Biomolecule-assisted synthesis of nickel sulfides/reduced graphene oxide nanocomposites as electrode materials for supercapacitors

•The nickel sulfides/rGO nanocomposites were biomolecule-assisted prepared.•The nanocomposites were applied in supercapacitors with good cycling stability.•The nanocomposites deliver a specific capacitance of 1169 F g−1 at 5 A g−1.•The nanocomposites deliver a specific capacitance of 761 F g−1 at 50 A g−1.

The present communication demonstrates the first environmentally friendly hydrothermal synthesis of nickel sulfide nanospheres/reduced graphene oxide (nickel sulfides/rGO) nanocomposites with the use of l-cysteine as a reducing agent, sulfur donor, and linker. The nanosphere consists of ultrafine particles leading to textural pores. The resulting nickel sulfides/rGO nanocomposites were further used as an electrode material for supercapacitors and found to exhibit very high specific capacitances of 1169 F g− 1 and 761 F g− 1 at current rates of 5 A g− 1 and 50 A g− 1, respectively, with good cycling stability.