Photoelectrocatalytic Water Splitting of CdSe and CdSe/CdS Quantum-Dots-Sensitized Electrodes
Lai-Hung Lai a, Maria A. Loi a, Loredana Protesescu b, Maksym Kovalenko b
a University of Groningen, The Netherlands, Nijenborgh, 4, Groningen, Netherlands
b ETH Zurich & EMPA, Wolfgang-Pauli-Strasse, 10, Zürich, Switzerland
Poster, Lai-Hung Lai, 008
Publication date: 31st March 2013


In this work, an efficient visible light photoelectrocatalytic water splitting device is demonstrated by CdSe quantum dots (QDs)-sensitized electrodes. CdSe QDs-sensitized electrodes show an external quantum efficiency (EQE) of 63% at 440nm under -0.5V vs SCE in an electrolyte composed by a mixture of 0.25M Na2S and 0.35M Na2SO3. In contrast with previous reports on CdSe/CdS co-sensitized electrodes1, 2, 3, mesoporous TiO2 sensitized with CdSe/CdS (core/shell) QDs shows worse performance (16% at 440nm) than CdSe QDs-sensitized electrodes. This indicates that CdS shell acts as a barrier which hampers charge separation. To passivate the surface of the QDs and prevent carriers recombination, ZnS was further deposited on the electrodes. A significant improvement in EQE from 63% to 90% at 440nm under -0.5V vs SCE is achieved. ZnS deposition increases the photocurrent and chemical stability the of QDs-sensitized electrodes. Impedance measurement results indicates that the carrier recombination resistance is enhanced by ZnS deposition.

EQE of CdSe and CdSe/CdS QDs-sensitized electrodes measured under -0.5V vs SCE in 0.25M Na2S and 0.35M Na2SO3
1. Lee, Y. L.; Chi, C. F.; Liau, S. Y. CdS/CdSe Co-Sensitized TiO2 Photoelectrode for Efficient Hydrogen Generation in a Photoelectrochemical Cell. Chem. Mater. 2010, 22, 922–927. 2. Yu, X. Y.; Liao J. Y.; Qiu, K. Q.; Kuang, D. B.; Su, C. Y. Dynamic Study of Highly Efficient CdS/CdSe Quantum Dot-Sensitized Solar Cells Fabricated by Electrodeposition. ACS Nano 2011, 5, 9494-9500. 3. Lin, K. H.; Chuang, C. Y.; Lee, Y. Y; Li, F. C.; Chang, Y. M. Charge Transfer in the Heterointerfaces of CdS/CdSe Cosensitized TiO2 Photoelectrode. J. Phys. Chem. C 2012, 116, 1550–1555.
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