An Integrated Sonication Technique for Electrodeposition of Platinum and Ruthenium on Carbon Nanotubes for Methanol Oxidation

An electrodeposition technique that could significantly improve the deposition of platinum-ruthenium (Pt-Ru) nanoparticles onto carbon nanotubes (CNTs) directly grown on carbon cloths was adopted in this study. Integrated sonication (IS) was activated during the electrodeposition process conducted in a sulfuric acid (H₂SO₄) solution containing Pt and Ru precursor chemicals of hexachloroplatinic acid and ruthenium trichloride, respectively, and ethylene glycol (EG) as a dispersing agent. In comparison with our earlier work, this new technique would further reduce the size of Pt-Ru particles from 4-6 nm to 2-3 nm and lead to a more even and higher surface distribution of these nanoparticles on the CNTs. In addition, the loadings of Pt and Ru on the CNTs were both markedly increased. Electrochemical characteristics of methanol oxidation on specimens bearing these catalysts (Pt-Ru/CNTs) were investigated via cyclic voltammetry analysis in mixed 1 M methanol and 0.5 M sulfuric acid solutions. It was found that the peak current density of methanol oxidation obtained from the cyclic voltammogram on the new Pt-Ru/CNTs specimen was nearly three times of that on the specimen prepared with EG in the absence of IS. The outcome signified better catalyst morphology and distribution and a significantly improved methanol oxidation efficiency of the new specimen prepared in the mixed EG and H₂SO₄ solution by electrodeposition in the presence of IS.