Lignin containing cellulose nanofiber/Ag2Se nanocomposite films: a promising material for thermoelectric film generators

This work deals with the fabrication of lignin containing cellulose nanofiber (LCNF)/Ag2Se films for thermoelectric applications. Ag2Se nanoparticles were synthesized within the LCNF network through in situ methods, employing Na2SeO3 and AgNO3 along with microwave energy treatment. LCNF/Ag2Se films fabricated with two LCNF : Ag2Se weight percent ratios (i.e., 50 : 50 and 30 : 70) were used to construct a flexible thermoelectric module. The obtained Ag2Se nanoparticles displayed a uniform size distribution in the LCNF network with smaller dimensions from the microwave energy treated group. The microstructure of LCNF/Ag2Se films was improved by hot-pressing, leading to enhanced film density thermoelectric properties. At a differential temperature of 50 K, films with 50% and 70% of Ag2Se exhibited output voltages of 18 and 21 mV; and Seebeck coefficients of −60 and −70 μV K−1 at 350 K, respectively. When microwave energy was applied, the films at 50% and 70% Ag2Se showed highest output voltages of 19 and 33 mV, respectively, and Seebeck coefficients of −63.3 and −110 μV K−1 at 350 K. The low-cost fabrication process associated with this module opens a pathway for applications such as energy harvesting.