Collectively Exhaustive Electrodes Based on Covalent Organic Framework and Antagonistic Co-Doping for Electroactive Ionic Artificial Muscles

In this study, high-performance ionic soft actuators are developed for the first time using collectively exhaustive boron and sulfur co-doped porous carbon electrodes (BS-COF-Cs), derived from thiophene-based boronate-linked covalent organic framework (T-COF) as a template. The one-electron deficiency of boron compared to carbon leads to the generation of hole charge carriers, while sulfur, owing to its high electron density, creates electron carriers in BS-COF-C electrodes. This antagonistic functionality of BS-COF-C electrodes assists the charge-transfer rate, leading to fast charge separation in the developed ionic soft actuator under alternating current input signals. Furthermore, the hierarchical porosity, high surface area, and synergistic effect of co-doping of the BS-COF-Cs play crucial roles in offering effective interaction of BS-COF-Cs with poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), leading to the generation of high electro-chemomechanical performance of the corresponding composite electrodes. Finally, the developed ionic soft actuator based on the BS-COF-C electrode exhibits large bending strain (0.62%), excellent durability (90% retention for 6 hours under operation), and 2.7 times higher bending displacement than PEDOT:PSS under extremely low harmonic input of 0.5 V. This study reveals that the antagonistic functionality of heteroatom co-doped electrodes plays a crucial role in accelerating the actuation performance of ionic artificial muscles.