Interplay between Defect Structure and Catalytic Activity in the Mo_10−xV_xO_y Mixed‐Oxide System

Abstract

The Mo(10-x)V(x)O(y) solid-solution systems (0≤x≤10) were studied by electron paramagnetic resonance spectroscopy. The results show the existence of paramagnetic vanadyl VO(2+) species, whose concentration becomes maximal for Mo(5)V(5)O(y·). A quantitative analysis of the [VO(2+)] concentration as a function of the Mo/V ratio allows it to characterize the prevailing defect chemistry in the Mo(10-x)V(x)O(y) system. In this respect, the semi-conducting properties of Mo(10-x)V(x)O(y) are p-type in an interval of Mo(9)V(1)O(y)-Mo(5)V(5)O(y) and switch into n-type because of the conduction electrons in a composition range of Mo(5)V(5)O(y)-Mo(1)V(9)O(y). Highest catalytic activity is obtained when vanadium acts as an acceptor center and oxygen vacancies ν(··)(O) are formed for reasons of charge compensation. In addition to the surface, ν(··)(O) and VO(2+) centers in the bulk have to be considered too for heterogeneous catalysis.

Molecular precursor derived and solution processed indium–zinc oxide as a semiconductor in a field-effect transistor device. Towards an improved understanding of semiconductor film composition

“…bond distance, bond angle) in the rst coordination sphere of a paramagnetic center. 49 Concerning the defect structure of the amorphous IZO phase, defect-chemical considerations that are valid in a point-defect model approximation, relevant for small amounts of indium-doping into a ZnO matrix, are extended to the In 2 O 3 -ZnO (IZO) solid solution system. Most recently, the validity of this approach has been reported for a different oxide solid solution system.…”

Characterization of V–Mo–W Mixed Oxide Catalyst Surface Species by 51V Solid-State Dynamic Nuclear Polarization NMR

“…Interestingly, sample 1 – pH 2.6 in its solid form after drying the D 2 O/H 2 O impregnated sample, shows no EPR signals in the same region (see SI Figure S1c), which means that the aqueous solution influences the sample in a reversible way. This may be explained by the presence of water-soluble VO 2+ species in the sample. − These VO 2+ species dissolve into solution while impregnating the sample with the water-containing DNP matrix. Thus, the resolved EPR spectrum observed with D 2 O/H 2 O is mostly determined by a fast molecular tumbling of VO 2+ , which makes the hyperfine interactions visible.…”