Ikumi Toda

Rice Husk‐Derived Graphene with Nano‐Sized Domains and Clean Edges

A new synthetic method is demonstrated for transforming rice husks into bulk amounts of graphene through its calcination and chemical activation. The bulk sample consists of crystalline nano-sized graphene and corrugated individual graphene sheets; the material generally contains one, two, or a few layers, and corrugated graphene domains are typically observed in monolayers containing topological defects within the hexagonal lattice and edges. Both types of graphenes exhibit atomically smooth surfaces and edges.

Detailed Structural Analyses of KOH Activated Carbon from Waste Coffee Beans

The relationship of the detailed structural change of KOH activated carbon and hydrogen storage ability was investigated in activated carbon materials fabricated from waste coffee beans. The specific surface area of porous carbon materials calculated from N2 adsorption isotherms stood at 2070 m2/g when the weight ratio of KOH to carbon materials was 5:1, and pore size was in the range of approximately 0.6 to 1.1 nm as micropores. In the structural analysis, X-ray diffraction analysis and Raman spectroscopy indicated structural change in these carbon materials through KOH activation. The order of the graphite structure changed to a smaller scale with this activation. It is theorized that specific surface area increased using micropores provided by carbon materials developed from the descent of the graphite structure. Hydrogen storage ability improved with these structural changes, and reached 0.6 wt % at 2070 m2/g. These results suggest that hydrogen storage ability is conferred by the chemical effect on graphite of carbon materials.