Composition-Dependent Structure and Electrochemical Performance of MXene/Polypyrrole/ZnO Ternary Nanocomposites for Supercapacitor Electrodes

The development of high-performance supercapacitor electrodes requires optimizing charge storage, electron transport, and active-site accessibility. In this study, MXene/polypyrrole/zinc oxide (MXene/PPy/ZnO) ternary nanocomposites were fabricated through in situ polymerization followed by hydrothermal synthesis, systematically varying PPy content and ZnO precursor concentration. Structural and morphological analyses revealed that composite composition influenced ZnO crystal growth and distribution, with excessive precursor concentrations promoting aggregation. M-3P-1Z exhibited uniformly distributed ZnO nanorods and the lowest charge-transfer resistance (0.4713 Ω), achieving the highest CV-derived specific capacitance of 888.01 F g−1 at 1 mV s−1. In contrast, M-1P-0.5Z, featuring ZnO nanorods with an aspect ratio of 10.1, achieved the highest GCD-derived specific capacitance of 1548.75 F g−1 at 0.1 A g−1 and a maximum estimated energy density of 161.2 Wh kg−1 at 160 W kg−1. Furthermore, its specific capacitance increased from 56.3 to 306.25 F g−1 after 1000 cycles at 5 A g−1, indicating progressive electrochemical activation. These findings highlight the importance of balancing ZnO morphology, accessible charge-storage sites, and MXene/PPy conductive networks, providing a composition-guided strategy for developing ternary nanocomposite electrodes with improved electrochemical energy storage performance.