Photocatalytic Deposition of Nickel Nanoparticles on Titanium Dioxide
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Photocatalytic Deposition of Nickel Nanoparticles on Titanium Dioxide
Julia L. Rodríguez (1,2), Francisco Pola(3), Miguel A. Valenzuela(1) and Tatiana Poznyak(2) 1 Lab. Catálisis y Materiales, ESIQIE – Instituto Politécnico Nacional. Zacatenco, 07738 México, D.F. México. Emails: [email protected], [email protected] 2 Lab. Ing. Química Ambiental, ESIQIE – Instituto Politécnico Nacional, Zacatenco, 07738 México, D.F. México. 3 Centro de Investigación en Materiales Avanzados, Miguel de Cervantes 120, 31109, Chihuahua, Chih., México
ABSTRACT Metallic nanoparticles may be tailored to obtain specific size and morphology. In this work we present the synthesis of Ni/TiO2 catalysts by a photodeposition method. Our investigation included the photochemical and photocatalytic reduction of the nickel organometallic precursor (Ni (II) acetylacetonate) over titania (Degussa P-25) support. The photo-reduction kinetics was followed by UV-Vis and the catalysts were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). According to the results, the photochemical reduction of the Ni precursor was only 30% at λ= 254 nm, whereas, the photocatalytic route was approximately 90 % (λ= 365 nm) yielding Ni nanoparticles with diameter ranging from 10 to 40 nm.
INTRODUCTION Nowadays, nanoparticle research is an area of intense scientific study due to a wide range of potential applications in the field of medicine, electronics, cosmetics, catalysis and among others. During the last two decades, several synthetic methods such as chemical, thermal, photochemical and radiation have been used in the preparation of metallic or metal oxide nanoparticles [1-5]. In particular, the photochemical synthesis has attracted much attention due to its high versatility, simplicity and space-selective fabrication [6,7]. The photochemical method proceeds by the direct photoreduction of a metal source (metal salt or organometallic complex). There are three alternative approaches for the photochemical synthesis: direct photoreduction, photosensitized reduction and photocatalytic deposition. By the last route, the photoirradiation is carried out for solutions containing metal ions, semiconductor support and hole scavenger. After irradiation, the semiconductor produces positive holes and electrons which are used for reduction of metal ions and oxidation of the scavenger compound, respectively. TiO2 is a most useful material for photocatalytic purposes owing to its exceptional optical and electronic properties, chemical stability, non-toxicity and low cost. The photocatalytic deposition has been used in the preparation of Au, Ag, Cu, Pt, Pd supported on TiO2 showing a high efficiency by suppressing the electron-hole recombination process [8-10]. To date, investigations devoted to the photocatalytic deposition of Ni nanoparticles on semiconductors are scarce [11,12]. In the present research, an experimental procedure was developed to obtain Ni nanoparticles deposited on TiO2, via the use of Ni (II) acetylacetonate in alcoholic solution.
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