Supercapacitive performance of CoMoO4 with oxygen vacancy porous nanosheet

CoMoO4 with oxygen vacancy (CoMoO4-x) porous nanosheet is prepared by hydrothermal synthesis and hydrogenation reduction method. The CoMoO4-x porous nanosheet has a higher specific surface area together with a more diverse pore size distribution than CoMoO4 nanosheet. The density functional theory calculation result exhibits that CoMoO4-x has lower energy band gap (0.041 eV) than CoMoO4(1.683 eV). The electronic density of states plots reveals that CoMoO4-x has more electron state distribution at Fermi energy level than CoMoO4. CoMoO4-x porous sheet achieves higher specific capacitance (1989 g(-1)) than CoMoO4 (917 F g(-1)) at 2 mA cm(-2) . It also achieves superior capacitance retention rate (91.3%) than CoMoO4 (83.9%) with the current density increasing from 2 to 20 mA cm(-2). The introduction of oxygen vacancy can increase the carrier density, accelerate the electron transfer, promote the electrical conductivity, and accordingly strengthen the redox reactivity of CoMoO4-x. An asymmetric supercapacitor is also constructed by using CoMoO4-x as positive electrode and activated carbon as negative electrode. It achieves high energy density of 62.3 W h kg(-1) at a power density of 800 W kg(-1), together with a good cyclic life. Both experimental measurement and theorical calculation are applied to prove the promotive role of oxygen vacancy in supercapacitive performance of CoMoO4-x. (C) 2019 Elsevier Ltd. All rights reserved.