Nickel silicate hydroxide on hierarchically porous carbon derived from rice husks as high-performance electrode material for supercapacitors

Nickel silicate hydroxide on hierarchically porous carbon derived from rice husks is prepared as electrode material for supercapacitors. AAEMs 1 in rice husks and CO 2 promote the development of pores, which act as pore-forming agent and catalyst respectively. The rice husks carbon is used as the substrate and the SiO 2 in rice husks is converted into Ni–Si compound by loading Ni. The C/NiSi-600-1 shows remarkable electrochemical performance with 237.07 F/g at 0.5 A/g. The performance declines with crystalline SiO 2 formed above 900 °C. A high-performance asymmetric water-system supercapacitor device is fabricated by C/NiSi-600-1 and activated carbon. This device shows capacitance of 142 mF/cm 2 at 4 mA/cm 2 , the energy density of 25.24 Wh/kg at 551.4 W/kg and great cycle stability with 90% after 10,000 cycles. This work provides new insights into the green application of rice husks and promotes the development of electrode materials for supercapacitors. Hierarchically porous rice husks-based nickel-silicon hydroxide composites are prepared by hydrothermal method. Alkali and alkaline earth metals in rice husks and CO 2 promote the development of pores. The SiO 2 anchored on the carbon is converted into Ni-Si compound. The C/NiSi-600-1 shows remarkable electrochemical performance with 237.07 F/g at 0.5 A/g. The C/NiSi-600-1//activated carbon asymmetric supercapacitor device achieves excellent electrochemical performance with energy density of 5.04 m Wh/cm 3 at power density of 110.1 mW/cm 3 and cycle stability with 90% after 10,000 cycles. • Hierarchically porous rice husks-based nickel-silicon hydroxide was prepared. • The AAEMs and CO 2 promote the production of hierarchical pores. • The optimal Ni-Si ratio at different carbonization temperature is investigated. • The best temperature is 600 °C, and C/NiSi-600-1 performs 237.07 F/g at 0.5 A/g. • The electrochemical performance declines above 900 °C when crystalline SiO 2 formed.