Characterizing nanostructured films using phase sensitive vibrational sum frequency spectroscopy Furong Yan, Carsten Placke-Yan, Aleyna Yasar, Zhipeng Huang, Gerd Bacher, et al. Journal of Chemical Physics, 2026 Nanoparticle films are ubiquitous thermal and electrocatalysts, yet their operando characterization remains challenging. Vibrational sum-frequency generation (vSFG) spectroscopy offers unique advantages due to its high sensitivity and surface specificity, but its application to systems with such intermediate length scale disorder, particularly with phase-resolved detection, has been challenging. In this study, we describe an approach to phase-resolved vSFG spectroscopy of nanoparticle films using z-cut α-quartz as a local reference. We show, by analysis of an octadecyltrichlorosilane film on quartz under the ppp polarization condition, that quantitative detection of absolute phase is possible and subsequently apply this protocol to a film of Mn-doped Co3O4 nanoparticles. Two OH species are resolved (∼3585 and ∼3770cm−1), both oriented H-up relative to the surface. This approach delivers a practical, internally referenced, phase-resolved vSFG methodology for nanoparticle ensembles on dielectric supports and, therefore, offers operando access to catalytic interfaces beyond metallic or plasmonically enhanced systems.
Double E─H Bond Activation of Ammonia and Water by Cyclic Gallaphosphene L(OCP)GaPGaL Mahendra K. Sharma, Christoph Wölper, Gebhard Haberhauer, Stephan Schulz Angewandte Chemie International Edition, 2026 Cyclic gallaphosphene L(PCO)GaPGaL 1 (L = HC[C(Me)NAr] 2 ; Ar = 2,6‐ i ‐Pr 2 ‐C 6 H 3 ) selectively reacts with NH 3 and H 2 O at ambient temperature with twofold N─H and O─H bond activation and formation of compounds LGa(μ‐PH)(μ‐NHC(O)PH)GaL 2 and LGa(μ‐PH)(μ‐OC(O)PH)GaL 3 . Both nucleophilic P atoms of 1 are protonated in these reactions, while the electrophilic carbon atom of the bridging PCO unit binds to the remaining NH group / O atom. The formation of heterocycles 2 and 3 , which were characterized by heteronuclear NMR ( 1 H, 13 C{ 1 H}, 31 P{ 1 H}) and IR spectroscopy, elemental analysis, and single‐crystal X‐ray diffraction (sc‐XRD), is only possible due to a beneficial interplay between the polar Ga─P double bond and the electrophilic nature of the C center in the bridging PCO unit. The reaction mechanism and energetics of the NH 3 reaction was investigated in detail by quantum chemical calculations, which also highlight the importance of bimolecular reaction processes with the involvement of an additional NH 3 molecule.
Interfacial Softening and Electrolyte Uptake in Co3O4 OER Catalysts: Insight from Operando Spectroscopy and Fast EQCM-D Christian Leppin, Carsten Placke‐Yan, Georg Bendt, Sheila Hernandez, Kristina Tschulik, et al. Chemcatchem, 2026 Cobalt spinel (Co 3 O 4 ) catalysts are widely studied in scope of the electrocatalytic oxygen evolution reaction (OER), yet the role of interfacial structural transformation under anodic bias remains under debate. Here, we employ an operando approach, combining a fast electrochemical quartz crystal microbalance with dissipation monitoring (EQCM‐D), electrochemical impedance spectroscopy (EIS), and Raman spectroscopy to investigate interfacial transformations of Co 3 O 4 nanoparticle electrodes in alkaline electrolyte. We identify two distinct regimes during the anodic sweep prior to the macroscopic OER onset. At lower potentials, the catalyst interface remains mechanically rigid while reversibly associating several OH − /H 2 O species per oxidized cobalt site. At higher potentials, pronounced softening of the interface occurs alongside further uptake of electrolyte species. This indicates amorphization and a ‘swelling process’ beyond simple adsorption. Notably, an electrochemical conditioning treatment can suppress mass and compliance hysteresis without affecting OER activity, suggesting that most incorporated electrolyte species do not participate in the OER. EIS further reveals that OER intermediates form well below the apparent OER onset potential. These results advance our mechanistic understanding of interfacial transformations in cobalt‐based OER catalysts and establish EQCM‐D as a sensitive operando technique for probing electrocatalyst transformations.
