title: Sub-3 nm Co3O4 nanofilms with enhanced supercapacitor properties.
abstract: Two-dimensional materials often show a range of intriguing electronic, catalytic, and optical properties that differ greatly from conventional nanoparticles. Herein, we demonstrate the large-scale preparation of sub-3 nm atomic layers Co3O4 nanofilms with a nonsurfactant and substrate-free hydrothermal method. This successful preparation of ultrathin nanofilms highlighted the reconstruction of cobalt-ammonia complexes and synergistic effect of free ammonia and nitrate on film growth control. Subsequent performance tests uncovered that these sub-3 nm atomic layer Co3O4 nanofilms exhibited an ultrahigh specific capacitance of 1400 F/g in the first galvanostatic charge/discharge test. The specific capacitance of Co3O4 nanofilms only slightly decayed less than 3% after 1500 cycling tests. With some parameter adjustments, similar Co(OH)2 nanofilms with a thickness of 3.70 ± 0.10 nm were also prepared. The Co(OH)2 nanofilms possessed maximum specific capacitance of 1076 F/g and peak performance attenuation of about 2% after a cycle stability test.
authors.affiliation: State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University , Shanghai 200240, People's Republic of China.
authors.forename: Chao
authors.initials: C
authors.lastname: Feng
authors.forename: Jinfeng
authors.initials: J
authors.lastname: Zhang
authors.forename: Yu
authors.initials: Y
authors.lastname: He
authors.forename: Cheng
authors.initials: C
authors.lastname: Zhong
authors.forename: Wenbin
authors.initials: W
authors.lastname: Hu
authors.forename: Lei
authors.initials: L
authors.lastname: Liu
authors.forename: Yida
authors.initials: Y
authors.lastname: Deng
keywords: Co3O4 nanofilms; atomic layers; cobalt−ammonia complexes; hydrothermal; supercapacitor