Ultrasmall nanoparticles of platinum group metal oxides (core diameter of about 1.8 nm) were prepared by alkaline hydrolysis of metal precursors in the presence of NaBH4 and by colloidal stabilization with tripeptide glutathione. We obtained water-dispersed nanoparticles of Rh2O3, PdO, RuO2, IrO2, Os/OsO2, and Pt/PtO. Their size was probed using high-resolution transmission electron microscopy, differential centrifugal sedimentation, small-angle X-ray scattering, and diffusion-ordered 1H NMR spectroscopy (1H DOSY). Their oxidation state was clearly determined using X-ray photoelectron spectroscopy, X-ray powder diffraction, and electron diffraction. The chemical composition of the nanoparticles, that is, the ratio of the metal oxide core and glutathione capping agent, was quantitatively determined by a combination of these methods.

Metallic nanoparticles were analysed with respect to size and shape by a machine learning approach. This involved a separation of particles from the background (segmentation), a separation of overlapping particles,...

Octahedral-shaped PtNi-alloy nanoparticles are highly active oxygen reduction reaction catalysts for the cathode in proton exchange membrane fuel cells. However, one major drawback in their application is their limited long-term morphological and compositional stability. Here, we present a detailed in situ electron microscopy characterization of thermal annealing on octahedral-shaped PtNi catalysts as well as on doped octahedral PtNi­(Mo) and PtNi­(MoRh) catalysts. The evolution of their morphology and composition was quantified during both ex situ and in situ experiments using energy dispersive X-ray spectroscopy in a scanning transmission electron microscope under a hydrogen atmosphere and in vacuum. Morphological changes upon heating, i.e., a gradual loss of the octahedral shape and a continuous rounding of the particles, were observed, as well as evidence for increased alloying. Furthermore, the evolution of the shape of the PtNi­(Mo) nanoparticles was quantified using in situ experiments under hydrogen atmosphere in a transmission electron microscope. The shape change of the particles was quantified using segmentation maps created by a neural network. It has been demonstrated that morphological changes crucially depend on the composition and surface doping: doping with Mo or Mo/Rh significantly stabilizes the structure, allowing for persistence of a truncated octahedral shape during heat treatments.

Transmission infrared in situ measurement technique was used to assess its feasibility for real-time process analysis. In particular, the advanced chemometric analysis by band-target entropy minimization (BTEM) was implemented to obtain pure component spectral estimates from the multicomponent reaction system. In this case study, the rhodium-catalyzed reductive amination of 1-decanal in thermomorphic multiphase systems was investigated. This complex reaction/separation approach consisted of more than 10 IR-active components so that the herein-implemented BTEM technique, built for improved data handling, was highly challenged. Seven parameters with significant impact on the BTEM algorithm were identified and investigated regarding the general resolution quality of each spectral estimate. Herein, the BTEM algorithm was extended with an automatic band-target selection and parameter limits regarding the Savitzki–Golay filter for tuning raw data. Finally, the source code of the algorithm for MATLAB is published to find use in extended spectroscopic applications.