Homogeneous growth of nano-sized β-Ni(OH)2 on reduced graphene oxide for high-performance supercapacitors

A reduced graphene oxide/β-Ni(OH)2 composite with excellent supercapacitive performance was prepared by a facile chemical precipitation. Reduced graphene oxide was ultrasonically dispersed in a Ni(NO3)2 solution, forming a suspension. Then let the prepared suspension stand for 0.5 h and 24 h, respectively, followed by stirring and adding NaOH solution into it for obtaining two types of composites. It was found that the standing time notably affected morphology and supercapacitive performance of the resulting composites. The composite derived from the 24 h-standing suspension presented an ideal morphology with nano-sized β-Ni(OH)2 particles homogeneously growing on the reduced graphene oxide sheets. The composite exhibited ultra-large specific capacitance, high rate capability and good cycling stability in 6 mol L−1 KOH electrolyte. Its maximum specific capacitance was 2134 F g−1 at a scan rate of 2 mV s−1, and a large specific capacitance of 882 F g−1 was still preserved at a high scan rate of 70 mV s−1. After 2000 cycles at a current density of 10 A g−1, the composite delivered a specific capacitance of 1141 F g−1, retaining about 81% of its initial capacitance. The high performance and the simple synthesis route allowed the obtained composite to be promising for supercapacitor applications.