A Review of Hydrothermal Carbonization of Carbohydrates for Carbon Spheres Preparation

Carbon spheres have attracted a great deal of attention due to their applications as super capacitors, catalyst supports, and adsorbents. Carbon spheres can be prepared with controlled size and with oxygenated functional groups on the surface. The further processed products have high surface area and high thermal stability. Among various methods for fabrication of carbon spheres, the hydrothermal carbonization (HTC) is favored because of its mild operating conditions (130-250 °C and self-generated pressures). In addition, HTC can synthesize micro- or nanoscale carbon spheres environmentally friendly without employing organic solvents, surfactants, or catalysts. In this review, we present the effects of process parameters, structural characteristics of carbon spheres, possible formation mechanisms of carbon spheres, and applications in catalysis.