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. 2015 Jun 8:5:11141.
doi: 10.1038/srep11141.

Photocatalytic generation of hydrogen by core-shell WO₃/BiVO₄ nanorods with ultimate water splitting efficiency

Yuriy Pihosh  1 , Ivan Turkevych  2   3 , Kazuma Mawatari  1 , Jin Uemura  1 , Yutaka Kazoe  1 , Sonya Kosar  1   4 , Kikuo Makita  2 , Takeyoshi Sugaya  2 , Takuya Matsui  2 , Daisuke Fujita  3 , Masahiro Tosa  3 , Michio Kondo  2 , Takehiko Kitamori  1
Affiliations

Photocatalytic generation of hydrogen by core-shell WO₃/BiVO₄ nanorods with ultimate water splitting efficiency

Yuriy Pihosh et al. Sci Rep. .

Abstract

Efficient photocatalytic water splitting requires effective generation, separation and transfer of photo-induced charge carriers that can hardly be achieved simultaneously in a single material. Here we show that the effectiveness of each process can be separately maximized in a nanostructured heterojunction with extremely thin absorber layer. We demonstrate this concept on WO3/BiVO4+CoPi core-shell nanostructured photoanode that achieves near theoretical water splitting efficiency. BiVO4 is characterized by a high recombination rate of photogenerated carriers that have much shorter diffusion length than the thickness required for sufficient light absorption. This issue can be resolved by the combination of BiVO4 with more conductive WO3 nanorods in a form of core-shell heterojunction, where the BiVO4 absorber layer is thinner than the carrier diffusion length while it's optical thickness is reestablished by light trapping in high aspect ratio nanostructures. Our photoanode demonstrates ultimate water splitting photocurrent of 6.72 mA cm(-2) under 1 sun illumination at 1.23 V(RHE) that corresponds to ~90% of the theoretically possible value for BiVO4. We also demonstrate a self-biased operation of the photoanode in tandem with a double-junction GaAs/InGaAsP photovoltaic cell with stable water splitting photocurrent of 6.56 mA cm(-2) that corresponds to the solar to hydrogen generation efficiency of 8.1%.

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Conflict of interest statement

The authors declare no competing financial interests.

Figures

Figure 1
Figure 1. Schematic illustration of a core-shell WO3-NRs/BiVO4 photoanode fabricated by glancing angle deposition (GLAD) of WO3-NRs followed by electrodeposition of BiVO4+CoPi.
The inset (a) illustrates GLAD. The SEM image (b) shows a cross section of the ITO/Pt/ITO/WO3-NRs/BiVO4+CoPi photoanode.
Figure 2
Figure 2. Photoelectrochemical performance of a WO3-NRs/BiVO4+CoPi photoanode measured by the two-electrode method under the bias of 1 V.
(a) IPCE measured at 25 °C (blue) and 50 °C (red), (b) I-V characteristics measured under chopped light at 1 sun, 25 °C and at 3 suns, 50 °C. (c) and (d) gas production rates (circles), faradaic efficiencies (rectangles) and theoretical gas production rates (dashed lines) of O2 (black) and H2 (red) for 1sun, 25 °C (c) and for 3 suns, 50 °C (d) with simultaneously recorded Jp-t profiles.
Figure 3
Figure 3. Characterization of PEC-PV tandem device.
(a) Schematic illustration of the PEC-PV tandem with the PV cell operating under reflected light from the photoanode. (b) I-V characteristics of the PV cell and the photoanode measured at standard (1 sun, 25 °C) and concentrated light (3 suns, 50 °C) conditions. (c) Utilization of the incident AM1.5G solar light by the tandem device calculated from the IPCE of the PEC-PV tandem sub-cells and the reflectance spectra of the photoanode. (d) Jp-t profiles measured for the PEC-PV tandem at 1 sun, 25 °C (blue) and 3 suns, 50 °C (red).
See this image and copyright information in PMC

References

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