B-Doped g-C3N4 Quantum Dots-Modified Ni(OH)2 Nanoflowers as an Efficient and Stable Electrode for Supercapacitors

For increasing the specific capacitance of supercapacitors, boron-doped g-C3N4 quantum dots (B-CNQDs) were synthesized by KOH cutting and further adsorbed on the surface of Ni(OH)2 nanoflowers (B-CNQDx-Ni) by a mild impregnation method via electrostatic force. The B-CNQDx-Ni nanocomposites exhibit an increased surface area and reduced band gap energy compared with pure Ni(OH)2, which result in a larger contact area between the electrode and the electrolyte and enhanced charge-transfer kinetics. The best B-CNQDx-Ni sample has an excellent specific capacitance of 1700 F/g at 1.5 A/g, low impedance at the alkaline conduction of 7.421 Ω, and a high stability cycling performance of 82% capacity retention after 5000 cycles, suggesting that B-CNQDx-Ni is a type of suitable electrode material used in supercapacitors.