Photoelectrochemical water splitting, consisting of photoanode and photocathode used for water reduction and oxidation, is a potential route to store the solar energy into chemical fuels. In terms of the required earth abundance, cheapness and proper band gap edges (1.12 eV), silicon is an attractive photoelectrode material. Unfortunately, silicon suffered from the instability and low efficiency due to the severe photocorrosion and passivation in the reaction electrolyte, even though limited performance has been achieved for water splitting development. [1-3].

In this work, in order to enhance the stability and photoelectrochemical efficiency, we fabricated silicon-based sandwich photoelectrodes with mediated protection layer of sputtered Molybdenum thin film, which is covered with hand-sprayed MoS₂ as the catalyst, as shown in the fig. 1(a). The samples are marked with a, b, c and d separately after different thermal annealing time of 0h, 1h, 2h, 3h in the static Nitrogen atmosphere. After proper annealing, the formed nanoporous surficial structure could be observed in the SEM images (fig. 1(b)) with pore diameters ranging from 10 to 50 nm. These porous networks offer much more active sites for water splitting. The effect of annealing temperature on optical response is shown in fig. 2(a). The UV-Vis spectra show that the annealed surficial MoS₂ exhibits extended optical responses to the longer wavelength region, indicating the potential enhanced visible light absorption. What’s more, in the photoluminescence (PL) spectra (Fig. 2(b)), the weaker PL intensity are observed after covering MoS₂ on the top surface of Mo and essential annealing process, suggesting the suppressed recommendation of the photoexcited electrons and holes in the interface and therefore improved solar energy conversion.

In conclusion, the silicon-based sandwich photoelectrode with enhanced visible light absorption and conversion is fabricated through facile processes. This novel low-cost silicon-based photoelectrode possess potential enhanced efficiency and stability applied in the photoelectrochemical water splitting system.

Acknowledgments: The authors gratefully acknowledge the financial support from Norwegian Research Council FRINATEK programme (231416/F20), and China Scholarship Council (CSC, Grant No.201506930002). The Research Council of Norway is acknowledged for the support to the NorFab, project number 245963/F50.

References

[1] M. J. Kenney, M. Gong, Y. Li, J. Z. Wu, J. Feng, M. Lanza, H. Dai, Science, 343 (6160), 836-840 (2013).

[2] S. Hu, M. R. Shaner, J. A. Beardslee, M. Lichterman, B. S. Brunschwig, N. S. Lewis, Science, 344 (6187), 1005-1009 (2014).

[3] J. Feng, M. Gong, M. J. Kenney, J., Z. Wu, B. Zhang, Y. Li, H. Dai, Nano Res., 8 (5), 1577–1583 (2015).