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Blocking the reverse reactions of overall water splitting on a Rh/GaN–ZnO photocatalyst modified with Al2O3


Sunlight-driven photocatalytic overall water splitting (OWS) presents a promising route towards solar-to-chemical energy conversion. However, OWS has been realized with only a few photocatalysts. Among the major reasons for this paucity are the reverse reactions that occur between OWS products, including hydrogen, oxygen and reactive intermediate species, on the photocatalyst surface. In this study we found that decorating the Rh co-catalyst of the benchmark photocatalyst GaN–ZnO with Al2O3 species by atomic layer deposition can suppress these reverse reactions to a great extent and consequently enhance the photocatalytic OWS activity by more than an order of magnitude, with an apparent quantum efficiency increase from 0.3% to 7.1% at 420 nm. The partial coverage of Rh surface sites with inert oxides can effectively suppress the reverse reactions by blocking the reduction/oxidation cycle of Rh atoms during the photocatalytic OWS reaction.

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Fig. 1: Effect of oxide deposition on the performance of GaN–ZnO photocatalysts.
Fig. 2: Role of Al2O3 species in promoting photocatalytic OWS on Rh/GaN–ZnO.
Fig. 3: Morphology and elemental distribution of the Al2O3-modified Rh/GaN–ZnO photocatalyst.
Fig. 4: Preferential deposition of Al2O3 species on the Rh surface by ALD.

Data availability

The data supporting the findings of this study are provided with the paper and are also available at or from the corresponding author upon reasonable request. Source data are provided with this paper.


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This work was conducted by the Fundamental Research Center of Artificial Photosynthesis (FReCAP), financially supported by the National Natural Science Foundation of China (22088102). The work was also supported by the National Key Research and Development Program of China (2021YFA1502300) and the National Natural Science Foundation of China (22090033). We thank F. Zhang and J. Han for help in the preparation of GaN–ZnO, B. Zeng for helpful discussions and H. Han for revision of the English.

Author information

Authors and Affiliations



C.L. conceived and supervised the research project. Z.L. and R.L. designed the experiments. Z.L. fabricated the photocatalysts and carried out the photocatalytic and electrochemical tests, XRD, UV–Vis DRS and TEM characterizations. H.J. and J.X. conducted the DFT calculations. H.X. and J.Z. helped with the ALD experiments. F.H. helped with the DRIFTS of CO adsorption. N.T. conducted the STEM and EDS measurements. X.Z. contributed to the conceptual discussion. C.L., Z.L. and R.L. analysed the results and wrote and revised the paper with input from the other authors.

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Correspondence to Can Li.

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Nature Catalysis thanks Hicham Idriss and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary information

Supplementary Information

Supplementary Methods, Notes 1 and 2, Figs. 1–15, Table and references.

Supplementary Data 1

Atomic coordinates of the optimized computational model structures.

Source data

Source Data Fig. 1

OWS activity.

Source Data Fig. 2

OWS activity and electrochemical current intensity.

Source Data Fig. 4

CO DRIFTS and theoretical simulations.

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Li, Z., Li, R., Jing, H. et al. Blocking the reverse reactions of overall water splitting on a Rh/GaN–ZnO photocatalyst modified with Al2O3. Nat Catal 6, 80–88 (2023).

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