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Quantum Dot Based Heterostructures for Unassisted Photoelectrochemical Hydrogen Generation

Authors

  • Pau Rodenas,

    1. Photovoltaics and Optoelectronic Devices Group, Departament de Física, Universitat Jaume I, 12071 Castelló, Spain
    Current affiliation:
    1. These authors contributed equally to this work.
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  • Taesup Song,

    1. World Class University Program Department of Energy Engineering and Center for Next Generation Dye-Sensitized Solar Cells and Division of Materials Science Engineering, Hanyang University, Seoul 133-791, South Korea
    Current affiliation:
    1. These authors contributed equally to this work.
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  • Pitchaimuthu Sudhagar,

    1. World Class University Program Department of Energy Engineering and Center for Next Generation Dye-Sensitized Solar Cells and Division of Materials Science Engineering, Hanyang University, Seoul 133-791, South Korea
    Current affiliation:
    1. These authors contributed equally to this work.
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  • Gabriela Marzari,

    1. Photovoltaics and Optoelectronic Devices Group, Departament de Física, Universitat Jaume I, 12071 Castelló, Spain
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  • Hyungkyu Han,

    1. World Class University Program Department of Energy Engineering and Center for Next Generation Dye-Sensitized Solar Cells and Division of Materials Science Engineering, Hanyang University, Seoul 133-791, South Korea
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  • Laura Badia-Bou,

    1. World Class University Program Department of Energy Engineering and Center for Next Generation Dye-Sensitized Solar Cells and Division of Materials Science Engineering, Hanyang University, Seoul 133-791, South Korea
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  • Sixto Gimenez,

    Corresponding author
    1. Photovoltaics and Optoelectronic Devices Group, Departament de Física, Universitat Jaume I, 12071 Castelló, Spain
    • Photovoltaics and Optoelectronic Devices Group, Departament de Física, Universitat Jaume I, 12071 Castelló, Spain.
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  • Francisco Fabregat-Santiago,

    1. Photovoltaics and Optoelectronic Devices Group, Departament de Física, Universitat Jaume I, 12071 Castelló, Spain
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  • Ivan Mora-Sero,

    1. Photovoltaics and Optoelectronic Devices Group, Departament de Física, Universitat Jaume I, 12071 Castelló, Spain
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  • Juan Bisquert,

    1. Photovoltaics and Optoelectronic Devices Group, Departament de Física, Universitat Jaume I, 12071 Castelló, Spain
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  • Ungyu Paik,

    Corresponding author
    1. World Class University Program Department of Energy Engineering and Center for Next Generation Dye-Sensitized Solar Cells and Division of Materials Science Engineering, Hanyang University, Seoul 133-791, South Korea
    • World Class University Program Department of Energy Engineering and Center for Next Generation Dye-Sensitized Solar Cells and Division of Materials Science Engineering, Hanyang University, Seoul 133-791, South Korea
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  • Yong Soo Kang

    Corresponding author
    1. World Class University Program Department of Energy Engineering and Center for Next Generation Dye-Sensitized Solar Cells and Division of Materials Science Engineering, Hanyang University, Seoul 133-791, South Korea
    • World Class University Program Department of Energy Engineering and Center for Next Generation Dye-Sensitized Solar Cells and Division of Materials Science Engineering, Hanyang University, Seoul 133-791, South Korea
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Abstract

TiO2 hollow nanowires (HNWs) and nanoparticles (NPs) constitute promising architectures for QDs sensitized photoanodes for H2 generation. We sensitize these structures with CdS/CdSe quantum dots by two different methods (chemical bath deposition, CBD and succesive ionic layer adsorption and reaction, SILAR) and evaluate the performance of these photoelectrodes. Remarkable photocurrents of 4 mA·cm and 8 mA·cm−2 and hydrogen generation rates of 40 ml·cm−2·day−1 and 80 ml·cm−2·day−1 have been obtained in a three electrode configuration with sacrificial hole scavengers (Na2S and Na2SO3), for HNWs and NPs respectively, which is confirmed through gas analysis. More importantly, autonomous generation of H2 (20 ml·cm−2·day−1 corresponding to 2 mA·cm−2 photocurrent) is obtained in a two electrode configuration at short circuit under 100 mW·cm−2 illumination, clearly showing that these photoanodes can produce hydrogen without the assistance of any external bias. To the best of the authors' knowledge, this is the highest unbiased solar H2 generation rate reported for these of QDs based heterostructures. Impedance spectroscopy measurements show similar electron density of trap states below the TiO2 conduction band while the recombination resistance was higher for HNWs, consistently with the much lower surface area compared to NPs. However, the conductivity of both structures is similar, in spite of the one dimensional character of HNWs, which leaves some room for improvement of these nanowired structures. The effect of the QDs deposition method is also evaluated. Both structures show remarkable stability without any appreciable photocurrent loss after 0.5 hour of operation. The findings of this study constitute a relevant step towards the feasibility of hydrogen generation with wide bandgap semiconductors/quantum dots based heterostructures.

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