Pt-Free Cathode Catalyst Performance in H2/O2 Anion-Exchange Membrane Fuel Cells (AMFCs)

Filpi, Antonio; Boccia, Massimiliano; Gasteiger, Hubert A.

doi:10.1149/1.2982024

Cited by 39 publications

(33 citation statements)

References 9 publications

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“…1d) environments. 8,[16][17][18] Similar losses have also been reported for electrolyzers 5,19 (Fig. 1c) and metal-air batteries 13,20 due to the poor kinetics of the oxygen oxidation reaction -more commonly referred to as the oxygen evolution reaction (OER).…”

Section: Introductionsupporting

confidence: 63%

“…This mechanism proceeds similarly to Energy & Environmental Science Review the acid-base mechanism, but the evolution of oxygen does not occur through the potentially rate-limiting OOH* species. While such reaction mechanisms have been shown to have large activation barriers on noble metal surfaces, 58 the presence of loosely bound lattice oxygen atoms in oxide surface terminations have been observed to facilitate such reaction steps in the OER by 18 O isotope studies on RuO 2 (ref. 105) and NiCo 2 O 4 .…”

Section: Proposed Reaction Mechanisms On Oxide Surfacesmentioning

confidence: 99%

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Toward the rational design of non-precious transition metal oxides for oxygen electrocatalysis

Hong

Risch

Stoerzinger

et al. 2015

Energy Environ. Sci.

1,753

1,491

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REVIEWThis journal is © The Royal Society of Chemistry 2013 J. Name., 2013, 00, 1-3 | 1 In this Review, we discuss the state-of-the-art understanding of non-precious transition metal oxides that catalyze the oxygen reduction and evolution reactions. Understanding and mastering the kinetics of oxygen electrocatalysis is instrumental to making use of photosynthesis, advancing solar fuels, fuel cells, electrolyzers, and metal-air batteries. We first present key insights, assumptions and limitations of well-known activity descriptors and reaction mechanisms in the past four decades. The turnover frequency of crystalline oxides as promising catalysts is also put into perspective with amorphous oxides and photosystem II. Particular attention is paid to electronic structure parameters that can potentially govern the adsorbate binding strength and thus provide simple rationales and design principles to predict new catalyst chemistries with enhanced activity. We share new perspective synthesizing mechanism and electronic descriptors developed from both molecular orbital and solid state band structure principles. We conclude with an outlook on the opportunities in future research within this rapidly developing field. Broader ContextThe formation of chemical bonds is an energy dense mode of storing energy. In both nature and technology, the electrochemical generation and consumption of fuels is one of the most efficient routes for energy usage. Solar and electrical energy can be stored in chemical bonds by splitting water or metal oxides to produce hydrogen and metal. These compounds can then be oxidized to produce energy when coupled to the reduction of oxygen. However, these device efficiencies are severely limited by the catalysis of oxygen electrochemical processes -namely the oxygen reduction reaction and oxygen evolution reaction, which have slow kinetics. Non-precious transition metal oxides show promise as cost-effective substitutes for noble metals in commercially viable renewable energy storage and conversion devices. Furthermore, this class of materials has ben efitted from a wealth of spectroscopic and first-principles studies in the past few decades, providing the frameworks and theories needed to understand the electronic structure and design optimal catalysts. The incredibly diverse range of chemistries and physical properties that can be explored in oxide families afford numerous degrees of freedom for conducting systematic investigations relating intrinsic mat erial properties to catalytic performance. Here, we present background on the fundamental concepts in catalysis for the rational design of transition metal perovskite oxide catalysts for oxygen electrocatalysis and critically examine the current understanding a nd its impact on future directions of perovskite catalysts.

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Section: Introductionsupporting

confidence: 63%

Section: Proposed Reaction Mechanisms On Oxide Surfacesmentioning

confidence: 99%

Toward the rational design of non-precious transition metal oxides for oxygen electrocatalysis

Hong

Risch

Stoerzinger

et al. 2015

Energy Environ. Sci.

