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Carbon-based electrocatalysts for advanced energy conversion and storage.

Zhang J, Xia Z, Dai L - Sci Adv (2015)

Bottom Line: Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) play curial roles in electrochemical energy conversion and storage, including fuel cells and metal-air batteries.Having rich multidimensional nanoarchitectures [for example, zero-dimensional (0D) fullerenes, 1D carbon nanotubes, 2D graphene, and 3D graphite] with tunable electronic and surface characteristics, various carbon nanomaterials have been demonstrated to act as efficient metal-free electrocatalysts for ORR and OER in fuel cells and batteries.We present a critical review on the recent advances in carbon-based metal-free catalysts for fuel cells and metal-air batteries, and discuss the perspectives and challenges in this rapidly developing field of practical significance.

View Article: PubMed Central - PubMed

Affiliation: Center of Advanced Science and Engineering for Carbon (Case4Carbon), Department of Macromolecular Science and Engineering, Case Western Reserve University, Cleveland, OH 44106, USA.

ABSTRACT
Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) play curial roles in electrochemical energy conversion and storage, including fuel cells and metal-air batteries. Having rich multidimensional nanoarchitectures [for example, zero-dimensional (0D) fullerenes, 1D carbon nanotubes, 2D graphene, and 3D graphite] with tunable electronic and surface characteristics, various carbon nanomaterials have been demonstrated to act as efficient metal-free electrocatalysts for ORR and OER in fuel cells and batteries. We present a critical review on the recent advances in carbon-based metal-free catalysts for fuel cells and metal-air batteries, and discuss the perspectives and challenges in this rapidly developing field of practical significance.

No MeSH data available.


Related in: MedlinePlus

Schematic illustration of the preparation of EFGnPs through the ball-milling method for ORR.(A) Schematic representation of the mechanochemical reaction between in situ generated active carbon species and reactant gases in a sealed ball-mill crusher. The cracking of graphite by ball milling in the presence of corresponding gases and subsequent exposure to air moisture resulted in the formation of EFGnPs. The red balls stand for reactant gases such as hydrogen, carbon dioxide, sulfur trioxide, and air moisture (oxygen and moisture). [Derived from (119), Copyright 2012 National Academy of Sciences.] (B) A schematic representation for the edge expansions of XGnPs caused by the edge halogens: ClGnP, BrGnP, and IGnP. (C) The optimized O2 adsorption geometries onto XGnPs, in which halogen covalently linked to two sp2 carbons. In (C), the O-O bond length and the shortest C-O bond are shown in angstrom. [From I.-Y. Jeon, H.-J. Choi, M. Choi, J.-M. Seo, S.-M. Jung, M.-J. Kim, S. Zhang, L. Zhang, Z. Xia, L. Dai, N. Park, J.-B. Baek, Facile, scalable synthesis of edge-halogenated graphene nanoplatelets as efficient metal-free eletrocatalysts for oxygen reduction reaction. Sci. Rep.3, 1810 (2013). Reprinted with permission from the Nature Publishing Group.]
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Figure 6: Schematic illustration of the preparation of EFGnPs through the ball-milling method for ORR.(A) Schematic representation of the mechanochemical reaction between in situ generated active carbon species and reactant gases in a sealed ball-mill crusher. The cracking of graphite by ball milling in the presence of corresponding gases and subsequent exposure to air moisture resulted in the formation of EFGnPs. The red balls stand for reactant gases such as hydrogen, carbon dioxide, sulfur trioxide, and air moisture (oxygen and moisture). [Derived from (119), Copyright 2012 National Academy of Sciences.] (B) A schematic representation for the edge expansions of XGnPs caused by the edge halogens: ClGnP, BrGnP, and IGnP. (C) The optimized O2 adsorption geometries onto XGnPs, in which halogen covalently linked to two sp2 carbons. In (C), the O-O bond length and the shortest C-O bond are shown in angstrom. [From I.-Y. Jeon, H.-J. Choi, M. Choi, J.-M. Seo, S.-M. Jung, M.-J. Kim, S. Zhang, L. Zhang, Z. Xia, L. Dai, N. Park, J.-B. Baek, Facile, scalable synthesis of edge-halogenated graphene nanoplatelets as efficient metal-free eletrocatalysts for oxygen reduction reaction. Sci. Rep.3, 1810 (2013). Reprinted with permission from the Nature Publishing Group.]

