Photochemistry at high temperatures - potential of ZnO as a high temperature photocatalyst

Schubnell, Markus; Kamber, I.; Beaud, P.

doi:10.1007/s003390050451

Cited by 23 publications

(19 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…For example, the photoluminescence intensity of TiO 2 drops by 50-60% upon raising the temperature from 20 to 200°C (57,58). At present, we observe an increase in productivity with temperature, showing a significant thermal component to the ratedetermining kinetic step in this photothermochemical reaction.…”

Section: See Retraction Published January 8 2018mentioning

confidence: 51%

RETRACTED: Solar photothermochemical alkane reverse combustion

Chanmanee

Islam

Dennis

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

A one-step, gas-phase photothermocatalytic process for the synthesis of hydrocarbons, including liquid alkanes, aromatics, and oxygenates, with carbon numbers (Cn) up to C13, from CO2 and water is demonstrated in a flow photoreactor operating at elevated temperatures (180–200 °C) and pressures (1–6 bar) using a 5% cobalt on TiO2 catalyst and under UV irradiation. A parametric study of temperature, pressure, and partial pressure ratio revealed that temperatures in excess of 160 °C are needed to obtain the higher Cn products in quantity and that the product distribution shifts toward higher Cn products with increasing pressure. In the best run so far, over 13% by mass of the products were C5+ hydrocarbons and some of these, i.e., octane, are drop-in replacements for existing liquid hydrocarbons fuels. Dioxygen was detected in yields ranging between 64% and 150%. In principle, this tandem photochemical–thermochemical process, fitted with a photocatalyst better matched to the solar spectrum, could provide a cheap and direct method to produce liquid hydrocarbons from CO2 and water via a solar process which uses concentrated sunlight for both photochemical excitation to generate high-energy intermediates and heat to drive important thermochemical carbon-chain-forming reactions.

show abstract

Section: See Retraction Published January 8 2018mentioning

confidence: 51%

RETRACTED: Solar photothermochemical alkane reverse combustion

Chanmanee

Islam

Dennis

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

show abstract

“…According to the literature reports, 27 the ZnO quantum yield varies depending on the crystal and surface quality, with a typical value of ⌽ = 0.02. The two-photon action cross-section is evaluated to be ZnO ͑TPEF͒ = 0.26 GM for an 18-nm particle typical for our experimental conditions.…”

Section: Discussionmentioning

confidence: 99%

Imaging of zinc oxide nanoparticle penetration in human skin in vitro and in vivo

et al. 2008

View full text Add to dashboard Cite

Abstract. Zinc oxide ͑ZnO-nano͒ and titanium dioxide nanoparticles ͑20 to 30 nm͒ are widely used in several topical skin care products, such as sunscreens. However, relatively few studies have addressed the subdermal absorption of these nanoparticles in vivo. We report on investigation of the distribution of topically applied ZnO in excised and in vivo human skin, using multiphoton microscopy ͑MPM͒ imaging with a combination of scanning electron microscopy ͑SEM͒ and an energy-dispersive x-ray ͑EDX͒ technique to determine the level of penetration of nanoparticles into the sub-dermal layers of the skin. The good visualization of ZnO in skin achieved appeared to result from two factors. First, the ZnO principal photoluminescence at 385 nm is in the "quiet" spectral band of skin autofluorescence dominated by the endogenous skin fluorophores, i.e., NAD͓P͔H and FAD. Second, the two-photon action cross section of ZnO-nano ͓ ZnO ͑TPEF͒ ϳ 0.26 GM; diameter, 18 nm͔ is high: ϳ500-fold of that inferred from its bulk third-order nonlinear susceptibility ͓Im ZnO ͑3͒ ͔, and is favorably compared to that of NAD͓P͔H and FAD. The overall outcome from MPM, SEM, and EDX studies was that, in humans in vivo, ZnO nanoparticles stayed in the stratum corneum ͑SC͒ and accumulated into skin folds and/or hair follicle roots of human skin. Given the lack of penetration of these nanoparticles past the SC and that the outermost layers of SC have a good turnover rate, these data suggest that the form of ZnO-nano studied here is unlikely to result in safety concerns.

