Enhanced methanol electro-oxidation activity of Pt/MWCNTs electro-catalyst using manganese oxide deposited on MWCNTs

• Promoting effects of manganese oxide (MnOx) on methanol electro-oxidation over Pt/MWCNTs are studied.
• 3.3 times higher activity and improved stability are observed on Pt/MnOx-MWCNTs in MOR.
• Both hydrogen spill over and bi-functional mechanism are facilitated in presence of MnOx.
• MnOx significantly enhances electrochemical active surface area and dispersion of Pt nanoparticles.
• Proton conductivity of electrocatalyst layer is improved upon MnOx incorporation.

Electro-oxidation of methanol on platinum nanoparticles supported on a nanocomposite of manganese oxide (MnOx) and multi-wall carbon nanotubes (MWCNTs) is investigated. The morphology, structure, and chemical composition of the electro-catalysts are characterized by TEM, XRD, EDS, TGA, and H2-TPR. The electro-catalytic properties of electrodes are examined by cyclic voltammetry, CO-stripping, electrochemical impedance spectroscopy (EIS), and linear sweep voltammetry (LSV). Compared to Pt/MWCNTs, the Pt/MnOx-MWCNTs electro-catalyst exhibits about 3.3 times higher forward peak current density, during cyclic voltammetry, and 4.6 times higher exchange current density in methanol electro-oxidation reaction. In addition, deposition of manganese oxide onto MWCNTs dramatically increases the electrochemical active surface area from 29.7 for Pt/MWCNTs to 89.4 m2 g−1Pt for Pt/MnOx-MWCNTs. The results of long-term cyclic voltammetry show superior stability of Pt nanoparticles upon addition of manganese oxide to the support. Furthermore, the kinetics of formation of the chemisorbed OH groups improves upon manganese oxide incorporation. This leads to a lower onset potential of COads oxidation on Pt/MnOx-MWCNTs than on Pt/MWCNTs.