Reliable assessment of electrocatalytic performance of novel materials to determine the oxygen reduction (ORR) activity plays a pivotal role in systematic-driven design of tailored composites. Unfortunately rotating disc electrode technique, typically employed for this purpose, is incapable to accurately predict the behaviour of promising candidates in membrane electrode assemblies (MEAs) which are finally used in fuel cells. Instead, miniature electrochemical setups based on floating electrode, which mimics MEA's three-phase boundary active sites, has recently been recognized as an adequate diagnostics substitute. Compared to conventional RDE the working electrode operating under floating regime makes the acquisition of catalysts' behaviour at low potentials easily achieved without being limited by the solubility and/or mass transport of O-2 in aqueous electrolyte. Accordingly, the present study employs a modified version of the floating electrode methodology (MFE) to accurately investigate the effect of electrocatalyst nanostructure on high-current density ORR performance. Two morphologically distinct platinum-based de-alloyed nanoparticle samples-porous and non-porous core-shell analogues-are compared. The analysis reveals that at the high current density region (< 0.8 V vs RHE) porous nanoparticles demonstrate significantly worse ORR specific activities in comparison to core-shell analogues. On the other hand, the performance is reversed at low current densities (> 0.8 V vs RHE) supporting the results from the RDE analysis. The observed trend is attributed to a reduction in the utilization of active surface area in nanoporous catalysts with increasing overpotential.

In the present work, we report on a synergistic relationship between platinum nanoparticles and a titanium oxynitride support (TiOxNy/C) in the context of oxygen reduction reaction (ORR) catalysis. As demonstrated herein, this composite configuration results in significantly improved electrocatalytic activity toward the ORR relative to platinum dispersed on carbon support (Pt/C) at high overpotentials. Specifically, the ORR performance was assessed under an elevated mass transport regime using the modified floating electrode configuration, which enabled us to pursue the reaction closer to PEMFC-relevant current densities. A comprehensive investigation attributes the ORR performance increase to a strong interaction between platinum and the TiOxNy/C support. In particular, according to the generated strain maps obtained via scanning transmission electron microscopy (STEM), the Pt-TiOxNy/C analogue exhibits a more localized strain in Pt nanoparticles in comparison to that in the Pt/C sample. The altered Pt structure could explain the measured ORR activity trend via the d-band theory, which lowers the platinum surface coverage with ORR intermediates. In terms of the Pt particle size effect, our observation presents an anomaly as the Pt-TiOxNy/C analogue, despite having almost two times smaller nanoparticles (2.9 nm) compared to the Pt/C benchmark (4.8 nm), manifests higher specific activity. This provides a promising strategy to further lower the Pt loading and increase the ECSA without sacrificing the catalytic activity under fuel cell-relevant potentials. Apart from the ORR, the platinum-TiOxNy/C interaction is of a sufficient magnitude not to follow the typical particle size effect also in the context of other reactions such as CO stripping, hydrogen oxidation reaction, and water discharge. The trend for the latter is ascribed to the lower oxophilicity of Pt-based on electrochemical surface coverage analysis. Namely, a lower surface coverage with oxygenated species is found for the Pt-TiOxNy/C analogue. Further insights were provided by performing a detailed STEM characterization via the identical location mode (IL-STEM) in particular, via 4DSTEM acquisition. This disclosed that Pt particles are partially encapsulated within a thin layer of TiOxNy origin.

