title: Well-Ordered Oxygen-Deficient CoMoO4and Fe2O3Nanoplate Arrays on 3D Graphene Foam: Toward Flexible Asymmetric Supercapacitors with Enhanced Capacitive Properties.
abstract: In this work, we report the development of well-ordered hydrogenated CoMoO4(H-CoMoO4) and hydrogenated Fe2O3(H-Fe2O3) nanoplate arrays on 3D graphene foam (GF) and explore their practice application as binder-free electrodes in assembling flexible all-solid-state asymmetric supercapacitor (ASC) devices. Our results show that the monolithic 3D porous GF prepared by solution casting method using Ni foam template possesses large surface area, superior electrical conductivity, and sufficient surface functional groups, which not only facilitate in situ growth of CoMoO4and Fe2O3nanoplates but also contribute the double-layer capacitance of the resultant supercapacitor. The well-ordered pseudocapacitive metal oxide nanoplate arrays standing up on 3D GF scaffold can provide efficient space and shorten the length for electrolyte diffusion from the outer to the inner region of the electrode material for Faradaic energy storage. Furthermore, one of our major findings is that the introduction of oxygen vacancies in CoMoO4and Fe2O3nanoplates by hydrogenation treatment can increase their electronic conductivity as well as improve their donor density and surface properties, which gives rise to a substantially improved electrochemical performance. Benefiting from the synergistic contributions of different components in the nanohybrid electrode, the resultant flexible ASC device with GF/H-CoMoO4as the positive electrode and GF/H-Fe2O3as the negative electrode achieves a wide operation voltage of 1.5 V and a maximum volumetric specific capacitance of 3.6 F cm-3, which is two times larger than that of the Ni/GF/CoMoO4//Ni/GF/Fe2O3device (1.8 F cm-3), and the rate capability is up to 70% as the current density increases from 2 to 200 mA cm-3. Moreover, the Ni/GF/H-CoMoO4//Ni/GF/H-Fe2O3device also exhibits a high energy density of 1.13 mWh cm-3and a high power density of 150 mW cm-3, good mechanical flexibility with the decrease in capacitance of less than 4% after being bent inward to different angles and inward to 90° 200 times, and good cycling stability of 93.1% capacitance retention after 5000 cycles.
authors.affiliation: Key Laboratory of Material Chemistry for Energy Conversion and Storage, Ministry of Education, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology , Wuhan 430074, P. R. China.
authors.forename: Kai
authors.initials: K
authors.lastname: Chi
authors.affiliation: Key Laboratory of Material Chemistry for Energy Conversion and Storage, Ministry of Education, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology , Wuhan 430074, P. R. China.
authors.forename: Zheye
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Material Chemistry for Energy Conversion and Storage, Ministry of Education, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology , Wuhan 430074, P. R. China.
authors.forename: Qiying
authors.initials: Q
authors.lastname: Lv
authors.affiliation: Key Laboratory of Material Chemistry for Energy Conversion and Storage, Ministry of Education, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology , Wuhan 430074, P. R. China.
authors.forename: Chuyi
authors.initials: C
authors.lastname: Xie
authors.affiliation: Key Laboratory of Material Chemistry for Energy Conversion and Storage, Ministry of Education, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology , Wuhan 430074, P. R. China.
authors.forename: Jian
authors.initials: J
authors.lastname: Xiao
authors.affiliation: Key Laboratory of Material Chemistry for Energy Conversion and Storage, Ministry of Education, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology , Wuhan 430074, P. R. China.
authors.forename: Fei
authors.initials: F
authors.lastname: Xiao
authors.affiliation: Key Laboratory of Material Chemistry for Energy Conversion and Storage, Ministry of Education, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology , Wuhan 430074, P. R. China.|State Key Laboratory of Digital Manufacturing Equipment and Technology, Ministry of Education, Flexible Electronics Research Center (FERC), School of Mechanical Science and Engineering, Huazhong University of Science and Technology , Wuhan 430074, P. R. China.
authors.forename: Shuai
authors.identifier: http://orcid.org/0000-0001-9328-0408
authors.initials: S
authors.lastname: Wang
keywords: all-solid-state asymmetric supercapacitor; binder-free flexible electrode; hydrogenated transition-metal oxide; ordered nanoplate arrays; three-dimensional graphene foam