Development of "Paper Tribo-Electrio Nano-Generator" Based on Carbon-Nanotube-Composite Papers

We propose unique tribo-electric nano-generator (TENG) based on CNT-composite papers. The CNT-composite paper we developed that is a composite material composed of CNTs and paper, can be made easily using the modified Japanese washi paper making method. It is known that it has many useful properties based on CNT and a paper. On the other hand, TENG consists of a combination of different materials, which are repeatedly touched and separated by vibration to generate electric power. Conventional TENGs may not be able to collect all of the generated power. For this, we focus on CNT-composite paper, because a paper is one of suitable materials for TENG, and a three-dimensional CNT network in the composite paper is expected to collect all of the generated power efficiently. Therefore, we develop “paper TENG” based on our CNT composite paper and further improve the power generation.
To prepare our CNT-composite paper, a CNT dispersion that contains CNT and a dispersant is firstly prepared by ultrasonication in pure water. At the same time, a pulp dispersion contains pulp, the raw material of the paper, dispersed in pure water. After that, two dispersions are mixed. Next, water is removed from this mixed dispersion with a fine mesh. It is then dried, molded, and completed. After that it is cut out into 3 cm squares. The cut composite paper is attached to an aluminum plate using conductive tape. It acts as an electrode in the paper TENG. The output voltage of it depends on the speed at which the different materials contact and separate repeatedly.
In this study, the influence of contained CNTs was investigated. The CNT dispersion to make the composite paper was prepared with 15 mg of CNTs (we choose one from SG101, chirality (6,5), (7,6), NC7000), 100 mg of surfactant (SDS) and 20 ml of pure water when making the composite paper. Pulps were also prepared with 100 mg each of eucalyptus. As a results, we found tribo-electricity generation from CNT-composite paper. Tribo-electricity was also observed for both SG101, (6,5), and (7,6) CNTs with semiconducting properties and NC7000 carbon nanotubes with metallic properties. Therefore, carbon nanotubes do not work to increase power output in triboelectricity generation using this carbon nanotube composite paper, and they are thought to work as a conductive material to assist charge transfer within the composite paper, regardless of their metallic or semiconducting properties.
We investigated the influence of changing the amount of contained CNTs on the power output. In concrete, the composite paper was prepared with 5, 15, and 30 mg of CNTs (SG101), 20 ml of pure water, and 200 mg of eucalyptus pulp material. Changing the amount of CNTs did not result in loss of tribo-electric performance, on the other hand did make a difference in output intensity. There was no significant difference in power output when the amount of CNTs was 5 mg and 30 mg, and about 3.7 times more power output was obtained when 15 mg was used than when 5 mg and 30 mg were used. This suggests that there is an optimal amount of CNTs. This is because CNTs are not fully dispersed in the composite paper when the amount of CNTs is small, and when the amount of CNTs is large, the area where CNTs and aluminum electrode are in direct contact becomes large, which is thought to lower the output.
From the above, feasibility of the paper TENG based on CNT-composite paper was confirmed in this study, and CNTs are thought to play a role in this tribo-electricity generation by efficiently transferring the electric charge generated by the pulp and electrodes to the electrodes.