Study of structural, morphological, and electrochemical performance of ZnO/SnO2 NC heterostructures for as potential electrode materials for supercapacitors

The versatile ZnO/SnO 2 NCs (NCs) were synthesized via a simple hydrothermal route using varying amounts of a zinc-oxide precursor to study their super-capacitive applications. XRD confirmed a well-defined crystalline structure with diffraction peaks corresponding to tetragonal rutile SnO 2 and hexagonal wurtzite ZnO phases. Increasing the ZnO precursor concentration systematically reduced the average crystallite size from 27 nm to 15 nm. FT-IR spectra revealed absorption bands at 623 cm −1 and 490 cm −1 , indicative of Sn O and Zn O bonds, respectively. Raman spectra confirmed the heterojunction formation of ZnO/SnO 2 by detecting the ZnO and SnO 2 materials. FE-SEM images showed that the nanocomposites consist of sphere-like nanoparticles. EDX and XPS confirmed the presence of Sn, Zn, and O, consistent with the intended composition. The ZSn2 sample exhibited a mesoporous texture with a BET specific surface area of 30.26 m 2 g −1 and a total pore volume of 1.3 cm 3 g −1 , favourable for ion transport. Electrochemically, the ZSn2 electrode (Zn:Sn = 0.7:1) delivered an excellent specific capacitance of 290 F g −1 at 10 mV s −1 and retained 75% of its initial capacitance after 2000 charge–discharge cycles. It also achieved an energy density of 38.64 Whkg −1 and a power density of 1300 Wkg −1 , In a practical two-electrode device configuration, ZSn2 delivered a specific capacitance of 77.13 F g −1 (CV, 10 mV s −1 ) and 50.21 F g −1 (GCD, 1 A g −1 ), with a low charge-transfer resistance (Rct) of 2.5 Ω cm 2 and a coulombic efficiency close to 100% over extended cycling, indicating its potential as a high-performance electrode material for supercapacitor applications.