One of the modern era's main concerns is securing the ever-increasing energy demand, which is currently achieved by increased exploitation of fossil fuels. Consequently, this triggers a number of issues, including environmental deterioration, climate changes, and occasional geopolitical and economic crises. This brings us to another critical task in front of our society: accelerating the transition toward green and renewable energy. In that regard, the hydrogen economy was proposed half a century ago as a concept of using hydrogen as the main energy carrier instead of fossils. Wide implementation of hydrogen energy would result in major decarbonization of the global energy supply systems, providing many benefits for our society and environment. Electrochemical energy conversion devices, such as low-temperature fuel cells, are of crucial importance for implementing this concept, as they can convert the chemical energy of hydrogen into electricity with zero emission. Therefore, the studies of electrocatalytic processes involved in fuel cells are at the forefront of the research that drives the transition to clean hydrogen energy. Although significant progress has been made in the last few decades, it is still challenging to evaluate, understand, or predict the performance of high surface area catalysts (HSACs) for proton exchange membrane fuel cells (PEMFCs). Studies of the electrode reaction mechanism and kinetics, especially related to oxygen reduction reaction (ORR) as the rate-limiting reaction in PEMFCs, demand the application of viable, laboratory-scale friendly methodologies to assess the performance of the candidate materials for application in these devices. Extensive research in the past few decades has led to the establishment of different experimental protocols and various techniques to study the performance of electrocatalysts. Here we refer primarily to the usage of the rotating disk electrode (RDE) methodology adapted to study the performance of HSACs in the form of thin films (TF-RDE). TF-RDE is by far the most widely used technique for the early-stage screening of the ORR activity and stability of novel catalysts because of its expedience, relatively simple operation, inexpensive equipment, and ability to make many tests with only a few micrograms of the catalysts. However, the trends obtained in TF-RDE can significantly differ from those in a membrane electrode assembly (MEA), due to the difference in the conditions in these two setups. To bridge this gap between TF-RDE predictions and real-life catalysts' performance, a few novel techniques have recently emerged, including high-temperature disc electrode (HT-DE), floating electrode technique (FET), and gas diffusion electrode (GDE). The idea behind the HT-DE setup is to perform durability tests at more realistic conditions in terms of elevated temperature (PEMFC usually operates at 60°C–80°C), which is very important since both Pt dissolution and corrosion of carbon support (i.e., the two main degradation mechanisms of PEMFCs catalysts) are temperature dependent. The main feature of the FET is a fast mass transport to the catalyst layer with extremely low loadings because the electrode is floating on the liquid phase; hence, gas reactants are delivered (or taken away) almost directly from the gas phase (or at least through a very thin liquid layer). This results in extremely high (specific) ORR current densities (normalized by Pt surface area). In the case of GDE, oxygen is provided on one side of GDE while the other side is in contact with a PEM ionomer (usually Nafion), which mimics MEA-like conditions with comparable oxygen mass transport. Besides activity, the other basic criterion that every viable catalyst must provide is long-term durability. The aforementioned techniques are mainly used to access the activity of PEMFC catalysts, while typically less information on the stability was extracted, with the exception of HT-DE. To address the stability of electrocatalysts in more detail, several advanced hybrid techniques were developed by connecting electrochemical and nonelectrochemical methods. One of the most important methods for understanding the dissolution of the catalysts was obtained by coupling the electrochemical flow cell (EFC) with inductively coupled plasma mass spectrometry (ICP-MS). Such setup provides a direct insight (in-situ) into the dissolution mechanism (i.e., time and potential resolved dissolution) and enables extremely precise quantification of the amount of dissolved metal. Therefore, EFC-ICP-MS became an irreplaceable tool that provides a significant amount of information on the dissolution behavior of the catalysts. Apart from identifying the dissolution of metallic sites, carbon support corrosion via carbon oxidation reaction (COR) is another primary degradation mechanism of PEMFC catalyst layers. COR may induce secondary degradation mechanisms, like platinum particle detachment or agglomeration, and additionally cause increased mass transport resistance of reactant gases and water transport issues. In this respect, sophisticated techniques that allow the in situ mass-resolved monitoring of gaseous electrochemical intermediates and products of COR in an electrochemical half-cell have proven indispensable diagnostic tools. To address the COR, two variations of mass spectrometry-based techniques are employed, namely differential electrochemical and online electrochemical mass spectrometry, DEMS and OLEMS, respectively. Most recent progress in mass spectrometry and electrochemistry coupling is manifested by the so-called electrochemistry-mass spectrometry (EC-MS) apparatus developed by Chorkendorff's group and also sold commercially by SpectroInlets. Regardless of specific configuration, these techniques are able to detect volatile products from electrochemical transformations, which makes it possible to study COR. Another powerful methodology for studies of the degradation of PEMFCs catalyst was obtained by coupling electrochemistry with identical location electron microscopy (IL-EM). Scanning electron microscopy (SEM) was successfully connected with TF-RDE studies by performing imaging of the catalyst films directly on an RDE, where typically information about the structure of the catalyst can be discerned down to the range of approximately 10 nm. In the case of transmission electron microscopy (TEM), a catalyst is coated onto a TEM finder grid, characterized by TEM and subjected to a certain electrochemical stability test. Afterwards, TEM imaging is performed on the identical locations of the catalyst after the electrochemical test, which provides unambiguous information on the degradation events caused by the test down to the atomic level. This chapter will aim to provide insight into the several methodologies used to study the performance of the catalysts for PEMFCs, their advantages, shortcomings, and experimental practices. This will range from RDE, TF-RDE, and HT-DE as rotating disk-based methods, through FET and GDE, to the hyphenated techniques such as EFC-ICP-MS, EC-MS, and IL-EM.

