Three-dimensional carbon dots/Prussian blue analogues nanocubes /nickel foams as self-standing electrodes for high-performance hybrid electrochemical capacitors.

Developing the high-performance supercapacitors is overwhelmingly dependent on the composition design and structure tailoring of electrode materials. By a one-step solution method, the composite of carbon dots/Prussian blue analogues nanocubes-incorporated three-dimensional Ni foams was prepared and used as a self-standing positive electrode for hybrid electrochemical capacitors (HEC). Aside from the role of Ni source for Prussian blue analogues (PBA), Ni foams acts as 3D conductive supports, making electrolytes more accessible to the internal surface of electrode. Meanwhile, carbon dots can be absorbed for the formation of carbon dots/PBA nanocubes on Ni foams surfaces, offering optimized interfaces for the interactions between electrodes and electrolytes and relieving the decomposition of PBA in alkaline electrolyte. With these merits, the carbon dots/Prussian blue analogues nanocubes-Ni foams electrode in the hybrid electrolyte of 0.5 M KOH and 1.3 M NaSO exhibits a maximum specific capacity of 659 C g at current density of 0.5 A g and 344 C g even under large current density of 5 A g. An extended working potential window of 1.8 V, high energy density of 65 Wh kg and high power density of 4.052 kW kg as well as improved cyclic stability are also achieved in the assembled HEC. This study builds a boulevard to improve the application potential of PBA in HEC, which will be beneficial for the development of supercapacitors.