The gas diffusion electrode setup as a testing platform for evaluating fuel cell catalysts: A comparative RDE‐GDE study

Gas diffusion electrode (GDE) setups have been recently introduced as a new experimental approach to test the performance of fuel cell catalysts under high mass transport conditions, while maintaining the simplicity of rotating disk electrode (RDE) setups. In contrast to experimental RDE protocols, for investigations using GDE setups only few systematic studies have been performed. In literature, different GDE arrangements were demonstrated, for example, with and without an incorporated proton exchange membrane. Herein, we chose a membrane-GDE approach for a comparative RDE–GDE study, where we investigate several commercial standard Pt/C fuel cell catalysts with respect to the oxygen reduction reaction (ORR). Our results demonstrate both the challenges and the strengths of the new fuel cell catalyst testing platform. We highlight the analysis and the optimization of catalyst film parameters. That is, instead of focusing on the intrinsic catalyst ORR activities that are typically derived in RDE investigations, we focus on parameters, such as the catalyst ink recipe, which can be optimized for an individual catalyst in a much simpler manner as compared to the elaborative membrane electrode assembly (MEA) testing. In particular, it is demonstrated that ∼50% improvement in ORR performance can be reached for a particular Pt/C catalyst by changing the Nafion content in the catalyst layer. The study therefore stresses the feasibility of the GDE approach used as an intermediate “testing step” between RDE and MEA tests when developing new fuel cell catalysts

Influence of Temperature on the Performance of Carbon- and ATO-supported Oxygen Evolution Reaction Catalysts in a Gas Diffusion Electrode Setup.

State-of-the-art industrial electrocatalysts for the oxygen evolution reaction (OER) under acidic conditions are Ir-based. Considering the scarce supply of Ir, it is imperative to use the precious metal as efficiently as possible. In this work, we immobilized ultrasmall Ir and Ir0.4Ru0.6 nanoparticles on two different supports to maximize their dispersion. One high-surface-area carbon support serves as a reference but has limited technological relevance due to its lack of stability. The other support, antimony-doped tin oxide (ATO), has been proposed in the literature as a possible better support for OER catalysts. Temperature-dependent measurements performed in a recently developed gas diffusion electrode (GDE) setup reveal that surprisingly the catalysts immobilized on commercial ATO performed worse than their carbon-immobilized counterparts. The measurements suggest that the ATO support deteriorates particularly fast at elevated temperatures

The Gas diffusion electrode setup as a testing platform for evaluating fuel cell catalysts: a comparative RDE-GDE study

Gas diffusion electrode (GDE) setups have been recently introduced as a new experimental approach to test the performance of fuel cell catalysts. As compared to the state-of-the-art in fundamental research, i.e., rotating disk electrode (RDE) measurements, GDE measurements offer several advantages. Most importantly mass transport limitations, inherent to RDE measurements are avoided. In a GDE setup the reactant, e.g., oxygen gas, is not dissolved into a liquid electrolyte but distributed through a gas diffusion layer (GDL), as it is actually the case in fuel cells. Consequently, much higher current densities can be achieved, and the catalysts can be studied in a wider and more relevant potential range. Furthermore, direct contact to a liquid electrolyte can be avoided and elevated temperatures can be employed in a straight-forward manner. However, the use of GDE setups also comes with some challenges. The determined performance is not strictly related to the catalyst itself (intrinsic activity), but also to the quality of the catalyst film preparation. Therefore, it might be even more important than in RDE testing to develop standardized procedures to prepare catalysts inks and films that can be reproduced effortlessly in research laboratories for fundamental and applied experimentation. To develop such standardized testing protocols, we present a comparative RDE – GDE study, where we investigate several commercial standard Pt/C fuel cell catalysts with respect to the oxygen reduction reaction (ORR). The study highlights the strengths of the GDE approach as an intermediate “testing step” between RDE and membrane electrode assembly (MEA) tests when developing new fuel catalysts

Influence of temperature on the performance of carbon- and ATO-supported OER catalysts in a GDE setup

State-of-the-art industrial electrocatalysts for the oxygen evolution reaction (OER) under acidic conditions are Ir-based. Considering the scarce supply of Ir, it is imperative to use the precious metal as efficiently as possible. In this work, we immobilized ultrasmall Ir and Ir0.4Ru0.6 nanoparticles on two different supports to maximize their dispersion. One high surface area carbon support serves as reference but has limited technological relevance due to its lack of stability. The other support, antimony-doped tin oxide (ATO), has been proposed in the literature as a possible better support for OER catalysts. Temperature-dependent measurements performed in a newly developed gas diffusion electrode (GDE) setup reveal that surprisingly the catalysts immobilized on commercial ATO performed worse than their carbon-immobilized counterparts. The measurements suggest that the ATO support deteriorates particularly fast at elevated temperatures