Aiming at speeding up the discovery and understanding of promising electrocatalysts, a novel experimental platform, i.e., the Nano Lab, is introduced. It is based on state-of-the-art physicochemical characterization and atomic-scale tracking of individual synthesis steps as well as subsequent electrochemical treatments targeting nanostructured composites. This is provided by having the entire experimental setup on a transmission electron microscopy (TEM) grid. Herein, the oxygen evolution reaction nanocomposite electrocatalyst, i.e., iridium nanoparticles dispersed on a high-surface-area TiOxNy support prepared on the Ti TEM grid, is investigated. By combining electrochemical concepts such as anodic oxidation of TEM grids, floating electrode-based electrochemical characterization, and identical location TEM analysis, relevant information from the entire composite's cycle, i.e., from the initial synthesis step to electrochemical operation, can be studied. We reveal that Ir nanoparticles as well as the TiOxNy support undergo dynamic changes during all steps. The most interesting findings made possible by the Nano Lab concept are the formation of Ir single atoms and only a small decrease in the N/O ratio of the TiOxNy-Ir catalyst during the electrochemical treatment. In this way, we show that the precise influence of the nanoscale structure, composition, morphology, and electrocatalyst's locally resolved surface sites can be deciphered on the atomic level. Furthermore, the Nano Lab's experimental setup is compatible with ex situ characterization and other analytical methods, such as Raman spectroscopy, X-ray photoelectron spectroscopy, and identical location scanning electron microscopy, hence providing a comprehensive understanding of structural changes and their effects. Overall, an experimental toolbox for the systematic development of supported electrocatalysts is now at hand.

Electrochemical crosslinking of alginate strands by in situ iron oxidation was explored using a potentiostatic regime. Carbon-based materials co-doped with iron, nitrogen, and/or sulfur were prepared via electrolyte composition variation with a nitrogen-rich compound (rivanol) or through post-treatments with sodium sulfide. Nanometer-sized iron particles were confirmed by transmission and field emission scanning electron microscopy in all samples as a consequence of the homogeneous dispersion of iron in the alginate scaffold and its concomitant growth-limiting effect of alginate chains. Raman spectra confirmed a rise in structural disorder with rivanol/Na2S treatment, which points to more defect sites and edges known to be active sites for oxygen reduction. Fourier transform infrared (FTIR) spectra confirmed the presence of different iron, nitrogen, and sulfur species, with a marked difference between Na2S treated/untreated samples. The most positive onset potential (-0.26 V vs. saturated calomel electrode, SCE) was evidenced for the sample co-doped with N, S, and Fe, surpassing the activity of those with single and/or double doping. The mechanism of oxygen reduction in 0.1 M KOH was dominated by the 2e(-) reduction pathway at low overpotentials and shifted towards complete 4e(-) reduction at the most negative explored values. The presented results put forward electrochemically formed alginate gels functionalized by homogeneously dispersed multivalent cations as an excellent starting point in nanomaterial design and engineering.

Water splitting in acidic media is a sustainable and efficient new way to produce hydrogen fuel. However, the main bottleneck preventing the wider use of electrolyzers is still the oxygen evolution reaction (OER). Currently, the best electrocatalysts for OER are Ir-based materials, but the mechanistic details are still not fully understood. In this work, we investigate the similarities and differences in the OER mechanism of three different Ir-based catalysts, namely Vulcan carbon-supported and unsupported metallic Ir and rutile IrO2 nanoparticles, and the process of Ir activation. For this purpose, we use large amplitude AC Voltammetry to distinguish between capacitive and faradaic processes. To quantify the data, we also use a mechanistic fit of the resolved harmonics. We show that all catalysts share the same OER mechanism but require different amounts of activation cycles. We have found three intrinsic properties, which can adequately describe a material for electrocatalysis. First is the activation threshold number (ATN), second is the current normalized to the number of active sites (intrinsic current), and lastly the mass normalized active site density. It was found that Ir on Vulcan has an intrinsic activity at least 3 times higher than the other two materials under consideration, as well as having the highest active site density. From the model fits we can also gain further insight into the mechanistic details for each material. For metallic Ir samples, the rate-limiting step is shown to be water adsorption, whereas for IrO2 the bottleneck is the inherently slower kinetics. This also indicates that IrO2 does not produce the same IrOH as Ir metal and therefore has different intrinsic properties. This study provides new insights into the intrinsic properties of different Ir nanocatalysts and highlights a general approach to studying the reaction mechanisms and intrinsic properties of electrocatalysts.

