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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

Morphology characterization and catalytic performance of VA-NCNTs.(A) Scanning electron microscopy image of the as-synthesized VA-NCNTs on a quartz substrate. Scale bar, 2 μm. (B) Digital photograph of the VA-NCNT array after having been transferred onto a polystyrene (PS) and nonaligned CNT conductive composite film. (C) RDE voltammograms for oxygen reduction in air-saturated 0.1 M KOH at the Pt/C (curve 1), VA-CCNT (curve 2), and VA-NCNT (curve 3) electrodes. (D) Cyclic voltammograms for the ORR at the Pt/C (top) and VA-NCNT (bottom) electrodes before (solid curves) and after (dotted curves) a continuous potentiodynamic sweep for about 100,000 cycles in air-saturated 0.1 M KOH at room temperature (25 ± 1°C). Scan rate: 100 mV s−1. (E) The CO poisoning effect on the i-t chronoamperometric response for the Pt/C (black curve) and VA-NCNT (red line) electrodes. CO gas (55 ml/min) was first added into the 550 ml/min O2 flow, and then the mixture gas of ~9% CO (v/v) was introduced into the electrochemical cell at about 1700s. (F) Calculated charge density distribution for the NCNTs. (G) Schematic representations of possible adsorption modes of an oxygen molecule at the CCNTs (top) and NCNTs (bottom). [From K. Gong, F. Du, Z. Xia, M. Durstock, L. Dai, Nitrogen-doped carbon nanotube arrays with high electrocatalytic activity for oxygen reduction. Science323, 760–764 (2009). Reprinted with permission from AAAS.]
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Figure 4: Morphology characterization and catalytic performance of VA-NCNTs.(A) Scanning electron microscopy image of the as-synthesized VA-NCNTs on a quartz substrate. Scale bar, 2 μm. (B) Digital photograph of the VA-NCNT array after having been transferred onto a polystyrene (PS) and nonaligned CNT conductive composite film. (C) RDE voltammograms for oxygen reduction in air-saturated 0.1 M KOH at the Pt/C (curve 1), VA-CCNT (curve 2), and VA-NCNT (curve 3) electrodes. (D) Cyclic voltammograms for the ORR at the Pt/C (top) and VA-NCNT (bottom) electrodes before (solid curves) and after (dotted curves) a continuous potentiodynamic sweep for about 100,000 cycles in air-saturated 0.1 M KOH at room temperature (25 ± 1°C). Scan rate: 100 mV s−1. (E) The CO poisoning effect on the i-t chronoamperometric response for the Pt/C (black curve) and VA-NCNT (red line) electrodes. CO gas (55 ml/min) was first added into the 550 ml/min O2 flow, and then the mixture gas of ~9% CO (v/v) was introduced into the electrochemical cell at about 1700s. (F) Calculated charge density distribution for the NCNTs. (G) Schematic representations of possible adsorption modes of an oxygen molecule at the CCNTs (top) and NCNTs (bottom). [From K. Gong, F. Du, Z. Xia, M. Durstock, L. Dai, Nitrogen-doped carbon nanotube arrays with high electrocatalytic activity for oxygen reduction. Science323, 760–764 (2009). Reprinted with permission from AAAS.]

Mentions: The location control of dopants in the heteroatom-doped carbon nanomaterials should provide us with powerful means to tailor the structure-property relationships for heteroatom-doped carbon-based metal-free catalysts. Although the accurate control of the nitrogen doping sites in carbon nanomaterials is still impossible, a few approaches, including the use of N-containing macromolecular precursors with N-rich cycles (for example, triazine and phthalocyanine derivatives) of precisely controlled locations of N atoms and hole sizes, followed by carbonization, have led to the formation of well-controlled N-doped holey graphene nanosheets (73, 74). We have also used N-containing iron phthalocyanine as the precursor for the synthesis of vertically aligned NCNTs (VA-NCNTs) by chemical vapor deposition (CVD) (Fig. 4A). After removal of iron residue, if any, the VA-NCNTs thus prepared were shown to catalyze a four-electron ORR process free from CO “poisoning” with a much higher electrocatalytic activity and better durability than those of commercially available Pt/C in alkaline electrolytes (Fig. 4, B to E) (7). According to the experimental observations and theoretical calculations by B3LYP hybrid density functional theory (DFT), the improved catalytic performance can be contributed to the electron-accepting ability of the nitrogen atoms, which creates a net positive charge on adjacent carbon atoms in the CNT plane of VA-NCNTs (Fig. 4F). The nitrogen-induced charge delocalization could also change the chemisorption mode of O2 from the usual end-on adsorption (Pauling model) at the nitrogen-free CNT (CCNT) surface (Fig. 4G, top) to a side-on adsorption (Yeager model) onto the NCNT electrodes (Fig. 4G, bottom). The N-doping induced charge transfer from adjacent carbon atoms could lower the ORR potential, whereas the parallel diatomic adsorption could effectively weaken the O-O bonding, facilitating ORR at the VA-NCNT electrodes. Uncovering this ORR mechanism in the NCNT electrodes is significant because the same principle has been applied to the development of various other metal-free efficient ORR catalysts for fuel cells and other applications (17, 35).