1,753

1,491

View full text Add to dashboard Cite

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“…4, may be expressed as Eq. 6: i k (0.8V) = e·(SD FeN2+2 ·ToF FeN2+2 + SD FeN4 ·ToF FeN4 ) [6] The activity of FeAc + NH 3 (or of ClFeTMPP + NH 3 ) is ~ 6 A·g -1 at both pH 1 and pH 13. Applying Equation 6 at pH 1 with i k (0.8V) = 6 A·g -1 , SD FeN2+2 =2.6·10 19 sites·g -1 , SD FeN4 =6.5·10 18 sites·g -1 and the value of ToF FeN4 = 6·10 -3 e·site -1 ·s -1 from our previous ECS Transactions, 25 (1) 117-128 (2009) calculation for ClFeTMPP + Ar, we get a minimum ToF FeN2+2 (pH 1) = 1.5 e·site -1 ·s -1 .…”

Section: Resultsmentioning

confidence: 99%

“…Meanwhile, fuel cell research shifted from basic to acidic electrolytes. While some Fe or Co/N/C catalysts can compete with Pt in alkaline media (6,7), most of them unfortunately still display insufficient activity and poor stability in acid media. This work attempts to better understanding the cause of these shortcomings in the latter in order to overcome the obstacles that they face in the PEM environment, by investigating the behaviors of three different Fe-based catalysts in both acid and alkaline media.…”

Section: Introductionmentioning

confidence: 99%

Electrochemical Evidence of Two Types of Active Sites for Oxygen Reduction in Fe-based Catalysts

Herranz¹,

Jaouen²,

Dodelet³

2009

ECS Trans.

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Fe-based catalysts for the reduction of oxygen were synthesized by wet-impregnation of FeII acetate or FeIII-porphyrin on pristine carbon black followed by pyrolysis in ammonia or argon. The catalysts were characterized using RDE and RRDE voltammetry in both acid and alkaline electrolytes. The results support the presence of two types of active sites for oxygen reduction in these catalysts: (i) the Fe-N4/C type, with a structure resembling the central porphyrin moiety, and (ii) the Fe-N2+2/C type, hosted in the micropores of the carbon support. Fe-N4/C sites are poorly active in acid but highly active in alkaline, whereas Fe-N2+2/C sites are highly active in both electrolytes.

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“…Although studies at RDE setup show the kinetics of HOR and ORR to be sufficiently fast, the performance of AMFC, however, can be limited due to additional problems such as water flooding at anode, water scarcity at cathode, low ionic conductivity of CL, and low mass transport of reactants. Filpi et al evaluated the performance of H 2 /O 2 AMFC and proposed that the difference between estimated performance after kinetic and ohmic correction and measured performance could be due to transport losses such as reactant transport and OH – transport. For a facile mass transport of reactant through the CL, permeability and diffusion coefficient of reactant in ionomer should be high.…”

Section: Introductionmentioning

confidence: 99%

Mass-Transport Characteristics of Oxygen at Pt/Anion Exchange Ionomer Interface

Khadke

Krewer

2014

J. Phys. Chem. C

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This work quantifies the mass-transport characteristics of O 2 at Pt/anion exchange ionomer by determining the solubility and diffusion coefficient of O 2 in Tokuyama AS-4 anion exchange ionomer film. Electrochemical methods such as linear sweep voltammetry and chronoamperometry are performed on rotating disk electrode to determine these parameters. The diffusion process in AS-4 ionomer film is found to be Fickian in nature; that is, it is shown that the diffusion coefficient is independent of concentration and film thickness by calculating the diffusion coefficient at various film thicknesses and rotation speed of electrode. In comparison with Nafion ionomer, the magnitude of diffusion coefficient in anion exchange ionomer is found to be one order higher, and solubility is found to be one order lower. However, the overall permeability, defined by product of diffusion coefficient and solubility is similar to Nafion ionomer film. In addition, durability studies of anion exchange ionomer-coated Pt disk shows electrochemical stability of anion ionomer in alkaline media. With these studies, it is shown that O 2 transport at the Pt/anion exchange ionomer interface is not expected to limit alkaline membrane fuel-cell cathode performance.

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Pt-Free Cathode Catalyst Performance in H2/O2 Anion-Exchange Membrane Fuel Cells (AMFCs)

Cited by 39 publications

References 9 publications

Toward the rational design of non-precious transition metal oxides for oxygen electrocatalysis

Toward the rational design of non-precious transition metal oxides for oxygen electrocatalysis

Electrochemical Evidence of Two Types of Active Sites for Oxygen Reduction in Fe-based Catalysts

Mass-Transport Characteristics of Oxygen at Pt/Anion Exchange Ionomer Interface

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