A simple one-pot Adams method route to conductive high surface area IrO<sub>2</sub>–TiO<sub>2</sub> materials

Oakton, Emma; Lebedev, Dmitry; Fedorov, Alexey; Krumeich, Frank; Tillier, Jérémy; Sereda, Olha; Schmidt, Thomas J.; Copéret, Christophe

doi:10.1039/c5nj02400e

Cited by 50 publications

(67 citation statements)

References 38 publications

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“…Energy Mater. Catalyst layer conductivities of 3 to 7 S cm −1 , equilibrated at the different gas phase humidity, are observed that are comparable to literature values of 1 to 4 S cm −1 [56] for materials with same Ir content (IrO 2 /TiO 2 catalysts > 60 %mol). To decode this missing link between optimal PTL microstructure and high catalyst utilization, the conduction mechanism in anodic catalyst layers needs to be analyzed.…”

Section: Elucidating the Mechanistic Of The Mpl Effectsupporting

confidence: 87%

“…[18] To better understand the effect of ionomer swelling on catalyst layer conductivity, the influence of ionomer weight fraction (3 to 18 %wt) at constant catalyst loading on electrical in-plane conductivity was analyzed ex situ during a humidification cycle (dry → 100 %rh → liquid water → dry), see Figure 5a. Catalyst layer conductivities of 3 to 7 S cm −1 , equilibrated at the different gas phase humidity, are observed that are comparable to literature values of 1 to 4 S cm −1 [56] for materials with same Ir content (IrO 2 /TiO 2 catalysts > 60 %mol). For ionomer contents up to 11 %wt, the conductivity differences are not significant and are within the standard deviation of the measurements.…”

Section: Elucidating the Mechanistic Of The Mpl Effectsupporting

confidence: 87%

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Hierarchically Structured Porous Transport Layers for Polymer Electrolyte Water Electrolysis

Schuler

Ciccone

Krentscher³

et al. 2019

Advanced Energy Materials

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121

162

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renewable power, from wind or solar by medium-to-long-term storage using hydrogen as the energy vector, [1,2] enabling effective decarbonisation of the energy sector. [3] PEWE converts electric power by electrochemical water splitting into storable chemical energy. [4][5][6][7] Hydrogen can be reconverted to power or used in other sectors, [8,9] such as fuel cell based mobility [10] and chemical industries. [11] To make hydrogen production with polymer electrolyte water electrolysis a technoeconomically relevant contender, capital and operational cost need to be reduced substantially. [12][13][14][15] Operational cost, which becomes the main cost driver for operation schemes with high duty ratio (≥6000 h p.a.), is governed by power prices and the hydrogen production efficiency of the PEWE plant, which in turn strongly depends on the electrochemical performance and efficiency of the PEWE cell technology employed. [16] The electrochemical efficiency is governed by the underlying electrochemical loss mechanisms of kinetic, ohmic, and mass transport losses, whereas capital cost is driven by limited power density and high noble metal catalyst loadings.Recent studies revealed that the structure of the interface between the anodic porous transport layer (PTL) and the catalyst layer (CL) is a crucial factor limiting cell efficiency. [17][18][19][20][21] Today's PEWE technology relies on porous, Ti based, transport layer materials in the form of sintered materials [17,18,[22][23][24][25] with original applications in filtration [26] or medical tissue growing. [27][28][29] The lack of PTL materials with suitable surface characteristics tailored for this application inhibits the further improvement of cell efficiency and development of PEWE technology.Kinetic losses are governed by the sluggish kinetics of the oxygen evolution reaction (OER). The related overpotential depends on intrinsic catalyst parameters, such as specific exchange current density, activation energy, and number of active catalyst sites. [30] It has been established with model experiments such as optical imaging of the PTL/CL interface [19,20,31] and correlation of in-depth electrochemical analysis with PTL surface structure [17,18] that the catalyst is only partially utilized and CL domains not directly contacted by the porous Timaterials showed no gas evolution hence no electrochemical activity. Schuler et al. [17,18] have quantified the effect, showing

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Section: Elucidating the Mechanistic Of The Mpl Effectsupporting

confidence: 87%

Section: Elucidating the Mechanistic Of The Mpl Effectsupporting

confidence: 87%

Hierarchically Structured Porous Transport Layers for Polymer Electrolyte Water Electrolysis

Schuler

Ciccone

Krentscher³

et al. 2019

Advanced Energy Materials

Self Cite

121

162

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“…Several authors attributed the improved conductivity to structural modifications of the Ti lattice . In contrast, percolation would rely on conductive oxide islands distributed throughout a matrix of non‐conductive TiO 2 . Only when a certain threshold of the content of conductive oxide is reached a sufficient number of conductive domains become connected and conductivity starts to increase.…”

