title: Chemical Strategies for Enhancing Activity and Charge Transfer in Ultrathin Pt Nanowires Immobilized onto Nanotube Supports for the Oxygen Reduction Reaction.
abstract: Multiwalled carbon nanotubes (MWNTs) represent a promising support medium for electrocatalysts, especially Pt nanoparticles (NPs). The advantages of using MWNTs include their large surface area, high conductivity, as well as long-term stability. Surface functionalization of MWNTs with various terminal groups, such as -COOH, -SH, and -NH2, allows for rational electronic tuning of catalyst-support interactions. However, several issues still need to be addressed for such systems. First, over the course of an electrochemical run, catalyst durability can decrease, due in part to metal NP dissolution, a process facilitated by the inherently high surface defect concentration within the support. Second, the covalent functionalization treatment of MWNTs adopted by most groups tends to lead to a loss of structural integrity of the nanotubes (NTs). To mitigate for all of these issues, we have utilized two different attachment approaches (i.e., covalent versus noncovalent) to functionalize the outer walls of pristine MWNTs and compared the catalytic performance of as-deposited ultrathin (<2 nm) 1D Pt nanowires with that of conventional Pt NPs toward the oxygen reduction reaction (ORR). Our results demonstrated that the electrochemical activity of Pt nanostructures immobilized onto functionalized carbon nanotube (CNT) supports could be dramatically improved by using ultrathin Pt nanowires (instead of NPs) with noncovalently (as opposed to covalently) functionalized CNT supports. Spectroscopic evidence corroborated the definitive presence of charge transfer between the metal catalysts and the underlying NT support, whose direction and magnitude are a direct function of (i) the terminal chemistry as well as (ii) the attachment methodology, both of which simultaneously impact upon the observed electrocatalytic performance. Specifically, the use of a noncovalent π-π stacking method coupled with a -COOH terminal moiety yielded the highest performance results, reported to date, for any similar system consisting of Pt (commercial NPs or otherwise) deposited onto carbon-based supports, a finding of broader interest toward the fabrication of high-performing electrocatalysts in general.
authors.affiliation: Department of Chemistry, State University of New York at Stony Brook , Stony Brook, New York 11794-3400, United States.
authors.forename: Luyao
authors.initials: L
authors.lastname: Li
authors.affiliation: Department of Chemistry, State University of New York at Stony Brook , Stony Brook, New York 11794-3400, United States.
authors.forename: Haiqing
authors.initials: H
authors.lastname: Liu
authors.affiliation: Department of Chemistry, State University of New York at Stony Brook , Stony Brook, New York 11794-3400, United States.
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
authors.affiliation: Department of Chemistry, State University of New York at Stony Brook , Stony Brook, New York 11794-3400, United States.
authors.forename: Shiyu
authors.initials: S
authors.lastname: Yue
authors.affiliation: Center for Functional Nanomaterials, Building 735, Brookhaven National Laboratory , Upton, New York 11973, United States.
authors.forename: Xiao
authors.initials: X
authors.lastname: Tong
authors.affiliation: School of Marine and Atmospheric Sciences, State University of New York at Stony Brook , Stony Brook, New York 11794-5000, United States.
authors.forename: Tatiana
authors.initials: T
authors.lastname: Zaliznyak
authors.affiliation: School of Marine and Atmospheric Sciences, State University of New York at Stony Brook , Stony Brook, New York 11794-5000, United States.
authors.forename: Gordon T
authors.initials: GT
authors.lastname: Taylor
authors.affiliation: Department of Chemistry, State University of New York at Stony Brook , Stony Brook, New York 11794-3400, United States.|Condensed Matter Physics and Materials Science Division, Brookhaven National Laboratory , Building 480, Upton, New York 11973, United States.
authors.forename: Stanislaus S
authors.identifier: http://orcid.org/0000-0001-7351-0739
authors.initials: SS
authors.lastname: Wong
keywords: Pt ultrathin nanowires; charge transfer; functionalized carbon nanotubes; noncovalent attachment; oxygen reduction reaction