scholarly journals The Challenge of Achieving a High Density of Fe-Based Active Sites in a Highly Graphitic Carbon Matrix

Catalysts ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 144 ◽  
Author(s):  
Jingkun Li ◽  
Qingying Jia ◽  
Sanjeev Mukerjee ◽  
Moulay-Tahar Sougrati ◽  
Goran Drazic ◽  
...  
Keyword(s):  
Porous Structure ◽  
Active Sites ◽  
Carbon Matrix ◽  
Platinum Group Metal ◽  
Reduction Reaction ◽  
High Specific Surface Area ◽  
High Density ◽  
Graphitic Carbon ◽  
High Degree ◽  
Degree Of Graphitization

As one of the most promising platinum group metal-free (PGM-free) catalysts for oxygen reduction reaction (ORR), Fe–N–C catalysts with a high density of FeNx moieties integrated in a highly graphitic carbon matrix with a proper porous structure have attracted extensive attention to combine the high activity, high stability and high accessibility of active sites. Herein, we investigated a ZnCl2/NaCl eutectic salts-assisted ionothermal carbonization method (ICM) to synthesize Fe–N–C catalysts with tailored porous structure, high specific surface area and a high degree of graphitization. However, it was found to be challenging to anchor a high density of FeNx sites onto highly graphitized carbon. Iron precursors with preexisting Fe–N coordination were required to form FeNx sites in the nitrogen-doped carbon with a high degree of graphitization, while individual Fe and N precursors led to a Fe–N–C catalyst with poor-ORR activity. This provides valuable insights into the synthesis-structure relationship. Moreover, the FeNx moieties were identified as the major active sites in acidic conditions, while both FeNx sites and Fe2O3 were found to be active in alkaline medium.

scholarly journals FeNxC Based Catalysts Prepared by the Calcination of Iron-Ethylenediamine@Polyaniline as the Cathode-Catalyst of Proton Exchange Membrane Fuel Cell

Polymers ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1368 ◽  
Author(s):  
Yen-Zen Wang ◽  
Wen-Yao Huang ◽  
Tar-Hwa Hsieh ◽  
Li-Cheng Jheng ◽  
Ko-Shan Ho ◽  
...  
Keyword(s):  
Fuel Cell ◽  
Power Density ◽  
Active Sites ◽  
Proton Exchange Membrane ◽  
Reduction Reaction ◽  
High Specific Surface Area ◽  
Proton Exchange ◽  
Metal Catalyst ◽  
Durability Test ◽  
Redox Cycles

Calcinated tris(ethylenediamine)iron(III) chloride was used as a non-precious metal catalyst (NPMCs) for a proton exchanged membrane fuel cell (PEMFC) under the protection of polyaniline (PANI), which behaves as both nitrogen source and carbon supporter. The optimal ratio of FeCl3/EDA was found to be close to 1/3 under the consideration of the electrocatalytic performance, such as better oxygen reduction reaction (ORR) and higher power density. Two-stage calcination, one at 900 °C in N2 and the other at 800 °C in mixed gases of N2 and NH3, result in an FeNxC catalyst (FeNC-900-800-A) with pretty high specific surface area of 1098 m2·g−1 covered with both micro- and mesopores. The ORR active sites focused mainly on Fe–Nx bonding made of various pyridinic, pyrrolic, and graphitic N-s after calcination. The max. power density reaches 140 mW·cm−2 for FeNC-900-800-A, which is superior to other FeNxC catalysts, experiencing only one-stage calcination in N2. The FeNxC demonstrates only 10 mV half-wave-voltage (HWV) loss at 1600 rpm after 1000 redox cycles, as compared to be 27 mV for commercial Pt/C catalyst in the durability test.

scholarly journals Highly Graphitized Fe-N-C Electrocatalysts Prepared from Chitosan Hydrogel Frameworks

2021 ◽  
Author(s):  
Giorgia Daniel ◽  
Tomasz Kosmala ◽  
Federico Brombin ◽  
Marco Mazzucato ◽  
Alessandro Facchin ◽  
...  
Keyword(s):  
Active Sites ◽  
Chemical Properties ◽  
Platinum Group Metal ◽  
Reduction Reaction ◽  
Point Of View ◽  
Thermochemical Conversion ◽  
Chitosan Hydrogel ◽  
Acidic Aqueous Solution ◽  
Before And After ◽  
Nitrogen Doped Carbon

