MXene–Transition Metal Dichalcogenide Hybrid Flexible Piezoelectric Nanogenerators for Self-Powered Systems: From Materials Engineering to Device Architectures

Growing need for sustainable and autonomous energy solutions has accelerated the advancement of piezoelectric nanogenerator (PENG)-driven self-powered systems. Two-dimensional (2D) materials, particularly MXenes and transition metal dichalcogenides (TMDs), have gained considerable interest because their structural flexibility, tunable surface chemistry, and strong interfacial interactions collectively enhance piezoelectric performance under low-frequency mechanical stimuli. This review systematically discusses recent progress in MXene and TMD-based hybrid flexible PENGs, spanning materials engineering, device architecture, and application-oriented system integration. It emphasizes the correlation between material design and performance, highlighting strategies such as defect engineering, phase modulation, surface functionalization, and interface engineering to improve polarization behavior, charge transport, and energy conversion efficiency. The paper critically analyzes key limitations in practical operation, including oxidation instability, charge screening, leakage pathways, and long-term mechanical degradation. The review further examines advances in flexible architectures and system-level integration, highlighting the role of hybrid PENGs in wearable health monitoring, human-machine interfaces, smart sensors, industrial diagnostics, Internet of Things (IoT), and robotics. Future opportunities are outlined emphasizing scalable fabrication, environmental stability, power-management integration, and reliability validation to accelerate the transition of MXene–TMD flexible PENGs from laboratory prototypes to practical self-powered systems.