Fabrication and Characterization of Multiwalled Carbon Nanotubes-Supported Pt∕SnO[sub x] Nanocomposites as Catalysts for Electro-oxidation of Methanol

Pt ∕ SnO x composite nanoparticles with controlled composition (nominal weight ratio of Pt : SnO 2 : MWCNTs = 1 : 1 : 9 ; 2.8 nm in average diam) were fabricated onto multiwalled carbon nanotubes (MWCNTs) by first assembling SnO 2 nanoparticles on MWCNTs with a simple method of hydrolysis-oxidation of SnCl 2 in water at room temperature, then loading Pt onto the obtained SnO 2 /MWCNTs with a colloidal method, and finally reducing in a hydrogen atmosphere at 150 ° C . The composition of the composite nanoparticles was characterized by X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopy.The microstructure was characterized by X-ray diffractometry and transmission electron microscopy. By cyclic voltammetry, we found that, compared with a reference sample of Pt/MWCNTs (nominal weight ratio of Pt : MWCNTs = 1 : 10 ; 1.6 nm in average diam), the Pt ∕ SnO x /MWCNTs nanocomposites showed approximately the same specific active surface area of Pt but twice the activity for electro-oxidation of methanol (EOM) at room temperature. Based on the finding that integrated charge quantity corresponding to OH ad adsorption on the Pt ∕ SnO x /MWCNTs is approximately twice that on the Pt/MWCNTs within the potential range from 0.6 to 0.9 V (vs Ag ∕ AgCl ), we propose that tin oxide promotes the EOM on Pt through providing extra adsorption sites for OH ad ∕ H 2 O ad or enhancing the affinity of Pt to OH ad ∕ H 2 O ad .