Facile one-pot synthesis of Ni2+-doped (NH4)2V3O8 nanoflakes@Ni foam with visible-light-driven photovoltaic behavior for supercapacitor application

In the present work, Ni 2+ -doped (NH 4 ) 2 V 3 O 8 nanoflakes are in situ grown on Ni foam through a facile one-pot hydrothermal technique in a NH 4 VO 3 aqueous solution. The Ni 2+ -doped (NH 4 ) 2 V 3 O 8 @Ni foam composite material can be used as binder- and conductivity agent-free electrode in supercapacitor, it manifests a large specific capacitance of 465.5 F g −1 at a current density of 0.2 A g −1 and a superior rate capability of 317.5 F g −1 at 10 A g −1 , which is beneficial from its three-dimensional porous architecture cross-linked by the ultrathin Ni 2+ -doped (NH 4 ) 2 V 3 O 8 nanoflakes on Ni foam. Meanwhile, the Ni 2+ -doped (NH 4 ) 2 V 3 O 8 @Ni foam//Activated carbon asymmetric supercapacitor can deliver a maximum energy density of 20.1 W h kg −1 at a power density of 752.0 W kg −1 . Significantly, the Ni 2+ -doped (NH 4 ) 2 V 3 O 8 @Ni foam electrode possesses reversible electrochromic behavior, and it shows obvious visible light-driven photoresponse with much higher specific capacitance (645.3 F g −1 at 0.5 A g −1 ) under illumination (650 nm > λ > 350 nm, 100 mW cm −2 ), which is probably associated with the semiconducting characteristics of the spin-polarized (NH 4 ) 2 V 3 O 8 and the quantum confinement effect of the nanoflakes.