Quantum capacitances of transition metal-oxides (CoO, CuO, NiO, and ZnO) doped graphene oxide nanosheet: Insight from DFT computation

Density functional theory (DFT) computation has been utilized to explore the effects of the transition metal oxides: CoO, CuO, NiO, and ZnO doping on the electronic properties, structural, and quantum capacitances of graphene oxide nanosheet. From the magnetic moment analysis CoO@GO was observed to have higher magnetic moment of 11.688 μ_B compared to the studied the transition metal oxide doped systems. Investigation into the electronic properties revealed that NiO@GO attained higher energy gap with value of 0.144 eV. It was observed that the GO O/C affects the bandgaps of the modelled systems. Perturbation theory analysis of fock matrix showed that CoO@GO and CuO@GO possessed higher second order stabilization energy with values 238.56 kcal/mol and 208.94 kcal/mol respectively. From the quantum capacitance studies, it was observed that the value of C_Q for graphene oxide (GO) increased slightly from 72.276 µF/cm² to ZnO@GO (121.550 µF/cm²) > NiO@GO (93.870 µF/cm²) > CoO@GO (90.52 µF/cm²) > CuO@GO (89.375 µF/cm²). The results obtained herein can provide an effective and simple new idea for the design of graphene-based supercapacitors that possess high energy density.