Two-Dimensional Nanomaterials for Moisture-Electric Generators: A Review

As an emerging candidate for a sustainable power supply, moisture-electric generators (MEGs) have attracted great attention in recent years. Unlike the conventional hydroelectric system, MEGs propose to harvest energy from ambient moisture, driven by either ion diffusion under a concentration gradient or the interaction between a solid–liquid interface governed by electrostatic theory. Two-dimensional (2D) nanomaterials, in particular hydrophilic graphene oxide (GO), have been considered as the most promising materials for high-performance MEGs owing to their unique structure and properties. In line with the development of 2D nanomaterials, the recent electrical output of a single MEG has been greatly raised from tens to hundreds of millivolts, which is capable of powering commercial electronics. Herein, we have reviewed the recent progress of 2D nanomaterials in MEGs. The mechanism of moisture-induced electricity generation and strategies for tailoring 2D nanomaterials to enhance the output performance of MEGs are discussed. The potential application of MEGs is also discussed in two categories: sensing and power supply. Finally, the existing challenges and the perspective of MEGs are proposed for future study.