Understanding performance and stability of photoelectrode interfaces
Francesca Toma a b, Mauricio Schieda a, Sehun Seo a
a Helmholtz Zentrum Hereon, Kantstraße, 55, Teltow, Germany
b Lawrence Berkeley National Lab, United States
Materials for Sustainable Development Conference (MATSUS)
Proceedings of MATSUS Spring 2024 Conference (MATSUS24)
#SolFuelScale - Practical aspects of solar fuel production: scalability, stability & outdoor operation
Barcelona, Spain, 2024 March 4th - 8th
Organizers: Fatwa Abdi and Virgil Andrei
Invited Speaker, Francesca Toma, presentation 361
DOI: https://doi.org/10.29363/nanoge.matsus.2024.361
Publication date: 18th December 2023

Photoelectrochemical cells (PECs) hold great promise as an environmentally friendly method of converting sunlight into energy-dense chemicals. For example, the PEC approach can find application in the synthesis of multi-carbon-based hydrocarbons (C2+) by solar driven reduction of carbon dioxide (CO2R), and in the generation of hydrogen by solar water splitting. However, the electrochemical environment poses significant challenges to the performance and stability of semiconductor based photoelectrodes. Tackling these challenges requires careful understanding of the behaviour of photoelectrode interfaces at the microscopic scale.

Here we show examples of characterization techniques that can help to quantify the performance and stability of photoelectrode surfaces with nanometer resolution, using, as a model system, thin films of TiO2 deposited for corrosion protection by atomic layer deposition (ALD). A detailed analysis of Kelvin probe force microscopy (KPFM) measurements under intermittent illumination allows us to analyze the evolution of surface potential over time and extract localized time constants for carrier dynamic processes on the surface. Furthermore, using operando spectroscopic ellipsometry (SE), we can directly quantify the intrinsic stability of these protective overlayers under PEC water splitting conditions, particularly as a function of the degree of crystallinity of the TiO2 film. In addition, we show how rationally designed catalytic environments can significantly improve the stability and performance of photoelectrodes for PEC CO2R. We demonstrate that by tuning microenvironmental factors such as pH, wettability, and CO2 mass transport, we can enhance C2+ selectivity on halide perovskite photoelectrodes. Understanding photoelectrode interfaces at the micro and nanoscale allows the systematic improvement of photoelectrode stability and performance, opening avenues for the implementation of PEC technologies towards sustainable energy production and climate change mitigation.

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