Microwave deposition synthesis of Ni(OH)2/sorghum stalk biomass carbon electrode materials for supercapacitors

Recycling of biomass wastes is an effective strategy to maximize resource utilization. Bio-waste derived carbon is a typical example of waste reuse, which has been used as supercapacitor electrode materials. Unfortunately, bare carbon usually possesses low specific capacitance and energy density. Combination of carbon and pseudocapacitive materials has been proved effective to achieve ideal capacitive performances. In this work, biomass carbon is firstly prepared using sorghum stalk as raw materials, and Ni(OH)2 is grown on sorghum stalk biomass carbon by a microwave deposition method. The resulting Ni(OH)2/sorghum stalk biomass carbon exhibits specific capacitances of 889.2 and 490.1 F g−1 at current densities of 2 and 20 A g−1, respectively. Moreover, 95.9% of capacitance is maintained over 30,000 cycles at 20 A g−1, unveiling exceptional cycling performances. Effective disposal of bio-wastes and preparation of electrode materials are both accomplished in this work. The microwave deposition allows fast growth of uniform Ni(OH)2 on sorghum stalk biomass carbon, ensuring outstanding capacitive performances.