Cobalt/zinc dual-sites coordinated with nitrogen in nanofibers enabling efficient and durable oxygen reduction reaction in acidic fuel cells

Zang, Jianbing; Wang, Feiteng; Cheng, Qian; Wang, Guoliang; Ma, Lushan; Chen, Chi; Yang, Lijun; Zou, Zhiqing; Xie, Daiqian; Yang, Hui

doi:10.1039/c9ta12207a

Cited by 87 publications

(70 citation statements)

References 40 publications

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“…[ 7 ] Thus, developing Fe‐free catalysts with outstanding performance takes priority for the implementation of non‐PGM catalysts in PEMFCs. [ 8 ] Unlike Fe, Co possesses much weaker catalytic ability towards Fenton reactions. Nevertheless, Co–N–C catalysts generally reveal inferior ORR activity to Fe–N–C because of the weaker adsorption energies of O 2 and the higher activation energy ( E a ) of OOH* dissociation (generally known as rate‐determining step for ORR on M‐N 4 ) on Co–N 4 /C sites compared to Fe–N 4 /C sites.…”

Section: Introductionmentioning

confidence: 99%

Constructing Co–N–C Catalyst via a Double Crosslinking Hydrogel Strategy for Enhanced Oxygen Reduction Catalysis in Fuel Cells

Miao

Xia

Liang

et al. 2021

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Exploiting platinum‐group‐metal (PGM)‐free electrocatalysts with remarkable activity and stability toward oxygen reduction reaction (ORR) is of significant importance to the large‐scale commercialization of proton exchange membrane fuel cells (PEMFCs). Here, a high‐performance and anti‐Fenton reaction cobalt–nitrogen–carbon (Co–N–C) catalyst is reported via employing double crosslinking (DC) hydrogel strategy, which consists of the chemical crosslinking between acrylic acid (AA) and acrylamide (AM) copolymerization and metal coordinated crosslinking between Co2+ and P(AA–AM) copolymer. The resultant DC hydrogel can benefit the Co2+ dispersion via chelated Co‐N/O bonds and relieve metal agglomeration during the subsequent pyrolysis, resulting in the atomically dispersed Co‐Nx/C active sites. By optimizing the ratio of AA/AM, the optimal P(AA–AM)(5‐1)–Co–N catalyst exhibits a high content of nitrogen doping (12.36 at%) and specific surface area (1397 m2 g−1), significantly larger than that of the PAA–Co–N catalyst (10.59 at%/746 m2 g−1) derived from single crosslinking (SC) hydrogel. The electrochemical measurements reveal that P(AA–AM)(5‐1)–Co–N possesses enhanced ORR activity (half‐wave potential (E1/2) ≈0.820 V versus the reversible hydrogen electrode (RHE)) and stability (≈4 mV shift in E1/2 after 5000 potential cycles in 0.5 m H2SO4 at 60 ºC) relative to PAA‐Co‐N, which is higher than most Co–N–C catalysts reported so far.

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Section: Introductionmentioning

confidence: 99%

Constructing Co–N–C Catalyst via a Double Crosslinking Hydrogel Strategy for Enhanced Oxygen Reduction Catalysis in Fuel Cells

Miao

Xia

Liang

et al. 2021

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“…[29][30][31][32][33] Electrospinning has proven a practical approach to introducing large meso-and macropores in nanomaterials. [15,[34][35][36][37][38][39][40][41][42][43][44][45][46][47] The carbon nanofiber (CNF) morphology obtained from this process is the key to ensuring high macroporosity in catalytic layers. Hence, we hypothesized that co-electrospinning ZIFs precursors with selected carrying polymers followed by thermal activation can produce CNFs with increasing distribution of macroporous carbon structures to mitigate particle agglomeration, while also maintaining sufficient microporosity in each nanofiber for hosting MN 4 active sites.…”

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confidence: 99%

Single Cobalt Sites Dispersed in Hierarchically Porous Nanofiber Networks for Durable and High‐Power PGM‐Free Cathodes in Fuel Cells

