highlights

TTB-Type Niobium Tungsten Oxides

Recent investigations revealed interesting electrochemical properties of several niobium tungsten oxides. To study the applicability of different characterization methods, we investigated two tetragonal tungsten bronze-type samples with slightly different oxygen:metal ratio. The real structures of the well-crystallized Nb₈W₉O₄₇ and the defect-rich Nb₇W₁₀O_47.5 can be imaged by HRTEM and HAADF-STEM with high resolution. An example is reproduced on the right side: the HAADF-STEM image of the interface between Nb₈W₉O₄₇ and Nb₄W₇O₃₁ demonstrates the close structural relationship between these phases enabling coherent intergrowth.
Rietveld refinements of powder XRD patterns were carried out on the basis of the threefold TTB-superstructure of Nb₈W₉O₄₇ and resulted in good fits for both samples. These results indicate that the samples with nominal composition Nb₁₈W₁₆O₉₃, which have recently been used for electrochemical studies in various studies, correspond in fact to disordered variants of the Nb₈W₉O₄₇ phase.

On the Arrangement of Pentagonal Columns in Tetragonal Tungsten Bronze-Type Nb₁₈W₁₆O₉₃
F. Krumeich, Crystals 2021, 11, 1514 DOI

Structural Developments During the Low-Temperature Oxidation of Nb₇W₁₀O₄₇
F. Krumeich and M. Wörle, J. Solid State Chem 2021, 302, 122430 DOI

On the Structural Complexity of Tetragonal Tungsten Bronze Type Niobium Tungsten Oxides
M. Wörle and F. Krumeich, Z. allg. anorg. Chem 2021, 647, 98-106 DOI

Intergrowth of Niobium Tungsten Oxides of the Tetragonal Tungsten Bronze Type
F. Krumeich, Z. Naturforsch. B 2020, 75, 913-919 DOI

HAADF-STEM image of an interface between Nb₄W₇O₃₁ (left) and Nb₈W₉O₄₇ (right)

Cover and HAADF-STEM image of single Pt atoms (bright spots) on the carbon support.

Single Pt Atom Catalysts

Single metal atom are becoming increasingly important in heterogeneous catalysis as every atom might be efficient in a process. The fixation on a suitable host material that firmly anchors the metal atoms reduces their tendency to aggregate and sinter. An example are Pt atoms on carboneous materials that are stable catalyst for the industrially important synthesis of vinyl chloride.

Tailoring Nitrogen-Doped Carbons as Hosts for Single-Atom Catalysts
S. Büchele, Z. Chen, S. Mitchell, R. Hauert, F. Krumeich, and J. Pérez‑Ramírez
ChemCatChem 2019, 11, 2812-2820 DOI

Tunability and Scalability of Single-Atom Catalysts Based on Carbon Nitrides
Z. Chen, S. Mitchell, F. Krumeich, R. Hauert, S. Yakunin, M. V. Kovalenko, and J. Pérez-Ramírez
ACS Sustainable Chem. Eng. 2019, 7, 5223–5230 DOI

Nanostructuring Unlocks High Performance of Platinum Single-Atom Catalysts for Stable Vinyl Chloride Production
S. K. Kaiser, E. Fako, G. Manzocchi, F. Krumeich, R. Hauert, A. Clark, O. V. Safonova, N. López, and J. Pérez-Ramírez
Nature Catal. 2020, 3, 376–385 DOI

Cryo STEM

Many material are sensitive to the electron beam and undergone modifications during the TEM and STEM investigation. A means to minimize this unwanted effect is cooling the sample with liquid nitrogen. This procedure has recently been utilized to image various perovskite lead halides by HAADF-STEM avoiding the decompositition and formation of lead nanoparticles.

Stable Ultra-Concentrated and Ultra-Dilute Colloids of CsPbX₃ (X = Cl, Br) Nanocrystals using Natural Lecithin as a Capping Ligand
F. Krieg, Q. K. Ong, M. Burian, G. Rainò, D. Naumenko, H. Amenitsch, A. Süess, M. Grotevent, F. Krumeich, M. I. Bodnarchuk, I. Shorubalko, F. Stellacci, and M. V. Kovalenko
J. Am. Chem. Soc. 2019, 141, 19839-19849 DOI

Scalable Photonic Sources Using Two-Dimensional Lead Halide Perovskite Superlattices
J. Jagielski, S. F. Solari, L. Jordan, D. Scullion, B. Blülle, Y.-T. Li, F. Krumeich, Y.-C. Chiu, B. Ruhstaller, E. J. G. Santos, and C.-J. Shih
Nature Commun. 2020, 11, 387 DOI

HAADF-STEM image of CsPbBr₃ nanocrystals obtained at cryogenic conditions

Recent Research Hightlights

Research Highlights 2021