Cobalt oxide (Co₃O₄) was homogeneously coated on multiwalled carbon nanotube through a simple chemical deposition method and employed in supercapacitor electrodes. SEM image indicated the uniform distribution of Co₃O₄ nanoparticles on the surface of the multiwalled carbon nanotube. A maximum specific capacitance of 273 Fg⁻¹ was obtained at the charge–discharge current density of 0.5 Ag⁻¹. After 500 cycles of continuous charge–discharge process, about 88% of the initial capacity could be retained.

Carbon-based hole-transport-layer free perovskite solar cells (C-PSCs) have attracted much attention due to their low cost, simple preparation process and high stability.