title: Highly Efficient Silver-Cobalt Composite Nanotube Electrocatalysts for Favorable Oxygen Reduction Reaction.
abstract: This paper reports the synthesis and characterization of silver-cobalt (AgCo) bimetallic composite nanotubes. Cobalt oxide (Co3O4) nanotubes were fabricated by electrospinning and subsequent calcination in air and then reduced to cobalt (Co) metal nanotubes via further calcination under a H2/Ar atmosphere. As-prepared Co nanotubes were then employed as templates for the following galvanic replacement reaction (GRR) with silver (Ag) precursor (AgNO3), which produced AgCo composite nanotubes. Various AgCo nanotubes were readily synthesized with applying different reaction times for the reduction of Co3O4nanotubes and GRR. One hour reduction was sufficiently long to convert Co3O4to Co metal, and 3 h GRR was enough to deposit Ag layer on Co nanotubes. The tube morphology and copresence of Ag and Co in AgCo composite nanotubes were confirmed with SEM, HRTEM, XPS, and XRD analyses. Electroactivity of as-prepared AgCo composite nanotubes was characterized for ORR with rotating disk electrode (RDE) voltammetry. Among differently synthesized AgCo composite nanotubes, the one synthesized via 1 h reduction and 3 h GRR showed the best ORR activity (the most positive onset potential, greatest limiting current density, and highest number of electrons transferred). Furthermore, the ORR performance of the optimized AgCo composite nanotubes was superior compared to pure Co nanotubes, pure Ag nanowires, and bare platinum (Pt). High ethanol tolerance of AgCo composite nanotubes was also compared with the commercial Pt/C and then verified its excellent resistance to ethanol contamination.
authors.affiliation: Department of Chemistry and Nano Science, Ewha Womans University , Seoul 03760, Korea.
authors.forename: Areum
authors.initials: A
authors.lastname: Yu
authors.affiliation: Department of Chemistry and Nano Science, Ewha Womans University , Seoul 03760, Korea.
authors.forename: Chongmok
authors.initials: C
authors.lastname: Lee
authors.affiliation: National Institute for Nanomaterials Technology (NINT), Pohang University of Science and Technology (POSTECH) , Pohang 37673, Korea.
authors.forename: Nam-Suk
authors.initials: NS
authors.lastname: Lee
authors.affiliation: Department of Chemistry and Nano Science, Ewha Womans University , Seoul 03760, Korea.
authors.forename: Myung Hwa
authors.initials: MH
authors.lastname: Kim
authors.affiliation: Department of Chemistry and Nano Science, Ewha Womans University , Seoul 03760, Korea.
authors.forename: Youngmi
authors.initials: Y
authors.lastname: Lee
keywords: bimetallic nanotubes; cobalt; electrocatalyst; electrospinning; oxygen reduction reaction; silver