Mentions: Recent efforts have led to solution-processable edge-functionalized graphene (EFG) sheets. Through a simple one-pot reaction, for example, Jeon and co-workers (118) have prepared edge-functionalized graphene nanoplatelets (EFGnPs) with aminobenzoyl moiety, which could be used as the in situ feedstock for “C-welding” and “N-doping” to produce high-quality NG films without introducing any oxygen-containing surface groups on the graphene basal plane. By solution casting the NG on a GC electrode and subsequent heat treatment, these authors demonstrated comparable ORR performance to the NG prepared by CVD. On the other hand, Jeon and co-workers (119) have also developed a low-cost and scalable ball milling method to produce high-quality, edge-functionalized NG films. By ball milling graphite with dry ice in a planetary ball-mill machine, Jeon and co-workers (119) initially produced edge-selectively carboxylated graphite (ECG), which is highly dispersable in many solvents to self-exfoliate into single- or few-layer graphene sheets. By replacing dry ice with N2 gas, the same authors have developed a simple approach to direct fixation of N2 into graphene nanoplatelets (GnPs) to form five- and six-membered aromatic rings at the broken edges (120), leading to solution-processable edge-nitrogenated graphene nanoplatelets (NGnPs) with superb electrocatalytic performance. As shown in Fig. 6, ball milling graphite in the presence of reactants other than dry ice or N2 (for example, halogen) is an efficient approach to scalable production of EFGnPs with various edge-functional groups (Fig. 6A) (21, 119). For instance, GnPs functionalized with hydrogen (HGnP), carboxylic acid (CGnP), sulfonic acid (SGnP), and mixed carboxylic acid/sulfonic acid (CSGnP) have been synthesized in the presence of hydrogen, carbon dioxide, sulfur trioxide, or carbon dioxide/sulfur trioxide mixture (21, 119). One of the salient features of EFGnPs is that the reaction medium does not intercalate into graphite but selectively functionalizes the sp2 C-H defects at the edges of graphite, leading to minimal carbon basal plane damage, and hence the formation of highly conductive electrodes. Electrochemical measurements indicated that the ORR activity of EFGnP electrodes follows the order of SGnP > CSGnP > CGnP > HGnP > pristine graphite. Among them, the sulfur-containing SGnP and CSGnP have superior ORR performance to the Pt/C electrocatalysts. Oxidation of SGnP into SOGnP further improved the ORR catalytic activity (12). Theoretical calculations showed that the electronic spin density, in addition to generally considered charge density, played a key role in the high ORR activity of SGnP and SOGnP. Furthermore, both SGnP and SOGnP demonstrated a better fuel selectivity with a longer-term stability than those of the pristine graphite and commercial Pt/C electrocatalysts.


Carbon-based electrocatalysts for advanced energy conversion and storage.

Zhang J, Xia Z, Dai L - Sci Adv (2015)

Schematic illustration of the preparation of EFGnPs through the ball-milling method for ORR.(A) Schematic representation of the mechanochemical reaction between in situ generated active carbon species and reactant gases in a sealed ball-mill crusher. The cracking of graphite by ball milling in the presence of corresponding gases and subsequent exposure to air moisture resulted in the formation of EFGnPs. The red balls stand for reactant gases such as hydrogen, carbon dioxide, sulfur trioxide, and air moisture (oxygen and moisture). [Derived from (119), Copyright 2012 National Academy of Sciences.] (B) A schematic representation for the edge expansions of XGnPs caused by the edge halogens: ClGnP, BrGnP, and IGnP. (C) The optimized O2 adsorption geometries onto XGnPs, in which halogen covalently linked to two sp2 carbons. In (C), the O-O bond length and the shortest C-O bond are shown in angstrom. [From I.-Y. Jeon, H.-J. Choi, M. Choi, J.-M. Seo, S.-M. Jung, M.-J. Kim, S. Zhang, L. Zhang, Z. Xia, L. Dai, N. Park, J.-B. Baek, Facile, scalable synthesis of edge-halogenated graphene nanoplatelets as efficient metal-free eletrocatalysts for oxygen reduction reaction. Sci. Rep.3, 1810 (2013). Reprinted with permission from the Nature Publishing Group.]
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Related In: Results  -  Collection

