Jasna Jankovic

As the world advances towards cleaner energy solutions, increased attention has been put towards researching electrochemical systems, such as fuel cells, electrolyzers, and batteries. However, before these technologies can be fully implemented, several key challenges must be addressed, among them nanoscale material degradation due to harsh working conditions. Understanding the degradation mechanisms holds the key to developing advanced materials and systems. Electron microscopy, particularly identical location electron microscopy (IL‐EM), offers a detailed way to study and visualize these degradation processes. This technique enables the scrutiny of specific locations, down to the nano or atomic scale, both before and after subjecting materials to simulated operational conditions. It also provides valuable insights into morphological, chemical, and structural changes that occur following electrochemical tests. By combining electrochemical testing with electron microscopy, IL‐EM has been advantageous for challenging old or formulating new hypotheses regarding materials degradation in a way that has been impossible with more traditional characterization approaches. This paper offers a comprehensive and up‐to‐date review of key aspects and findings related to the degradation of catalytic and electrode materials observed through IL‐EM. It mainly focuses on IL transmission EM (IL‐TEM) and applications to fuel cells due to the prevalence of published literature in this particular area; however, applications in electrolyzers and batteries, although limited, are also included in the review. In addition, less‐utilized IL techniques such as scanning EM (IL‐SEM) and electron tomography approaches are discussed as well. The versatility and efficiency of the IL technique are explored and discussed through a wealth of up‐to‐date, thought‐provoking, and interrelated studies.

In recent years, significant efforts have been devoted to the reduction of sulfur levels in transportation fuels in order to reach regulatory limits and reduce the emission of harmful SO _x into the atmosphere. In particular, adsorptive desulfurization (ADS) has the potential to produce zero-sulfur fuels without the need for a high energy intensity process, high H₂ pressure, and long process times as in the case of other technologies such as hydrodesulfurization. In this work, we have demonstrated the effectiveness of renewable activated carbons derived from food waste (FWAC) for the ADS of model jet and diesel fuels. The optimal FWAC materials were those fabricated to maximize the micropore volume, providing available sites for the adsorption of dibenzothiophene (DBT) and dimethyldibenzothiophene (DMDBT). The FWAC had a greater sulfur adsorption capacity than commercial AC, Y zeolite sorbents, and AC derived from other biomass sources including miscanthus, coconut shell, and walnut shell. Elemental analysis suggests that the inorganic impurities inherent in food waste, notably K, Ca, P, and Na, may contribute to its improved sulfur adsorption compared to other AC materials. Microscopy and X-ray diffraction studies further demonstrated the presence of inorganic species on FWAC that may provide active sites for the chemisorption of sulfur molecules.

Single‐atom catalysts (SACs) possessing well‐defined active sites of singular metal atoms have gained prominence in the field of electrocatalysis as they can be tuned to enhance activity and stability. In this study, a critical‐raw‐material (CRM)‐free SAC is synthesized for the oxygen reduction reaction (ORR) in alkaline media by pyrolyzing polyimide nanoparticles and Fe without using a sacrificial template. Upon purification, the resulting catalyst demonstrates outstanding performance as cathodes in anion‐exchange membrane fuel cells (AEMFCs) owing to sufficiently stabilized Fe single‐atoms at the FeN ₄ sites yielding a peak power density ( P _max ) as high as ∼1.8 W cm ⁻² and specific power values up to 11.3 W ; the latter being the greatest reported among CRM‐free cathode AEMFCs. The SAC also shows remarkable in situ durability under a very high current density of 1000 mA cm ⁻² , a first introduced here, with only a 2 mV h ⁻¹ decay. Most impressively, when the SAC is combined with a NiMo anode to test a completely CRM‐free high‐temperature (HT)‐AEMFC at 118 °C, a P _max of 372 mW cm ⁻² and limiting current density of ∼1.14 A cm ⁻² are achieved. This work represents a significant milestone in the development of durable SAC cathode catalysts for the next generation of CRM‐free AEMFCs.

3D imaging of porous materials in polymer electrolyte membrane (PEM)-based devices, coupled with in situ diagnostics and advanced multi-scale modelling approaches, is pivotal to deciphering the interplay of mass transport phenomena, performance, and durability. The characterization of porous electrode media in PEM-based cells encompassing gas diffusion layers and catalyst layers often relies on traditional analytical techniques such as 2D scanning electron microscopy, followed by image processing such as Otsu thresholding and manual annotation. These methods lack the 3D context needed to capture the complex physical properties of porous electrode media, while also struggling to accurately and effectively discriminate porous and solid domains. To achieve an enhanced, automated segmentation of porous structures, we present a 3D deep learning-based approach trained on calibrated 3D micro-CT, focused ion beam-scanning electron microscopy datasets, and data from physical porosity measurements. Our approach includes binary segmentation for porous layers and a multiclass segmentation method to distinguish the microporous layers from the gas diffusion layers. The presented analysis framework integrates functions for pore size distribution, porosity, permeability, and tortuosity simulation analyses from the resulting binary masks and enables quantitative correlation assessments. Segmentations achieved can be interactively visualized on-site in a 3D environment.