Key Takeaways & Executive Findings
- •• • Ov-HE-LDHs achieve an overpotential of 210 mV at 10 mA cm−2 in 1.0 M KOH, outperforming pristine HE-LDHs (315 mV) and commercial IrO2 (330 mV), indicating a 33% reduction in overpotential relative to IrO2, which is critical for reducing energy consumption in industrial water electrolysis. • • The catalyst sustains stable operation for 500 hours at a high current density of ~200 mA cm−2, demonstrating exceptional durability that addresses the activity-stability trade-off typical of LOM-based catalysts, essential for long-term industrial deployment. • • XAFS analysis confirms lower metal valence states, evidencing oxygen vacancy formation, while isotope labeling and in-situ Raman spectroscopy validate the activation of the LOM pathway, providing mechanistic proof of the shift from AEM to LOM. • • DFT calculations reveal that oxygen vacancies shift the O 2p band closer to the Fermi level, reducing the reaction energy barrier, which explains the enhanced intrinsic activity and offers a design principle for high-entropy electrocatalysts.
Abstract
Developing highly active and stable electrocatalysts based on the lattice oxygen mechanism (LOM) for the oxygen evolution reaction (OER) represents a significant challenge in water splitting. Herein, we successfully introduce oxygen vacancies (Ov) into high-entropy MnFeCoNiCu layered double hydroxides (HE-LDHs) via a solution chemical reduction method utilizing a defect engineering strategy. By precisely tuning the concentration of oxygen vacancies, we effectively activate the lattice oxygen within the HE-LDHs. The optimized Ov-rich high-entropy LDHs (Ov-HE-LDHs) exhibit excellent OER catalytic performance, achieving a current density of 10 mA cm−2 with a remarkably low overpotential of only 210 mV in 1.0 M KOH electrolyte, which is substantially superior to pristine HE-LDHs (315 mV) and commercial IrO2 (330 mV). Furthermore, the catalyst demonstrates outstanding long-term stability, capable of stable operation for 500 h at a high current density of approximately 200 mA cm−2. Advanced X-ray absorption fine structure analysis elucidates the lower metal valence states, indicating the existence of oxygen vacancies, while isotope labeling experiments and in-situ electrochemical Raman spectroscopy strongly confirm the successful activation of the LOM pathway. Density functional theory calculations further validate that the shift in the OER mechanism towards LOM and the resulting reduction in the reaction energy barrier are the fundamental reasons for the catalyst’s enhanced intrinsic activity. This work proposes a novel strategy for activating lattice oxygen in high-entropy LDHs through defect engineering, offering new insights and experimental guidance for the design and development of highly efficient and stable high-entropy OER electrocatalysts.
1. Introduction
The oxygen evolution reaction (OER) remains the kinetic bottleneck in water electrolysis, constrained by the linear scaling relationship of adsorbate evolution mechanism (AEM) intermediates, which imposes a theoretical overpotential limit of ~370 mV. Lattice oxygen mechanism (LOM) bypasses this limitation by directly involving lattice oxygen in O–O bond formation, yet its practical application is hindered by severe surface reconstruction and structural collapse at high current densities. High-entropy layered double hydroxides (HE-LDHs) offer a promising platform to stabilize the LOM pathway, but their intrinsic activity is often limited by the lack of activated lattice oxygen.
This study introduces oxygen vacancies into MnFeCoNiCu HE-LDHs via a solution chemical reduction method, precisely tuning vacancy concentration to activate lattice oxygen. The resulting Ov-HE-LDHs exhibit a remarkable overpotential of 210 mV at 10 mA cm−2 and maintain stability for 500 hours at 200 mA cm−2, outperforming both pristine HE-LDHs and commercial IrO2. By combining advanced characterization and DFT calculations, the work establishes a scalable defect-engineering strategy to shift the OER mechanism from AEM to LOM, addressing the critical bottleneck of activity-stability trade-off in high-performance electrocatalysts.
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Ying Li, Jiaxing Wang, Yue Shang, Yifan Dou, Limin Liang, Qiuyan Hao, Sijia Li, Hui Liu (2026). Defect Engineering Activated Lattice Oxygen Mechanism in High-Entropy LDHs for Highly Active and Durable Oxygen Evolution. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-026-4180-9
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Frequently Asked Questions
What is the specific role of oxygen vacancies in activating the lattice oxygen mechanism, and how does this affect the OER activity and stability?
Oxygen vacancies lower the metal valence states, as confirmed by XAFS, and shift the O 2p band closer to the Fermi level, reducing the reaction energy barrier for LOM. This results in an overpotential of 210 mV at 10 mA cm−2 and stability for 500 h at 200 mA cm−2, outperforming pristine HE-LDHs (315 mV) and IrO2 (330 mV).
How does the performance of Ov-HE-LDHs compare to state-of-the-art OER catalysts in terms of overpotential and durability under industrial conditions?
Ov-HE-LDHs achieve an overpotential of 210 mV at 10 mA cm−2, which is 120 mV lower than pristine HE-LDHs and 120 mV lower than IrO2. They also maintain stable operation for 500 hours at ~200 mA cm−2, demonstrating superior durability compared to typical LOM catalysts that suffer from structural collapse.
What experimental evidence confirms the activation of the LOM pathway in Ov-HE-LDHs?
Isotope labeling experiments and in-situ electrochemical Raman spectroscopy provide direct evidence of lattice oxygen participation in OER, confirming the LOM pathway. XAFS analysis further indicates lower metal valence states, consistent with the presence of oxygen vacancies.
What is the scalability potential of the solution chemical reduction method for industrial production of high-entropy LDH electrocatalysts?
The solution chemical reduction method is a scalable, low-cost approach that can be easily adapted for large-scale synthesis. The resulting catalyst shows high activity and stability, making it a viable candidate for industrial water electrolysis, though further optimization of synthesis parameters and electrode fabrication is needed.
What are the main degradation mechanisms that could limit the long-term stability of Ov-HE-LDHs at high current densities, and how does the high-entropy design mitigate them?
In LOM-based catalysts, irreversible lattice oxygen loss can cause surface reconstruction and metal dissolution. The high-entropy configuration with multiple metal cations (Mn, Fe, Co, Ni, Cu) provides a stable lattice framework that mitigates structural collapse, as evidenced by 500 h stability at 200 mA cm−2. The presence of oxygen vacancies is carefully controlled to balance activity and stability.
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