Degradation of carbon-supported Pt nanocatalysts in fuel cells and electrolyzers hinders widespread commercialization of these green technologies. Transition between oxidized and reduced states of Pt during fast potential spikes triggers significant Pt dissolution. Therefore, designing Pt-based catalysts able to withstand such conditions is of critical importance. We report here on a strategy to suppress Pt dissolution by using an organic matrix tris(aza)pentacene (TAP) as an alternative support material for Pt. The major benefit of TAP is its potential-dependent conductivity in aqueous media, which was directly evidenced by electrochemical impedance spectroscopy. At potentials below ∼0.45 VRHE, TAP is protonated and its conductivity is improved, which enables supported Pt to run hydrogen reactions. At potentials corresponding to Pt oxidation/reduction (>∼0.45 VRHE), TAP is deprotonated and its conductivity is restricted. Tunable conductivity of TAP enhanced the durability of the Pt/TAP with respect to Pt/C when these two materials were subjected to the same degradation protocol (0.1 M HClO4 electrolyte, 3000 voltammetric scans, 1 V/s, 0.05-1.4 VRHE). The exceptional stability of Pt/TAP composite on a nanoscale level was confirmed by identical location TEM imaging before and after the used degradation protocol. Suppression of transient Pt dissolution from Pt/TAP with respect to the Pt/C benchmark was directly measured in a setup consisting of an electrochemical flow cell connected to inductively coupled plasma-mass spectrometry.

Decreasing iridium loading in the electrocatalyst presents a crucial challenge in the implementation of proton exchange membrane (PEM) electrolyzers. In this respect, fine dispersion of Ir on electrically conductive ceramic supports is a promising strategy. However, the supporting material needs to meet the demanding requirements such as structural stability and electrical conductivity under harsh oxygen evolution reaction (OER) conditions. Herein, nanotubular titanium oxynitride (TiON) is studied as a support for iridium nanoparticles. Atomically resolved structural and compositional transformations of TiON during OER were followed using a task-specific advanced characterization platform. This combined the electrochemical treatment under floating electrode configuration and identical location transmission electron microscopy (IL-TEM) analysis of an in-house-prepared Ir-TiON TEM grid. Exhaustive characterization, supported by density functional theory (DFT) calculations, demonstrates and confirms that both the Ir nanoparticles and single atoms induce a stabilizing effect on the ceramic support via marked suppression of the oxidation tendency of TiON under OER conditions.

Observing and quantifying information at the atomic scale plays an essential role in assessing the structure–property relationships in electrocatalysis. Particularly, when studying supported nanoparticulate fuel cell and electrolyzer electrocatalysts, resolving nanoparticles' structural features at the atomic scale and their evolution as a response to external stimuli is of great relevance. Atomically resolved electron micrographs of identical locations before and after induced changes are a still vastly unexplored resource of quantifiable data that can be used to elucidate structure–activity and–stability relationships of studied materials. In this short review, we highlight the recent approaches and opportunities in processing electron microscopy images and the development of their analysis algorithms enabling the acquirement of unprecedented structural information, focusing on systems of metallic nanoparticles.

