Nanorod-Structured NiCo ₂ O ₄ /Moss-Like Ni(OH) ₂ Composites with Enhanced Capacitive Performance for Photorechargeable Devices

Nickel hydroxide, Ni(OH)₂, is regarded as an attractive electrode material for supercapacitors, owing to its high theoretical specific capacitance, low cost, and facile preparation. However, its capacitive performance is limited by low conductivity, sluggish ion diffusion kinetics, and poor structural stability. In this work, we systematically regulate the nanostructure of NiCo₂O₄/Ni(OH)₂ composites, which significantly enhances the capacitive properties of Ni(OH)₂, providing a promising energy storage material for photorechargeable devices. The nanorod-structured NiCo₂O₄ with a high specific surface area facilitates rapid electron transfer and provides abundant sites for Ni(OH)₂ loading. Notably, the cetyltrimethylammonium bromide (CTAB)-induced porous Ni(OH)₂ grows continuously and uniformly over the NiCo₂O₄ framework, allowing more materials to be utilized for energy storage. Furthermore, the robust NiCo₂O₄ nanorods serve as a structural backbone, effectively suppressing the pulverization and detachment of the Ni(OH)₂ during prolonged cycling. The results show that the composite electrodes exhibit a specific capacitance of 2170.22 F/g (301.42 mAh/g) at 1 A/g and a capacitance retention of 82.3% at 20 A/g, with the assembled supercapacitor maintaining 91.94% of its initial capacitance after 6000 cycles at 2 A/g. Benefiting from the improved performance, particularly the rate capability, the resulting photorechargeable supercapacitors achieve a solar-to-electrochemical energy efficiency of 16.21%. This study provides a nanostructure engineering strategy for improving the capacitive behaviors of materials, advancing high-performance photorechargeable devices.