Decoration carbon nanotubes with Pd and Ru nanocrystals via an inorganic reaction route in supercritical carbon dioxide–methanol solution

This work describes a method to decorate carbon nanotubes (CNTs) with metallic Pd and Ru nanocrystals via inorganic reactions in supercritical (SC) CO 2–methanol solutions. In this route, PdCl 2 or RuCl 3⋅3H 2O dissolved in SC CO 2–methanol solution acted as a metal precursor and CNTs functioned as a template to direct the deposition of produced nanoparticles. Methanol served as the reductant for the precursors as well as cosolvent to enhance the dissolution of precursors in SC CO 2. Dry products were readily obtained through in situ extraction with SC CO 2 after reactions. The products were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. It was demonstrated that the loading content and particle size of the nanoparticles deposited on CNTs could be tuned by changing the weight ratio of the precursor to CNTs. This simple and efficient approach may also be utilized to synthesize other high-purity materials using inorganic salt precursors in SC CO 2-based solution. The metal (Pd, Ru)-carbon nanotube (CNT) nanocomposites have been fabricated in supercritical CO 2–methanol solutions using PdCl 2 and RuCl 3⋅3H 2O as a precursor, respectively. The loading content and particle size of the nanoparticles deposited on CNTs could be readily tuned by changing the weight ratio of the precursor to CNTs. This simple and efficient approach may be extended to synthesize other metal–CNT composites, which opens up avenues for further exploration of the properties of CNT-based composites.