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Electrochemical oxygen evolution reaction (OER) is the efficiency-determining process of water splitting, which is considered one of the most promising strategies for generating hydrogen. Although some progress has been made in the development of transition metal-based OER catalysts, most are still inferior to their noble metal counterparts. Another drawback is that most of them cannot be used as bifunctional electrocatalysts for both OER and hydrogen evolution reaction (HER). Layered double hydroxides based on Ni and Fe (NiFe LDH) have been reported to exhibit relatively high OER activity, while the enhancement of intrinsic activity and specific surface area is still needed to further improve the catalytic performance. In our previous work, efficient strategies such as morphology design, composition tuning, and heterostructure were explored to meet the needs. Recently, vacancy engineering has been proposed to be a promising protocol for improving the electrocatalytic activity of transition metal LDHs.
In the current work, Ni2+-Fe3+ LDHs were synthesized using a homogeneous precipitation method in the presence of hexamethylenetetramine (HMT, C6H12N4) and anthraquinone-2-sulfonate (AQS, C14H7O5S-). Herein, doping with a designated amount of Zn2+ into Ni2+-Fe3+ LDHs was carried out. After successfully exfoliating the bulk Ni2-x/3Znx/3Fe1/3 LDHs (x = 0-0.2) into single-layer nanosheets, vacancies were generated through chemical etching out Zn2+ in a NaOH solution. The NiVFe-LDH nanosheets was then flocculated with anionic CO32- to produce catalysts in powder form for OER measurements. The results show that vacancies in the resultant NiVFe-LDH nanosheets help significantly improve the intrinsic activity for OER. Furthermore, these nanosheets can be hetero-assembled with HER-active molybdenum disulfide (MoS2) nanosheets to serve as a bifunctional catalyst for water splitting.

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Keyword: vacancy

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Conference: MANA International Symposium 2023 (2023-11-09 - 2023-11-10)

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Manuscript type: Not a journal article

MDR DOI: https://doi.org/10.48505/nims.4881

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Updated at: 2025-04-10 21:51:01 +0900

Published on MDR: 2024-10-23 12:30:21 +0900