Immersed effects of Ta and Zr compounds on activity of oxygen reduction reaction in sulfuric acid

Matsuzawa, Koichi; Nozawa, Kazuhiro; Yamauchi, Kyosuke; Ishihara, Akimitsu; Mitsushima, Shigenori; Ota, Ken Ichiro

doi:10.1016/j.jpowsour.2012.10.050

Cited by 4 publications

(5 citation statements)

References 10 publications

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“…Without further distinction, their promises and drawbacks are that they offer reasonable activities, but that they generally lack long-term stability in the acidic environment of a proton exchange membrane fuel cell (PEMFC). 1 In an approach to improve the stability of non-noble-metal ORR electrocatalysts, valve-metal oxide based analogues that exhibit high stability against chemical dissolution in acidic environment have been explored [2][3][4][5][6][7] mostly by Ota and co-workers, who studied the ORR activity of sputtered oxides based on Nb, Ta, Ti and Zr, [8][9][10] with Zr based oxides exhibiting the highest ORR activity so far. Surprisingly, beyond their work, only very few studies on this class of catalysts have been published, [11][12][13] although a benefit of this class of materials was found in their robustness against methanol poisoning.…”

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confidence: 99%

“…Surprisingly, beyond their work, only very few studies on this class of catalysts have been published, [11][12][13] although a benefit of this class of materials was found in their robustness against methanol poisoning. 11, 13 Ota and co-workers also investigated the ORR activity of micrometric Ta and Zr oxides produced by heat-treatment of carbides, 11,14 nitrides, 14 or carbonitrides, 6,10,15,16 concluding that the formation of understoichiometric or defective oxides (i.e., of oxygen vacancies) would enhance their ORR activity, which was based on the observation that partial reduction of the formed oxides lead to improved ORR activity. 15,16 The same group also applied surface sensitive X-Ray absorption spectroscopy, which suggested a correlation between ORR activity and defect-induced strain of the Ta 2 O 5 oxide layer formed on top of a μm-sized TaCN core upon high-temperature oxidation.…”

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confidence: 99%

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ZrO₂Based Oxygen Reduction Catalysts for PEMFCs: Towards a Better Understanding

Mittermeier

Madkikar

Wang

et al. 2016

J. Electrochem. Soc.

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The oxygen reduction reaction (ORR) activity of ZrO 2 based, carbon-supported nanoparticles is not conclusively reported in literature. This study examines the dependence of the ORR activity on the used precursors as well as on the heat-treatment atmosphere and temperature. We further determine the ORR activation energy and the ORR mechanism. Various precursors containing Zr and/or N were employed in the synthesis, and the ORR activity was measured by rotating (ring) disk electrode (R(R)DE) voltammetry in both acidic and alkaline electrolyte as well as by measurements in a single-cell polymer electrolyte membrane fuel cell (PEMFC) configuration. We show that even the most active ZrO 2 based ORR catalysts exhibit an activity gap of ca. two orders of magnitude compared to the DOE target of 300 A/cm 3 for PGM-free ORR catalysts, thus requiring further development. Our RRDE analysis suggests a primarily 2-electron ORR mechanism in the case of the tested catalysts in acid, which in turn provides a consistent temperature dependence between RDE and PEMFC experiments, allowing also for a mechanistic (re-) interpretation of experimental results in the literature.

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confidence: 99%

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confidence: 99%

ZrO₂Based Oxygen Reduction Catalysts for PEMFCs: Towards a Better Understanding

Mittermeier

Madkikar

Wang

et al. 2016

J. Electrochem. Soc.

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“…and auxiliary power units (APUs). [25] Groups 4 and 5 metal oxides become active towards the ORR if their surface stoichiometry is conveniently tailored. [2,3] In the case of a DAFC, the poisoning effect of the alcohol that permeates through the membrane is an additional concern to the sluggishness of the electrochemical reactions at both the anode and the cathode.…”

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confidence: 99%

“…Surface modifications are aimed to change the oxidation state of metal species to form active and stable catalytic sites able to adsorb oxygen molecules and to introduce electronic levels in the energy gap. [22][23][24][25][26][27][28][29][30] Herein, we report on a new ORR catalyst formulation based on a substoichiometric sodium tantalate (Na 2 Ta 8 O 21Àx ) characterized by high crystallinity and supported on high-surfacearea (450 m 2 g À1 ) graphene (50 wt % Na 2 Ta 8 O 21Àx /graphene). [26] Four modification methods for such metal oxides have been described by Ota et al: [22] 1) formation of complex oxide layers containing active sites; 2) substitutional doping with nitrogen; 3) creation of oxygen defects; 4) partial oxidation of metals with carbon and/or nitrogen.…”

