Abstract

WO3 and Cr-WO3 powders were prepared by sol-gel process, with Cr:W atomic concentration ranging from 2% to 8.8%. WCl6 was used as W precursor and reacted with methanol in presence of acetyacetone as stabilizer. The required amount of Cr 2-ethylhexanoate was then added to the resulting solution, which was subsequently dried. The resulting powder was heat-treated at temperatures ranging from 200 to 700 degrees C. With increasing the Cr concentration, the samples heat-treated at 500 degrees C contained an increasing amount of the additional phase Cr2WO6, as evidenced by X-ray diffraction and Transmission Electron Microscopy. The sensing tests toward ammonia gas, from 50 to 500 ppm showed that, up to 5% concentration, Cr addition lowered the best operating temperatures and/or enhanced the response with respect to pure WO3, then the response remarkably decayed. DFT modeling showed that Cr(III) incorporation was more favorable in interstitial position while Cr (VI) was more favored in substitutional configuration. In this case, highly acidic Cr sites are present, enhancing the adsorption of ammonia species and reactions not involving NO2 as by-product. Beyond 5% Cr concentration, Cr2WO6 formation extracts Cr from the WO3 structure, so decreasing the ammonia response. Moreover, the appearance of Cr2WO6 seems to deactivate the surface adsorption properties of the material.

Autore Pugliese

• Epifani Mauro Salvatore , Siciliano Pietro Aleardo

Tutti gli autori

• Epifani M.; Garcia-Castello N.; Prades J.D.; Cirera A.; Andreu T.; Arbiol J.; Siciliano P.; Morante J.R.

Titolo volume/Rivista

Sensors and actuators. B, Chemical

Anno di pubblicazione

2013

ISSN

0925-4005

ISBN

Non Disponibile

Numero di citazioni Wos

Nessuna citazione

Ultimo Aggiornamento Citazioni

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Numero di citazioni Scopus

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Ultimo Aggiornamento Citazioni

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Settori ERC

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Codici ASJC

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