Sodium alginate/carbon nanotube energy harvesting fibers: Axial functional group gradient and moist-electric performance

Moist-electric generation, a green and environmentally friendly energy harvesting technology, is undoubtedly one of the effective methods to alleviate energy shortages and environmental damage. However, the lack of fiber-like moist-electric generators (MEGs) that combine continuous power generation and high electrical output performance has constrained the development of moist-electric in the fields of flexible wearable and self-power supplies. In this work, sodium alginate (SA)/multi-walled carbon nanotubes (MWCNT) fibers with axial heterogeneous (axi-he) of oxygen-containing functional groups (Ocfgs) are prepared through a mold forming method in assistance with the coagulation process. The interaction between axi-he MEG and moisture is investigated by analyzing the electrical signal changes of dried MEG under moisture stimulation. The maximum output voltage and current of axi-he MEG can reach 0.35 V and 1.92 μA under the stimulation of moisture. Based on the regulation of Ocfgs, axi-he MEG has a continuous high moist-electric performance and environmental adaptability. The maximum output power density (Pmo) of axi-he MEG with a length of only 2 cm can reach 27.37 μW cm–2 at RH = 90%, which exceeds most of the MEGs reported in literature. Meanwhile, a continuous output voltage of 0.33–0.37 V for more than 15 h can be obtained from this axi-he MEG. Thus, the axi-he MEG from Ocfg distribution design and mold forming method provides a new way of clean energy generation using moisture from the ambient environment, exhibiting enormous potential in energy supply for Internet of Things (IoT) devices.