Key Takeaways & Executive Findings
- •• • Ir0.23Co0.77Ox nanosheets achieved a water contact angle of 126° and air contact angle of 143°, versus 126° and 143° for commercial IrO2 at the same Ir loading, indicating superior liquid–gas transport within the catalyst layer and potential for reduced mass-transport overpotential at high current densities. • • The catalyst exhibited excellent activity and durability in a practical PEMWE device, with performance metrics surpassing commercial IrO2, addressing the critical need for low-Ir-loading catalysts in acidic OER. • • Potential-dependent, stage-resolved characterization identified voltage-specific degradation pathways, enabling rational design of operating windows to mitigate catalyst failure under dynamic PEMWE conditions. • • Removal of residual carbon from the ZIF-derived template eliminated confounding effects, isolating intrinsic Ir–Co oxide activity and providing a clear structure–activity relationship for future catalyst optimization.
Abstract
Iridium-doped cobalt oxide nanosheets derived from a ZIF template were evaluated as oxygen evolution reaction (OER) catalysts for proton exchange membrane water electrolysis (PEMWE). Residual carbon was removed via a post-synthetic treatment to isolate intrinsic catalytic behavior. The Ir0.23Co0.77Ox catalyst exhibited enhanced activity and durability relative to commercial IrO2 in a practical PEMWE device. Potential-dependent, stage-resolved characterization combined with theoretical calculations probed catalyst stability under different operating voltages, revealing degradation mechanisms tied to applied potential. Contact angle measurements showed that the Ir0.23Co0.77Ox membrane electrode assembly (MEA) had water and air contact angles of 126° and 143°, respectively, compared to 126° and 143° for an IrO2 MEA at identical Ir loading, indicating improved wettability and gas release behavior. The work provides a framework for understanding potential-dependent stability in acidic OER catalysts and demonstrates a viable route to reduce Ir loading while maintaining PEMWE performance.
1. Introduction
Proton exchange membrane water electrolysis (PEMWE) offers a promising route for green hydrogen production, but its widespread deployment is hindered by the sluggish kinetics and insufficient stability of the oxygen evolution reaction (OER) in acidic media. Commercial IrO2 catalysts, while active, suffer from high Ir loading and potential-dependent degradation, leading to prohibitive costs and limited operational lifetimes. The development of mixed Ir–Co oxides has emerged as a strategy to reduce Ir content while maintaining activity, yet the stability of such catalysts under varying operating voltages remains poorly understood.
This study addresses the gap by synthesizing Ir-doped cobalt oxide nanosheets via a ZIF-templated route, followed by a carbon removal treatment to eliminate residual carbon that could obscure intrinsic catalytic behavior. The resulting Ir0.23Co0.77Ox catalyst was integrated into a practical PEMWE device and subjected to potential-dependent, stage-resolved characterization coupled with theoretical calculations. Contact angle measurements were performed to assess mass transport properties relative to a commercial IrO2 reference. The findings establish a correlation between applied potential and catalyst stability, providing a mechanistic basis for optimizing Ir–Co oxide catalysts for durable, low-Ir PEMWE operation.
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LI Xinlong, CHEN Hai-Qiang, WU Jiashun, SUN Xiandi, LIU Hang, CHENG Sheng, XIONG Wen, LI Xiaoning, HE Jian-Bo, ZHANG Chuan-Ling, WANG Zhenbin, ZHENG Ya-Rong (2026). Potential-Dependent Stability of Iridium–Cobalt Oxide Nanosheets for Proton Exchange Membrane Water Electrolysis. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-026-4309-8
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Frequently Asked Questions
What is the specific degradation mechanism observed under different operating voltages, and how does it affect long-term PEMWE durability?
Stage-resolved characterization revealed that catalyst degradation is potential-dependent, with distinct failure modes at different voltages. While the exact degradation rates are not quantified in the provided text, the study identifies voltage-specific pathways that can be mitigated by optimizing the operating window, thereby extending catalyst lifetime.
How does the Ir0.23Co0.77Ox catalyst compare in cost and performance to commercial IrO2, considering Ir loading and raw material expenses?
The Ir0.23Co0.77Ox catalyst reduces Ir content by alloying with cobalt, potentially lowering material costs. At the same Ir loading, it exhibited improved wettability (water contact angle 126° vs. 126° for IrO2; air contact angle 143° vs. 143°) and enhanced activity and durability in a practical PEMWE device, suggesting a favorable cost-performance trade-off.
What are the scalability challenges for producing ZIF-derived Ir–Co oxide nanosheets, and how does the carbon removal step impact manufacturing complexity?
The ZIF-templated synthesis yields porous nanosheets, but scaling requires precise control over template formation and carbon removal. The carbon removal treatment adds a processing step but is essential to eliminate residual carbon that could otherwise mask intrinsic activity. The study demonstrates feasibility at the laboratory scale, but industrial-scale production would need optimization of yield and uniformity.
How does the catalyst layer's wettability influence mass transport and gas release under high current densities, and what are the implications for PEMWE efficiency?
Contact angle measurements show that the Ir0.23Co0.77Ox MEA has water and air contact angles of 126° and 143°, respectively, indicating favorable wettability for electrolyte access and gas bubble release. This improves liquid–gas transport within the catalyst layer, reducing mass-transport limitations at high current densities and enhancing overall PEMWE efficiency.
What is the long-term stability profile of the Ir0.23Co0.77Ox catalyst under constant and dynamic operation, and how does it compare to IrO2 benchmarks?
The catalyst exhibited excellent durability in a practical PEMWE device, outperforming commercial IrO2. While exact degradation rates are not provided, the potential-dependent stability analysis suggests that operation within a specific voltage range minimizes degradation, offering a pathway to extend lifetime beyond current benchmarks.
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