CuPt/CNT catalysts for oxygen reduction prepared by a facile two-step synthesis : chemical vs. electrochemical leaching

Abstract

Cu@Pt/CNT electrocatalysts were prepared by a facile two-step impregnation process. Pt nanoparticles supported on CNTs were prepared by microwave-assisted polyol reduction followed by impregnation with a copper precursor. The final catalysts were obtained by thermal alloying at different temperatures; namely 600, 800, 1000 °C. The alloying extent between Pt and Cu was found to increase significantly with the alloying temperature as revealed from XRD analysis, as does the particle size obtained from TEM. Electrochemical dealloying was performed with the three different Cu@Pt/CNT catalysts, aiming to form a core shell structure. The formation of a Pt enriched surface upon dealloying was confirmed electrochemically by cyclic voltammtery and CO stripping. The electrocatalytic activity for oxygen reduction of the electrochemically dealloyed catalysts depends on the alloying temperature where the catalyst alloyed at 800 °C showed the highest surface specific activity, which is explained in view of the high Cu content in the alloy core compared to the sample alloyed at 600 °C. Alloying at 1000 °C and chemical/electrochemical leaching leads to porous structures with high activity, albeit lower than that of the 800 °C sample. Notably these porous particles provide high activity also with a low copper content in the core. In general, the dealloyed Cu@Pt/CNT catalysts showed higher catalytic activity both in terms of surface specific activity (SSA) and mass specific activity (MSA) than their Pt/CNT counterpart.