We are working on practical production of nanomaterials and their application to clean energy devices. Materials wealth has been realized by using various chemical elements in the 20th century. But the materials and energy resources are limited. Even using the abundant chemical elements such as C and Si, various functions can be realized by controlling nanostructures. New materials with wonderful functions are being reported daily. But they are not widely used because it is uneasy to produce tiny materials at large scales. We try to understand how the nanostructures form, think freely how to make them, and produce them practically.

Carbon nanotubes (CNTs) are a one-dimensional nanomaterial having nanometer diameter and millimeter length. Physics and science have revealed their unique properties and potential applications. But poor production makes high-quality CNTs as expensive as noble metals. Practical production is a mission for chemistry and engineering. We have realized high-yield production of sub-millimeter-long, >99 wt%-pure few-wall CNTs by fluidized-bed, that is now under R&D with a chemical company (Fig. 1).

Rechargeable batteries including Li-ion batteries (LIBs) are important for electric vehicles and renewable energy. Present battery electrodes are made on metal foils that have large masses and only two faces. We propose a new battery architecture using sponge-like, self-supporting CNT papers as current collectors that have small masses and huge interior surfaces. Thin active layer on each CNT realizes good electrical connections between them as well as high loading of active materials in the total electrodes/cells (Fig. 2).

Solar cells are important for the enhanced use of renewable energy. Their increasing introduction now causes problems in their connection to the electric grids. If breakthrough is realized in their cost down, such problem will be solved by sending the electricity from the solar cells to the grids only when they are needed. We have developed the one-minute process forming highly crystalline Si films by vapor deposition that uses high-quality Si sources at an efficiency several-ten times higher than the conventional bulk Si technology. We are also developing a facile junction formation process by coating CNTs and/or p-type organic semiconductors on n-Si surface. Our goal is a facile, low-cost, fast fabrication process of solar cells in a similar manner for newspaper printing (Fig. 3).