Hierarchical Cu(OH)₂/Co₂(OH)₂CO₃ nanohybrid arrays grown on copper foam for high-performance battery-type supercapacitors

Hierarchical Cu(OH)₂/Co₂(OH)₂CO₃ nanohybrid arrays grown on copper foam were realized by a simple two-step solution route for the first time, Cu(OH)₂ nanowires were utilized as a scaffold to form Cu(OH)₂ nanowire/Co₂(OH)₂CO₃ nanoneedle core–shell structures and upper dispersed Co₂(OH)₂CO₃ ball-flowers structures. And time gradient experiments were also considered to understand the growth mechanism for the Cu(OH)₂/Co₂(OH)₂CO₃ nanohybrid arrays, the optimized hierarchical architecture electrode of Cu(OH)₂/Co₂(OH)₂CO₃ yields a high areal capacitance of 1.31 F cm⁻² at 2 mA cm⁻², which is more than three times higher than that of single Cu(OH)₂ electrode (0.37 F cm⁻²) and also superior than that of Co₂(OH)₂CO₃, an excellent rate property (0.74 F cm⁻² at 50 mA cm⁻²), and good cycling stability (91.5% capacity retention after 5000 cycles). Also, the hierarchical Cu(OH)₂/Co₂(OH)₂CO₃ nanohybrid arrays//active carbon asymmetric supercapacitors (ASCs) were fabricated, exhibiting a high energy density of 656 mWh cm⁻² with a power density of 28.8 W cm⁻². And three different colors (two red, two yellow, two green) of LED indicators can be lighted up by two ASC devices in series, which demonstrate that the hierarchical Cu(OH)₂/Co₂(OH)₂CO₃ nanohybrid arrays on copper foam are promising candidate electrode materials for supercapacitors.