show abstract

“…7 Nanopartículas de ZnO recentemente têm recebido grande atenção devido a uma variedade de aplicações tais como, absorção no UV, desodorização e tratamento antibacteriano. 8,9 O semicondutor ZnO tem um bandgap de 3,37 eV em temperatura ambiente e é um dos mais importantes materiais inorgânicos, com propriedades catalítica, 10,11 elétrica, 12,13 opticoeletrônica, 14,15 e fotoquímica, 16 o que tem estimulado cada vez mais a ampla investigação em sua aplicabilidade. O uso do ZnO como material fotocatalisador para a degradação de poluentes ambientais tem sido vantajoso em relação a outros materiais devido à sua natureza não-tóxica, seu baixo custo e alta reatividade, 17,18 como também ocorre para o dióxido de titânio.…”

Section: Introductionunclassified

Nanocompósitos semicondutores ZnO/TiO2: testes fotocatalíticos

Silva¹,

Magalhães²,

Sansiviero³

2010

Quím. Nova

View full text Add to dashboard Cite

Recebido em 8/1/09; aceito em 15/6/09; publicado na web em 25/11/09 ZnO/TiO 2 SEMICONDUCTOR NANOCOMPOSITES. PHOTOCATALYTIC TESTS. Titanium dioxide is an efficient photocatalist, being possible to improve its efficiency with better charge separation which occurs when it is coupled with other semiconductors. Nanometric particles of ZnO were used to impregnate TiO 2 P25 in order to optimize its photocatalytic properties. ZnO/TiO 2 composites were obtained at different proportions and were characterized by X-ray diffraction (XRD), micro-Raman and diffuse reflectance spectroscopies, measurement of surface area (BET) and scanning electron microscopy (SEM). Raman spectroscopy data revealed a change on the TiO 2 surface due the presence of ZnO which was observed by an enlargement of TiO 2 peaks and a change on the relation rate between anatase and rutile phases of the composites. The photodegradation of azo-dye Drimaren red revealed better efficiency for ZnO/TiO 2 3% nanocomposite and for ZnO pure.Keywords: semiconductor nanocomposites; photocatalysis, Raman spectroscopy. INTRODUÇÃOO dióxido de titânio é um semicondutor (E gap = 3,2 eV) que se encontra principalmente na forma de três estruturas cristalinas, anatásio, rutilo e brokita. A forma anatásio é aquela que apresenta maior atividade fotocatalítica, 1,2 sendo grandemente usado como fotocatalisador devido à sua alta eficiência e baixo custo. Algumas aplicações de grande relevância envolvendo o semicondutor TiO 2 são: fotocatálises assistidas por semicondutor para produzir combustíveis, tais como hidrogênio e, células solares baseadas em nanoestruturas de semicondutor. 3 O princípio de funcionamento do TiO 2 como fotocatalisador baseia-se na geração do par elétron-lacuna positiva, através da absorção de energia. 4 A luz UV é a fonte de energia mais comumente empregada. Sob irradiação, elétrons da banda de valência recebem energia suficiente para transpor a lacuna de energia do TiO 2 e podem, desta forma, serem transferidos para a banda de condução. As lacunas positivas são fortes agentes oxidantes e são responsáveis pela mineralização de vários compostos orgânicos. 5 Nos últimos 30 anos, vários estudos têm sido realizados para investigar as possíveis aplicações do TiO 2 como fotocatalisador. A maior parte desses estudos está concentrada no tratamento de sistemas aquosos contaminados por poluentes orgânicos considerados potencialmente tóxicos. 6 Materiais semicondutores nanoparticulados têm algumas propriedades peculiares e a elucidação destas propriedades tem levado à descoberta de diferentes campos da ciência e da tecnologia. 7 Nanopartículas de ZnO recentemente têm recebido grande atenção devido a uma variedade de aplicações tais como, absorção no UV, desodorização e tratamento antibacteriano. 8,9 O semicondutor ZnO tem um bandgap de 3,37 eV em temperatura ambiente e é um dos mais importantes materiais inorgânicos, com propriedades catalítica, 10,11 elétrica, 12,13 opticoeletrônica, 14,15 e fotoquímica, 16 o que tem estimulado cada vez mais a ampla investigação em...

show abstract

Photochemistry at high temperatures - potential of ZnO as a high temperature photocatalyst

Cited by 23 publications

References 2 publications

RETRACTED: Solar photothermochemical alkane reverse combustion

RETRACTED: Solar photothermochemical alkane reverse combustion

Imaging of zinc oxide nanoparticle penetration in human skin in vitro and in vivo

Nanocompósitos semicondutores ZnO/TiO2: testes fotocatalíticos

Contact Info

Product

Resources

About