Nanolignin–polypyrrole nanocomposites: synthesis, electrical properties, and their performance in energy conversion applications

Abstract

Nanocomposites based on nanolignin (NL) and polypyrrole (PPy) are prepared via in situ oxidation polymerization. The chemical structure of the obtained nanocomposites was studied using FTIR and XRD and their morphology was studied by SEM. Broadband dielectric spectroscopy (BDS) was used to study the electrical and dielectric properties of the nanocomposites. The results showed that the dc-conductivity decreases remarkably as the NL concentration increases. It decreases significantly from 2.88 × 10⁻⁵ to 1.82 × 10⁻⁸ S cm⁻¹ as the NL concentration increases tenfold in the 5% composite form. However, an interfacial polarization that originated from the accumulation of charge carriers at PPy–NL interface became clearer as NL concentration increased. Moreover, NL exhibits weak electrical conductivity due to its semiconducting nature, resulting in a band gap of 1.25 eV in the near-infrared (IR) region. Pure NL yields low efficiencies when used as an electrolyte in dye-sensitized solar cells (DSSCs). However, incorporating the conducting polymer PPy significantly improves the performance of NL-based electrolytes. Increasing the NL ratio to 50% optimized the DSSC efficiency, leading to enhanced performance. Overall, the study demonstrates that the integration of PPy with NL significantly promotes the electrical and dielectric properties of the nanocomposites, improving their performance in energy conversion applications.