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 PtCl₆²⁻ and TeO₃²⁻ 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.