Controllable synthesis of palladium nanoparticles via a simple sonoelectrochemical method
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Jian-Ming Zhu National Laboratory of Solid State Microstructures, Nanjing University, Nanjing, 210093, People’s Republic of China
Jun-Jie Zhu,a) Shu Xu, and Hong-Yuan Chen Laboratory of Mesoscopie Materials Science, Department of Chemistry, Nanjing University, Nanjing 210093, People’s Republic of China (Received 8 January 2003; accepted 17 February 2003)
A simple pulse sonoelectrochemical technique was used to synthesize highly dispersed spherical palladium particles and a dendritic Pd superstructure in the presence of cethyltrimethylammonium bromide (CTAB) at room temperature. The shape and size of spherical nanocrystalline Pd can be controlled by varying current density, the interval between two continuous ultrasonic pulses, ultrasonic intensity, and the concentration of CTAB. The possible growth mechanism of dendritic-structured Pd is discussed.
I. INTRODUCTION
In recent years nanometer-scale noble metals have received considerable interests in various scientific disciplines due to their remarkable catalytic, electronic, magnetic, optical, and mechanical properties, which differ from the bulk materials.1 The specific catalytic properties of nano-sized metal clusters are usually associated with a change in their electron properties relative to the bulk samples. This change is requisitioned by the quantum-size effect and is usually prevailing with a great enhancement in catalytic activity.2,3 Hence, the preparation methods of noble metal nanoparticles have been widely investigated, and various synthetic approaches including the reduction method,4 metal vaporization,5 the sol-gel process,6 the laser ablation method,7 and sonochemical methods8 have been reported. However, the procedures for size- and shape-controlled preparation of monodispersed nanoparticles are limited.9 Sonochemistry has been in use for a while.10 The effect of ultrasonic radiation on chemical reaction is due to cavitation, whereby very high temperatures and pressures are transiently formed (submicrosecond) in collapsing bubbles.11 Recently, the potential benefits of combining sonochemistry with electrochemistry became increasingly studied. Some of these beneficial effects
a)
Address all correspondence to this author. e-mail: [email protected] J. Mater. Res., Vol. 18, No. 6, Jun 2003
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include acceleration of mass transport, cleaning and degassing of the electrode surface, and increased reaction rates.12 Sonoelectrochemical formation of nanoscale metal and semiconductor powder was accomplished by applying an electric current pulse to nucleate the electrodeposit, followed by a burst of untransonic energy that removes the particles from the sonic probe cathode.13–16 In this report, we describe a sonoelectrochemical route to prepare highly dispersed palladium nanoparticles with different shapes including various sized spherules and dendritic crystals. The experiment is based on electroreduction of PdCl2 in the presence of cethyltrimethylammonium bromide (CTAB). Experimental conditions that in
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