EPR investigations of polymeric and H2O2 -modified C3N4 -based photocatalysts

Dvoranova, D.; Barbierikova, Z.; Mazur, M.; Garcia-Lopez, E.; Marci, G.; Luspai, K.; Brezova, V.

doi:10.1016/j.jphotochem.2019.02.006

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The C3N4 -based nanopowders prepared by thermal condensation of melamine (MCN) with subsequent thermal etching (MCN-TE) and H2O2 -treatment were investigated by Q- and X-band EPR spectroscopy in dark and upon in situ UVA or visible-light exposure. Lorentzian signal at g = 2.003, more pronounced in the case of the thermally etched material, dominates EPR spectra of MCN and MCN-TE. More complex spectra were found for H2O2 -treated photocatalysts revealing the presence of signals attributed to the radicals produced via H2O2 interaction with C/N sites in the C3N4 polymeric network. The X-band spectra monitored upon in situ irradiation of the C3N4 -based photocatalysts evidenced the intensity growth of the single line at g = 2.0033 indicating the photoinduced generation of electrons in localized paramagnetic states with the Curie dependence on temperature in the temperature range 100–180 K. The response towards UV or visible-light exposure was significantly limited in the case of H2O2 -treated photocatalysts. EPR spin trapping experiments performed in aqueous suspensions demonstrated the formation of HO2[rad] and HO [rad] spin-adducts, and the increased stability of the primary photogenerated O2 javax.xml.bind.JAXBElement@3a251187 – in aprotic media was well documented by the irradiation of the photocatalysts in the dimethylsulfoxide/water mixed solvent. The highest activities in the production of the non-persistent radical species spin-adducts were found for the thermally etched and pristine photocatalysts, confirming the negative effect of H2O2 -treatment.

Data di pubblicazione:	2019
Titolo:	EPR investigations of polymeric and H2O2 -modified C3N4 -based photocatalysts
Autori:	Dvoranova D. Barbierikova Z. Mazur M. GARCIA LOPEZ, Elisa Isabel MARCI', Giuseppe Luspai K. Brezova V. (Corresponding) mostra contributor esterni nascondi contributor esterni
Citazione:	Dvoranova, D., Barbierikova, Z., Mazur, M., Garcia-Lopez, E., Marci, G., Luspai, K., et al. (2019). EPR investigations of polymeric and H2O2 -modified C3N4 -based photocatalysts. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY. A, CHEMISTRY, 375, 100-113.
Rivista:	JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY. A, CHEMISTRY
Digital Object Identifier (DOI):	10.1016/j.jphotochem.2019.02.006
Abstract:	The C3N4 -based nanopowders prepared by thermal condensation of melamine (MCN) with subsequent thermal etching (MCN-TE) and H2O2 -treatment were investigated by Q- and X-band EPR spectroscopy in dark and upon in situ UVA or visible-light exposure. Lorentzian signal at g = 2.003, more pronounced in the case of the thermally etched material, dominates EPR spectra of MCN and MCN-TE. More complex spectra were found for H2O2 -treated photocatalysts revealing the presence of signals attributed to the radicals produced via H2O2 interaction with C/N sites in the C3N4 polymeric network. The X-band spectra monitored upon in situ irradiation of the C3N4 -based photocatalysts evidenced the intensity growth of the single line at g = 2.0033 indicating the photoinduced generation of electrons in localized paramagnetic states with the Curie dependence on temperature in the temperature range 100–180 K. The response towards UV or visible-light exposure was significantly limited in the case of H2O2 -treated photocatalysts. EPR spin trapping experiments performed in aqueous suspensions demonstrated the formation of HO2[rad] and HO [rad] spin-adducts, and the increased stability of the primary photogenerated O2 javax.xml.bind.JAXBElement@3a251187 – in aprotic media was well documented by the irradiation of the photocatalysts in the dimethylsulfoxide/water mixed solvent. The highest activities in the production of the non-persistent radical species spin-adducts were found for the thermally etched and pristine photocatalysts, confirming the negative effect of H2O2 -treatment.
URL:	http://www.elsevier.com/locate/jphotochem
Settore Scientifico Disciplinare:	Settore CHIM/07 - Fondamenti Chimici Delle Tecnologie
Appare nelle tipologie:	1.01 Articolo in rivista

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