LAUSR

Abstract Catalytic activity and stability in a formic acid electro-oxidation, chemical and structural properties of AuPd nanoparticles deposited (a polyol method) on ZrO2 decorated functionalised multiwall carbon nanotubes (f-MWCNTs) (a hydrothermal method) were investigated using a fuel cell test, scanning transmission electron microscopy (STEM), high resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Non-stoichiometric ZrOx nanoparticles of a cubic phase (C-phase) and average size of 5–10 nm (STEM, HR-TEM), 4.5–5.0 nm (XRD) are anchored by f-MWCNTs carboxylic group through Zr-O-C bonds. Decoration by AuPd nanoparticles leads to ternary Pd/AuPd/Au phase of 6.9 nm crystallite size (XRD) with metallic Pd, oxidised (PdO, PdO2) and Pd-O-Zr phases (XPS). Oxidation/reduction at 300 °C/200 °C leads to nanoparticles sintering, increasing/decreasing Pd surface coverage, oxides/oxygen groups content and ZrOx stoichiometry. Catalysts after oxidation (the largest nanoparticle size, Pd oxides content, ZrOx stoichiometry) showed the highest activity and stability. Activity of AuPd-ZrO2/f-MWCNTs catalysts is smaller than that of these catalysts without ZrO2, however, the stability is remarkably larger, i.e. AuPd-ZrO2/f-MWCNTs > Pd-ZrO2/f-MWCNTs > AuPd/f-MWCNTs > Pd/f-MWCNTs, what is attributed to electronic properties of AuPd and role of ZrOx and oxygen functional groups in COad desorption and oxidation to CO2 releasing catalyst active sites.