Performance enhancement and degradation mechanism identification of a single-atom Co–N–C catalyst for proton exchange membrane fuel cells

Xie, Xiaohong; He, Cheng; Li, Boyang; He, Yanghua; Cullen, David A.; Wegener, Evan C.; Kropf, A. Jeremy; Martinez, Ulises; Cheng, Yingwen; Engelhard, Mark H.; Bowden, Mark E.; Song, Miao; Lemmon, Teresa; Li, Xiaohong S.; Nie, Zimin; Liu, Jian; Myers, Deborah J.; Zelenay, Piotr; Wang, Guofeng; Wu, Gang; Ramani, Vijay; Shao, Yuyan

doi:10.1038/s41929-020-00546-1

Cited by 477 publications

(417 citation statements)

References 69 publications

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“…Both ROS and H 2 O 2 could attack the FeN 4 active sites, carbon support, organic ionomers, and polymer membranes, thereby accelerating performance degradation [22–24] . An alternative Co‐N‐C catalyst, which does not significantly promote Fenton reactions, has recently garnered attention due to prominent improvements in ORR activity and stability in acidic electrolytes (Table S1), [25–30] and, most importantly, encouraging fuel cell power density and performance durability [14, 28, 29, 31–34] …”

Section: Introductionmentioning

confidence: 99%

Dynamically Unveiling Metal–Nitrogen Coordination during Thermal Activation to Design High‐Efficient Atomically Dispersed CoN₄ Active Sites

et al. 2021

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We elucidate the structural evolution of CoN4 sites during thermal activation by developing a zeolitic imidazolate framework (ZIF)‐8‐derived carbon host as an ideal model for Co2+ ion adsorption. Subsequent in situ X‐ray absorption spectroscopy analysis can dynamically track the conversion from inactive Co−OH and Co−O species into active CoN4 sites. The critical transition occurs at 700 °C and becomes optimal at 900 °C, generating the highest intrinsic activity and four‐electron selectivity for the oxygen reduction reaction (ORR). DFT calculations elucidate that the ORR is kinetically favored by the thermal‐induced compressive strain of Co−N bonds in CoN4 active sites formed at 900 °C. Further, we developed a two‐step (i.e., Co ion doping and adsorption) Co‐N‐C catalyst with increased CoN4 site density and optimized porosity for mass transport, and demonstrated its outstanding fuel cell performance and durability.

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Section: Introductionmentioning

confidence: 99%

Dynamically Unveiling Metal–Nitrogen Coordination during Thermal Activation to Design High‐Efficient Atomically Dispersed CoN₄ Active Sites

et al. 2021

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“…Such an approach only asks for one time of heat‐treatment without obtaining N‐doped carbon first and then a secondary vaporing process. Since Fe centers often favor the formation of hydroperoxide and then hydroxyl radical, which is the main contributor to PGM‐free degradation, Shao and co‐workers [ 110 ] developed Co–N single‐atom sites to show four‐time enhanced durability than Fe–N counterparts. In their approach, Co(acca) 3 complex was incorporated in ZIF‐8, followed by ligand exchange to Co(mIm) 4 (Figure 10F).…”

Section: Pyrolyzed Zeolitic‐imidazolate Framework (Zif) For Oxygen Electrocatalysismentioning

confidence: 99%

Metal–Organic Frameworks and Metal–Organic Gels for Oxygen Electrocatalysis: Structural and Compositional Considerations

2021

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Increasing demand for sustainable and clean energy is calling for the next‐generation energy conversion and storage technologies such as fuel cells, water electrolyzers, CO2/N2 reduction electrolyzers, metal–air batteries, etc. All these electrochemical processes involve oxygen electrocatalysis. Boosting the intrinsic activity and the active‐site density through rational design of metal–organic frameworks (MOFs) and metal–organic gels (MOGs) as precursors represents a new approach toward improving oxygen electrocatalysis efficiency. MOFs/MOGs afford a broad selection of combinations between metal nodes and organic linkers and are known to produce electrocatalysts with high surface areas, variable porosity, and excellent activity after pyrolysis. Some recent studies on MOFs/MOGs for oxygen electrocatalysis and their new perspectives in synthesis, characterization, and performance are discussed. New insights on the structural and compositional design in MOF/MOG‐derived oxygen electrocatalysts are summarized. Critical challenges and future research directions are also outlined.

