20.500.12556/DiRROS-30902 Combining ToF-SIMS and multivariate analysis to resolve active sites on Ni-based HER catalysts Unambiguous identification of active sites in heterogeneous catalysis remains a major challenge, particularly formaterials with ultrathin, chemically mixed surface layers. Here, we demonstrate a generalizable approach that combinestime-of-flight secondary ion mass spectrometry (ToF-SIMS) with multivariate statistical analysis (principal componentanalysis [PCA] and multivariate curve resolution [MCR]) to resolve catalytically relevant motifs at the nanoscale. Using Nielectrodes as a model system, PCA distinguished hydroxide-enriched domains from oxide- and metal-rich regions, whileMCR decomposed depth profiles and 3D images into hydroxide, oxide, and metallic layers with nanometer resolution.A unique secondary-ion fragment, NiO3 H 3− (m/z 108.94), emerged as a marker of hydroxide-rich environments andcorrelated with hydrogen evolution reaction (HER) activity across a series of Ni electrodes. Complementary densityfunctional theory (DFT) calculations revealed that Ni(OH)2 clusters adjacent to metallic Ni offer the most favorable waterdissociation energetics, establishing the structural origin of the marker. While illustrated here for Ni-based HER, thisworkflow provides a broadly applicable framework to isolate and rank near-surface patterns that govern catalytic activity,thereby extending ToF-SIMS from a qualitative probe to a predictive tool for active site identification. HER active sites multivariate statistical analysis nickel catalysts ToF-SIMS aktivne spojine statistične analize kataliza niklja true false true Angleški jezik Slovenski jezik © 2026 The Author(s). Angewandte Chemie International Edition published by Wiley-VCH GmbH. Neznano 2026-07-08 12:11:52 2026-07-08 12:12:15 2026-07-09 03:56:56 0000-00-00 00:00:00 2026 0 0 Nasl. z nasl. zaslona; Soavtorji: Katja Andrina Varda, Dzevad K. Kozlica, Matej Huš, Milena Martins, and Dušan Strmčnik; Opis vira z dne 20. 1. 2026; str. 1-12 issue 8, [article no.] e19929 Vol. 65 16 Feb. 2026 0000-00-00 Zaloznikova Objavljeno NiDoloceno 0000-00-00 0000-00-00 2026-02-16 54 1521-3773 10.1002%2Fanie.202519929 265392899 https://onlinelibrary.wiley.com/doi/epdf/10.1002/anie.202519929 1 7240381f-7ab5-11f1-bd8a-001a4af901a5 https://dirros.openscience.si/Dokument.php?lang=slv&id=47427 RAZ_Finsgar_Matjaz_2026.pdf RAZ_Finsgar_Matjaz_2026.pdf 1 F7ED85C6707DDFB489832F89B56224E4 4ed4d1ee5b748ce6f3011b9701964ceffb345c6ed5b0e368d1fa9621fc99b1bc 5319c085-7ab6-11f1-bd8a-001a4af901a5 https://dirros.openscience.si/Dokument.php?lang=slv&id=47432 Kemijski inštitut 0 0 0