ZIF-67-derived Co3O4@carbon protected by oxygen-buffering CeO2 as an efficient catalyst for boosting oxygen reduction/evolution reactions

2019 ◽  
Vol 7 (45) ◽  
pp. 25853-25864 ◽  
Author(s):  
Xuerui Li ◽  
Shijie You ◽  
Jiannan Du ◽  
Ying Dai ◽  
Hun Chen ◽  
...  
Keyword(s):  
Oxygen Reduction ◽  
Active Sites ◽  
Efficient Catalyst

The oxygen-buffering CeO2 effectively protects the available active sites of the ZIF-67-derived Co3O4@carbon to improve oxygen reduction/evolution reaction activities.

scholarly journals Polyacrylamide Microspheres-Derived Fe3C@N-doped Carbon Nanospheres as Efficient Catalyst for Oxygen Reduction Reaction

Polymers ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 767 ◽  
Author(s):  
Ming Chen ◽  
Yu Jiang ◽  
Ping Mei ◽  
Yan Zhang ◽  
Xianfeng Zheng ◽  
...  
Keyword(s):  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Electrocatalytic Activity ◽  
Active Sites ◽  
Reduction Reaction ◽  
Limiting Current ◽  
Alkaline Solutions ◽  
Carbon Nanospheres ◽  
Hydrogen Electrode ◽  
Efficient Catalyst

High-performance non-precious metal catalysts exhibit high electrocatalytic activity for the oxygen-reduction reaction (ORR), which is indispensable for facilitating the development of multifarious renewable energy systems. In this work; N-doped carbon-encapsulated Fe3C nanosphere ORR catalysts were prepared through simple carbonization of iron precursors loaded with polyacrylamide microspheres. The effect of iron precursors loading on the electrocatalytic activity for ORR was investigated in detail. The electrochemical measurements revealed that the N-doped carbon-encapsulated Fe3C nanospheres exhibited outstanding electrocatalytic activity for ORR in alkaline solutions. The optimized catalyst possessed more positive onset potential (0.94 V vs. reversible hydrogen electrode (RHE)), higher diffusion limiting current (5.78 mA cm−2), better selectivity (the transferred electron number n > 3.98 at 0.19 V vs. RHE) and higher durability towards ORR than a commercial Pt/C catalyst. The efficient electrocatalytic performance towards ORR can be attributed to the synergistic effect between N-doped carbon and Fe3C as catalytic active sites; and the excellent stability results from the core-shell structure of the catalysts.

ZIF-67-derived N-doped double layer carbon cage as efficient catalyst for oxygen reduction reaction

2021 ◽  
Author(s):  
Wenwen Zhang ◽  
Ximeng Zhao ◽  
Weixing Niu ◽  
Hang Yu ◽  
Tongtao Wan ◽  
...  
Keyword(s):  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Double Layer ◽  
Active Sites ◽  
Specific Capacity ◽  
Hollow Structure ◽  
Protective Layer ◽  
Reduction Reaction ◽  
Efficient Catalyst ◽  
Carbon Cage

Abstract The slow kinetic of oxygen reduction reaction (ORR) hampers the practical application of energy conversion devices, such as fuel cells, metal-air batteries. Here, an efficient ORR electrocatalyst consists of Co, Ni co-decorated nitrogen-doped double shell hollow carbon cage (Ni-Co@NHC) was fabricated by pyrolyzing Ni-doped polydopamine wrapped ZIF-67. During the preparation, polydopamine served as a protective layer can effectively prevented the aggregation of Co and Ni nanoparticles during the pyrolysis process, and at the same time forming a carbon layer to grow a double layer carbon cage. This unique hollow structure endows the catalyst with a high specific surface area as well as more exposed active sites. Also benefited from the synergistic effect between Ni and Co nanoparticles, the Ni-Co@NHC catalyst lead to an outstanding ORR performance of half-wave potential (E1/2, 0.862 V), outperforms that of commercial Pt/C catalyst. Additionally, when Ni-Co@NHC was used in the cathode for the zinc-air battery, the cell exhibits high power density (108 mW cm-2) and high specific capacity (806 mAh g-1) at 20 mA cm-2 outperforming Pt/C. This work offers a promising design strategy for the development of high-performance ORR electrocatalysts.

A Pyridinic Fe-N4 Macrocycle Effectively Models the Active Sites in Fe/N-Doped Carbon Electrocatalysts

2020 ◽  
Author(s):  
Travis Marshall-Roth ◽  
Nicole J. Libretto ◽  
Alexandra T. Wrobel ◽  
Kevin Anderton ◽  
Nathan D. Ricke ◽  
...  
Keyword(s):  
Oxygen Reduction ◽  
Active Sites ◽  
Catalytic Properties ◽  
Reduction Reaction ◽  
Iron Phthalocyanine ◽  
Electrochemical Studies ◽  
Onset Potential ◽  
Nitrogen Doped Carbon ◽  
Iron Active Sites

