Silicon nanowire/ionic hydrogel-based hybrid moist-electric generators with enhanced voltage output and operational stability

Abstract

Moist electric generators (MEGs) are promising portable power sources for harvesting energy from atmospheric moisture. However, the lack of an efficient device design and the associated working mechanisms related to ion interactions have resulted in relatively low electrical performance and short output times. In this study, we developed an efficient organic–inorganic hybrid MEG by in situ preparation of highly hygroscopic polyacrylamide ionic hydrogels on silicon nanowire arrays. The device yielded a record open-circuit voltage of 1.28 V at a relative humidity of 60% and 35 °C, and it maintained 60% of the peak performance even after 800 h of continuous operation. This exceeds the operating times of similar devices reported to date by a factor of approximately three. The outstanding performance achieved was due to the synergistic effect of the hybrid design: the increased dissociated ions from the ionic hydrogels, enhanced ion migration rate caused by the ion-induced Hofmeister effect, and rich cation-selective nanochannels of the robust silicon nanowires. More importantly, ions with smaller hydration radii and lower valence states can migrate faster within the nanochannels, thereby enhancing the electrical output of MEGs. This study provides a general ion-selection mechanism for improving the electrical output and operating time of MEGs.