH dependence of flat band potential in aqueous dye-sensitized electrodes
Journal
Journal of Physical Chemistry C
Journal Volume
123
Journal Issue
14
Pages
8681-8687
Date Issued
2019
Author(s)
Abstract
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. ? 2019 American Chemical Society.
Subjects
Dye-sensitized solar cells
Electrodes
Electrolytes
Nickel oxide
Oxide semiconductors
Redox reactions
Aqueous dye
Band edge position
Dye molecule
Flat band potential
Mott-Schottky
PH dependence
Photo-electrochemistry
Relative energies
Phosphorus compounds
SDGs
Type
journal article