Comparison of photelectochemical water oxidation activity of a synthetic photocatalyst system with Photosystem II
Royal Society of Chemistry
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Lai, Y., Kato, M., Mersch, D., & Reisner, E. (2014). Comparison of photelectochemical water oxidation activity of a synthetic photocatalyst system with Photosystem II. Faraday Discussions, 176 199-211. https://doi.org/10.1039/C4FD00059E
This discussion describes a direct comparison of photoelectrochemical (PEC) water oxidation activity between a photosystem II (PSII)-functionalised photoanode and a synthetic nanocomposite photoanode. The semi-biological photoanode is composed of PSII from the thermophilic cyanobacterium Thermosynechococcus elongatus on a mesoporous indium tin oxide electrode (mesoITO|PSII). PSII embeds all of the required functionalities for light absorption, charge separation and water oxidation and ITO serves solely as the electron collector. The synthetic photoanode consists of a TiO2 and NiOx coated nanosheet-structured WO3 electrode (nanoWO3|TiO2|NiOx). The composite structure of the synthetic electrode allows mimicry of the functional key features in PSII: visible light is absorbed by WO3, TiO2 serves as a protection and charge separation layer and NiOx serves as the water oxidation electrocatalyst. MesoITO|PSII uses low energy red light, whereas nanoWO3|TiO2|NiOx requires high energy photons of blue-end visible and UV regions to oxidise water. The electrodes have a comparable onset potential at approximately 0.6 V vs. reversible hydrogen electrode (RHE). MesoITO|PSII reaches its saturation photocurrent at 0.84 V vs. RHE, whereas nanoWO3|TiO2|NiOx requires more than 1.34 V vs. RHE. This suggests that mesoITO|PSII suffers from fewer limitations from charge recombination and slow water oxidation catalysis than the synthetic electrode. MesoITO|PSII displays a higher ‘per active’ site activity, but is less photostable and displays a much lower photocurrent per geometrical surface area and incident photon to current conversion efficiency (IPCE) than nanoWO3|TiO2|NiOx.
Financial support from EPSRC (EP/H00338X/2 to E. R. and nanoDTC to D. M.), the Christian Doppler Research Association (Austrian Federal Ministry of Science, Research and Economy and National Foundation for Research, Technology and Development), the OMV Group (to E. R.) and Cambridge Trust (to Y.-H. L.) are gratefully acknowledged.
External DOI: https://doi.org/10.1039/C4FD00059E
This record's URL: https://www.repository.cam.ac.uk/handle/1810/246569
Attribution 2.0 UK: England & Wales
Licence URL: http://creativecommons.org/licenses/by/2.0/uk/
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