The development of platinum group metal-free (PGM-free) electrocatalysts derived from cheap and environmentally friendly biomasses for oxygen reduction reaction (ORR) is a topic of relevant interest, particularly from the point of view of sustainability. Fe-nitrogen-doped carbon materials (Fe-N-C) have attracted particular interest as alternative to Pt-based materials, due to the high activity and selectivity of Fe-Nx active sites, the high availability and good tolerance to poisoning. Recently, many studies focused on developing synthetic strategies, which could transform N-containing biomasses into N-doped carbons. In this paper chitosan was employed as a suitable N-containing biomass for preparing Fe-N-C catalyst in virtue of its high N content (7.1%) and unique chemical structure. Moreover, the major application of chitosan is based on its ability to strongly coordinate metal ions, a precondition for the formation of Fe-Nx active sites. The synthesis of Fe-N-C consists in a double step thermochemical conversion of a dried chitosan hydrogel. In acidic aqueous solution, the preparation of physical cross-linked hydrogel allows to obtain sophisticated organization, which assure an optimal mesoporosity before and after the pyrolysis. After the second thermal treatment at 900 °C, a highly graphitized material was obtained, which has been fully characterized in term of textural, morphological and chemical properties. RRDE technique was used for understanding the activity and the selectivity of the material versus the ORR in 0.5 M H2SO4 electrolyte. Special attention was put in the determination of the active site density according to nitrite electrochemical reduction measurements. It was clearly established that the catalytic activity expressed as half wave potential linearly scales with the number of Fe-Nx sites. It was also established that the addition of the iron precursor after the first pyrolysis step leads to an increased activity because of both an increased number of active sites and of a hierarchical structure, which improves the access to active sites. At the same time, the increased graphitization degree, and a reduced density of pyrrolic nitrogen groups are helpful to increase the selectivity toward the 4e- ORR pathway.

scholarly journals High-performance fuel cell cathodes exclusively containing atomically dispersed iron active sites

2019 ◽  
Vol 12 (8) ◽  
pp. 2548-2558 ◽  
Author(s):  
Hanguang Zhang ◽  
Hoon T. Chung ◽  
David A. Cullen ◽  
Stephan Wagner ◽  
Ulrike I. Kramm ◽  
...  
Keyword(s):  
Fuel Cell ◽  
Active Sites ◽  
High Performance ◽  
Platinum Group Metal ◽  
Reduction Reaction ◽  
Polymer Electrolyte Fuel Cells ◽  
Metal Free ◽  
Fuel Cell Cathodes ◽  
Iron Active Sites ◽  
Cell Cathodes

Platinum group metal-free (PGM-free) catalysts for the oxygen reduction reaction (ORR) with atomically dispersed FeN4 sites have emerged as a potential replacement for low-PGM catalysts in acidic polymer electrolyte fuel cells (PEFCs).

scholarly journals Multi-Walled Carbon Nanotubes Supported Pd(II) Complexes: A Supramolecular Approach towards Single-Ion Oxygen Reduction Reaction Catalysts

Energies ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 5539
Author(s):  
Matteo Savastano ◽  
Maurizio Passaponti ◽  
Walter Giurlani ◽  
Leonardo Lari ◽  
Antonio Bianchi ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Photoelectron Spectroscopy ◽  
Active Sites ◽  
Platinum Group Metal ◽  
Reduction Reaction ◽  
Rotating Disk Electrode ◽  
Disk Electrode ◽  
Supported Pd

Lowering the platinum group metal content of oxygen reduction reaction catalysts is among the most prevalent research focuses in the field. This target is herein approached through supported Pd(II) complexes. Starting from a commercial macrocycle, a new ligand is synthesized, its solution behavior and binding properties briefly explored (potentiometry, UV-Vis) and then used to prepare a new catalyst. A supramolecular approach is used in order to obtain homogeneous decoration of carbon nanotubes surfaces, fostering novel possibilities to access single-ion active sites. The novel catalyst is characterized through X-ray photoelectron spectroscopy and scanning transmission electron microscopy and its promising oxygen reduction reaction performance is evaluated via rotating ring-disk electrode and rotating disk electrode in half-cell studies.

