Preparation Of Bio Based Nanofiber Aerogel Power Generation Devices By Qingdao Energy Institute

With the increasing energy crisis and environmental problems, the research and application of green and renewable energy devices have attracted worldwide attention. Among them, solar energy, thermal energy, mechanical energy, wind energy, bio electrochemical energy and so on have been used to generate electricity, and have wide application prospects in the field of self power supply system and wearable. However, there are still many limitations in the application of these energy forms. For example, solar power generation devices need continuous illumination. Friction or pressure power generation requires continuous relative movement, which requires higher mechanical performance of materials and devices.

Recently, the widespread existence of moisture as a natural and biological resource is being used to generate electricity and expand the resources that can be used to generate electricity in nature. At present, however, wet gas power generation relies mainly on the interaction between carbon nanomaterials and water (water vapor). For example, after the electrochemical treatment of graphene oxide films by Qu Liang, et al., the oxygen functional groups on the upper and lower surfaces of the films show a controllable gradient distribution. The gradient distribution structure of the oxygen-containing functional groups makes the humidity of the upper and lower surfaces appear gradient distribution once the film contacts the moisture. This leads to the separation of positive and negative charges and the directional movement, thus causing the potential difference between the upper and lower surfaces to generate 0.2V. However, the macro fabrication of carbon nanomaterials is difficult and costly, and the complex device structure also affects large-scale applications. Low cost and high performance research and development of materials and devices for wet gas power generation is still the focus and difficulty in this field.

On the other hand, in nature, many organisms and human physiological processes are accompanied by bioelectric phenomena based on body fluid / tissue fluid. For example, the transport of sap from the bottom up in the trunk will generate a flow potential; there is a transmembrane potential due to the difference of ions and concentrations between the cell membrane. Although biomass production is huge, low cost and green renewable, it is still a great challenge to generate electricity generation devices by the interaction of bio based materials and water / moisture.

Recently, the Li Zhaoxu research group of the Qingdao Institute of bioenergy and process, Chinese Academy of Sciences has found that the aerogels of biomass nanofibers (cellulose nanofibers, silk nanofibers, chitin nanofibers, Amyloid nanofibers, etc.) have good air hygroscopic properties. This is mainly due to the fact that there are abundant hydrophilic groups (such as hydroxyl, carboxyl, quaternary ammonium groups and amino groups) on the surface of bio based nanofiber materials. On the other hand, based on Kelvin capillary condensation principle, the small size effect of nanofibers (<10nm in diameter) and the hierarchical pore structure of gas condensate are more conducive to steam condensation (Fig. 1). Therefore, when the airflow of a certain humidity (relative humidity >50%) passes through the aerogel, the vapor will be captured by aerogels in the form of combined water and free water. The carboxyl groups on the fiber surface will dissociate and form a double electric layer on the surface of the fiber. There is a difference in humidity between the aerogels before and after, and the moisture condensation at the front ends with the evaporation of the water at the rear end. The flow of the solution in the inner surface and the channel of the aerogel will form a flow potential, thus making the bio based nanofiber aerogel wet gas generator. Further studies show that the generator basically meets the smurhovsky flow potential formula (Fig. 2).

　　 The bio based nanofiber aerogel generator produced in this study has many advantages such as low cost, high biocompatibility and biodegradability, and biological nanofibers can be prepared from agricultural and fishery wastes. The device is suitable for the power supply of small wearable electronic devices, and because of the humidity generated by human activities (breathing, sweating, etc.), its power generation signals may be closely related to violent activities, and are expected to be used in self powered health monitoring devices. The research is published in the recent journal of advanced functional materials.