Abstract
Different proportions of oxide-rich PdCu/C nanoparticle catalysts were prepared by the NaBH4 reduction method, and their compositions were tuned by the molar ratios of the metal precursors. Among them, oxide-rich Pd0.9Cu0.1/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 CuOx in the as-prepared Pd0.9Cu0.1/C. About 74% of the Cu atoms are in their oxide form (CuO or Cu2O). Besides the synergistic effect of Cu, CuOx 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 CuOx and the spill-over of oxygen-containing species from CuOx to Pd. The low Pd 3d electron density will decrease the adsorption of CH3COads intermediates. As a result, the electrocatalytic activity is enhanced. The onset potential of oxide-rich Pd0.9Cu0.1/C is negative shifted 150 mV compared to Pd/C. The oxide-rich Pd0.9Cu0.1/C also exhibited high stability, which indicated that it is a candidate for the anode of direct ethanol fuel cells (DEFCs).
Highlights
Fuel cell is a device of translating the chemical energy into electrical energy [1]
Pt-based catalysts are most widely used for ethanol oxidation reaction (EOR) in acidic media, e.g., Pt [8,9], Pt-Rh [10], Pt-Ir [11], and so on
A question appears: Can the combination of the second metal and its coexisted oxides improve the electrocatalytic performance in EOR better? We examined the related references, and noticed an interesting example about Pd-Ni system
Summary
Fuel cell is a device of translating the chemical energy into electrical energy [1]. Hydrogen fueled proton exchange membrane fuel cells have attracted widespread attention, owing to their high energy conversion efficiency and low or zero emissions [2]. Pt-based catalysts are most widely used for ethanol oxidation reaction (EOR) in acidic media, e.g., Pt [8,9], Pt-Rh [10], Pt-Ir [11], and so on. Oxides affect the electrocatalytic performance of Pd-based electrocatalysts for EOR Transition metal oxides such as Co3 O4 , SnO2 , CeO2 and NiO [18,32] have been used as promoters to improve the electrocatalytic performance. The energy efficient role of Ni/NiO in Pd-Ni catalysts has not been discussed until the report published in 2014 [32] This enlightened us to focus on the new oxide-rich Pd-M systems (M: second metal) and the role of M/MOx. Recently, Pd-Cu system has been discovered by former studies to have optimal electroactivity [34,35,36,37,38].
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