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Figure 6: Schematic illustration of the preparation of EFGnPs through the ball-milling method for ORR.(A) Schematic representation of the mechanochemical reaction between in situ generated active carbon species and reactant gases in a sealed ball-mill crusher. The cracking of graphite by ball milling in the presence of corresponding gases and subsequent exposure to air moisture resulted in the formation of EFGnPs. The red balls stand for reactant gases such as hydrogen, carbon dioxide, sulfur trioxide, and air moisture (oxygen and moisture). [Derived from (119), Copyright 2012 National Academy of Sciences.] (B) A schematic representation for the edge expansions of XGnPs caused by the edge halogens: ClGnP, BrGnP, and IGnP. (C) The optimized O2 adsorption geometries onto XGnPs, in which halogen covalently linked to two sp2 carbons. In (C), the O-O bond length and the shortest C-O bond are shown in angstrom. [From I.-Y. Jeon, H.-J. Choi, M. Choi, J.-M. Seo, S.-M. Jung, M.-J. Kim, S. Zhang, L. Zhang, Z. Xia, L. Dai, N. Park, J.-B. Baek, Facile, scalable synthesis of edge-halogenated graphene nanoplatelets as efficient metal-free eletrocatalysts for oxygen reduction reaction. Sci. Rep.3, 1810 (2013). Reprinted with permission from the Nature Publishing Group.]
Mentions: Recent efforts have led to solution-processable edge-functionalized graphene (EFG) sheets. Through a simple one-pot reaction, for example, Jeon and co-workers (118) have prepared edge-functionalized graphene nanoplatelets (EFGnPs) with aminobenzoyl moiety, which could be used as the in situ feedstock for “C-welding” and “N-doping” to produce high-quality NG films without introducing any oxygen-containing surface groups on the graphene basal plane. By solution casting the NG on a GC electrode and subsequent heat treatment, these authors demonstrated comparable ORR performance to the NG prepared by CVD. On the other hand, Jeon and co-workers (119) have also developed a low-cost and scalable ball milling method to produce high-quality, edge-functionalized NG films. By ball milling graphite with dry ice in a planetary ball-mill machine, Jeon and co-workers (119) initially produced edge-selectively carboxylated graphite (ECG), which is highly dispersable in many solvents to self-exfoliate into single- or few-layer graphene sheets. By replacing dry ice with N2 gas, the same authors have developed a simple approach to direct fixation of N2 into graphene nanoplatelets (GnPs) to form five- and six-membered aromatic rings at the broken edges (120), leading to solution-processable edge-nitrogenated graphene nanoplatelets (NGnPs) with superb electrocatalytic performance. As shown in Fig. 6, ball milling graphite in the presence of reactants other than dry ice or N2 (for example, halogen) is an efficient approach to scalable production of EFGnPs with various edge-functional groups (Fig. 6A) (21, 119). For instance, GnPs functionalized with hydrogen (HGnP), carboxylic acid (CGnP), sulfonic acid (SGnP), and mixed carboxylic acid/sulfonic acid (CSGnP) have been synthesized in the presence of hydrogen, carbon dioxide, sulfur trioxide, or carbon dioxide/sulfur trioxide mixture (21, 119). One of the salient features of EFGnPs is that the reaction medium does not intercalate into graphite but selectively functionalizes the sp2 C-H defects at the edges of graphite, leading to minimal carbon basal plane damage, and hence the formation of highly conductive electrodes. Electrochemical measurements indicated that the ORR activity of EFGnP electrodes follows the order of SGnP > CSGnP > CGnP > HGnP > pristine graphite. Among them, the sulfur-containing SGnP and CSGnP have superior ORR performance to the Pt/C electrocatalysts. Oxidation of SGnP into SOGnP further improved the ORR catalytic activity (12). Theoretical calculations showed that the electronic spin density, in addition to generally considered charge density, played a key role in the high ORR activity of SGnP and SOGnP. Furthermore, both SGnP and SOGnP demonstrated a better fuel selectivity with a longer-term stability than those of the pristine graphite and commercial Pt/C electrocatalysts.

Bottom Line: Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) play curial roles in electrochemical energy conversion and storage, including fuel cells and metal-air batteries.Having rich multidimensional nanoarchitectures [for example, zero-dimensional (0D) fullerenes, 1D carbon nanotubes, 2D graphene, and 3D graphite] with tunable electronic and surface characteristics, various carbon nanomaterials have been demonstrated to act as efficient metal-free electrocatalysts for ORR and OER in fuel cells and batteries.We present a critical review on the recent advances in carbon-based metal-free catalysts for fuel cells and metal-air batteries, and discuss the perspectives and challenges in this rapidly developing field of practical significance.

View Article: PubMed Central - PubMed

Affiliation: Center of Advanced Science and Engineering for Carbon (Case4Carbon), Department of Macromolecular Science and Engineering, Case Western Reserve University, Cleveland, OH 44106, USA.

ABSTRACT
Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) play curial roles in electrochemical energy conversion and storage, including fuel cells and metal-air batteries. Having rich multidimensional nanoarchitectures [for example, zero-dimensional (0D) fullerenes, 1D carbon nanotubes, 2D graphene, and 3D graphite] with tunable electronic and surface characteristics, various carbon nanomaterials have been demonstrated to act as efficient metal-free electrocatalysts for ORR and OER in fuel cells and batteries. We present a critical review on the recent advances in carbon-based metal-free catalysts for fuel cells and metal-air batteries, and discuss the perspectives and challenges in this rapidly developing field of practical significance.

No MeSH data available.


Related in: MedlinePlus