Testing fuel cell catalysts under more realistic reaction conditions: accelerated stress tests in a gas diffusion electrode setup

Abstract

Gas diffusion electrode (GDE) setups have very recently received increasing attention as a fast and straightforward tool for testing the oxygen reduction reaction (ORR) activity of surface area proton exchange membrane fuel cell (PEMFC) catalysts under more realistic reaction conditions. In the work presented here, we demonstrate that our recently introduced GDE setup is suitable for benchmarking the stability of PEMFC catalysts as well. Based on the obtained results, it is argued that the GDE setup offers inherent advantages for accelerated degradation tests (ADT) over classical three-electrode setups using liquid electrolytes. Instead of the solid-liquid electrolyte interface in classical electrochemical cells, in the GDE setup a realistic three-phase boundary of (humidified) reactant gas, proton exchange polymer (e.g. Nafion) and the electrocatalyst is formed. Therefore, the GDE setup not only allows accurate potential control but also independent control over the reactant atmosphere, humidity and temperature. In addition, the identical location transmission electron microscopy (IL-TEM) technique can easily be adopted into the setup, enabling a combination of benchmarking with mechanistic studies.

A New Approach to Probe the Degradation of Fuel Catalysts Under Realistic Conditions: Combining Tests in a Gas Diffusion Electrode Setup with Small Angle X-Ray Scattering

“…In a recent work we showed that ASTs can be performed in our GDE setup but the used catalyst loading was comparable to loadings for RDE measurements and hence far from realistic fuel cell loadings. 15 In the present work, the catalyst film on the GDL (i.e. the GDE) is prepared by vacuum filtration as described by Yarlagadda et al 21 4 In the SI it is demonstrated that with the established procedure, reproducible particle size distributions of the different Pt/C catalysts could be determined before ( Figure S5) as well as after the ASTs (Figure S6).…”

“…In contrast, the GDE setup provides more realistic conditions than the RDE method but is at the same time a more simple and faster methodology than flow cell or MEA measurements. 14,15 Several repeats of the measurements can be performed and their reproducibility be discussed.…”

“…Applying conditions close to MEA testing (regarding the setup, 15 loading, 8 and temperature 4 ) the degradation mechanism can be analyzed based on the change in the size distribution and the ECSA obtained by CO stripping. It is found that after applying the ASTs, catalysts with small NPs exhibit significant degradation and particle growth.…”

“…An in-house gas diffusion electrode setup as described before 14,15 was used in the In an initial cleaning the Teflon upperpart was soaked in acid (H2SO4:HNO3 = 1:1, v:v) overnight. After rinsing it with ultrapure water, it was boiled twice in ultrapure water.…”

Carbon-supported Platinum Electrocatalysts probed in a Gas Diffusion Setup with Alkaline Environment: how Particle Size and Mesoscopic Environment influence the Degradation Mechanism

“…In the present work, we investigate the degradation of Pt/C catalysts in alkaline conditions under more realistic reaction conditions as compared to conventional electrochemical cells where the catalyst is exposed to an aqueous electrolyte. Instead, a gas diffusion electrode (GDE) setup [13][14][15] is employed, which has been used recently to study the stability of carbon-supported platinum catalysts in acidic media 16 . To obtain alkaline conditions, for the present study the Nafion membrane from a PEMFC has been replaced with an anion exchange membrane (AEM) and an alkaline ionomer was mixed into the catalyst layer.…”