Ni–Co oxides nanowire arrays grown on ordered TiO2 nanotubes with high performance in supercapacitors

Abstract

We develop a facile hydrothermal synthesis method to fabricate mesoporous Ni–Co oxides nanowire arrays on ordered TiO₂ nanotubes (Ni–Co oxides NWs@TiO₂NTs) as a high-capacity pseudocapacitor material. The composite electrode presented the highest specific capacitance of 2353 F g⁻¹ at a charge and discharge current density of 2.5 A g⁻¹ with excellent cycling ability, retaining 95% of the maximum capacitance after 3000 cycles. Even at a high current density of 50 A g⁻¹, the electrode exhibited a specific capacitance of up to 2173 F g⁻¹. In addition, the testing of a (Ni–Co oxides NWs@TiO₂NTs)//(Ni–Co oxides NWs@TiO₂NTs) symmetric cell yielded a specific capacitance of up to 144 F g⁻¹ at a current density of 4 A g⁻¹. The much improved capacity and cycling stability may be attributed to the superior conductivity and the aligned structure of the Ni–Co oxides NWs and the TiO₂NTs substrate, which can improve electron/ion transport and enhance the kinetics of the redox reactions.