Dopamine-Assisted Hydrothermal Synthesis of Porous Co ₃ O ₄ Spherical Nanostructures for High-Performance Supercapacitor Applications

Porous cobalt oxide (Co 3 O 4 ) nanostructures were synthesized using a dopamine-assisted hydrothermal method followed by calcination to improve their electrochemical performance for supercapacitors. In this process, dopamine served as both a chelating and structure-directing agent, guiding the nucleation and growth of cobalt precursors into uniform, porous, sphere-like structures. The optimized D 2.0 –Co 3 O 4 sample, consisting of interconnected nanoparticles, showed a large surface area of 90.25 m 2 g –1 and open-pore channels, facilitating efficient ion diffusion and charge transport. Calcination at 400 °C finished the phase transition of cobalt hydroxide intermediates into crystalline Co 3 O 4 . Comparative studies with D 1.0 –Co 3 O 4 and dopamine-free Co 3 O 4 revealed that the dopamine concentration significantly affects the structural and electrochemical properties of the final material. The D 2.0 –Co 3 O 4 electrode exhibited exceptional pseudocapacitive behavior, achieving a high specific capacitance of 930.2 F g –1 at 1 A g –1, a 99% rate capability, and outstanding cycling stability, retaining 96% of its capacitance after 3800 cycles. The improved performance results from the optimized porosity and surface features of D 2.0 –Co 3 O 4 . Therefore, the dopamine-assisted synthesis offers an effective approach for designing structurally controlled transition metal oxides for high-performance energy storage devices.