A new ZnO-ZnS-CdS heterostructure on Ni substrate: A binder-free electrode for advanced asymmetric supercapacitors with improved performance

Abstract

ZnO is an appealing electrode material for supercapacitors due to its high capacitance, low cost, environmental friendliness, and good electrochemical reversibility. In this paper, we present the synthesis of a newly designed ZnO covered with ZnS and paired with CdS to produce a ternary heterostructure. According to the morphological research, ZnO has an urchin-like shape coated with ZnS and CdS nanoparticles on the surface with no undesired by-product residues, which improves the surface functionalities. First, we combined ZnO and ZnS to make a binary nanocomposite that outperformed its bulk equivalent ZnO by 322 mAh g−1 at 175 mAh g−1 during the charge-discharge process when a low current flow of 1 A g−1 was used. Meanwhile, the synergistic effect of multiple components, a new class of ternary ZnO-ZnS-CdS heterostructure was developed which effectively improved the electrochemical properties of the individual constituents, e.g., a capacity of 434 mAh g−1, and charged transfer kinetics (over pristine ZnO, and ZnO-ZnS electrodes). Inspired from the good capacitive behavior in a three-electrode mode, we further assembled an ASC that exhibits exceptional energy-storage performance of 36 Wh kg−1, 5422 W kg−1 after adding an optimal voltage (1.8 V), and retain only ∼91% at a higher current response. Last but not least, compositing is a vital strategy to boost the overall capacitive performance of the nanomaterials.