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Hydrogel protection strategy to stabilize water-splitting photoelectrodes


Photoelectrochemical water splitting is an attractive solar-to-hydrogen pathway. However, the lifetime of photoelectrochemical devices is hampered by severe photocorrosion of semiconductors and instability of co-catalysts. Here we report a strategy for stabilizing photoelectrochemical devices that use a polyacrylamide hydrogel as a highly permeable and transparent device-on-top protector. A hydrogel-protected Sb2Se3 photocathode exhibits stability over 100 h, maintaining ~70% of the initial photocurrent, and the degradation rate gradually decreases to the saturation level. The structural stability of a Pt/TiO2/Sb2Se3 photocathode remains unchanged beyond this duration, and effective bubble escape is ensured through the micro gas tunnel formed in the hydrogel to achieve a mechanically stable protector. We demonstrate the versatility of the device-on-top hydrogel protector under a wide electrolyte pH range and by using a SnS photocathode and a BiVO4 photoanode with ~500 h of lifetime.

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Fig. 1: Highly permeable and transparent device-on-top hydrogel protector of the PEC device.
Fig. 2: PEC characteristics of the Sb2Se3 photocathodes with and without the device-on-top hydrogel protector.
Fig. 3: Enhancement of catalyst stability by the device-on-top hydrogel protector.
Fig. 4: Suppression of TiO2 photocorrosion by the device-on-top hydrogel protector.
Fig. 5: Effect of PAAM monomer concentration on the bubble dynamics in the device-on-top hydrogel protector.
Fig. 6: Effect of hydrogel thickness on the bubble dynamics in the device-on-top hydrogel protector.
Fig. 7: Generation and effective escape of the hydrogen bubble through the micro gas tunnel formed in the device-on-top hydrogel protector.
Fig. 8: Versatility of the device-on-top hydrogel protector.

Data availability

The authors declare that all data supporting the findings of this study are available within the paper and its Supplementary Information. Source data are provided with this paper.


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This work was supported by the National Research Foundation (NRF) of Korea grant (numbers 2021R1A3B1068920 (J.M.), 2021M3H4A1A03049662 (J.M.), 2021R1A2C2009070 (Hyungsuk Lee) and 2021R1I1A1A01060058 (J.T.)), funded by the Ministry of Science and ICT. This research was also supported by the Yonsei Signature Research Cluster Program of 2021 (2021–22-0002, J.M.). We thank M. Na for TEM analysis.

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Authors and Affiliations



J.T., B.K., Hyungsuk Lee, and J.M. conceived the project idea. J.T. and B.K. conducted experiments, analysed the data and drafted the manuscript. K.K. conducted the experiments and analysed the data. D.K. conducted a simulation-based analysis. Hyungsoo Lee, S.M. and G.J. supported the experiments. Hyungsuk Lee and J.M. supervised the project, directed the research and contributed to writing the manuscript.

Corresponding authors

Correspondence to Hyungsuk Lee or Jooho Moon.

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Supplementary information

Supplementary Information

Supplementary Figs. 1–26, Notes 1–6 and Tables 1–8.

Supplementary Video 1

Propagation of stress during the bubble expansion in the hydrogel protectors with thicknesses of R, 2 R and 10 R. Here R denotes the final radius of the bubble. Scale bar represents 2 μm.

Supplementary Video 2

High-speed imaging of the bubble growth and escape in PAAM. Scale bar represents 100 μm.

Supplementary Video 3

High-speed imaging of the bubble growth and detachment in No PAAM. Scale bar represents 100 μm.

Supplementary Data 1

Source data for Supplementary Figs. 1–5, 8, 9, 16, 17, 19–21 and 23–26.

Source data

Source Data Fig. 2

Source data for Fig. 2a,b,c,d,e.

Source Data Fig. 4

Source data for Fig. 4b.

Source Data Fig. 5

Source data for Fig. 5a.

Source Data Fig. 6

Source data for Fig. 6a,b.

Source Data Fig. 8

Source data for Fig. 8a,b,c,d.

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Tan, J., Kang, B., Kim, K. et al. Hydrogel protection strategy to stabilize water-splitting photoelectrodes. Nat Energy 7, 537–547 (2022).

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