Novel cobalt doped hafnium oxide/reduced graphene oxide nanosphere composite materials exhibit superior supercapacitor performance and long cyclic stability

• Novel 6% Co doped HfO 2 /rGO nanocomposite were synthesized by a simple single step hydrothermal method. • The rGO in the middle of the nanosphere like 6% Co doped HfO 2 /rGO can remarkably improve the conductivity. • 6% Co doped HfO 2 /rGO (1015 F/g) nanocomposite showed higher electrochemical performance compared to 6% Co doped HfO 2 (396 F/g). • The synthesized electrode of 6% Co doped HfO 2 /rGO exhibits 97% capacitance retention after 4000 cycles of long-term cycling stability. This paper describes a unique synthesized nanosphere using 6% Cobalt doped hafnium oxide/reduced graphene oxide nanocomposite (6% Co doped HfO 2 /rGO) for its feasibility as electrode material in supercapacitor applications utilizing a simple one-step hydrothermal technique. The structural behavior, binding energies, and quality of the synthesized 6% Co doped HfO 2 /rGO nanocomposite were exhibited by XRD, FTIR, XPS, and Raman analyses. The 6% Co doped HfO 2 nanospheres in the 6% Co doped HfO 2 /rGO nanocomposite were coated across the exterior of the rGO sheet, according to HR-SEM and HR-TEM imaging. The 6% Co doped HfO 2 /rGO nanocomposite revealed enhanced specific capacitance (1015 F/g at 1A/g), which was compared to 6% Co doped HfO 2 (396 F/g at 1A/g) electrode in the redox active 1 M H 2 SO 4 electrolyte (0.0 to 0.7 V). After 4000 continuous cycles, the electrode material maintained 97 % of its capability and exceptional long-term cyclic stability. The superior super-capacitive performance established the 6% Co doped HfO 2 /rGO nanocomposite as a promising electrode for supercapacitor applications.