水热碳化技术是实现生物质资源化利用的新型技术，具有可直接处理湿生物质、反应温度低、反应时间短、减量化效果明显等优势。由于水热炭具有发达的孔隙结构、丰富的含氧官能团、大比表面积、高热值等性质，在环境、能源、电化学和催化等领域获得了广泛的应用。简述了水热碳化技术的反应条件及反应过程，介绍了水热炭的物理活化和化学活化等传统改性方法，重点分析了低温等离子体、厌氧发酵、磁化、固态微波、聚乙烯亚胺、杂原子掺杂等新型改性方法对水热炭结构和表面官能团的作用效果。综述了水热炭作为重金属、有机物、CO₂吸附剂，土壤改良剂，固态燃料、电极材料及催化剂的应用进展。作为吸附剂，水热炭对水体重金属元素(Cr、Cu、Zn等)的去除率可以达到82%～99%，对CO₂的吸附量可以达到1.2～8.3 mmol/g。作为土壤改良剂，添加水热炭可以减少氮肥的施用量。作为固态燃料，木质纤维素制备的水热炭热值较高，可达30 MJ/kg，接近于烟煤的热值。作为电极材料，通过改善水热炭的孔径分布，提升水热炭中含氧及含氮官能团的数量可大幅提升其电化学性能，水热炭的比电容可达到300 F/g以上。在催化领域，水热炭本身可以作为催化剂或负载活性组分作为催化剂载体。最后，指出了未来应重点开展水热炭的复合改性、回收利用、对植物和土壤微生物的毒害机理等方面的研究，并进一步提升其燃烧性能、比电容、能量密度和稳定性，以实现水热炭的商业化应用。

Hydrothermal carbonization is an innovation technology to realize the resource utilization of biomass. It has the advantages of directly treating wet biomass, low reaction temperature, short reaction time and obvious reduction effect. For its well-developed pore structure, rich oxygen-containing functional group, large specific surface area and high heating value, the hydrochar has been widely applied in the fields of environment, energy, electrochemistry and catalysis. Reaction conditions and reaction processes of hydrothermal carbonization technology were briefly described. Conventional modification methods such as the physical activation and chemical activation of hydrochar were also introduced. In particular, the effects of new modification methods, including non-thermal plasma, anaerobic fermentation, magnetization, solid-state microwave, polyethyleneimine and heteroatom doping, on the structure and surface functional groups of hydrochar were emphatically analyzed. The application progresses of hydrochar as adsorbents for heavy metal, organic matter and CO₂, soil amendment, solid fuel, electrode material and catalysts were also reviewed. As adsorbents, hydrochar can remove 82%−99% of heavy metal elements (Cr, Cu, Zn, etc.) from wastewater and adsorb 1.2−8.3 mmol/g of CO₂. As soil amendments, adding hydrochar can reduce the amount of nitrogen fertilizer. As solid fuels, the heating value of hydrochar produced from lignocellulose is as high as 30 MJ/kg. This value is close to the heating value of bituminous coal. As electrode materials, by improving the pore size distribution and increasing the number of oxygen- and nitrogen-containing functional groups, the electrochemical performance of hydrochar can be greatly improved, and the specific capacitance of hydrochar can reach more than 300 F/g. In the field of catalysis, hydrochar can serve as a catalyst or as a catalyst support for active components. Finally, it is pointed out that the future research should focus on the composite modification, the recycling and utilization of hydrochar, and its toxic mechanism to plants and soil microorganisms. Its combustion performance, specific capacitance, energy density and stability should be further improved to realize the commercial application of hydrochar.