Electroreduction of Dioxygen for Fuel-Cell Applications: Materials and Challenges

Gewirth, Andrew A.; Thorum, Matthew S.

doi:10.1021/ic9022486

Cited by 678 publications

(563 citation statements)

References 153 publications

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“…The experimental elucidation of the reaction mechanism is challenging (and often controversial), in particular as the intermediates cannot be easily probed in situ. 42,43 The theoretical modelling of electrochemical reactions is equally complex, as it needs to account for the effect of the solvent on the adsorbed intermediates, the highly charged electric field in the double layer, the free energy of the electrons in the solid and the free energy of the solvated reactants as a function of potential. [44][45][46][47][48][49][50][51][52][53][54] However, it turns out that the overall trends can be 7 ‡ We note that a fuel cell would probably be operated at potentials lower than 0.9 V, to maximise the power output.…”

Section: Theoretical Trends In Activity For Pt and Its Alloysmentioning

confidence: 99%

Understanding the electrocatalysis of oxygen reduction on platinum and its alloys

Stephens

Bondarenko

Grønbjerg

et al. 2012

Energy Environ. Sci.

1,085

1,024

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The high cost of low temperature fuel cells is to a large part dictated by the high loading of Pt required to catalyse the oxygen reduction reaction (ORR). Arguably the most viable route to decrease the Pt loading, and to hence commercialise these devices, is to improve the ORR activity of Pt by alloying it with other metals. In this perspective paper we provide an overview of the fundamentals underlying the reduction of oxygen on platinum and its alloys. We also report the ORR activity of Pt 5 La for the first time, which shows a 3.5-to 4.5-fold improvement in activity over Pt in the range 0.9 to 0.87 V, respectively. We employ angle resolved X-ray photoelectron spectroscopy and density functional theory calculations to understand the activity of Pt 5 La.

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Section: Theoretical Trends In Activity For Pt and Its Alloysmentioning

confidence: 99%

Understanding the electrocatalysis of oxygen reduction on platinum and its alloys

Stephens

Bondarenko

Grønbjerg

et al. 2012

Energy Environ. Sci.

1,085

1,024

View full text Add to dashboard Cite

show abstract

“…However, even on the best catalysts (Pt and Pt-based materials), the ORR suffers from sluggish kinetics and requires a high overpotential. 35 The mechanism and kinetics of the ORR on Pt have been studied [6][7][8] to understand the cause of the sub-optimal performance and to identify strategies to optimize the catalytic properties of Pt surfaces. [9][10][11] A common strategy is to identify the most efficient surface structure for the ORR and then try to expose these micro- 40 or nano-structures in the catalysts.…”

Section: Introductionmentioning

confidence: 99%

High resolution mapping of oxygen reduction reaction kinetics at polycrystalline platinum electrodes

Chen

Meadows

Cuharuc

et al. 2014

Phys. Chem. Chem. Phys.

111

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The scanning droplet-based technique, scanning electrochemical cell microscopy (SECCM), combined with electron backscatter diffraction (EBSD), is demonstrated as a powerful approach for visualizing surface structure effects on the rate of the oxygen reduction reaction (ORR) at polycrystalline platinum electrodes. Elucidating the effect of electrode structure on the ORR is of major interest in connection to 10 electrocatalysis for energy-related applications. The attributes of the approach herein stem from: (i) the ease with which the polycrystalline substrate electrode can be prepared; (ii) the wide range of surface character open to study; (iii) the possibility of mapping reactivity within a particular facet (or grain), in a pseudo-single crystal approach, and acquiring a high volume of data as a consequence; (iv) the ready ability to measure the activity at grain boundaries; and (v) an experimental arrangement (SECCM) that 15 mimics the three-phase boundary in low temperature fuel cells. The kinetics of the ORR was analyzed and a finite element model was developed to explore the effect of the three-phase boundary, in particular to examine pH variations in the droplet and the differential transport rates of the reactants and products. We have found a significant variation of activity across the platinum substrate, inherently linked to the crystallographic orientation, but do not detect any enhanced activity at grain boundaries. Grains with 20 (111) and (100) contributions exhibit considerably higher activity than those with (110) and (100) contributions. These results, which can be explained by reference to previous single crystal measurements, enhance our understanding of ORR structure-activity relationships on complex high-index platinum surfaces, and further demonstrate the power of high resolution flux imaging techniques to visualize and understand complex electrocatalyst materials.

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“…17), and were then thoroughly investigated as potential cathode catalyst in fuel cells and metal-air batteries 18 . To date, however, limited progress has been made in improving their electrocatalytic activity and durability 19 . In particular, macrocycle compounds have been demonstrated for a long time to suffer from severe degradation in fuel cell environments due to demetalation and/or degradation of iron phthalocyanine (FePc) by ORR intermediates 20,21 .…”

mentioning

confidence: 99%

Promotion of oxygen reduction by a bio-inspired tethered iron phthalocyanine carbon nanotube-based catalyst

et al. 2013

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Electrocatalysts for oxygen reduction are a critical component that may dramatically enhance the performance of fuel cells and metal-air batteries, which may provide the power for future electric vehicles. Here we report a novel bio-inspired composite electrocatalyst, iron phthalocyanine with an axial ligand anchored on single-walled carbon nanotubes, demonstrating higher electrocatalytic activity for oxygen reduction than the state-of-the-art Pt/C catalyst as well as exceptional durability during cycling in alkaline media. Theoretical calculations suggest that the rehybridization of Fe 3d orbitals with the ligand orbitals coordinated from the axial direction results in a significant change in electronic and geometric structure, which greatly increases the rate of oxygen reduction reaction. Our results demonstrate a new strategy to rationally design inexpensive and durable electrochemical oxygen reduction catalysts for metal-air batteries and fuel cells.

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Electroreduction of Dioxygen for Fuel-Cell Applications: Materials and Challenges

Cited by 678 publications

References 153 publications

Understanding the electrocatalysis of oxygen reduction on platinum and its alloys

Understanding the electrocatalysis of oxygen reduction on platinum and its alloys

High resolution mapping of oxygen reduction reaction kinetics at polycrystalline platinum electrodes

Promotion of oxygen reduction by a bio-inspired tethered iron phthalocyanine carbon nanotube-based catalyst

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