ADVERTISEMENT RETURN TO ISSUEPREVEnergy FocusNEXTBenchmarking Fuel Cell Electrocatalysts Using Gas Diffusion Electrodes: Inter-lab Comparison and Best PracticesKonrad Ehelebe*Konrad EhelebeHelmholtz-Institute Erlangen-Nürnberg for Renewable Energy (IEK-11), Forschungszentrum Jülich GmbH, Cauerstrasse 1, 91058 Erlangen, GermanyDepartment of Chemical and Biological Engineering, Friedrich-Alexander University Erlangen-Nürnberg, Cauerstrasse 1, 91058 Erlangen, Germany*[email protected]More by Konrad Ehelebehttps://orcid.org/0000-0001-9441-5642, Nicolai SchmittNicolai SchmittDepartment of Chemistry, Technical University of Darmstadt, Ernst-Berl-Institut für Technische und Makromolekulare Chemie, Alarich-Weiss-Strasse 8, 64287 Darmstadt, GermanyMore by Nicolai Schmitthttps://orcid.org/0000-0001-8668-288X, Gustav SieversGustav SieversLeibniz Institute for Plasma Science and Technology, Felix-Hausdorff-Strasse 2, 17489 Greifswald, GermanyMore by Gustav Sievers, Anders W. JensenAnders W. 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Aiming at speeding up the discovery and understanding of promising electrocatalysts, a versatile experimental platform, i.e., the Nano Lab concept is introduced. It is based on state-of-the-art physicochemical characterization and atomic scale tracking of individual synthesis steps as well as subsequent electrochemical treatments. This is provided by having the entire experimental setup on a transmission electron microscopy (TEM) grid. Herein, oxygen evolution reaction (OER) nanocomposite electrocatalyst, i.e iridium nanoparticles dispersed on a high surface area TiO x N y support prepared on Ti TEM grid, is investigated. By combining advanced electrochemical concepts such as anodic oxidation of TEM grids, floating electrode-based electrochemical characterization, and identical location TEM analysis, relevant information from the entire composite’s cycle, i.e., from initial synthesis step to electrochemical operation can be studied. For instance, we reveal that Ir nanoparticles as well as TiO x N y support undergo dynamic changes during all steps. The most interesting findings made possible by the Nano Lab concept are the formation of Ir single atoms and only a small decrease in N/O ratio of the TiO x N y -Ir catalyst during the electrochemical treatment. In this way, we show that the precise influence of structure, composition, morphology and electrocatalyst’s locally resolved surface sites are deciphered on the atomic level. Furtheremore, the Nano Lab ’s experimental setup is compatible with ex-situ characterization and other analytical methods besides the ones in the TEM, such as Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and identical location scanning electron microscopy (IL-SEM), hence providing a comprehensive understanding of structural changes and their effects. Overall, an experimental toolbox for the systematic development of supported electrocatalysts is now at hand.

The production of hydrogen via a proton-exchange membrane water electrolyzer (PEM-WE) is directly dependent on the rational design of electrocatalysts for the anodic oxygen evolution reaction (OER), which is the bottleneck of the process. Here, we present a smart design strategy for enhancing Ir utilization and stabilization. We showcase it on a catalyst, where Ir nanoparticles are efficiently anchored on a conductive support titanium oxynitride (TiON x ) dispersed over carbon-based Ketjen Black and covered by a thin layer of copper (Ir/CuTiON x /C), which gets removed in the preconditioning step. Electrochemical OER activity, stability, and structural changes were compared to the Ir-based catalyst, where Ir nanoparticles without Cu are deposited on the same support (Ir/TiON x /C). To study the effect of the sacrificial less-noble metal layer on the catalytic performance of the synthesized material, characterization methods, namely X-ray powder diffraction, X-ray photoemission spectroscopy, and identical location transmission electron microscopy were employed and complemented with scanning flow cell coupled to an inductively coupled plasma mass spectrometer, which allowed studying the online dissolution during the catalytic reaction. Utilization of these advanced methods revealed that the sacrificial Cu layer positively affects both Ir OER mass activity and its durability, which was assessed via S-number, a recently reported stability metric. Improved activity of Cu analogue was ascribed to the higher surface area of smaller Ir nanoparticles, which are better stabilized through a strong metal-support interaction (SMSI) effect.

Upon exposure to an electrochemical environment, structural properties of nanoparticulate electrocatalysts at the atomic scale are not stagnant but rather dynamic. These have a direct effect on catalysts' performance via structure-property relationships. The active surface structure is constantly changing via complex phenomena dependant on their nature and reaction conditions. State-of-the-art transmission electron microscopy (TEM) can already provide us with atomically precise structures of individual nanoparticles, which are a key to exploring structure-property relations. However, with the analysis of random nanoparticles with unknown structural history, it is impossible to realise the exact structural alternation mechanisms. In order to study these phenomena operando, in-situ or quasi-in-situ methods need to be developed and used. In the present study, we highlight a recently introduced methodological approach named modified floating electrode (MFE), which enables the assessment of (i) proton exchange membrane fuel cell (PEMFC) cathode oxygen reduction reaction (ORR) at the industry-relevant current densities and (ii) atomic-level structural changes of the same nanoparticle, via identical location scanning electron microscopy (SEM) and TEM approach (IL-SEM and IL-TEM), in one measurement. Careful analysis and comparison of atomically resolved high-resolution scanning TEM (HR-STEM) images of the same nanoparticle before and after MFE measurements were conducted via homemade microscopy image analysis algorithms. We reveal structural changes on the atomic-scale of the industrial benchmark Pt-Co nanoalloy ORR electrocatalyst upon exposure to electrochemical activation and high ORR current densities. Observing and comparing the detailed structure and morphology of the same nanoparticle reveals atomic-scale processes such as particle anisotropic etching and redeposition, besides other processes such as particle necking, anti-necking, pore formation, particle movement, coalescence, etc. The understanding of the dynamics behind these changes is crucial for the interpretation of ORR electrocatalyst's activity and stability. Our bottom-up approach enables direct investigation of nanoparticles’ structure-stability relationships.

