Plasmonic Ag@SiO 2 core/shell structure modified g-C 3 N 4 with enhanced visible light photocatalytic activity
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gh rate of charge carrier recombination is a critical factor limiting the photocatalytic activity of g-C3N4. In this contribution, we demonstrate that this issue can be alleviated by constructing a plasmonic photocatalyst with tailored plasmonic-metal nanostructures, i.e., core–shell-typed Ag@SiO2 nanoparticles. Compared with pure g-C3N4, the photocatalytic hydrogen production activity was enhanced by 63% for Ag@SiO2/g-C3N4. As analysis from the photoluminescence results, the enhancement could be attributed to that plasmonic nanostructures favored the separation of electron–hole pairs in the semiconductor due to localized surface plasmons resonance effect. It was found that the silica shell between the Ag nanoparticles and g-C3N4 was essential for the better photocatalytic activity of Ag@SiO2/g-C3N4 than that of Ag/g-C3N4 by limiting the energy-loss Förster energy transfer process.
I. INTRODUCTION
Global energy crisis and environmental pollution are two challenges the world faces. By far, constructing solar– hydrogen energy systems with semiconductor photocatalysts has been proved a promising technology among the solution options.1,2 To date, many kinds of semiconductors have been explored for photocatalytic hydrogen production. They are mainly inorganic semiconductors, such as oxides,3,4 (oxy)sulfides,5 and (oxy)nitrides.6 However, materials with efficient activity and adequate stability for water splitting under visible light irradiation are still unavailable, and their development remains a significant challenge. In recent years, a novel metal-free polymer semiconductor, graphitic carbon nitride (g-C3N4) with band gap of about 2.7 eV, has showed promising performance for hydrogen production under visible light irradiation.7 However, the photocatalytic efficiency of pure g-C3N4 was relatively low mainly due to the fast recombination of photogenerated electron–hole pairs.8 To solve this problem, one strategy is to form heterojunction with matched band structure of the two components (type II band alignment) to separate the photo charge carriers.9–18 Another strategy is to load noble metals19,20 such as Au, Pt on g-C3N4 to trap and store the photogenerated electrons. Since the representative demonstration of plasmonic photocatalysis with plasmonic nanostructures of noble metals (mainly silver and gold),21–23 it has been widely investigated in the field of photocatalytic water splitting. Address all correspondence to these authors. a) e-mail: [email protected] b) e-mail: [email protected] DOI: 10.1557/jmr.2013.200 64
J. Mater. Res., Vol. 29, No. 1, Jan 14, 2014
http://journals.cambridge.org
Downloaded: 12 Jun 2014
Awazu et al.24 embedded silver nanoparticles (Ag NPs) in TiO2, achieving enhanced photocatalytic activity that is confirmed exclusively due to the localized surface plasmon resonance (LSPR) induced electric field amplitude on the surface of Ag NPs. The electric field would consequently induce the plasmon resonance energy transfer (PRET) process, shortening the carriers transfer distance to the
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