scholarly journals Highly Graphitized Fe-N-C Electrocatalysts Prepared from Chitosan Hydrogel Frameworks

Catalysts ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 390
Author(s):  
Giorgia Daniel ◽  
Tomasz Kosmala ◽  
Federico Brombin ◽  
Marco Mazzucato ◽  
Alessandro Facchin ◽  
...  
Keyword(s):  
Active Sites ◽  
Chemical Properties ◽  
Platinum Group Metal ◽  
Reduction Reaction ◽  
Point Of View ◽  
Thermochemical Conversion ◽  
Chitosan Hydrogel ◽  
Acidic Aqueous Solution ◽  
Before And After ◽  
Nitrogen Doped Carbon

The development of platinum group metal-free (PGM-free) electrocatalysts derived from cheap and environmentally friendly biomasses for oxygen reduction reaction (ORR) is a topic of relevant interest, particularly from the point of view of sustainability. Fe-nitrogen-doped carbon materials (Fe-N-C) have attracted particular interest as alternative to Pt-based materials, due to the high activity and selectivity of Fe-Nx active sites, the high availability and good tolerance to poisoning. Recently, many studies focused on developing synthetic strategies, which could transform N-containing biomasses into N-doped carbons. In this paper, chitosan was employed as a suitable N-containing biomass for preparing Fe-N-C catalyst in virtue of its high N content (7.1%) and unique chemical structure. Moreover, the major application of chitosan is based on its ability to strongly coordinate metal ions, a precondition for the formation of Fe-Nx active sites. The synthesis of Fe-N-C consists in a double step thermochemical conversion of a dried chitosan hydrogel. In acidic aqueous solution, the preparation of physical cross-linked hydrogel allows to obtain sophisticated organization, which assure an optimal mesoporosity before and after the pyrolysis. After the second thermal treatment at 900 °C, a highly graphitized material was obtained, which has been fully characterized in terms of textural, morphological and chemical properties. RRDE technique was used for understanding the activity and the selectivity of the material versus the ORR in 0.5 M H2SO4 electrolyte. Special attention was put in the determination of the active site density according to nitrite electrochemical reduction measurements. It was clearly established that the catalytic activity expressed as half wave potential linearly scales with the number of Fe-Nx sites. It was also established that the addition of the iron precursor after the first pyrolysis step leads to an increased activity due to both an increased number of active sites and of a hierarchical structure, which improves the access to active sites. At the same time, the increased graphitization degree, and a reduced density of pyrrolic nitrogen groups are helpful to increase the selectivity toward the 4e- ORR pathway.

scholarly journals Two-Dimensional MoS2: Structural Properties, Synthesis Methods, and Regulation Strategies toward Oxygen Reduction

Micromachines ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 240
Author(s):  
Hanwen Xu ◽  
Jiawei Zhu ◽  
Qianli Ma ◽  
Jingjing Ma ◽  
Huawei Bai ◽  
...  
Keyword(s):  
Oxygen Reduction ◽  
Active Sites ◽  
Three Dimensional ◽  
Reduction Reaction ◽  
High Specific Surface Area ◽  
Electromagnetic Properties ◽  
Synthesis Methods ◽  
Two Dimensional ◽  
Challenges And Opportunities ◽  
Regulation Strategies

Compared with three-dimensional (3D) and other materials, two-dimensional (2D) materials with unique properties such as high specific surface area, structurally adjustable band structure, and electromagnetic properties have attracted wide attention. In recent years, great progress has been made for 2D MoS2 in the field of electrocatalysis, and its exposed unsaturated edges are considered to be active sites of electrocatalytic reactions. In this review, we focus on the latest progress of 2D MoS2 in the oxygen reduction reaction (ORR) that has not received much attention. First, the basic properties of 2D MoS2 and its advantages in the ORR are introduced. Then, the synthesis methods of 2D MoS2 are summarized, and specific strategies for optimizing the performance of 2D MoS2 in ORRs, and the challenges and opportunities faced are discussed. Finally, the future of the 2D MoS2-based ORR catalysts is explored.

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