Section: Resultsmentioning

confidence: 98%

“…However, low calcination temperatures typically coincide with a high content of TiO 2 crystals that remain in the mixed phase. Oakton et al . reported that IrO 2 /TiO 2 materials synthesized by an one‐pot Adams method from NaNO 3 , IrCl 3 ⋅0.6 H 2 O, and TiOSO 4 ⋅0.6 H 2 O at 350 °C retained three different phases, that is, TiO 2 anatase, TiO 2 rutile, and IrO 2 rutile, with IrO 2 nanoparticles (ca.…”

Section: Introductionmentioning

confidence: 99%

Oxygen Evolution Catalysts Based on Ir–Ti Mixed Oxides with Templated Mesopore Structure: Impact of Ir on Activity and Conductivity

et al. 2018

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The efficient generation of hydrogen via water electrolysis requires highly active oxygen evolution catalysts. Among the active metals, iridium oxide provides the best compromise in terms of activity and stability. The limited availability and usage in other applications demands an efficient utilization of this precious metal. Forming mixed oxides with titania promises improved Ir utilization, but often at the cost of a low catalyst surface area. Moreover, the role of Ir in establishing a sufficiently conductive mixed oxide has not been elucidated so far. We report a new approach for the synthesis of Ir/TiO mixed-oxide catalysts with defined template-controlled mesoporous structure, low crystallinity, and superior oxygen evolution reaction (OER) activity. The highly accessible pore system provides excellent Ir dispersion and avoids transport limitations. A controlled variation of the oxides Ir content reveals the importance of the catalysts electrical conductivity: at least 0.1 S m are required to avoid limitations owing to slow electron transport. For sufficiently conductive oxides a clear linear correlation between Ir surface sites and OER currents can be established, where all accessible Ir sites equally contribute to the reaction. The optimized catalysts outperform Ir/TiO materials reported in literature by about a factor of at least four.

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“…On the other hand, titanium dioxide (TiO 2 ) is a stable, commercially available, and inexpensive material , and is frequently used as a catalyst support for Ir , . However, a relatively high amount of Ir or IrO 2 (> 40 wt %) is required to generate sufficient electric conductivity by forming a contiguous network/film of Ir or IrO 2 nanoparticles , , since TiO 2 itself is not conductive. A conductive and stable support material would eliminate the need for a percolating network of Ir or IrO 2 to provide sufficient conductivity across the catalyst layer and, hence, enable lower Ir loadings.…”

Section: Concepts For Ir‐based Oer Catalyst Developmentmentioning

confidence: 99%

Current Challenges in Catalyst Development for PEM Water Electrolyzers

Bernt

Hartig‐Weiß

Tovini

et al. 2019

Chemie Ingenieur Technik

192

185

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This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.This work addresses current challenges in catalyst development for proton exchange membrane water electrolyzers (PEM-WEs). To reduce the amount of iridium at the oxygen anode to levels commensurate with large-scale application of PEM-WEs, high-structured catalysts with a low packing density are required. To allow an efficient development of such catalysts, activity and durability screening tests are essential. Rotating disk electrode measurements are suitable to determine catalyst activity, while accelerated stress tests on the MEA level are required to evaluate catalyst stability.

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A simple one-pot Adams method route to conductive high surface area IrO₂–TiO₂ materials

Abstract: The Adams method is used to prepare IrO2–TiO2 materials, composed of nanoparticles, whose electrical conductivity follows percolation theory.

Cited by 50 publications

References 38 publications

Hierarchically Structured Porous Transport Layers for Polymer Electrolyte Water Electrolysis

Hierarchically Structured Porous Transport Layers for Polymer Electrolyte Water Electrolysis

Oxygen Evolution Catalysts Based on Ir–Ti Mixed Oxides with Templated Mesopore Structure: Impact of Ir on Activity and Conductivity

Current Challenges in Catalyst Development for PEM Water Electrolyzers

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A simple one-pot Adams method route to conductive high surface area IrO2–TiO2 materials

Abstract: The Adams method is used to prepare IrO2–TiO2 materials, composed of nanoparticles, whose electrical conductivity follows percolation theory.

Cited by 50 publications

References 38 publications

Hierarchically Structured Porous Transport Layers for Polymer Electrolyte Water Electrolysis

Hierarchically Structured Porous Transport Layers for Polymer Electrolyte Water Electrolysis

Oxygen Evolution Catalysts Based on Ir–Ti Mixed Oxides with Templated Mesopore Structure: Impact of Ir on Activity and Conductivity

Current Challenges in Catalyst Development for PEM Water Electrolyzers

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A simple one-pot Adams method route to conductive high surface area IrO₂–TiO₂ materials