Flexible Moisture-Driven Electricity Generators Based on Heterogeneous Gels and Carbon Nanotubes

Recently developed asymmetric heterogeneous moisture-driven electricity generators (AHMEGs) are advantageous for harvesting energy from ubiquitous moisture due to their superior output performance and possible flexibility. However, the regeneration of AHMEG has seldom been explored. Here, we report the fabrication of flexible AHMEGs with regeneration ability simply by asymmetrically incorporating carbon nanotubes into a bilayer-structured gel with heterogeneities of both hygroscopicity and charge. The bilayered gel consists of a Na+-containing macroporous aerogel and a highly hygroscopic Cl--containing hydrogel. After assembly, the resulting flexible AHMEG unit shows excellent output performance, with a stable voltage of 1.03 V, a current density of 23.8 μA cm-2, a power density of up to 9.12 μW cm-2 and a high stability over 7 days, resulting from a synergistic effect between hygroscopicity and charge heterogeneities of the bilayered gel. The regeneration of the AHMEGs has been realized via light irradiation of the aerogel containing carbon nanotubes, and the regeneration can be repeated for at least 30 cycles, significantly expanding the lifecycle of moisture-driven electricity generators. Regeneration imposed by carbon nanotubes, combined with flexibility, simple preparation, and excellent electrical performance, enables the AHMEGs to be excellent moisture-driven electricity generators for advantageous applications.