Abstract
In this talk, I will show how operando electrochemical techniques can be used to gain a deeper understanding of the underlying photophysical charge carrier processes taking place in photoelectrodes under practical water splitting conditions. High performance semiconductor-based electrodes are often multilayer systems (for maximizing the photovoltage, stability, etc.), and the relatively high number of interfaces in these devices makes characterization challenging. The characterization of both photocathodes and photoanodes will be discussed utilizing the dual working electrode (DWE) technique as well as photoelectrochemical impedance spectroscopy (PEIS). Using a certain architecture of DWE that preserves the catalytic interface, the performance of water splitting photoelectrodes can be de-convoluted to observe changes in the photovoltaic output separately from changes in the surface catalyst, rapidly identifying mechanisms of degradation in these systems.[1] This technique can also be used to detect the band position of the surface layer under operation in photoanode systems, which provided evidence for a certain mechanism of charge transfer.[2] Finally, I will show how PEIS can be used to characterize complex systems such as Au/Cu2O/Ga2O3/TiO2/RuOx, identifying the problematic interfaces in this promising system.[3][1] Cui, W.; Niu, W.; Wick-Joliat, R.; Moehl, T.; Tilley, S. D.* Operando Deconvolution of Photovoltaic and Electrocatalytic Performance in ALD TiO2 Protected Water Splitting Photocathodes Chem. Sci., 2018, 9,6062-6067. doi: 10.1039/C8SC01453A [2] Cui, W.; Moehl, T.; Siol, S.; Tilley, S. D.* Operando electrochemical study of charge carrier processes in water splitting photoanodes protected by atomic layer deposited TiO2 Sustainable Energy Fuels 2019, 3, 3085 - 3092. doi: 10.1039/C9SE00399A [3] Moehl, T.; Cui, W.; Wick-Joliat, R.; Tilley, S. D.* Resistance-based analysis of limiting interfaces in multilayer water splitting photocathodes by impedance spectroscopy Sustainable Energy Fuels, 2019, 3, 2067–2075. doi: 10.1039/C9SE00248K
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