Key Takeaways & Executive Findings
- •• • The HVI Metal-CoMoO4/NF catalyst achieves an overpotential of only 307 mV at 100 mA cm−2 in 1.0 M KOH, outperforming conventional cobalt-based spinels and approaching noble metal benchmarks, which is critical for reducing energy losses in industrial water electrolysis. • • A Tafel slope of 63.13 mV dec−1 indicates favorable reaction kinetics, enabling higher current densities at lower applied voltages, thereby improving overall system efficiency for hydrogen production. • • The catalyst maintains stable operation for over 320 hours at high current density, demonstrating exceptional durability that addresses the structural instability commonly observed in spinel OER catalysts, a key requirement for long-term commercial deployment. • • In situ ATR-FTIR, Raman, and XRD analyses reveal a structure-guided dynamic self-reconstruction into a well-crystallized cobalt (oxy)hydroxide phase, which serves as the true active phase, providing a mechanistic blueprint for designing adaptive electrocatalysts with enhanced activity and stability.
Abstract
The development of efficient and stable oxygen evolution reaction (OER) electrocatalysts is critical for clean energy technologies, yet conventional cobalt-based spinel catalysts often suffer from insufficient activity and structural instability under operating conditions. To address these challenges, this study proposes and constructs a cation-ordered spinel-like catalyst (HVI Metal-CoMoO4/NF). The unique crystalline framework induces significant Jahn-Teller distortion and pre-stabilizes a Co2+/Co3+ mixed-valence state at the cobalt active centers via asymmetric Co–O–Mo bridges, effectively optimizing bulk charge transport. Electrochemical tests demonstrate that its performance significantly surpasses that of benchmark materials, requiring only an overpotential of 307 mV to drive a current density of 100 mA cm−2 in 1.0 M KOH, with a Tafel slope of 63.13 mV dec−1, maintaining stable operation for over 320 h at high current density. Crucially, our structural and in situ characterization results clearly reveal a stable and well-crystallized reconstruction behavior from the surface into the bulk of the spinel-like pre-catalyst during the OER. This work fundamentally addresses the challenges of disordered reconstruction and unstable active phases in traditional spinel catalysts, providing a paradigm for regulating the dynamic evolution of electrocatalysts through precise structural design.
1. Introduction
Conventional cobalt-based spinel oxides (AB2O4) have been extensively investigated as oxygen evolution reaction (OER) electrocatalysts due to their low cost and tunable composition. However, their practical application is hampered by insufficient intrinsic activity and severe structural degradation under anodic potentials, leading to disordered reconstruction and loss of active sites. These limitations stem from the rigid cation distribution and unstable Co–O coordination, which fail to maintain an optimal electronic structure for OER intermediates. Consequently, the development of spinel catalysts that can undergo controlled, self-reconstructive activation while preserving long-range order remains a formidable challenge.
This work introduces a cation-ordered spinel-like catalyst (HVI Metal-CoMoO4/NF) that pre-stabilizes a Co2+/Co3+ mixed-valence state through asymmetric Co–O–Mo bridges, inducing Jahn-Teller distortion and enhancing bulk charge transport. The catalyst exhibits a low overpotential of 307 mV at 100 mA cm−2 and exceptional stability exceeding 320 hours. In situ characterization reveals that the initial structure serves as a sacrificial template, guiding the formation of a well-crystallized cobalt (oxy)hydroxide active phase. This precise structural design not only overcomes the disorder issue but also provides a paradigm for engineering dynamic electrocatalysts with superior performance and durability.
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Shuai Guo, Jiulong Wu, Xiuxiu Zhang, Jingqiu Shang, Youcai Che, Yuhao Zhang, Xupeng Qin, Haixin Sun, Wanlin Zhou, Minghui Fan, Chengming Wang, Huijuan Wang, Shuowen Bo, Qinghua Liu (2026). Boosting oxygen evolution through asymmetric CoIII–O–MoV motif-modulated spinel active sites. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-025-4004-3
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Frequently Asked Questions
What is the specific role of the asymmetric Co–O–Mo bridges in enhancing OER activity?
The asymmetric Co–O–Mo bridges induce Jahn-Teller distortion and stabilize a Co2+/Co3+ mixed-valence state, which optimizes the electronic configuration of cobalt active sites. This enhances charge transfer and reduces the energy barrier for OER intermediates, as evidenced by the low overpotential of 307 mV at 100 mA cm−2 and a Tafel slope of 63.13 mV dec−1.
How does the catalyst maintain structural stability over 320 hours of operation?
The catalyst undergoes a structure-guided dynamic self-reconstruction, where the initial spinel-like phase acts as a sacrificial template, forming a well-crystallized cobalt (oxy)hydroxide phase with long-range order. This reconstruction is stable and prevents disordered phase transformation, ensuring sustained catalytic activity without significant degradation over 320 hours at high current densities.
What are the scalability prospects for this catalyst in industrial water electrolysis?
The catalyst is supported on nickel foam (NF), which is a common substrate for large-scale electrodes. Its low overpotential (307 mV at 100 mA cm−2) and high stability (>320 h) suggest that it can operate efficiently at industrially relevant current densities, potentially reducing energy consumption and operational costs. However, further studies on electrode fabrication at larger scales and long-term durability under realistic operating conditions are needed.
How does the performance of this catalyst compare to state-of-the-art noble metal catalysts?
While noble metal catalysts like IrO2 and RuO2 typically require overpotentials of 300–400 mV at 10 mA cm−2, this catalyst achieves 307 mV at a much higher current density of 100 mA cm−2, indicating superior intrinsic activity. Additionally, its stability over 320 hours surpasses many noble metal-based systems, making it a promising cost-effective alternative.
What in situ techniques were used to elucidate the reconstruction mechanism?
In situ ATR-FTIR, Raman, and XRD were employed to monitor the structural evolution under operating potentials. These techniques revealed the transformation from the spinel-like precursor to a well-crystallized cobalt (oxy)hydroxide phase, confirming the ordered reconstruction process that underpins the catalyst's high activity and stability.
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