Influence of crystalline titanium oxide layer smoothness on the performance of inverted organic bilayer solar cells

Due to the small exciton diffusion length in organic materials, the donor-acceptor heterointerface in simple bilayer solar cells must be placed in close proximity to the bottom electrode. This makes great demands on the planarity of the base layer, since a non-uniform topography can cause adverse shorting through overlying layers. We fabricated indium tin oxide (ITO)/titanium oxide (TiOx)/fullerene (C-60)/cyanine dye/molybdenum oxide (MoO3)/silver (Ag) solar cells with TiOx layers deposited via sputtering, coated from a nanoparticle suspension or prepared via a sol-gel process. A power conversion efficiency of 3.7% was measured when using a smooth sol-gel derived TiOx film. (C) 2013 AIP Publishing LLC

Smart tools and orthogonal click-like reactions onto small unilamellar vesicles

International audienc

Smart tools and orthogonal click-like reactions onto small unilamellar vesicles: Additional molecular data

We present here the synthetic routes and the experimental data (NMR and MS spectra) for model reactions for copper-free Huisgen 1,4-cycloaddition, Staudinger ligation and for addition of a dithiol on a dibromomaleimide ring. Starting materials were synthesized from the commercially available 4-chlorophenethylamine, previously described 2-(cyclooct-2-yn-1-yloxy)acetic acid, 1-fluorocyclooct-2-ynecarboxylic acid, commercial 2-(diphenylphosphino)terephthalic acid 1-methyl 4-pentafluorophenyl diester and dibromomaleimide. In all cases, the expected compounds were obtained with good yield (50% to quantitative). A novel synthesis of the lipid anchor DOGP3NH2 is also described. These data were used as basis for the study reported in the article “Smart Tools and Orthogonal Click-like Reactions onto Small Unilamellar Vesicles” in Chemistry and Physics of Lipids [1]

Elucidating the Steady-State OER Activity of (Ni1-xFex)OOH Binary Nanoparticles in As-prepared and Purified KOH Electrolyte Solutions

Replacing critical raw materials employed in water electrolysis applications as electrocatalysts with earth-abundant materials is paramount for the future upscaling to industrial dimensions. In that regard, Ni and Ni-based multimetallic hydroxides, above all NiFe-hydroxides, have shown promising performance towards the oxygen evolution reaction (OER) in alkaline conditions. However, it has been shown that the extraordinary performance of these materials is owed largely to Fe impurities found in commercial KOH from which electrolyte solutions are prepared. The mechanism of action of these impurities is still not fully understood, and therefore, at the heart of ongoing discussions. In this study, we investigate the OER activity of different nanostrcutured (Ni1-xFex)OOH samples and find their activities to be influenced differently by the presence of Fe impurities in the electrolyte. From the gathered data, we conclude that the presence of Fe impurities impacts gravely the structure sensitivity of the OER. In purified electrolyte solutions the OER appears to be a structure-sensitive reaction while this seems not to be the case in the presence of said impurities

The Gas Diffusion Electrode Setup as Straightforward Testing Device for Proton Exchange Membrane Water Electrolyzer Catalysts

[Image: see text] Hydrogen production from renewable resources and its reconversion into electricity are two important pillars toward a more sustainable energy use. The efficiency and viability of these technologies heavily rely on active and stable electrocatalysts. Basic research to develop superior electrocatalysts is commonly performed in conventional electrochemical setups such as a rotating disk electrode (RDE) configuration or H-type electrochemical cells. These experiments are easy to set up; however, there is a large gap to real electrochemical conversion devices such as fuel cells or electrolyzers. To close this gap, gas diffusion electrode (GDE) setups were recently presented as a straightforward technique for testing fuel cell catalysts under more realistic conditions. Here, we demonstrate for the first time a GDE setup for measuring the oxygen evolution reaction (OER) of catalysts for proton exchange membrane water electrolyzers (PEMWEs). Using a commercially available benchmark IrO(2) catalyst deposited on a carbon gas diffusion layer (GDL), it is shown that key parameters such as the OER mass activity, the activation energy, and even reasonable estimates of the exchange current density can be extracted in a realistic range of catalyst loadings for PEMWEs. It is furthermore shown that the carbon-based GDL is not only suitable for activity determination but also short-term stability testing. Alternatively, the GDL can be replaced by Ti-based porous transport layers (PTLs) typically used in commercial PEMWEs. Here a simple preparation is shown involving the hot-pressing of a Nafion membrane onto a drop-cast glycerol-based ink on a Ti-PTL