Hierarchical rod-like structure MnO2/NiCo-layered double hydroxide on nickel foam for a high-performance supercapacitor electrode

Abstract

Nickel foam (NF) surface was successfully modified to produce a hierarchical structure MnO₂-modified NiCo-layered double hydroxide (MnO₂/NiCo-LDH) for a high-performance supercapacitor. A two-step hydrothermal method was applied, including the synthesis of hierarchical one-dimension NiCo-carbonate onto NF, followed by the synthesis of MnO₂. The characterization results showed the growth of nanoneedle-like NiCo-carbonate particles perpendicular on the NF surface covered with δ-MnO₂. MnO₂ attachment disrupted the nanoneedles structure forming the hierarchical rod shapes and changing the structure of NiCo carbonate to NiCo-LDH. This change significantly increases the material's electroactive surface area and enhances the specific capacitance. At 1 A g⁻¹ current density, the specific capacitance of 2572.73 F g⁻¹ was achieved, which is substantially higher than those of NiCo/NF and MnO₂/NF. Furthermore, good stability was shown by 10,000 repetitive charge-discharge cycles (at 20 A g⁻¹) with a specific capacity retention of 78.95 % indicating that the developed material was suitable for supercapacitors.