Cellulase-mediated surface engineering of cellulose fibers for high-performance cellulose fibers/polyaniline composites flexible electrodes

Cellulose-based flexible supercapacitor electrodes, exemplified by cellulose fibers/polyaniline (CFs/PANI) composite electrodes, have emerged as promising candidates for sustainable energy storage. However, their practical application is severely impeded by inherent interfacial incompatibility between CFs and PANI, which restricts PANI mass loading and compromises electrochemical performance. Herein, we propose a novel bio-etching strategy as a targeted pretreatment concept for cellulose surface engineering. The bio-etching process selectively modulates the surface morphology and chemical functionality of CFs, especially increasing the surface roughness and titratable carboxyl group content of CFs while preserving the continuous fiber framework at the optimized treatment time. These changes are consistent with improved PANI deposition during in situ polymerization, potentially aided by electrostatic and hydrogen bonding interactions. The optimized bio-etching (10 min) yields a high PANI:sulfosalicylic acid (SSA) active-phase loading of 2.93 mg/cm2. Benefiting from the bio-etched fiber architecture and increased active-phase loading, the as-fabricated paper-based electrode delivers an areal capacitance of 2,098 mF/cm2 at 1 mA/cm2. In addition, the assembled symmetric supercapacitor exhibits an areal energy density of 111.6 μWh/cm2 at 1 mA/cm2. This work identifies controlled bio-etching as a promising surface engineering strategy for cellulose-based flexible energy-storage electrodes.