Here is a selection of recent scientific papers I (co-)authored. A complete list can be found on my Google Scholar. All code that led to published works can be found on my GitHub.
Platinum-copper nanoparticles catalyze the oxygen reduction reaction in a hydrogen fuel cell. Understanding which structural features do and don’t influence activity or stability helps focus research on changes that truly improve catalyst performance.
At the atomic scale, platinum and copper atoms may be randomly mixed or arranged in an ordered structure. We found that ordered sites near the particle surface, where the reaction occurs, are more stable during electrochemical activation that prepares the catalyst for long-term use. This was made possible by a new approach that combines identical-location 4D-STEM with unsupervised learning.
Structure–Stability Relationships in Pt-Alloy Nanoparticles Using Identical-Location Four-Dimensional Scanning Transmission Electron Microscopy and Unsupervised Machine Learning.
A.R. Kamšek, F. Ruiz-Zepeda, M. Bele, A. Logar, G. Dražič, N. Hodnik. ACS Nano, 19 (2), 2334–2344, 2025.
Within the ordered phase, defects known as anti-phase boundaries can form, as previously seen in bulk alloys. In this work, we confirmed they also appear in nanoparticles, but found no effect on the catalytic activity.
Periodic anti-phase boundaries and crystal superstructures in PtCu₃ nanoparticles as fuel cell electrocatalysts.
A.R. Kamšek, A. Meden, I. Arčon, P. Jovanovič, M. Šala, F. Ruiz-Zepeda, G. Dražić, M. Gaberšček, M. Bele, N. Hodnik. Materials Today Nano, 23, 100377, 2023.
Atomically resolved microscopy images hold far more detail than the human eye can process. This review explains how computer algorithms can unlock that hidden information, providing objective insights and enabling the analysis of electrocatalyst image datasets too large or too tricky for manual work.
Bringing into play automated electron microscopy data processing for understanding nanoparticulate electrocatalysts’ structure–property relationships.
A.R. Kamšek, F. Ruiz-Zepeda, A. Pavlišič, A. Hrnjić, N. Hodnik. Current Opinion in Electrochemistry, 35, 101052, 2022.
Linking structural changes to performance helps guide the design of more durable, efficient fuel-cell catalysts. Modern electrocatalysts for catalyzing the oxygen reduction reaction are commonly made up of platinum-alloy nanoparticles on a carbon support. Their varied structures mean they degrade differently under operating conditions. We showed how identical-location microscopy tracks their local history, which complements the bulk information gathered using other methods such as electrochemical measurements.
The first paper is a comparison of commercial electrocatalysts for the oxygen reduction reaction of acidic media, and the second is a detailed investigation of platinum-cobalt nanoparticles at the atomic scale.
Resolving the nanoparticles’ structure–property relationships at the atomic level: a study of Pt-based electrocatalysts.
L.J. Moriau, A. Hrnjić, A. Pavlišič, A.R. Kamšek, U. Petek, F. Ruiz-Zepeda, M. Šala, L. Pavko, V.S. Šelih, M. Bele, P. Jovanovič, M. Gatalo, N. Hodnik. iScience, 24 (2), 102102, 2021.
Observing, tracking and analysing electrochemically induced atomic-scale structural changes of an individual Pt–Co nanoparticle as a fuel cell electrocatalyst by combining complementary electron microscopy techniques.
A. Hrnjić, A.R. Kamšek, A. Pavlišič, M. Šala, M. Bele, L. Moriau, M. Gatalo, F. Ruiz-Zepeda, P. Jovanovič, N. Hodnik. Electrochimica Acta, 388, 138513, 2021.
The performance of electrocatalysts with supported nanoparticles can be improved not only by optimizing the noble-metal-based nanoparticles, but also by tailoring the support. Certain supports, such as ceramics, can interact with nanoparticles in ways that improve the catalytic performance, even though the support alone is not highly catalytic.
These three papers are examples of how using a titanium oxynitride support created beneficial metal–support interactions compared to the commonly used carbon support for reactions in hydrogen fuel cells and water electrolyzers.
Metal–support interaction between titanium oxynitride and Pt nanoparticles enables efficient low-Pt-loaded high-performance electrodes at relevant oxygen reduction reaction conditions.
A. Hrnjić, A.R. Kamšek, L. Bijelić, A. Logar, N. Maselj, M. Smiljanić, J. Trputec, N. Vovk, L. Pavko, F. Ruiz-Zepeda, M. Bele, P. Jovanovič, N. Hodnik. ACS Catalysis, 14 (4), 2473–2486, 2024.
Titanium oxynitride-supported Ru nanoparticles as exceptional electrocatalysts for alkaline hydrogen evolution reaction.
M. Smiljanić, M. Bele, L. Pavko, A. Hrnjić, F. Ruiz-Zepeda, L. Bijelić, A.R. Kamšek, M. Nuhanović, A. Marsel, L. Gašparič, A. Kokalj, N. Hodnik. Chemical Engineering Journal, 164204, 2025.
Iridium Stabilizes Ceramic Titanium Oxynitride Support for Oxygen Evolution Reaction.
G. Koderman Podboršek, L. Suhadolnik, A. Lončar, M. Bele, A. Hrnjić, Ž. Marinko, J. Kovač, A. Kokalj, L. Gašparič, A.K. Surca, A.R. Kamšek, G. Dražić, M. Gaberšček, N. Hodnik, P. Jovanovič. ACS Catalysis, 12 (24), 15135–15145, 2022.
These two papers step outside my usual focus on hydrogen technologies.
The first explores electrocatalytic CO₂ reduction, a carbon capture and utilization technology. Copper catalysts speed up the reaction, but their structural changes during operation affect long-term performance.
The second examines Ni-rich NMC, a commercial battery cathode material. It proposes a methodology for reliable, accurate impedance measurements of active electrodes and meaningful interpretation of the results.
Deactivation of copper electrocatalysts during CO₂ reduction occurs via dissolution and selective redeposition mechanism.
B. Tomc, M. Bele, M.A. Nazrulla, P. Šket, M. Finšgar, A.K. Surca, A.R. Kamšek, M. Šala, J. Šiler Hudoklin, M. Huš, B. Likozar, N. Hodnik. Journal of Materials Chemistry A, 13 (6), 4119–4128, 2025.
Novel Methodology of General Scaling-Approach Normalization of Impedance Parameters of Insertion Battery Electrodes – Case Study on Ni-Rich NMC Cathode: Part I. Experimental and Theoretical Insights.
M. Firm, J. Moškon, G. Kapun, S. Drvarič Talian, A.R. Kamšek, M. Štefančič, S. Hočevar, R. Dominko, M. Gaberšček. Journal of The Electrochemical Society, 171 (12), 120540, 2024.
