Double gradient and active electrode synergistic enhancement of cellulose nanofiber/sodium alginate aerogel moisture...

Currently, moisture-electric generators (MEGs), which can convert the energy of ubiquitous moisture into electricity, have become a trend. In this work, biomass-based generator (CMEG) with double gradient structures was prepared by two-step directed freeze-drying and Ca²⁺ induced crosslinking reaction using cellulose nanofibrils (CNF), sodium alginate (SA) and calcium chloride. The composite aerogel with Ca²⁺ ion concentration gradient structure was constructed by using the CNF/SA bilayer aerogel with the gradient structure of oxygen functional group as the template. The introduction of Ca²⁺ ions not only further stabilized the structure of the aerogel, but also endowed the asymmetric hygroscopic between the upper and lower layers of the aerogel, resulting in a built-in water gradient. In addition, the ion gradient difference inside the aerogel was significantly enhanced by introducing an active metal electrode. Based on the above design, the CMEG exhibited leading maximum power density (128.04 μW·cm^-2), wide temperature range (273-353 K) and long duration (110h) by adjusting the operating environment. And in addition to easily lighting multiple light-emitting diodes (LEDs), CMEGs could also satisfy the power supply needs of various devices through different series-parallel connection designs. More importantly, it was compatible for applications in respiratory sensing and pressure monitoring. This work provides a new strategy for the biomass-based moisture-electric generators.