Iron- and nitrogen-doped carbon (Fe-N-C) materials are leading candidates to replace platinum in fuel cells, but their active site structures are poorly understood. A leading postulate is that iron active sites in this class of materials exist in an Fe-N<sub>4</sub> pyridinic ligation environment. Yet, molecular Fe-based catalysts for the oxygen reduction reaction (ORR) generally feature pyrrolic coordination and pyridinic Fe-N<sub>4</sub> catalysts are, to the best of our knowledge, non-existent. We report the synthesis and characterization of a molecular pyridinic hexaazacyclophane macrocycle, (phen<sub>2</sub>N<sub>2</sub>)Fe, and compare its spectroscopic, electrochemical, and catalytic properties for oxygen reduction to a prototypical Fe-N-C material, as well as iron phthalocyanine, (Pc)Fe, and iron octaethylporphyrin, (OEP)Fe, prototypical pyrrolic iron macrocycles. N 1s XPS signatures for coordinated N atoms in (phen<sub>2</sub>N<sub>2</sub>)Fe are positively shifted relative to (Pc)Fe and (OEP)Fe, and overlay with those of Fe-N-C. Likewise, spectroscopic XAS signatures of (phen<sub>2</sub>N<sub>2</sub>)Fe are distinct from those of both (Pc)Fe and (OEP)Fe, and are remarkably similar to those of Fe-N-C with compressed Fe–N bond lengths of 1.97 Å in (phen<sub>2</sub>N<sub>2</sub>)Fe that are close to the average 1.94 Å length in Fe-N-C. Electrochemical studies establish that both (Pc)Fe and (phen<sub>2</sub>N<sub>2</sub>)Fe have relatively high Fe(III/II) potentials at ~0.6 V, ~300 mV positive of (OEP)Fe. The ORR onset potential is found to directly correlate with the Fe(III/II) potential leading to a ~300 mV positive shift in the onset of ORR for (Pc)Fe and (phen<sub>2</sub>N<sub>2</sub>)Fe relative to (OEP)Fe. Consequently, the ORR onset for (phen<sub>2</sub>N<sub>2</sub>)Fe and (Pc)Fe is within 150 mV of Fe-N-C. Unlike (OEP)Fe and (Pc)Fe, (phen<sub>2</sub>N<sub>2</sub>)Fe displays excellent selectivity for 4-electron ORR with <4% maximum H<sub>2</sub>O<sub>2</sub> production, comparable to Fe-N-C materials. The aggregate spectroscopic and electrochemical data establish (phen<sub>2</sub>N<sub>2</sub>)Fe as a pyridinic iron macrocycle that effectively models Fe-N-C active sites, thereby providing a rich molecular platform for understanding this important class of catalytic materials.<p><b></b></p>

scholarly journals Degradation and regeneration of Fe-Nx active sites for oxygen reduction reaction: the role of surface oxidation, Fe demetallation and local carbon microporosity

2021 ◽  
Author(s):  
Dongsheng Xia ◽  
Chenchen Yu ◽  
Yinghao Zhao ◽  
Yinping Wei ◽  
Haiyan Wu ◽  
...  
Keyword(s):  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Active Sites ◽  
Proton Exchange Membrane ◽  
Degradation Mechanism ◽  
Surface Oxidation ◽  
Reduction Reaction ◽  
Proton Exchange ◽  
Exchange Membrane

The severe degradation of Fe-N-C electrocatalysts during long-term oxygen reduction reaction (ORR) has become a major obstacle for application in proton-exchange membrane fuel cells. Understanding the degradation mechanism and regeneration...

Co3Fe7 nanoparticles encapsulated in porous nitrogen-doped carbon nanofiber as bifunctional electrocatalysts for rechargeable zinc-air battery

2021 ◽  
Author(s):  
Miaomiao Liu ◽  
Yulong He ◽  
Jintao Zhang
Keyword(s):  
Oxygen Reduction ◽  
Active Sites ◽  
Carbon Nanofiber ◽  
Nitrogen Doped ◽  
Bifunctional Electrocatalysts ◽  
Air Battery ◽  
Nitrogen Doped Carbon ◽  
Carbon Based

Exploration of inexpensitive and high perfomance carbon-based electrocatalyst with abundant active sites for oxygen reduction and evolution reactions is vital for enhancing the performance of zinc air battery. Herein, the...

scholarly journals Superior FexN electrocatalyst derived from 1,1′-diacetylferrocene for oxygen reduction reaction in alkaline and acidic media

2020 ◽  
Vol 9 (1) ◽  
pp. 843-852
Author(s):  
Hunan Jiang ◽  
Jinyang Li ◽  
Mengni Liang ◽  
Hanpeng Deng ◽  
Zuowan Zhou
Keyword(s):  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Current Density ◽  
Active Sites ◽  
Reduction Reaction ◽  
Alkaline Media ◽  
Acidic Media ◽  
Onset Potential ◽  
Acidic And Alkaline Media ◽  
The Stability

AbstractAlthough Fe–N/C catalysts have received increasing attention in recent years for oxygen reduction reaction (ORR), it is still challenging to precisely control the active sites during the preparation. Herein, we report FexN@RGO catalysts with the size of 2–6 nm derived from the pyrolysis of graphene oxide and 1,1′-diacetylferrocene as C and Fe precursors under the NH3/Ar atmosphere as N source. The 1,1′-diacetylferrocene transforms to Fe3O4 at 600°C and transforms to Fe3N and Fe2N at 700°C and 800°C, respectively. The as-prepared FexN@RGO catalysts exhibited superior electrocatalytic activities in acidic and alkaline media compared with the commercial 10% Pt/C, in terms of electrochemical surface area, onset potential, half-wave potential, number of electrons transferred, kinetic current density, and exchange current density. In addition, the stability of FGN-8 also outperformed commercial 10% Pt/C after 10000 cycles, which demonstrates the as-prepared FexN@RGO as durable and active ORR catalysts in acidic media.

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