et al. 2020

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Atomically dispersed and nitrogencoordinated single metal sites embedded in carbon (denoted as M-N-C) have emerged as promising platinum-groupmetal-free (PGM-free) catalysts for the oxygen reduction reaction (ORR) cathode in proton-exchange-membrane fuel cells (PEMFCs). [1-5] The MN 4 (M: Fe, Co, or Mn) moieties have been theoretically predicted and then experimentally verified as the active sites in M-N-C catalysts. [6-13] Among the many studied precursors, zinc-based zeolitic imidazolate frameworks (ZIF-8s) are effective in creating atomically dispersed MN 4 sites embedded in defect-rich carbon during the hightemperature carbonization. [8,10,14-17] Despite their encouraging ORR activity demonstrated in aqueous acidic electrolytes recently, [18] the trend is often difficult to reproduce in the membrane electrode assemblies (MEAs) of PEMFCs using solid-state electrolytes (i.e., Nafion) (Table S1, Supporting Information). [19] Low catalyst utilization, severe carbon corrosion, and inferior mass transport within the Increasing catalytic activity and durability of atomically dispersed metalnitrogen-carbon (M-N-C) catalysts for the oxygen reduction reaction (ORR) cathode in proton-exchange-membrane fuel cells remains a grand challenge. Here, a high-power and durable CoN -C nanofiber catalyst synthesized through electrospinning cobalt-doped zeolitic imidazolate frameworks into selected polyacrylonitrile and poly(vinylpyrrolidone) polymers is reported. The distinct porous fibrous morphology and hierarchical structures play a vital role in boosting electrode performance by exposing more accessible active sites, providing facile electron conductivity, and facilitating the mass transport of reactant. The enhanced intrinsic activity is attributed to the extra graphitic N dopants surrounding the CoN 4 moieties. The highly graphitized carbon matrix in the catalyst is beneficial for enhancing the carbon corrosion resistance, thereby promoting catalyst stability. The unique nanoscale X-ray computed tomography verifies the well-distributed ionomer coverage throughout the fibrous carbon network in the catalyst. The membrane electrode assembly achieves a power density of 0.40 W cm −2 in a practical H 2 /air cell (1.0 bar) and demonstrates significantly enhanced durability under accelerated stability tests. The combination of the intrinsic activity and stability of single Co sites, along with unique catalyst architecture, provide new insight into designing efficient PGM-free electrodes with improved performance and durability.

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“…This pyridinic N-O peak can be interpreted as an enhanced potential for forming single-atom metals surrounded by N; this concept has also been reported in other studies of transition metal-N-C catalysts. [42][43][44][45] From these results, we think that single-atom Zn can be coordinated with N species.…”

Section: Characterization Of the Structure Of Ag Nanoparticleembedded Cnfs Where Zn Is Atomically Dispersed Catalystmentioning

confidence: 78%

Thermodynamically driven self-formation of Ag nanoparticles in Zn-embedded carbon nanofibers for efficient electrochemical CO₂ reduction

et al. 2021

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Cobalt/zinc dual-sites coordinated with nitrogen in nanofibers enabling efficient and durable oxygen reduction reaction in acidic fuel cells

Abstract: Co/Zn atomic dual-sites anchored on N doped carbon nanofibers for efficient and durable H2–O2 fuel cells (∼0.65 V @ 400 mA cm−2, 150 hours).

Cited by 87 publications

References 40 publications

Constructing Co–N–C Catalyst via a Double Crosslinking Hydrogel Strategy for Enhanced Oxygen Reduction Catalysis in Fuel Cells

Constructing Co–N–C Catalyst via a Double Crosslinking Hydrogel Strategy for Enhanced Oxygen Reduction Catalysis in Fuel Cells

Single Cobalt Sites Dispersed in Hierarchically Porous Nanofiber Networks for Durable and High‐Power PGM‐Free Cathodes in Fuel Cells

Thermodynamically driven self-formation of Ag nanoparticles in Zn-embedded carbon nanofibers for efficient electrochemical CO₂ reduction

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Cobalt/zinc dual-sites coordinated with nitrogen in nanofibers enabling efficient and durable oxygen reduction reaction in acidic fuel cells

Abstract: Co/Zn atomic dual-sites anchored on N doped carbon nanofibers for efficient and durable H2–O2 fuel cells (∼0.65 V @ 400 mA cm−2, 150 hours).

Cited by 87 publications

References 40 publications

Constructing Co–N–C Catalyst via a Double Crosslinking Hydrogel Strategy for Enhanced Oxygen Reduction Catalysis in Fuel Cells

Constructing Co–N–C Catalyst via a Double Crosslinking Hydrogel Strategy for Enhanced Oxygen Reduction Catalysis in Fuel Cells

Single Cobalt Sites Dispersed in Hierarchically Porous Nanofiber Networks for Durable and High‐Power PGM‐Free Cathodes in Fuel Cells

Thermodynamically driven self-formation of Ag nanoparticles in Zn-embedded carbon nanofibers for efficient electrochemical CO2 reduction

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Thermodynamically driven self-formation of Ag nanoparticles in Zn-embedded carbon nanofibers for efficient electrochemical CO₂ reduction