Carbon Supported Oxide-Rich Pd-Cu Bimetallic Electrocatalysts for Ethanol Electrooxidation in Alkaline Media Enhanced by Cu/CuO x

摘要

Different proportions of oxide-rich PdCu/C nanoparticle catalysts were prepared by the NaBH 4 reduction method, and their compositions were tuned by the molar ratios of the metal precursors. Among them, oxide-rich Pd 0.9 Cu 0.1 /C (Pd:Cu = 9:1, metal atomic ratio) exhibits the highest electrocatalytic activity for ethanol oxidation reaction (EOR) in alkaline media. X-ray photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM) confirmed the existence of both Cu and CuO x in the as-prepared Pd 0.9 Cu 0.1 /C. About 74% of the Cu atoms are in their oxide form (CuO or Cu 2 O). Besides the synergistic effect of Cu, CuO x existed in the Pd-Cu bimetallic nanoparticles works as a promoter for the EOR. The decreased Pd 3d electron density disclosed by XPS is ascribed to the formation of CuO x and the spill-over of oxygen-containing species from CuO x to Pd. The low Pd 3d electron density will decrease the adsorption of CH 3 CO ads intermediates. As a result, the electrocatalytic activity is enhanced. The onset potential of oxide-rich Pd 0.9 Cu 0.1 /C is negative shifted 150 mV compared to Pd/C. The oxide-rich Pd 0.9 Cu 0.1 /C also exhibited high stability, which indicated that it is a candidate for the anode of direct ethanol fuel cells (DEFCs).