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Graphene‐Supported Substoichiometric Sodium Tantalate as a Methanol‐Tolerant, Non‐Noble‐Metal Catalyst for the Electroreduction of Oxygen

et al. 2015

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For the oxygen reduction reaction (ORR) in acidic medium, a good combination of an active and stable catalyst highly dispersed on a conductive and durable support is required. Moreover, for direct methanol fuel-cell applications, a suitable tolerance to methanol poisoning is also necessary. In this communication, we report on a new graphene-supported sodium tantalate (Na 2 Ta 8 O 21Àx ) electrocatalyst obtained at high temperature and characterized by significant substoichiometry. The synthesis includes the precipitation of tantalum oxide on a high surface area graphene and subsequent thermal treatment at 900 8C. A novel sodium tantalate phase with oxygen vacancies is thereafter obtained. This catalyst formulation shows promising activity towards the ORR especially in the presence of a high methanol concentration, as evidenced by a high tolerance to methanol poisoning. Accelerated stress tests and chemical leaching experiments also show the remarkable stability of the catalyst. This material presents good perspectives for application in cost-effective fuel cells.A highly active, durable, and cost-effective catalyst for the oxygen reduction reaction (ORR) is essential for the large-scale application of low-temperature fuel cells. State-of-the-art catalysts for fuel cells are based on precious metals, essentially platinum (Pt). The prohibitive cost of Pt, its scarce resources, and its insufficient durability hinder the commercialization of this fuel-cell technology. [1,2] Direct alcohol fuel cells (DAFCs) will presumably reach wide-scale commercialization earlier than hydrogen-fuelled cells owing to the easy handling and high energy density of organic fuels, especially covering portable power application (laptops, mobile phones, etc.) and auxiliary power units (APUs). Application of DAFCs in portable and APU devices can accelerate the fuel-cell technology diffusion. [2,3] In the case of a DAFC, the poisoning effect of the alcohol that permeates through the membrane is an additional concern to the sluggishness of the electrochemical reactions at both the anode and the cathode. [3,4] Now, only a few types of electrocatalysts based on nonprecious metal formulations have been found to be active towards the ORR in acid media. These include carbon-supported transition-metal/nitrogen compounds (Fe/N/C, Co/N/C), [5][6][7][8][9][10][11] metal-free nitrogen-doped carbon materials, [12,13] and transition-metal chalcogenides. [14,15] Although Fe-and Co-based catalysts have been studied for the ORR for over 50 years, a suitable enhancement in the catalytic activity has been achieved only very recently. [5,8,16] These catalysts are potential competitors to Pt in terms of activity, [5,8] whereas significant efforts are still required to further enhance their stability. [6,7] Piela et al. have also reported promising tolerance to methanol poisoning for a Co-based catalyst. [17] Graphene, a free-standing atomic thin layer of sp 2 carbon atoms, has emerged as the most interesting carbon material in the last decade because of its unp...

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“…Another interesting approach is the use of group 4 and 5 metal oxides (Ti, V, Zr, Nb, Hf, Ta) [7,8], which are characterized by an excellent stability in acid media [9]. Group 4 and 5 metal oxides become active towards ORR when their surface is suitably modified.…”

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confidence: 99%

Facile synthesis of Zr- and Ta-based catalysts for the oxygen reduction reaction

Sebastián

Baglio

Sun

et al. 2015

Chinese Journal of Catalysis

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Immersed effects of Ta and Zr compounds on activity of oxygen reduction reaction in sulfuric acid

Cited by 4 publications

References 10 publications

ZrO₂Based Oxygen Reduction Catalysts for PEMFCs: Towards a Better Understanding

ZrO₂Based Oxygen Reduction Catalysts for PEMFCs: Towards a Better Understanding

Graphene‐Supported Substoichiometric Sodium Tantalate as a Methanol‐Tolerant, Non‐Noble‐Metal Catalyst for the Electroreduction of Oxygen

Facile synthesis of Zr- and Ta-based catalysts for the oxygen reduction reaction

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Immersed effects of Ta and Zr compounds on activity of oxygen reduction reaction in sulfuric acid

Cited by 4 publications

References 10 publications

ZrO2Based Oxygen Reduction Catalysts for PEMFCs: Towards a Better Understanding

ZrO2Based Oxygen Reduction Catalysts for PEMFCs: Towards a Better Understanding

Graphene‐Supported Substoichiometric Sodium Tantalate as a Methanol‐Tolerant, Non‐Noble‐Metal Catalyst for the Electroreduction of Oxygen

Facile synthesis of Zr- and Ta-based catalysts for the oxygen reduction reaction

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ZrO₂Based Oxygen Reduction Catalysts for PEMFCs: Towards a Better Understanding

ZrO₂Based Oxygen Reduction Catalysts for PEMFCs: Towards a Better Understanding