Unravelling charge carrier dynamics in nanostructured photoelectrodes for water splitting via intensity-modulated photocurrent spectroscopy Juan Carlos Expósito-Gálvez 1 , Francisco J. Peón-Díaz 2 , Abhishek Rawat 3 , Krishnan Rajeshwar 3 , Gerko Oskam 1 1 Center for Nanoscience and Sustainable Technologies (CNATS), Department of Physical, Chemical, and Natural Systems, Universidad Pablo de Olavide, Sevilla 41013, Spain, 2 Institute of Chemistry and Biochemistry, Universidad de Valparaiso, Valparaiso, Chile, 3 Department of Chemistry & Biochemistry, The University of Texas at Arlington, Arlington, TX-76019, USA The production of green hydrogen through photoelectrochemical water splitting is a promising strategy for sustainable energy conversion and storage. This approach aims to directly utilize solar energy to drive water oxidation and hydrogen evolution, offering a clean alternative to fossil fuel-based hydrogen production. However, achieving high efficiency and long-term stability remains a major challenge. Critical factors such as light absorption, charge separation, surface kinetics, and recombination dynamics must be carefully optimized. A comprehensive understanding of material properties and interfacial processes is essential for advancing this technology toward large-scale implementation and contributing to the transition to a renewable energy economy. Intensity-modulated photocurrent spectroscopy (IMPS) is a powerful technique to elucidate the carrier dynamics in a photoelectrochemical system, in which the incident light intensity is modulated over a wide frequency range, and the resulting response is measured, and a transfer function is subsequently defined. This technique allows the differentiation of processes occurring on similar time scales, such as charge separation, electron transport, hole transfer, bulk and surface recombination. Based on the results, strategies can be developed to improve the performance of the system by specifically addressing the main causes of the low efficiency. (1) In this study, the charge carrier dynamics of several oxide semiconductors were studied using IMPS, including Bi 2 Fe 4 O 9 , CuV 2 O 6 and alloys. IMPS was measured as a function of potential, photon flux (i.e. light intensity), illumination wavelength, and hole scavenger concentration, resulting in valuable insights. A kinetic model is developed that is capable of predicting the behaviour of the hole transfer and surface recombination constants under two limiting situations, when recombination is fast and when recombination is negligible. References 1. Oskam, G.; Quiñones, S. D. C.; Expósito-Gálvez, J. C.; Sandoval, O. J.; Gutiérrez, I. G. R. Chapter 11 - Photoelectrochemical Characterization of Metal Oxide Semiconductors for Solar Water Splitting Using Intensity-Modulated Photocurrent Spectroscopy. In Photoelectrochemical Engineering for Solar Harvesting ; Kazim, S., Tahir, M. N., Ahmad, S., Mathur, S., Eds.; Nanophotonics; Elsevier, 2024; pp 311–352. https://doi.org/10.1016/B978-0-323-95494-5.00013-6.
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