Two-Dimensional SnO₂-ZnO Nanohybrid Electrode Fabricated via Atomic Layer Deposition for Electrochemical Supercapacitors

Abstract

Two-dimensional (2D) heterostructures of transition metal oxides (TMOs) are promising candidates for high-performance electrochemical supercapacitors (ESCs). Herein, sub-10 nm 2D SnO2-ZnO heterostructures were constructed on Au-modified SiO2/Si wafers by an atomic layer deposition (ALD) technique for ESC application. The cyclic voltammetry (CV) study revealed the pseudocapacitive-type Faradaic redox reactions of the 2D SnO2- ZnO heterostructure electrode with good reversibility. The electrode exhibited high energy storage capability with a high specific capacitance (Cs) of 538.90 F g-1 at a scan rate and current density of 10 mV s-1 and 8.0 A g-1, respectively. The corresponding energy density and the power density were 14.80 Wh kg-1 and 2512.35 W kg-1, respectively, at 8.0 A g-1. The high energy storage capacity of the heterostructure electrode can be ascribed to the combination of improved infiltration and intercalation/deintercalation of electrolyte ions induced by the nanoscale thickness and enhanced redox activity of the heterostructure. Furthermore, the 2D electrode displayed excellent electrochemical robustness with a capacitance retention of 96.3% after 5000 charge/discharge cycles.