One-Pot Synthesis of Nanostructured Ni@Ni(OH)₂ and Co-Doped Ni@Ni(OH)₂ via Chemical Reduction Method for Supercapacitor Applications

Crystalline Ni@Ni(OH)₂ (cNNH) and Co-doped cNNH were obtained via a simple one-pot hydrothermal synthesis using a modified chemical reduction method. The effect of each reagent on the synthesis of the nanostructures was investigated concerning the presence or absence of each reagent. The detailed morphology shows that both nanostructures consist of a Ni core and Ni(OH)₂ shell layer (~5 nm). Co-doping influences the morphology and suppresses the particle agglomeration of cNNH. Co-doped cNNH showed a specific capacitance of 1238 F g⁻¹ at 1 A g⁻¹ and a capacitance retention of 76%, which are significantly higher than those of cNNH. The enhanced performance of the co-doped cNNH is attributed to the reduced path length of the electrons caused by the decrease in the size of the nanostructure and the increased conductivity due to Co ions substituting Ni ions. The reported synthesis method and electrochemical behaviors of cNNH and Co-doped cNNH affirm their potential as electrochemically active materials for supercapacitor applications.