Achieving highly active and stable oxygen reduction reaction performance at low platinum-group-metal loadings remains one of the grand challenges in the proton-exchange membrane fuel cells community. Currently, state-of-the-art electrocatalysts are high-surface-area-carbon-supported nanoalloys of platinum with different transition metals (Cu, Ni, Fe, and Co). Despite years of focused research, the established structure-property relationships are not able to explain and predict the electrochemical performance and behavior of the real nanoparticulate systems. In the first part of this work, we reveal the complexity of commercially available platinum-based electrocatalysts and their electrochemical behavior. In the second part, we introduce a bottom-up approach where atomically resolved properties, structural changes, and strain analysis are recorded as well as analyzed on an individual nanoparticle before and after electrochemical conditions (e.g. high current density). Our methodology offers a new level of understanding of structure-stability relationships of practically viable nanoparticulate systems.

Herein a modified floating electrode (MFE) approach for investigating the electrochemical phenomena at a gas/electrode/liquid reaction interface is introduced. Such investigation is in sharp contrast to conventional electrochemical techniques, which measure the properties of electrode/liquid interfaces. MFE is based on an apparatus that enables electrocatalytic conversion under enhanced mass transport of reactant gas. This is enabled by the floating regime of the working electrode that presents a low mass transport barrier for the gas. The present MFE is designed to take the advantage of transmission electron microscopy (TEM) grids with a deposited electrocatalyst of choice, to be used as working electrodes. The applicability of MFE is demonstrated on the example of oxygen reduction reaction (ORR), an essential segment in the sector of electrochemical energy conversion. The approach is validated on two state-of-the-art industrial benchmarks ORR electrocatalysts, a carbon-supported platinum (Pt/C) nanoparticulated electrocatalyst and an alloyed counterpart (Pt-Co/C). It is shown that MFE enables acquisition of the two most vital catalyst features in one measurement sequence. Firstly, it allows for rapid electrochemical performance measurements of potential ORR electrocatalysts under high oxygen transport, specifically high current densities. Secondly, it enables the local characterization of nanostructural events via identical location transmission electron microscopy (IL-TEM).

Achieving highly active and stable oxygen reduction reaction (ORR) performance at low platinum-group-metal (PGM) loadings remains one of the grand challenges in the proton-exchange membrane fuel cells (PEMFCs) community. Currently, state-of-the-art electrocatalysts are high-surface-area-carbon-supported nanoalloys of platinum (Pt) with different transition metals M (M = Cu, Ni, Fe, Co, etc.). Nevertheless, despite years of focused research, the established structure-property relationships are not able to explain and predict the electrochemical performance and behaviour of the real nanoparticulate systems. Unlike the perfect core-shell systems, usually used to model the observed behaviour of the electrocatalysts by the community, nanoparticles in real nanocatalysts exhibit much greater local atomic-scale structural complexity. Structure-property relationships addressing averaged material properties, such as the actual ORR activity and metal degradation (e.g. dissolution) behaviour, are at risk of oversimplifying the underlying phenomena when they rely on top-down characterization techniques and attribute averaged affects to idealized nanoparticle structures. In this work, we reveal the complexity of commercially available Pt/C and Pt-M/C electrocatalysts and discuss the relevance of understanding their stability behaviour in fuel cell systems. We expose the limitations of the established top-down characterization methodologies for studying degradation and provide a conceptual approach that offers a new dimension and transcends the limits of conventional structure-stability studies. We outline a bottom-up approach where atomically resolved properties, structural changes and strain analysis are recorded as well as analysed in great detail on an individual nanoparticle. While fundamental, this approach addresses the complexity of practical electrocatalysts and enables studying their stability when exposed to realistic electrochemical conditions (i.e. high current density). This methodology, in our opinion, offers the new level of understanding structure-stability relationships of practically viable nanoparticulate systems.