Exploiting the flexibility of the pyrochlore composition for acid-resilient iridium oxide electrocatalysts in proton exchange membranes

Burnett, David L.; Petrucco, Enrico; Kashtiban, Reza J.; Parker, Stewart F.; Sharman, Jonathan; Walton, Richard I.

doi:10.1039/d1ta05457k

Cited by 8 publications

(4 citation statements)

References 63 publications

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“…The outstanding features of pyrochlore, like good thermal stability, oxygen mobility, inherent oxygen vacancy, and good ionic transport, make this structure suitable for use in several areas, such as the manufacture of fuel cells, [29][30][31][32] in the production of hydrogen, 33 as gas sensors, 34,35 as a thermal barrier coating, 36,37 and for photocatalysis. 38 Recently, pyrochlore structures have been studied for soot oxidation, 39 ammonia oxidation, 40 methane dry reforming, 41 electrocatalysis, 42,43 and photocatalysis. 44 The stable crystalline phase for pyrochlore-type structures has already been unveiled by previous literature [45][46][47] and depends on the ratio between the ionic radius of the atoms located on sites A and B.…”

Section: Introductionmentioning

confidence: 99%

The catalytic activity of the Pr₂Zr₂₋_xFe_xO_7±_δ system for the CO oxidation reaction

et al. 2022

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One of the alternatives to decrease the concentration of CO is its oxidation reaction to CO 2 , which can be made more efficient using catalysts. In this work, it is shown that pyrochlore structures are a promising candidate to act as heterogeneous catalysts due to their chemical and physical properties. For use as a catalyst in this reaction, the Pr 2 Zr 2−x Fe x O 7±δ (x = 0, 0.05, 0.10, and 0.15) system was synthesized by the solvothermal method, firing the powder obtained at temperatures of 1200 and 1400 • C. The diffraction patterns confirmed the pyrochlore structure as the single phase in all the nominal compositions. The Brunauer-Emmett-Teller method and dynamic light-scattering analysis showed an increase in the particle size and a decrease in the specific surface area when increasing the iron concentration and increasing the calcination temperature. The compositions that presented the best catalytic activity were the samples with the highest iron concentration. Moreover, these samples were able to convert all the CO oxidation reactions in a narrower temperature range than a conventional CeO 2 sample. The presence of vacancies and the redox behavior of the elements present are the key factors for the catalysis of this system in the CO oxidation reaction.

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Section: Introductionmentioning

confidence: 99%

The catalytic activity of the Pr₂Zr₂₋_xFe_xO_7±_δ system for the CO oxidation reaction

et al. 2022

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“…In the early stage, dimensionally stable anodes for oxygen evolution typically choose Ti as the substrate and other oxides such as Ta 2 O 5 and SnO 2 to further enhance their catalytic performance. In recent years, many other compounds integrated with iridium have been investigated, which includes IrM (M = Ni, Co, Fe) alloys, perovskites such as Ba 2 MIrO 6 , BaIrO 3 , and SrIrO 3 , − pyrochlores Y 2 Ir 2 O 7 , , and mixed oxides such as Ta 0.1 Tm 0.1 Ir 0.8 O 2−δ , IrTi x O y , IrHf x O y , IrW x O y , ,, IrRu x O y , and IrNi x O y . , Some of these materials are selected, and their performances are compared in the Appendix. These composites typically can reduce the loading amount of iridium by diluting it in a matrix of less expensive and stable materials.…”

Section: Iridium-based Water Oxidation Catalystsmentioning

confidence: 99%

Progress of Heterogeneous Iridium-Based Water Oxidation Catalysts

Gao

Liu

et al. 2022

ACS Nano

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The water oxidation reaction (or oxygen evolution reaction, OER) plays a critical role in green hydrogen production via water splitting, electrochemical CO 2 reduction, and nitrogen fixation. The four-electron and four-proton transfer OER process involves multiple reaction intermediates and elementary steps that lead to sluggish kinetics; therefore, a high overpotential is necessary to drive the reaction. Among the different water-splitting electrolyzers, the proton exchange membrane type electrolyzer has greater advantages, but its anode catalysts are limited to iridium-based materials. The iridium catalyst has been extensively studied in recent years due to its balanced activity and stability for acidic OER, and many exciting signs of progress have been made. In this review, the surface and bulk Pourbaix diagrams of iridium species in an aqueous solution are introduced. The iridium-based catalysts, including metallic or oxides, amorphous or crystalline, single crystals, atomically dispersed or nanostructured, and iridium compounds for OER, are then elaborated. The latest progress of active sites, reaction intermediates, reaction kinetics, and elementary steps is summarized. Finally, future research directions regarding iridium catalysts for acidic OER are discussed.

