IR spectroscopic investigation of structural hydroxyl groups in W−Si heteropolycompound supported on Al2O3

Abstract

Structural hydroxyl and deuteroxyl groups within the K4[SiWI20.~0]/AI20 3 and K6[SiW )IPdO391/A1203 systems were studied by diffuse-reflectance FTIR spectroscopy in a spectral range of fundamental stretching vibrations, first overtones, and combination bands of stretching and bending vibrations. For hydroxyl groups, the region o[' combination vibrations is the most informative. The calculated frequencies of bending vibrations of hydroxyl groups (865 and 730 cm -t) are characteristic of acidic OH groups.

Study of the state of rhodium in the potassium rhodiumundecatungstosilicate/alumina system by diffuse-reflectance IR spectroscopy

“…4 The obtained spectral data differ slightly from those of the first redox cycle for the Rh-HPC/AI20 3 system (Fig. 5, a and b).…”

“…I Active bifunctional catalysts are characterized by a similar combination, z Previously we have studied catalytic systems based on mixed H PC with Pd and Pt atoms in the Keggin unit: K6ISiWIL PdO391/AI203 3 and K4[SiWll PtO~I/AI_,O~. 4 The supported H PC was shown to exhibit an increased thermal stability under oxidative conditions below -800 K. The systems withstand the action of redox cycles up to -670 K, unlike individual HPC that begin to decompose at temperatures of redox treatments close to 370 K. t-4 The highly dispersed state of platinoids remains unchanged virtually to the complete decomposition of the H PC structure.…”

Co‐Dissolved Isostructural Polyoxovanadates to Construct Single‐Atom‐Site Catalysts for Efficient CO2Photoreduction

“…The metal centers can be firmly fixed and well separated by the surrounding metal‐oxo shell in these heterometallic POMs. To date, a large amount of mono‐metal‐substituted POMs have been reported, such as [H 3 Pt IV W 6 O 24 ] 5− , [Pt IV Mo 6 O 24 ] 8− , [PtV 9 O 28 ] 7− (PtV 9 ) and [CoW 12 O 40 ] 3− [33–37] . In theory, it should be much more easier to disperse nano‐sized clusters compared to disperse an ultra‐small atom [38–40] .…”

“…To date, a large amount of mono-metal-substituted POMs have been reported, such as [H 3 Pt IV W 6 O 24 ] 5À , [Pt IV Mo 6 O 24 ] 8À , [PtV 9 O 28 ] 7À (PtV 9 ) and [CoW 12 O 40 ] 3À . [33][34][35][36][37] In theory, it should be much more easier to disperse nano-sized clusters compared to disperse an ultra-small atom. [38][39][40] As a result, the uniform dispersion of mono-metal-substituted POMs should represent an ideal strategy to anchor single-atom centers on the functional supports.…”