Hydrochar is a black carbonaceous solid which is derived from biomass via hydrothermal carbonization condition: using water as solvent and reaction medium, at the temperature of 150~375 ℃ and autogenously pressure. Rich oxygen-containing functional groups, together with high heat value (HHV) are the distinguished properties of hydrochar. Their properties are influenced by raw materials type, hydrothermal carbonization temperature and time. It has revealed a promising perspective in absorbent, preparation of porous carbon, catalyst carrier and clean energy. In this study, the production, properties and formation mechanism of hydrochar are summarized. Meanwhile, the applications of hydrochar are reviewed and the future development is prospected.

Contents
1 Introduction
2 Production of hydrochar
2.1 Influence of feedstock
2.2 Influence of hydrothermal temperature
3 Properties of hydrochar
3.1 Surface chemical properties
3.2 High heat value
3.3 Microcrystalline structure
3.4 Morphological characterization
4 Formation mechanism of hydrochar
5 Applications of hydrochar
5.1 Adsorption of heavy metal ion
5.2 Preparation of porous carbon
5.3 Solid acid catalyst
5.4 Clean energy
6 Conclusion