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“…Fe-N-C catalyst is used as an accelerator for the generation of highly oxidative free radicals via the so-called Fenton reaction, which will significantly decrease the PEM fuel cell durability, so that the iron-free and PGM-free catalysts, e.g., Co-N-C and Mn-N-C catalysts, have been developed [48][49][50][51][52][53][54]. Since this iron-free catalyst concept is more relevant to the durability issues, it will be discussed in Sect.…”

Section: Beyond Fe-n-c Catalystsmentioning

confidence: 99%

“…Particularly, in the presence of free radicals, which are generated by the iron ions and peroxide via Fenton reactions, the oxidation and corrosion would be more severe because of the highly oxidative environments. Recently, it was reported that the Co-N-C catalyst also suffers from catalyst oxidation and demetallation, leading to performance decay [54].…”

Section: Understanding Degradation Mechanismsmentioning

confidence: 99%

Proton Exchange Membrane (PEM) Fuel Cells with Platinum Group Metal (PGM)-Free Cathode

Zhang

Sun

2021

Automot. Innov.

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Proton exchange membrane (PEM) fuel cells have gained increasing interest from academia and industry, due to its remarkable advantages including high efficiency, high energy density, high power density, and fast refueling, also because of the urgent demand for clean and renewable energy. One of the biggest challenges for PEM fuel cell technology is the high cost, attributed to the use of precious platinum group metals (PGM), e.g., Pt, particularly at cathodes where sluggish oxygen reduction reaction takes place. Two primary ways have been paved to address this cost challenge: one named low-loading PGM-based catalysts and another one is non-precious metal-based or PGM-free catalysts. Particularly for the PGM-free catalysts, tremendous efforts have been made to improve the performance and durability—milestones have been achieved in the corresponding PEM fuel cells. Even though the current status is still far from meeting the expectations. More efforts are thus required to further research and develop the desired PGM-free catalysts for cathodes in PEM fuel cells. Herein, this paper discusses the most recent progress of PGM-free catalysts and their applications in the practical membrane electrolyte assembly and PEM fuel cells. The most promising directions for future research and development are pointed out in terms of enhancing the intrinsic activity, reducing the degradation, as well as the study at the level of fuel cell stacks.

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Performance enhancement and degradation mechanism identification of a single-atom Co–N–C catalyst for proton exchange membrane fuel cells

Cited by 477 publications

References 69 publications

Dynamically Unveiling Metal–Nitrogen Coordination during Thermal Activation to Design High‐Efficient Atomically Dispersed CoN₄ Active Sites

Dynamically Unveiling Metal–Nitrogen Coordination during Thermal Activation to Design High‐Efficient Atomically Dispersed CoN₄ Active Sites

Metal–Organic Frameworks and Metal–Organic Gels for Oxygen Electrocatalysis: Structural and Compositional Considerations

Proton Exchange Membrane (PEM) Fuel Cells with Platinum Group Metal (PGM)-Free Cathode

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Performance enhancement and degradation mechanism identification of a single-atom Co–N–C catalyst for proton exchange membrane fuel cells

Cited by 477 publications

References 69 publications

Dynamically Unveiling Metal–Nitrogen Coordination during Thermal Activation to Design High‐Efficient Atomically Dispersed CoN4 Active Sites

Dynamically Unveiling Metal–Nitrogen Coordination during Thermal Activation to Design High‐Efficient Atomically Dispersed CoN4 Active Sites

Metal–Organic Frameworks and Metal–Organic Gels for Oxygen Electrocatalysis: Structural and Compositional Considerations

Proton Exchange Membrane (PEM) Fuel Cells with Platinum Group Metal (PGM)-Free Cathode

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Dynamically Unveiling Metal–Nitrogen Coordination during Thermal Activation to Design High‐Efficient Atomically Dispersed CoN₄ Active Sites

Dynamically Unveiling Metal–Nitrogen Coordination during Thermal Activation to Design High‐Efficient Atomically Dispersed CoN₄ Active Sites