Mechanistic Understanding of Laser-Induced Defect Engineering of Anisotropic Cobalt Oxide Spinel Platelets in Water Dana Schellenburg, Thomas Bihnam, Carsten Placke‐Yan, Georg Bendt, Oleg Prymak, et al. Chemcatchem, 2026 In this study, we employ the pulsed laser defect engineering in liquid (PUDEL) to tailor the surface properties of cobalt (II, III) oxide (Co 3 O 4 ) platelets grown in the < 111 > direction. By varying the laser intensity and pulse number, we systematically investigate the relationship between defect formation and catalytic performance in the oxygen evolution reaction (OER) and selective oxidation of two alcohols. Our results reveal that the PUDEL processing leads to the formation of lattice distortions, the gradual alteration of three different paramagnetic defect sites, a partial reduction of Co 3 O 4 , and enrichment of the Co 3 O 4 (111) surface with hydroxyl groups (*OH), which significantly enhances OER activity. Theoretical investigations confirm that optimized hydroxyl coverage is critical for determining OER activity. The observed trends in selectivity and conversion efficiency for the selective oxidation of cinnamyl alcohol (CA) and ethylene glycol (EG) suggest different reaction mechanisms. The activity trend of the selective oxidation of CA appears to follow the trend of a defect‐attributed paramagnetic species that was assigned to a surface‐near, distorted high‐spin (S = 3/2) Co 2+ . In turn, the catalytic activity and OER activity trends for the EG oxidation showed similar trends, which followed the density of a paramagnetic CoO x species observed during EPR spectroscopy. In particular, the highest OER activity and EG conversion were both found for moderate (2 PPV, ), yet not too intense PUDEL processing. Our findings establish PUDEL as a precise method for catalyst optimization, both for thermal and electro‐catalytic oxidation over defect‐enriched cobalt oxides, which enables the correlation of specific laser‐induced defects with catalytic activity trends.
Unifying Scaling Relations and Multiple Reaction Mechanisms for Screening Transition Metal-Doped Co3O4 for Oxygen Evolution Reaction Kapil Dhaka, Hatem M. A. Amin, Davide Beschi, Dana Schellenburg, Benjamin Mockenhaupt, et al. Angewandte Chemie International Edition, 2026 Accelerating the discovery of oxygen‐evolution reaction (OER) catalysts requires high‐throughput screening strategies combining descriptor‐based frameworks with dedicated mechanistic analyses. In this study, we present a unified methodology using the example of doped Co 3 O 4 in the OER by developing a mechanistically resolved, potential‐dependent volcano approach that accounts for the uncertainty of adsorption free energies when analyzing activity trends. We evaluate the influence of different dopants (Cr, Mn, Fe, Ni, Cu, and V) on the OER activity by selectively substituting octahedral Co sites on the (001) facet of Co 3 O 4 using density functional theory calculations (DFT). We identify Cr, Fe, Ni, and V as promising dopants as they exhibit increased OER activity compared to undoped Co 3 O 4 , while Cr shows the strongest promoting effect among all dopants considered in this study. We compare our theoretical predictions with two different series of synthesized Co 3 O 4 nanoparticle catalysts and find good agreement regarding the qualitative trends of OER activity. To validate the strong promoting effect of Cr, we synthesize surface‐enriched, Cr‐doped Co 3 O 4 nanoparticles, which confirms the theoretical prediction of increased OER activity. The theoretical model developed in this work is a transferable framework that can be equally applied to other materials and electrocatalytic processes for quantifying dopant effects by considering uncertainty and promoting effects when analyzing activity trends.
