The Importance of Temperature and Potential Window in Stability Evaluation of Supported Pt-Based Oxygen Reduction Reaction Electrocatalysts in Thin Film Rotating Disc Electrode Setup

Abstract

The present study showcases the importance of temperature and potential window for evaluation of Pt-based supported electrocatalyst stability. A platinum based commercial material with an average size of Pt nanoparticles between 2-3 nm (Pt/C) and its thermally annealed analogue with an average particle size of ∼5 nm (Pt/C-HT) are considered. X-ray diffraction (XRD), ex situ transmission electron microscopy (TEM) imaging and thin film rotating disc electrode (TF-RDE) along with proprietary hightemperature disc electrode (HT-DE) are used for electrocatalysts inspection. The study shows a clear dependence between the electrochemical surface area (ECSA) loss and the temperature increase during the potentiodynamic accelerated degradation test (ADT). Additionally it is demonstrated that selection of the lower and upper potential limits in ADT protocol plays an important role in ECSA loss. Comparing various results obtained on Pt/C and Pt/C-HT, we show that varying ADT conditions of temperature and different potential windows is crucial for adequate evaluation and stability interpretation of potentially promising novel electrocatalysts and that relatively mild ADT conditions (i.e. 0.4-1.0 V RHE , RT) can be potentially misleading.

Resolving the nanoparticles' structure-property relationships at the atomic level: a study of Pt-based electrocatalysts

“…Although all electrocatalysts have a high enough ECSA (above 40 m 2 g −1 Pt ( Kongkanand and Mathias, 2016 )) to perform well in an MEA, better initial dispersion of Pt over carbon allows for retaining a higher ECSA after thermal annealing ( Gatalo et al., 2019c ). The thermal annealing is immensely important in terms of electrocatalyst stability because of better resistance to Pt dissolution due to larger average particle size, crystallinity, and improved stability of the carbon support ( Jovanovič et al., 2014 ; Maselj et al., 2020 ; Matsutani et al., 2010 ). For practical use at the MEA level, the authors recommend the PEMFC scientific community to use TEC10E50E-HT or Elyst Pt50 0550 as a benchmark cathode and/or anode Pt/C electrocatalyst (or similar Pt-Co analogues available at TKK/Umicore).…”

“…( Kongkanand and Mathias, 2016 ; Padgett et al., 2019 ; Stephens et al., 2012 ). Despite these carbon supports being relatively stable under relevant electrochemical conditions, carbon corrosion is still one of the inherent largest contributors to the loss of ECSA as a result of secondary degradation mechanisms of Pt-based nanoparticles, resulting in the agglomeration and/or detachment ( Gu et al., 2007 ; Maselj et al., 2020 ; Meier et al., 2014 ). Slowing down support corrosion is a major challenge; on one hand, electrochemical carbon oxidation is thermodynamically feasible already at a very low standard electrode potential E CO2/C 0 = 0.207 V RHE and on the other, the kinetics of oxidation is accelerated by Pt, especially at the operational conditions of the PEMFC (e.g.…”

“…Slowing down support corrosion is a major challenge; on one hand, electrochemical carbon oxidation is thermodynamically feasible already at a very low standard electrode potential E CO2/C 0 = 0.207 V RHE and on the other, the kinetics of oxidation is accelerated by Pt, especially at the operational conditions of the PEMFC (e.g. 80 C) (Maselj et al, 2020;Pizzutilo et al, 2016). Based on the comparisons from the present study, looking merely on the long-term ORR activity and the resilience toward the leaching of M, Pt-Cu seems as the best choice.…”

Platinum Dissolution in Realistic Fuel Cell Catalyst Layers

“…However, to further approach realistic fuel cell conditions,t he elevated temperature in fuel cell applications needs to be considered as this leads to significant increase of catalyst degradation. [32] In general, it has to be stated that GDE half-cell experiments offer unique opportunities to study catalyst layers and their degradation by combining them with different analytical methods such as identical location transmission electron microscopy (IL-TEM), [33] operando X-ray and neutron imaging, [34] small-angle X-ray scattering (SAXS), [35] mass spectrometry for gaseous and volatile products, [36] and with the present work also ICP-MS.…”

Understanding the Crucial Significance of the Temperature and Potential Window on the Stability of Carbon Supported Pt-alloy Nanoparticles as Oxygen Reduction Reaction Electrocatalysts

“…4 Because the degradation of Pt-alloy electrocatalysts is caused by various extremely complicated phenomena, 19 significant efforts have to be invested into clarifying and understanding individual mechanisms. There are two basic groups of degradation mechanisms: i) electrochemically-induced (transient) dissolution of Pt, which is closely related with the dynamics of formation/reduction of the Pt-oxide 20 , resulting in Ostwald ripening 21 and/or formation of metallic Pt bands in the membrane 22 ; ii) electrochemical and chemical carbon support corrosion 23 , leading to the agglomeration 24 and/or detachment 19 of Pt NPs. In the case of Pt-alloy NPs, one also has to deal with the dissolution of the less noble metal dissolution.…”