Carbon-based electrocatalysts for advanced energy conversion and storage.

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

Morphology characterization and catalytic performance of VA-NCNTs.(A) Scanning electron microscopy image of the as-synthesized VA-NCNTs on a quartz substrate. Scale bar, 2 μm. (B) Digital photograph of the VA-NCNT array after having been transferred onto a polystyrene (PS) and nonaligned CNT conductive composite film. (C) RDE voltammograms for oxygen reduction in air-saturated 0.1 M KOH at the Pt/C (curve 1), VA-CCNT (curve 2), and VA-NCNT (curve 3) electrodes. (D) Cyclic voltammograms for the ORR at the Pt/C (top) and VA-NCNT (bottom) electrodes before (solid curves) and after (dotted curves) a continuous potentiodynamic sweep for about 100,000 cycles in air-saturated 0.1 M KOH at room temperature (25 ± 1°C). Scan rate: 100 mV s−1. (E) The CO poisoning effect on the i-t chronoamperometric response for the Pt/C (black curve) and VA-NCNT (red line) electrodes. CO gas (55 ml/min) was first added into the 550 ml/min O2 flow, and then the mixture gas of ~9% CO (v/v) was introduced into the electrochemical cell at about 1700s. (F) Calculated charge density distribution for the NCNTs. (G) Schematic representations of possible adsorption modes of an oxygen molecule at the CCNTs (top) and NCNTs (bottom). [From K. Gong, F. Du, Z. Xia, M. Durstock, L. Dai, Nitrogen-doped carbon nanotube arrays with high electrocatalytic activity for oxygen reduction. Science323, 760–764 (2009). Reprinted with permission from AAAS.]
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Figure 4: Morphology characterization and catalytic performance of VA-NCNTs.(A) Scanning electron microscopy image of the as-synthesized VA-NCNTs on a quartz substrate. Scale bar, 2 μm. (B) Digital photograph of the VA-NCNT array after having been transferred onto a polystyrene (PS) and nonaligned CNT conductive composite film. (C) RDE voltammograms for oxygen reduction in air-saturated 0.1 M KOH at the Pt/C (curve 1), VA-CCNT (curve 2), and VA-NCNT (curve 3) electrodes. (D) Cyclic voltammograms for the ORR at the Pt/C (top) and VA-NCNT (bottom) electrodes before (solid curves) and after (dotted curves) a continuous potentiodynamic sweep for about 100,000 cycles in air-saturated 0.1 M KOH at room temperature (25 ± 1°C). Scan rate: 100 mV s−1. (E) The CO poisoning effect on the i-t chronoamperometric response for the Pt/C (black curve) and VA-NCNT (red line) electrodes. CO gas (55 ml/min) was first added into the 550 ml/min O2 flow, and then the mixture gas of ~9% CO (v/v) was introduced into the electrochemical cell at about 1700s. (F) Calculated charge density distribution for the NCNTs. (G) Schematic representations of possible adsorption modes of an oxygen molecule at the CCNTs (top) and NCNTs (bottom). [From K. Gong, F. Du, Z. Xia, M. Durstock, L. Dai, Nitrogen-doped carbon nanotube arrays with high electrocatalytic activity for oxygen reduction. Science323, 760–764 (2009). Reprinted with permission from AAAS.]
Mentions: The location control of dopants in the heteroatom-doped carbon nanomaterials should provide us with powerful means to tailor the structure-property relationships for heteroatom-doped carbon-based metal-free catalysts. Although the accurate control of the nitrogen doping sites in carbon nanomaterials is still impossible, a few approaches, including the use of N-containing macromolecular precursors with N-rich cycles (for example, triazine and phthalocyanine derivatives) of precisely controlled locations of N atoms and hole sizes, followed by carbonization, have led to the formation of well-controlled N-doped holey graphene nanosheets (73, 74). We have also used N-containing iron phthalocyanine as the precursor for the synthesis of vertically aligned NCNTs (VA-NCNTs) by chemical vapor deposition (CVD) (Fig. 4A). After removal of iron residue, if any, the VA-NCNTs thus prepared were shown to catalyze a four-electron ORR process free from CO “poisoning” with a much higher electrocatalytic activity and better durability than those of commercially available Pt/C in alkaline electrolytes (Fig. 4, B to E) (7). According to the experimental observations and theoretical calculations by B3LYP hybrid density functional theory (DFT), the improved catalytic performance can be contributed to the electron-accepting ability of the nitrogen atoms, which creates a net positive charge on adjacent carbon atoms in the CNT plane of VA-NCNTs (Fig. 4F). The nitrogen-induced charge delocalization could also change the chemisorption mode of O2 from the usual end-on adsorption (Pauling model) at the nitrogen-free CNT (CCNT) surface (Fig. 4G, top) to a side-on adsorption (Yeager model) onto the NCNT electrodes (Fig. 4G, bottom). The N-doping induced charge transfer from adjacent carbon atoms could lower the ORR potential, whereas the parallel diatomic adsorption could effectively weaken the O-O bonding, facilitating ORR at the VA-NCNT electrodes. Uncovering this ORR mechanism in the NCNT electrodes is significant because the same principle has been applied to the development of various other metal-free efficient ORR catalysts for fuel cells and other applications (17, 35).

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