Passive radiation-modulated cellulose-based thermoelectric assemblies for efficient low-grade heat harvesting

The efficient conversion of low-grade waste heat into sustainable electricity is essential for advancing thermoelectric energy harvesting technologies. However, maintaining a stable temperature gradient and achieving scalable fabrication remain critical challenges. To address these challenges, this study proposes a self-assembled radiation-modulated thermoelectric strategy for constructing a biomass-based thermoelectric assembly. This system, based on cellulose nanofibril (CNF), integrates a thermoelectric gel with a passive radiation-cooling layer, enhancing thermoelectric performance by maintaining a temperature gradient of 9.9 K, leveraging radiative cooling at high solar irradiance. The prepared radiative cooling layer has 96.23 % solar reflectivity. The developed thermoelectric assembly achieves a high ionic thermovoltage of 41.01 mV K⁻¹, an impressive ionic figure of merit (ZT_i) of 1.42. In addition, the addition of MXene gives the material an impressive 38.18 dB electromagnetic interference (EMI) shielding efficiency, effectively improving the overall operational stability of the device. This study not only provides an innovative and efficient strategy for converting low-grade waste heat but also demonstrates the significance of integrating radiative cooling to optimize thermoelectric conversion. Furthermore, it offers a scalable and eco-friendly approach for future thermoelectric applications.