Design of a ZnMoO porous nanosheet with oxygen vacancies as a better performance electrode material for supercapacitors

A ZnMoO 4 porous nanosheet with oxygen vacancies (ZnMoO 4 -OV) was synthesized by hydrothermal synthesis and the hydrogenation reduction method. The ZnMoO 4 -OV porous nanosheet delivers a higher specific surface area together with a more diverse pore size distribution compared to the ZnMoO 4 nanosheet. The density functional theory calculation results exhibit that ZnMoO 4 -OV has lower energy band gap (3.019 eV) than ZnMoO 4 (1.92 eV). The electronic density of states plots reveal that ZnMoO 4 -OV possesses higher electron state distribution at the Fermi energy level than ZnMoO 4 . ZnMoO 4 -OV porous sheet achieves higher specific capacitance (1673 g −1 ) than ZnMoO 4 (797 F g −1 ) at 2 mA cm −2 . It also achieves superior capacitance retention rate (82.9%) to ZnMoO 4 (48.6%) with the current density increasing from 2 to 20 mA cm −2 . The introduction of oxygen vacancies can increase the carrier density, accelerate the electron transfer, promote the electrical conductivity, and accordingly strengthen the redox reactivity of ZnMoO 4 -OV. An asymmetric supercapacitor is also constructed by using ZnMoO 4 -OV as the positive electrode and activated carbon as the negative electrode. It achieves a high energy density of 60.1 W h kg −1 at a power density of 800 W kg −1 , together with a good cycle life. Both experimental measurements and theorical calculations are applied to prove the promotive role of oxygen vacancies to achieve the supercapacitive performance of ZnMoO 4 -OV. A ZnMoO 4 porous nanosheet with oxygen vacancies (ZnMoO 4 -OV) was synthesized which delivers a preferable energy storage performance.