Carbon nanomaterial-based nanogenerators for harvesting energy from environment

A significant bottleneck that hampers the adoption of many current technologies and wearable devices is power supply requirements. The quest to innovate portable self-powered systems has shed light on miniaturized energy harvesting devices called nanogenerators (NGs) that apply a wide variety of nanomaterials to achieve feasibility, flexibility, and enhanced electrical output. This systematic review provides a nearly complete list of all the NG devices present in the literature that have used carbon nanomaterials and harnessed renewable energy sources, namely mechanical, thermal, and fluid/blue energies, which were separately discussed and only deliberated to a certain limit with little demonstration of the materials and devices in previous publications. This review also draws attention to the overall aspects of carbon nanomaterial-based NGs, particularly in terms of electrical performance, and the role of carbon nanomaterials in how they have contributed to the advancement and application of energy harvesting devices, such as carbon nanotubes, graphene, reduced graphene oxide, activated carbon, and graphitic carbon. Finally, the concluding section addresses the current challenges and provides an outlook on the potential future trends in energy harvesting.