Facile synthesis of Pd/PDDA-GN/PMo11Co composite and its enhanced catalytic performance for formic acid oxidation

Abstract

A novel Pd-based catalyst, Pd/poly(diallyldimethylammonium chloride) functionalized graphene (PDDA-GN)/transition-metal-substituted polyoxometalate H₇PMo₁₁CoO₄₀·xH₂O (PMo₁₁Co), for direct formic acid fuel cells (DFAFC) has been prepared by a layer by layer (LBL) electrostatic assembly method combined with electro-deposition of Pd particles in situ. The morphology, particle size and composition of the as-prepared Pd/PDDA-GN/PMo₁₁Co composite were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive spectroscopy (EDS). The results reveal that Pd particles are uniformly deposited on the surface of PDDA-GN/PMo₁₁Co. Electrochemical analysis shows that the Pd/PDDA-GN/PMo₁₁Co composite exhibits higher electrocatalytic activity, better electrochemical stability, and higher resistance to CO poisoning than the Pd/PDDA-GN/PMo₁₂ and Pd/C catalysts for the formic acid oxidation reaction (FAOR). The current density of the anodic peak at the Pd/PDDA-GN/PMo₁₂ modified electrode in the formic acid oxidation process is up to 639.3 mA mg⁻¹, which is 4.2 times that of the Pd/C and 1.2 times that of the Pd/PDDA-GN/PMo₁₂. The experimental investigations indicate that PDDA-GN as a support preserves superior electric conductivity of graphene sheets of the composite, and the introduction of electroactive PMo₁₁Co into the composite contributes to convert intermediate species CO into CO₂. The synergistic effects of PDDA-GN and PMo₁₁Co remarkably enhance the electrocatalytic activity and stability of nano-Pd regarding formic acid oxidation.