Structural effects of iron oxide nanoparticles and iron ions on the hydrothermal carbonization of starch and rice carbohydrates

The role of iron ions and iron oxide nanoparticles as catalysts in the hydrothermal carbonization of starch and rice grains under mild conditions is described. Commercial soluble starch and rice grains containing a variety of both soluble and insoluble carbohydrates were chosen as carbon sources. It was seen that in the presence of either free iron ions or iron oxide nanoparticles, hydrothermal carbonization under very mild conditions leads to very fine, ropelike carbon nanostructures. Raman spectroscopy shows that the catalyzed hydrothermal heating in a sealed vessel is an efficient method to promote dehydration, condensation, and carbonization of carbohydrates, with similarities to traditional charcoal preparation.