Assembling the PdCu/rGO catalysts for methanol oxidation reaction in alkaline media by tuning the electronic structure

Direct methanol fuel cells (DMFCs) have attracted extensive attention due to clean, efficient characteristics and portable applications. In this work, a series of Pd_xCu_y/reduced graphene oxide (rGO) catalysts are assembled and the catalytic performances are investigated for methanol oxidation reaction (MOR) in alkaline media. The intrinsic surface electronic structures of the Pd_xCu_y/rGO bimetallic catalysts are also studied to clarify the reaction mechanism. The results reveal that Pd_1.2Cu_0.2/rGO exhibits superior catalytic activity (1101.58 A g_Pd ⁻¹), 4.2 and 5.2 times higher than those of the commercial PtRu/C and Pd/C catalysts. CO stripping suggests that the onset potential for CO oxidation on the Pd_1.2Cu_0.2/rGO catalyst is lower than those on the commercial PtRu/C and Pd/C catalysts, implying that the anti-CO poisoning ability is enhanced. Combined with the analysis of X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and Raman, the enhanced catalytic activity and anti-CO poisoning ability are attributed to the charge transfer and lattice compression between Pd and Cu, which modify the d-band center and weaken the adsorption of CO. Furthermore, a volcano plot is found between the MOR activity and d-band center, indicating that the excellent MOR activity is attributed to the optimal d-band center with the moderate adsorption strength of CO-like intermediates.