TY - JOUR

T1 - Photoinduced Adsorption of Hydrogen and Methane on γ-Alumina. The Photoinduced Chesorluminescence (PhICL) Effect

AU - Andreev, N. S.

AU - Emeline, A. V.

AU - Polikhova, S. V.

AU - Ryabchuk, V. K.

AU - Serpone, N.

PY - 2004/1/6

Y1 - 2004/1/6

N2 - Adsorption of hydrogen and methane on a preirradiated surface of γ-Al2O3 produces an afterglow, which has been described as a photoinduced chesorluminescence (PhICL), whose spectral features identify with the intrinsic photoluminescence of alumina. The emission spectrum consists of at least four overlapping single emission bands. For methane adsorption, the PhICL phenomenon is seen only if the solid is preirradiated in the presence of oxygen. Emission decay kinetics of the PhICL effect for γ-Al2O3 reveal two wavelength regimes: a short wavelength regime at λ = 300-370 nm (decay time τ = 1.1 ± 0.2 s; signal width = 2.8 s), and a longer wavelength regime at λ = 380-700 nm (decay time τ = 2.1 ± 0.1 s; signal width = 4.3 s). A model is proposed in which there exist two different emission centers and, thus, two different pathways for emission decay. In the first, emission originates with electron trapping by such deep energy traps as anion vacancies {e- + Va → F+ + hv1} to yield electron F-type color centers, whereas in the second, emission originates from electron/trapped hole recombination {e- + Oṡ- → O s2- + hv2}. The first common step of the pathways is homolytic dissociative chemisorption of hydrogen and methane upon interaction with surface-active hole centers Oṡ-, produced upon preirradiation of alumina, to give atomic hydrogen H ̇ and methyl radicals CH3̇. Thermoprogrammed desorption spectra of photoadsorbed or postsorbed oxygen show that adsorbed oxygen interacts with atomic hydrogen and methyl radicals. The products of thermodesorption were H2O for hydrogen and H 2O, CO2, and CH3CH3 for methane. The Solonitsyn memory effect coefficient was also evaluated for oxygen photoadsorption.

AB - Adsorption of hydrogen and methane on a preirradiated surface of γ-Al2O3 produces an afterglow, which has been described as a photoinduced chesorluminescence (PhICL), whose spectral features identify with the intrinsic photoluminescence of alumina. The emission spectrum consists of at least four overlapping single emission bands. For methane adsorption, the PhICL phenomenon is seen only if the solid is preirradiated in the presence of oxygen. Emission decay kinetics of the PhICL effect for γ-Al2O3 reveal two wavelength regimes: a short wavelength regime at λ = 300-370 nm (decay time τ = 1.1 ± 0.2 s; signal width = 2.8 s), and a longer wavelength regime at λ = 380-700 nm (decay time τ = 2.1 ± 0.1 s; signal width = 4.3 s). A model is proposed in which there exist two different emission centers and, thus, two different pathways for emission decay. In the first, emission originates with electron trapping by such deep energy traps as anion vacancies {e- + Va → F+ + hv1} to yield electron F-type color centers, whereas in the second, emission originates from electron/trapped hole recombination {e- + Oṡ- → O s2- + hv2}. The first common step of the pathways is homolytic dissociative chemisorption of hydrogen and methane upon interaction with surface-active hole centers Oṡ-, produced upon preirradiation of alumina, to give atomic hydrogen H ̇ and methyl radicals CH3̇. Thermoprogrammed desorption spectra of photoadsorbed or postsorbed oxygen show that adsorbed oxygen interacts with atomic hydrogen and methyl radicals. The products of thermodesorption were H2O for hydrogen and H 2O, CO2, and CH3CH3 for methane. The Solonitsyn memory effect coefficient was also evaluated for oxygen photoadsorption.

UR - http://www.scopus.com/inward/record.url?scp=0345866710&partnerID=8YFLogxK

U2 - 10.1021/la030228a

DO - 10.1021/la030228a

M3 - Article

C2 - 15745010

AN - SCOPUS:0345866710

VL - 20

SP - 129

EP - 135

JO - Langmuir

JF - Langmuir

SN - 0743-7463

IS - 1

ER -