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Alkaline electrochemical water oxidation powered by renewable energies is a promising and environmentally friendly way to produce hydrogen. The industrial water electrolyzers are commonly operated at a high current density, calling for abundant and durable active sites to participate in. The rational design of hierarchically structured electrocatalysts is thus essential to industrial water electrolyzers. Herein, we develop a Fe3+ induced nanosizing strategy for fabricating such a hierarchical FeCo LDH@Co3O4 (LDH: layered double hydroxide) nanostructure array for high-rate water oxidation. Density functional theory (DFT) simulations indicate that the introduction of Fe3+ with a small ion radius and high electrical repulsion in the LDH layer distorted the LDH layer, resulting in a reduced nanosheet size and enabling the formation of a hierarchical structure. Such structure cannot be achieved without the participation of Fe3+ cations. Benefiting from the significantly enhanced electrochemical surface areas and charge/mass transport due to the hierarchical structure together with the boosted intrinsic activity by electronic modulation of Fe3+, such FeCo LDH@Co3O4 electrode can deliver an industrial-level current density of 1,000 mA·cm−2 at a small overpotential of 392 mV for water oxidation. When assembled in a water electrolyzer, it delivers a current density of 100 mA·cm−2 at a low operation voltage of 1.61 V. Powered by solar light, the electrolyzer demonstrates high solar-to-hydrogen efficiency of 18.15% with stable and reproducible photoresponse. These results provide new insights for constructing hierarchical nanostructures for advanced water oxidation and other diverse applications.

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Publication history
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Acknowledgements

Publication history

Received: 29 May 2022
Revised: 13 August 2022
Accepted: 24 September 2022
Published: 14 October 2022
Issue date: December 2022

Copyright

© Tsinghua University Press 2022

Acknowledgements

Acknowledgements

The authors acknowledge the financial support from the National Natural Science Foundation of China (Nos. 22025208, 22075300, and 21902162), the China National Postdoctoral Program for Innovative Talents (No. BX2021319), the DNL Cooperation Fund, CAS (No. DNL202008), and the Chinese Academy of Sciences. We also thank Dr. Z.-J. Z., X.-Y. Z., and B.-L. Q. for the XPS analysis; Y. S. for the XRD analysis; and Dr. B. G., Y.-X. C., and J.-L. Y. for SEM and TEM support.

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