ZrO 2 /g-C 3 N 4 with enhanced photocatalytic degradation of methylene blue under visible light irradiation
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The ZrO2 and graphitic carbon nitride (g-C3N4) composite photocatalyst has been prepared by calcination process and hydrothermal treatment. The photocatalyst was characterized by x-ray diffraction, scanning electron microscopy, x-ray photoelectron spectroscopy, UV–vis diffuse reflection spectroscopy, Brunauer–Emmett–Teller and photoluminescence spectra. The photocatalytic activity of the photocatalysts was evaluated by degradation of methylene blue under visible light irradiation. The results showed that the activity of the composite photocatalyst ZrO2/g-C3N4 for photodegradation of MB is much higher than that of either pure g-C3N4 or ZrO2, which is ascribed to the effective electron–hole separation based on the photoluminescence spectra. The dO2 might be the main active species in MB photodegradation, and the dOH and photogenerated electrons are also partly involved in the process of photocatalytic degradation.
I. INTRODUCTION
Nowadays, the photocatalytic purification and treatment of slops using nanostructured semiconductor under sunlight is an efficient technology for producing environmentally clean energy, in which one can use the sunlight as an energy source and it offers the possibility of accomplishing energy cycles without polluting the environment and additional heating of the earth.1,2 Nevertheless, most of the widely used photocatalysts have two main limitations in practical application: (1) the low solar energy conversion efficiency due to their wide band gap and (2) the high recombination ratio of photoinduced electron–hole pairs. Therefore, development of efficient visible light driven photocatalysts is still an intensifying endeavor worldwide.3,4 A metal-free semiconductor, graphitic carbon nitride (g-C3N4), has been proved a kind of efficient photocatalyst due to its characteristics of high thermal, chemical stability, versatile optical, electronic, tribological, and catalytic properties.5,6 However, g-C3N4 photocatalyst suffers from the disadvantages of low surface area, low quantum efficiency, and high recombination rate of the photoinduced electron–hole pair, which reduce its photocatalytic activities. Therefore, many attempts have been made to improve the photocatalytic performance of g-C3N4. For example, S-doped g-C3N4 displays much higher activity than g-C3N4 for water splitting.7 The g-C3N4/TaON shows stronger photocatalytic activity a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2014.276 J. Mater. Res., Vol. 29, No. 20, Oct 28, 2014
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than either single phase of g-C 3 N4 or TaON in rhodamine B photodegradation.8 Recently, the novel Bi2WO6/g-C3N4,9 graphene/g-C3N4,10 N-In2TiO5/g-C3N4,11 and GdVO4/g-C3N4 (Ref. 12) composite photocatalysts have been prepared and used for photodegradation of organic dyes. ZrO2-based composite materials are of considerable interest for many applications such as solid electrolytes,13 catalyst supports,14 and organic catalysts.15,16 Recently, ZrO2 composite materials as effe
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