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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 19: Energy Storage and Batteries II

CPP 19.11: Talk

Tuesday, March 19, 2024, 12:15–12:30, H 0111

The wavelength-dependent photogeneration and mobility of holes in hematite for photoelectrochemical water splitting — •Yuke Yang, Felix Zerres, Yujin Tong, and Richard Kramer Campen — Faculty of Physics, University of Duisburg-Essen, 47057 Duisburg, Germany

Photoelectrochemical water splitting is a promising technique for converting solar energy into hydrogen fuel. It is well-established that a significant percentage of absorbed photons in common photoelectrodes do not contribute to chemical reactions. This effect in oxides is usually attributed to polaron formation and subsequent recombination of some fraction of the excited charge carriers. Methods to directly probe polaron populations are, therefore, an essential part of any materials optimization strategy. Most of these methods are suitable for application only by specialists: they require amplified laser systems and ultrasensitive detection schemes. Here we conduct chopped photocurrent measurements in a hematite(α-Fe₂O₃) photoanode as a function of photon energy. The bias and wavelength dependence of the resulting kinetics, and their change when adding the hole scavenger H₂O₂ to the electrolyte, allow us to characterize electron polarons (that adversely affect device performance) and hole polarons that are OER intermediates. This straightforward way of characterizing polaron energies and relaxation time in this model oxide photoanode offers a useful complementary tool to more complicated experimental techniques that are well matched to high throughput anode creation to empirically changes in polaron stability with changes in catalyst or electrolyte composition.

Keywords: Photoelectrochemical water splitting; OER; Wavelength-dependent photocurrent; Polaron; Photoelectrode