Photoinduced hole transfer from TiO[sub 2] to methanol molecules in aqueous solution studied by electron paramagnetic resonance

Journal Article · Thu Dec 16 00:00:00 EST 1993 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100152a036· OSTI ID:5114883

Micic, O I; Zhang, Y; Cromack, K R; Trifunac, A D; Thurnauer, M C ^[1]

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1. Argonne National Lab., IL (United States)

An electron paramagnetic resonance (EPR) study is reported on the paramagnetic species formed on irradiation of aqueous TiO[sub 2] colloids in the presence of methanol. In laser (308 nm) irradiated aqueous solution of methanol at 1.9 K, the observed EPR signals are centered around g = 2 and have a line shape characteristic of the CH[sub 2]OH radical. The appearance of these radicals at the very low temperature of 1.9 K implicates charge transfer from the oxygen lattice holes to methanol molecules within a few monolayers of the surface of the TiO[sub 2] particles. Different radicals are formed when CH[sub 3]OH is chemisorbed on TiO[sub 2]. The EPR signals detected in TiO[sub 2] colloidal solution prepared in methanol and then evaporated and dissolved in water also show the formation of the CH[sub 2]OH radical due to oxidation of chemisorbed methanol on the TiO[sub 2] surface. These particles, with high laser pulse intensities, oxidize the chemisorbed methanol further to give the CHO radical. In addition, the CH[sub 3] radical is formed from reducing processes and observed at 6-50 K. In the absence of methanol, holes are trapped by surface hydroxide groups forming TI[sup IV]-O-Ti[sup IV]-O[sup [sm bullet]]. At higher temperature (150 K) in aqueous methanol solution, the CH[sub 2]OH radical transfers an electron to TiO[sub 2], doubling the yield of formation of surface Ti[sup III] ions which are stable in air-free solution. When an electron scavenger such as Hg[sup 2+] is present in solution, the EPR signal of Ti[sup III] disappears since mercury ions are reduced. 44 refs., 7 figs.

• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 5114883
• Journal Information: Journal of Physical Chemistry; (United States), Vol. 97:50; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
METHANOL
CHEMISORPTION
OXIDATION
TITANIUM OXIDES
SURFACE PROPERTIES
AQUEOUS SOLUTIONS
CHARGE TRANSPORT
CHEMICAL REACTION KINETICS
COLLOIDS
ELECTRON SPIN RESONANCE
ELECTRON TRANSFER
HOLE MOBILITY
LASER RADIATION
PHOTOCHEMICAL REACTIONS
RADIATION EFFECTS
RADICALS
TRAPS
ALCOHOLS
CHALCOGENIDES
CHEMICAL REACTIONS
DISPERSIONS
ELECTROMAGNETIC RADIATION
HYDROXY COMPOUNDS
KINETICS
MAGNETIC RESONANCE
MIXTURES
MOBILITY
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
RADIATIONS
REACTION KINETICS
RESONANCE
SEPARATION PROCESSES
SOLUTIONS
SORPTION
TITANIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
400201* - Chemical & Physicochemical Properties
661300 - Other Aspects of Physical Science- (1992-)