20.500.12556/DKUM-96692 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 WILEY Angleški jezik Slovenski jezik https://onlinelibrary.wiley.com/journal/15213773 © 2026 The Author(s) Članek v reviji 2026-01-23 13:20:38 2026-01-23 13:20:38 2026-07-21 03:10:00 0000-00-00 00:00:00 2026 0 0 12 str. [article no.] e19929 First published: 15 January 2026 0000-00-00 Zaloznikova Objavljeno NiDoloceno 2025-09-10 2026-01-08 2026-01-15 54 265392899 10.1002%2Fanie.202519929 1521-3773 Angew_Chem_Int_Ed_-_2026_-_Finsgar_-_Combining_ToF‐SIMS_and_Multivariate_Analysis_to_Resolve_Active_Sites_on_Ni‐Based_HER.pdf Angew_Chem_Int_Ed_-_2026_-_Finsgar_-_Combining_ToF‐SIMS_and_Multivariate_Analysis_to_Resolve_Active_Sites_on_Ni‐Based_HER.pdf 1 A0247A4A000E2A9584045E5414FF7D78 3b2d5ba4dcf7d874c1e9167cccf222d7bae503084611af2437d4c2fedecaa526 3098d5ae-8428-11f1-a07d-00155d580e34 https://dk.um.si/Dokument.php?lang=slv&id=208415 https://onlinelibrary.wiley.com/doi/epdf/10.1002/anie.202519929 1 edfd4b78-f855-11f0-8c23-00155d00018d https://dk.um.si/Dokument.php?lang=slv&id=202492 Fakulteta za kemijo in kemijsko tehnologijo 0 0 0