Surface Characterization of Cu−M (M = Ti, Zr, or Hf) Alloy Powder Catalysts

Abstract

X-ray photoelectron spectroscopy was used for surface characterization of amorphous Cu−M alloy powders (Cu40Ti60, Cu50Zr50, and Cu65Hf35) produced by mechanical alloying of the constituents. When used as catalyst in the dehydrogenation of alcohols Cu−Zr and Cu−Hf were found to undergo structural changes resulting in surface copper enrichment with a substantial fraction of copper being in fully reduced, metallic (Cu0) state. This result accounts for the high and stable catalytic activity of Cu−Zr and Cu−Hf in the transformations of alcohols. In contrast, when Cu−Ti is used in inert atmosphere, surface enrichment of titanium is observed. Although segregation of copper occurs in the presence of hydrogen, only oxidized copper species are detected on the surface. In either case, the catalytic activity of Cu−Ti is inferior to the other two alloy samples. TiH2 is shown by XRD to be the characteristic species formed under hydrogen. This is stable in the presence of hydrogen and, therefore, Cu acts as an oxygen scavenger and forms oxidized surface species that do not show catalytic activity.

Structure and State of Copper Oxide Species Supported on Yttria-Stabilized Zirconia

“…The BE value obtained here is close to that reported by Espinos et al for dispersed CuO species supported on the zirconia (934.4 eV) . The peaks at 932.9 eV are characteristics for Cu 0 or Cu 2 O species. , Detection of a significant amount of Cu 0 or Cu + contradicts data from other methods. Observation of the reduced copper species probably results from photoreduction in the spectrometer, when X-ray radiation under the high vacuum environment affects removal of the labile oxygen species of highly dispersed copper(II) oxide clusters.…”

Development of Hierarchical Porous MOF‐Based Catalyst of UiO‐66(Hf) and Its Application for 5‐Hydroxymethylfurfural Production from Cellulose

“…To investigate the bonding configuration of samples, the XPS survey spectrum range of PHs, PHs‐SO 3 H and catalyst‐2 from 0 to 1000 eV (a) and the amplified spectra of S 2p (b) and Hf 4 f (c) were revealed, just as Figure shown. The spectras were shown in Figure a confirmed that all four samples show two main peaks at 286.6 eV and 530.4 eV corresponding to C 1 s and O 1 s . As shown in Figure b‐c, the peaks at about 170.61 eV and 20.59 eV could be singly regarded as S 2p and Hf 4 f. Correspondingly, the emerging signal of C 1s was connected with the C−S of these samples.…”

Choline Chloride Based Deep Eutectic Solvents as a Tuneable Medium for Synthesis of Coumarinyl 1,2,4‐Triazoles: Effect of Solvent Type and Temperature

“…[17] Some coumarinyl triazoles, like compound 4b synthesized within this research, have already proven to possess a good antimicrobial activity against Klebsiella pneumonia and Aspergillus fumigates. [22] 1,2,4-Triazoles are often prepared from thiosemicarbazides, in basic conditions with sodium hydroxide [23][24][25] or trimethylamine, [26] as well as from 1,3,4-oxadiazoles and substituted hidrazides [27] or by reductive rearrangement of 1,2,4-oxadiazoles in reaction with hydrazine. [28] Azzouni et al synthesized 1,2,4-triazoles from acryloylimidates with hydrazines at room temperature in methanol, expanding the possibilities of introducing substituents in positions N(1), C(3) and C(5) of 1,2,4triazole ring.…”