Journal
JOURNAL OF CHROMATOGRAPHY A
Volume 1218, Issue 27, Pages 4179-4187Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.chroma.2010.11.061
Keywords
WO3; Colloids; Photocatalytic films; Electrochemical characterization; Field flow fractionation
Funding
- University of Ferrara (Fondo di Ateneo per la Ricerca Scientifica FAR)
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WO3 colloidal suspensions obtained through a simple sol-gel procedure were subjected to a controlled temperature aging process whose time evolution in terms of particle mass and size distribution was followed by sedimentation field flow fractionation (SdFFF) and flow field flow fractionation (FIFFF). The experiments performed at a temperature of 60 degrees C showed that in a few hours the initially transparent sol of WO3 particles, whose size was less than 25 nm, undergoes a progressive size increase allowing nanoparticles to reach a maximum equivalent spherical size of about 130 nm after 5 h. The observed shift in particle size distribution maxima (SdFFF), the broadening of the curves (FIFFF) and the SEM-TEM observations suggest a mixed mechanism of growth-aggregation of initial nanocrystals to form larger particles. The photoelectrochemical properties of thin WO3 films obtained from the aged suspensions at regular intervals, were tested in a biased photoelectrocatalytic cell with 1 M H2SO4 under solar simulated irradiation. The current-voltage polarization curves recorded in the potential range 0-1.8 V (vs. SCE) showed a diminution of the maximum photocurrent from 3.7 mA cm(-2) to 2.8 mA cm(-2) with aging times of 1 h and 5 h, respectively. This loss of performance was mainly attributed to the reduction of the electroactive surface area of the sintered particles as suggested by the satisfactory linear correlation between the integrated photocurrent and the cyclic voltammetry cathodic wave area of the W(VI)-> W(V) process measured in the dark.(C) 2010 Elsevier B.V. All rights reserved.
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