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A graded catalytic–protective layer for an efficient and stable water-splitting photocathode

Abstract

Achieving solar-to-hydrogen efficiencies above 15% is key for the commercial success of photoelectrochemical water-splitting devices. While tandem cells can reach those efficiencies, increasing the catalytic activity and long-term stability remains a significant challenge. Here we show that annealing a bilayer of amorphous titanium dioxide (TiOx) and molybdenum sulfide (MoSx) deposited onto GaInP2 results in a photocathode with high catalytic activity (current density of 11 mA cm−2 at 0 V versus the reversible hydrogen electrode under 1 sun illumination) and stability (retention of 80% of initial photocurrent density over a 20 h durability test) for the hydrogen evolution reaction. Microscopy and spectroscopy reveal that annealing results in a graded MoSx/MoOx/TiO2 layer that retains much of the high catalytic activity of amorphous MoSx but with stability similar to crystalline MoS2. Our findings demonstrate the potential of utilizing a hybridized, heterogeneous surface layer as a cost-effective catalytic and protective interface for solar hydrogen production.

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Figure 1: Photoelectrochemical measurements of GaInP2-based photocathodes for hydrogen evolution.
Figure 2: Structural and chemical profiling of the a-MoSx/TiO2x–GaInP2 and g-MoSx/TiOx–GaInP2 electrodes.
Figure 3: Chemical profiling of the non-annealed (a-MoSx/TiOx–GaInP2) and annealed (g-MoSx/TiO2–GaInP2) electrodes.
Figure 4: XPS spectra of the MoSx/TiOx–GaInP2 electrode before and after annealing and before and after electrolysis for 20 h.

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Acknowledgements

This material is based on work supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, Solar Photochemistry Program under contract number DEAC36-08GO28308. We gratefully acknowledge C. Antunes for ICP-MS measurement, A. Norman for the helpful discussions and plan-view TEM measurement for the PtRu–GaInP2 electrode.

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Authors

Contributions

J.G., J.A.A., S.F., N.R.N. and J.A.T. wrote the manuscript. J.G. and S.F. conceived the experiments. J.G. conducted the photoelectrochemical characterization. J.A.A. conducted the STEM, EDS and EELS measurements. J.A.A. and M.A.-J. analysed and interpreted the STEM, EDS and EELS data. K.X.S. conducted the XPS experiment and related analysis. Y.Y. conducted the initial testing for MoSx catalyst deposition. C.X. conducted the SEM measurements and J.L.Y. conducted the atomic layer TiO2 deposition.

Corresponding authors

Correspondence to Jing Gu or John A. Turner.

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The authors declare no competing financial interests.

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Supplementary Figures 1–5, Supplementary Tables 1–2 and Supplementary References. (PDF 1022 kb)

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Gu, J., Aguiar, J., Ferrere, S. et al. A graded catalytic–protective layer for an efficient and stable water-splitting photocathode. Nat Energy 2, 16192 (2017). https://doi.org/10.1038/nenergy.2016.192

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