title: Ultrafine Co-based Nanoparticle@Mesoporous Carbon Nanospheres toward High-Performance Supercapacitors.
abstract: A general synthetic methodology is reported to grow ultrafine cobalt-based nanoparticles (NPs, 2-7 nm) within high-surface-area mesoporous carbon (MC) frameworks. Our design strategy is based on colloidal amphiphile (CAM) templated oxidative self-polymerization of dopamine. The CAM templates consisting of a hydrophobic silica-like core and a hydrophilic PEO shell can coassemble with dopamine and template its self-polymerization to form polydopamine (PDA) nanospheres. Given that PDA has rich binding sites such as catechol and amine to coordinate metal ions (e.g., Co2+), PDA nanospheres containing Co2+ions can be converted into hierarchical porous carbon frameworks containing ultrafine metallic Co NPs (Co@MC) using high-temperature pyrolysis. The CAM templates offer strong "nanoconfinements" to prevent the overgrowth of Co NPs within carbon frameworks. The yielded ultrafine Co NPs have an average size of <7 nm even at a very high loading of 65 wt %. Co@MC can be further converted into various oxides and sulfides, e.g., CoO, Co3O4, CoS2and transition-metal doped bimetallic CoxM1-xS2, without significantly changing the size of NPs. As a proof-of-concept application, the porous Co-based NPs@MC hybrids were used as electrode materials for supercapacitors, which exhibit excellent supercapacitive performance with outstanding long-term cycling stability, due to the features such as ultrafine size, controllable chemical compositions, hierarchical porous structures, and full coverage of conductive carbons.
authors.forename: Ben
authors.initials: B
authors.lastname: Liu
authors.forename: Lei
authors.initials: L
authors.lastname: Jin
authors.affiliation: School of Chemistry and Chemical Engineering, Shaanxi Normal University , Xi'an 710062, China.
authors.forename: Haoquan
authors.initials: H
authors.lastname: Zheng
authors.affiliation: Department of Chemistry, Ningxia Medical University , Yinchuan 750004, China.
authors.forename: Huiqin
authors.initials: H
authors.lastname: Yao
authors.forename: Yang
authors.initials: Y
authors.lastname: Wu
authors.forename: Aaron
authors.initials: A
authors.lastname: Lopes
authors.forename: Jie
authors.identifier: http://orcid.org/0000-0003-0252-3094
authors.initials: J
authors.lastname: He
keywords: cobalt nanoparticles; electrode materials; mesoporous carbon; supercapacitors; ultrafine nanoparticles