Environmentally sustainable moisture energy harvester with chemically networked cellulose nanofiber

Abstract

Moisture-driven energy generators (MEGs) utilizing cellulose, which are renowned for their inherent eco-friendliness, have garnered considerable attention; however, their stability, recyclability, and high performance remain to be demonstrated. Specifically, compromised structural integrity, particularly under moist conditions, severely curtails their long-term operational viability. We developed a highly stable cellulose MEG that operated continuously for 350 h with a maintained open circuit voltage of 0.703 V. The enhancement of cellulose MEG performance was achieved via a robust structural framework realized through a composite of cellulose nanofibers (CNFs) cross-linked with citric acid, alongside electrically conductive carbon nanotubes (CNTs). We engineered a free-standing bilayer-type cellulose MEG featuring a chemically networked CNF/CNT composite onto a moisture-supplying ionic organohydrogel. Our crosslinked cellulose MEG achieved a short-circuit current density of 39 μA cm⁻² and a maximum power density of 28.9 μW cm⁻². Moreover, the crosslinked CNF/CNT aerogel was successfully biodegraded with an enzyme after energy generation. The recycled cellulose MEG, utilizing recovered CNTs and reused ionic organohydrogel, achieved an impressive output of 98.8% compared with that of the original MEG. Our MEG finds practical utility as a temperature sensor in smart packaging for continuous monitoring. Our crosslinked cellulose MEG achieves sustainability via recyclability and enhancing its practical applicability.