Dealloyed Pt_(2)Os nanoparticles for enhanced oxygen reduction reaction in acidic electrolytes
Yi-Juei Lee, Yu-Chi Hsieh, Ho-Cheng Tsai, I-Te Lu, Yue-Han Wu, Ted H. Yu, Jyh-Fu Lee, Boris V. Merinov, William A. Goddard III, Pu-Wei Wu
Abstract
Carbon-supported Pt2Os (Pt_(2)Os/C) nanoparticles in 3.55 nm sizes are synthesized from a wet chemical reflux process. Subsequently, the Pt_(2)Os/C undergoes a dealloying treatment in which multiple cyclic voltammetric scans are imposed to dissolve the Os atoms selectively from the surface of the Pt_(2)Os nanoparticles. X-ray diffraction signals from the dealloyed sample (DA–Pt_(2)Os/C) indicate a fcc phase and composition analysis suggests Pt4Os. Line scans from the scanning transmission electron microscope confirm that the surface of Pt_(4)Os is depleted with the Os atoms. This agrees with our quantum mechanics (Density Funtional theory) calculations, which predict for the Pt_(3)Os composition that the surface skin layer is pure Pt. The DA–Pt_(2)Os/C shows impressive electrocatalytic behaviors (0.29 mA μgPt^(−1) in mass activity and 1.03 mA cmPt^(−2) in specific activity) for the oxygen reduction reaction (ORR) in oxygen-saturated 0.1 M aqueous HClO_4 solution, as compared to those of commercially available Pt/C and as-synthesized Pt_(2)Os/C. In stability test, the DA–Pt_(2)Os/C demonstrates a better retention of ORR activities and a smaller loss of electrochemical active surface area. We verify experimentally that a four-electron step is responsible for the ORR process occurring on the DA–Pt_(2)Os/C.
Group Members
Lee, Y., Hsieh, Y., Tsai, H., Lu, I., Wu, Y., Yu, T. H., Lee, J., Merinov, B. V., III, W. A. G., & Wu, P. (2014). Dealloyed Pt_(2)Os nanoparticles for enhanced oxygen reduction reaction in acidic electrolytes. *Applied Catalysis B: Environment and Energy*, *150-151*, 636-646.