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“…[ 15 ] In addition, A + may potentially maintain some stability of the system due to multiple coordination environments and the constant redox chemistry. [ 16 ] As a result, Na + was chosen to partially replace Gd 3+ , which has a relatively close radius. Simultaneously, the flexible crystal structure of pyrochlore provides a prerequisite for the introduction of Na + .…”

Section: Introductionmentioning

confidence: 99%

Na Substitution Steering RuO₆ Unit in Ruthenium Pyrochlores for Enhanced Oxygen Evolution in Acid

Shang,

Wang,

et al. 2023

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Although Ruthenium‐based pyrochlore oxides can function as promising catalysts for acidic water oxidation, their limitations in terms of stability and activity still need to be addressed for further application in practical conditions. In this work, the possibility to enhance both oxygen evolution reaction activity and durability of Gd2Ru2O7‐δ through partial replacement with Na+ in Gd3+ sites is first offered, leading to the electronic and geometric regulation of active center RuO6. Na+ triggers the emergence of Ru<4+ and the electron rearrangement of active‐centered RuO6. Specifically, Ru ions with a negative d‐band center after Na+ doping exhibit weaker adsorption energies of *O and result in the conversion of the rate‐limiting step from *O/*OOH to *OH/O*, reducing energy barriers for boosting activities. Therefore, the NaxGd2‐xRu2O7‐δ requires a low overpotential of 260 mV at 10 mA cm−2 in 0.1 m HClO4 electrolyte. Moreover, the higher formation energy of Ru vacancy and less distorted RuO6 enable the as‐prepared NaxGd2‐xRu2O7‐δ to operate steadily at 10 mA cm−2 for 300 h and multi‐current chronopotentiometry with current densities from 20 to 100 mA cm−2 for 60 h in acidic proton exchange membrane electrolyzer, respectively.

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Exploiting the flexibility of the pyrochlore composition for acid-resilient iridium oxide electrocatalysts in proton exchange membranes

Abstract: Iridate pyrochlores formed by hydrothermal synthesis provide robust OER catalysts for membrane electrode assemblies, giving effective oxygen evolution with minimal carbon corrosion.

Cited by 8 publications

References 63 publications

The catalytic activity of the Pr₂Zr₂₋_xFe_xO_7±_δ system for the CO oxidation reaction

The catalytic activity of the Pr₂Zr₂₋_xFe_xO_7±_δ system for the CO oxidation reaction

Progress of Heterogeneous Iridium-Based Water Oxidation Catalysts

Na Substitution Steering RuO₆ Unit in Ruthenium Pyrochlores for Enhanced Oxygen Evolution in Acid

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Exploiting the flexibility of the pyrochlore composition for acid-resilient iridium oxide electrocatalysts in proton exchange membranes

Abstract: Iridate pyrochlores formed by hydrothermal synthesis provide robust OER catalysts for membrane electrode assemblies, giving effective oxygen evolution with minimal carbon corrosion.

Cited by 8 publications

References 63 publications

The catalytic activity of the Pr2Zr2−xFexO7±δ system for the CO oxidation reaction

The catalytic activity of the Pr2Zr2−xFexO7±δ system for the CO oxidation reaction

Progress of Heterogeneous Iridium-Based Water Oxidation Catalysts

Na Substitution Steering RuO6 Unit in Ruthenium Pyrochlores for Enhanced Oxygen Evolution in Acid

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The catalytic activity of the Pr₂Zr₂₋_xFe_xO_7±_δ system for the CO oxidation reaction

The catalytic activity of the Pr₂Zr₂₋_xFe_xO_7±_δ system for the CO oxidation reaction

Na Substitution Steering RuO₆ Unit in Ruthenium Pyrochlores for Enhanced Oxygen Evolution in Acid