From contact electrification to power output: physics, materials selection and environmental factors of triboelectric nanogenerators

Triboelectric nanogenerators (TENGs) have emerged as a promising technology for harvesting ambient mechanical energy into electrical energy, offering advantages such as high power output, cost-effectiveness, flexibility and lightweight design. This review systematically explores the fundamentals of TENGs and emphasizes on the critical role of material selection, particularly focusing on the integration of two-dimensional (2D) materials and their composites. Additionally, we investigate how environmental factors such as temperature and relative humidity impact TENG performance. Furthermore, the review categorizes the operational modes of TENGs, i.e., contact-separation, single-electrode, lateral-sliding, and free-standing modes. These modes illustrate their unique operational principles and application-specific benefits. A comprehensive discussion on the charge transfer mechanisms within TENGs is also presented that focus on both electron and ion interactions. Finally, we demonstrate the broad applicability of TENGs across various fields, including biomedical sensors, environmental monitoring, consumer electronics, and Internet of Things (IoT) applications, underscoring their potential for real-world implementation. • Five important criteria for selecting materials for triboelectric nanogenerators have been proposed, offering a concise framework for material choice. • Potential environmental factors, including the effects of relative humidity and temperature, have been discussed to highlight their influence on device performance. • Performance-enhancement strategies, such as the incorporation of two-dimensional materials, have been explored to demonstrate pathways for improving output. • A wide range of applications has been included to provide a comprehensive understanding of recent developments in the field.