Te-induced fabrication of Pt3PdTe0.2 alloy nanocages by the self-diffusion of Pd atoms with unique MOR electrocatalytic performance

Abstract

The key to the application of direct methanol fuel cells is to improve the activity and durability of Pt-based catalysts. Based on the upshift of the d-band centre and exposure to more Pt active sites, Pt₃PdTe_0.2 catalysts with significantly enhanced electrocatalytic performance for the methanol oxidation reaction (MOR) were designed in this study. A series of different Pt₃PdTe_x (x = 0.2, 0.35, and 0.4) alloy nanocages with hollow and hierarchical structures were synthesized using cubic Pd nanoparticles as sacrificial templates and PtCl₆^2- and TeO₃^2- metal precursors as oxidative etching agents. The Pd nanocubes were oxidized into an ionic complex, which was further co-reduced with Pt and Te precursors by reducing agents to form the hollow Pt₃PdTe_x alloy nanocages with a face-centred cubic lattice. The sizes of the nanocages were around 30-40 nm, which were larger than the Pd templates (18 nm) and the thicknesses of the walls were 7-9 nm. The Pt₃PdTe_0.2 alloy nanocages exhibited the highest catalytic activities and stabilities toward the MOR after electrochemical activation in sulfuric acid solution. CO-stripping tests suggested the enhanced CO-tolerant ability due to the doping of Te. The specific activity of Pt₃PdTe_0.2 for the MOR reached 2.71 mA cm^-2 in acidic conditions, which was higher than those of Pd@Pt core-shell and PtPd_1.5 alloy nanoparticles and commercial Pt/C. A DMFC with Pt₃PdTe_0.2 as the anodic catalyst output a higher power density by 2.6 times than that of commercial Pt/C, demonstrating its practicable application in clean energy conversions. Density functional theory (DFT) confirmed that the alloyed Te atoms altered the electron distributions of Pt₃PdTe_0.2, which could lower the Gibbs free energy of the rate-determining methanol dehydrogenation step and greatly improve the MOR catalytic activity and durability.