煤炭因其碳含量高、储量丰富及价格低廉，而成为优质的多孔碳碳前驱体。以煤炭为原料制备超级电容器用多孔电极材料是实现煤炭高附加值利用的重要方向之一。研究表明，通过调整孔结构、改善表面化学活性均能有效提高煤基多孔碳电极材料的电化学性能。其中调整孔径分布可利用物理活化和化学活化联合、模板法和化学活化联合以及不同化学活化剂联合三种方法。物理活化和化学活化联合法主要是通过水蒸气或CO2对KOH活化过程进行辅助，在得到大量微孔的同时获得一定量的介孔，并实现煤基多孔碳孔隙与润湿性的协同调控。模板法与化学活化联合则可在获得与模板剂相同孔结构的同时，通过KOH活化进一步造出丰富微孔，从而实现合理的孔径分布。除使用模板剂外，也可利用碳前驱体自身含有的大量杂质充当自模板。采用不同化学活化剂联合的方法也能实现孔结构的调节，例如K+和Na+的离子尺寸不同，联合利用便可得到不同的孔径分布；利用KCl在高温下的流动性，可以将KOH的中间产物带入更广范围和更深层次，从而实现微孔向介孔的转化。改善表面化学活性则可通过炭前驱体预氧化和引入杂原子两种方式。如通过强酸或强氧化剂对原煤进行预处理，可以提高所制备碳材料的有机氧含量，增加活性位点并提高润湿性。通过掺杂剂掺杂可在碳材料中引入杂原子，其中应用最多的是N掺杂，所引入的含氮结构包括吡咯-N（N-5）、吡啶-N（N-6）、季铵-N(N-Q)和氧化-N（N-X）四种。此外，O、B、S和P也是常见的掺杂原子。另一种引入杂原子的方法是通过煤与生物质共碳化，此时生物质既充当碳源也充当杂原子源。杂原子掺杂可改善碳材料的润湿性、导电性和结构稳定性，并可产生一定量的赝电容。本文从以上这些方面综述了近几年来煤基多孔碳电极材料的研究进展，分析了不同改性方法的优缺点，并对目前研究所存在的问题进行了讨论，对超级电容器用煤基多孔碳未来研究趋势进行了展望。

Coal is a promising carbonaceous precursor for high-quality porous carbon because of its high carbon content, abundant reserves and low price. The preparation of porous electrode materials for supercapacitors from coal is one of the important routes to realize the high value-added utilization of coal. The results show that the electrochemical properties of coal-based porous carbon electrode materials can be effectively improved by adjusting the pore structure and improving the surface chemical activity. The pore size distribution can be adjusted by three methods: physical and chemical co-activation, template method combined with chemical activation and combination of different chemical activators. The combined physical activation and chemical activation method mainly uses water vapor or CO2 to assist the activation process of KOH, so as to obtain a large number of micropores and a certain amount of mesoporous pores, and realize the synergistic control of the pore structure and wettability of coal-based porous carbon. The combination of template method and chemical activation can obtain the same pore structure as template agent, and at the same time, KOH activation can further produce abundant micropores, thus achieving reasonable pore size distribution. In addition to using template agent, a large number of impurities contained in the carbon precursor can also be used as self-template. The adjustment of pore structure can also be realized by combining different chemical activators. For example, different pore size distribution can be obtained by combining K+ and Na+ ions with different ionic sizes. Using the fluidity of KCl at high temperature, the intermediate products of KOH can be carried to a wider and deeper extent, so as to realize the transformation from microporous to mesoporous. The surface chemical activity can be improved in 2 ways: by the pre-oxidation of carbon precursors and the introduction of heteroatoms. If the raw coal is pretreated by strong acid or strong oxidant, the organic oxygen content of the prepared carbon material can be increased, the active sites are increased and the wettability is improved. Heteroatoms can be introduced into carbon materials by dopant doping, the most applied of which is N doping. The introduced nitrogen-containing structures mainly include pyrro-N (N-5), pyridin-N (N-6), Quaternary N(N-Q), and pyridine-N-oxide (N-X). In addition, O, B, S and P are the common doped heteroatoms. Another way to introduce heteroatoms is through co-carbonization of coal with biomass, in which biomass acts as both carbon and heteroatom source. The wettability, electrical conductivity and structural stability of carbon materials can be improved by doping heteroatoms, and a certain amount of pseudocapacitance can be produced. In this paper, the research progress of coal-based porous carbon electrode materials in recent years was reviewed from the above aspects, the advantages and disadvantages of different modification methods were analyzed, the existing problems were discussed, and the future research trend of coal-based porous carbon for supercapacitors was prospected.

0 引言

1 孔径分布调整

   1.1 物理活化和化学活化联合调孔

   1.2 模板法与化学活化联合调孔

   1.3 不同化学活化剂联合调孔

2 表面化学活性改善

   2.1 前驱体预氧化

   2.2 杂原子掺杂

   2.3 生物质与煤共碳化

3 结语及展望