Sustainable Cellulose- and Pectin-Rich Triboelectric Nanogenerator for Mechanical Energy Harvesting and Self-Powered Humidity Sensing

This study develops a high-performance triboelectric nanogenerator (TENG) through <i>Citrullus lanatus</i> rind powder (CLP) which originates from watermelon waste to generate sustainable power and detect humidity. The SEM and FTIR results showed that CLP contains a natural porous structure and multiple polar functional groups which improve both the charge transfer and retention capabilities. The CLP-TENG device operated in vertical contact-separation mode with PTFE as the counter layer to generate a 255 V open-circuit voltage and 30 µA short-circuit current and 35 µW peak power output at 4 Hz and 20 MΩ load. The device successfully charged a 4.7 µF capacitor to 5 V during a 80 s period and operated low-power electronic devices to prove its ability as a sustainable power source. The device output increased with increasing operating frequency while showing operation stability throughout more than 1000 cycles and seven days of continuous operation. The device demonstrated a strong humidity detection ability through its voltage response which decreased from 250 V to 120 V when the relative humidity rose from 30% to 90%. The research proves that agricultural waste can be transformed into environmentally friendly materials which perform well in green energy systems and environmental monitoring applications.