Study of niobium and tantalum doped titania-supported Pt electrocatalysts for methanol oxidation and oxygen reduction reactions

Abstract

Niobium and tantalum doped TiO₂ nanoparticles were prepared as catalyst substrates by an improved sol–gel method. Catalysts consisting of 20 wt.% Pt supported on these substrates were synthesised and studied for the methanol oxidation reaction (MOR) and the oxygen reduction reaction (ORR). The catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Results indicated that the support materials had an average particle size of 26 nm and that the dopants were evenly distributed in the TiO₂. The catalysts were also investigated with a range of electrochemical analyses and benchmarked against pure TiO₂ nanoparticles and carbon-supported Pt catalysts with the same composition. The samples showed dramatically better stability than the carbon-supported Pt catalysts in an accelerated degradation test (ADT) under various experimental conditions. The MOR activities of these samples were also increased due to the presence of oxide material substrates, which provide active sites at lower potentials. Thus, the Nb and Ta doped TiO₂-supported Pt catalysts were found to be promising methanol oxidation catalysts in terms of their catalytic activity and stability.