汉麻杆基活性炭表面织构与储氢性能的研究

以天然汉麻杆为原料，采用KOH化学活化的方法改变活化时间制备出了高比表面积活性炭，并且对其表面进行硝酸氧化处理，研究活性炭表面化学状态对其吸附性能的影响。采用77 K低温氮气吸附和FTIR对样品进行了表征，并在77 K、100 kPa的条件下测定样品的氢气吸附等温线。结果表明，所有样品具有较高的比表面积(2 435.93～3 240.95 m²·g^-1)和总孔容(1.3～1.98 cm³·g^-1)，且随活化时间的延长而增加，3.5 h达到最大值，之后由于骨架坍塌有所减小。所有样品的孔径分布较为一致呈多峰型分布，主要以小于2 nm的微孔为主，同时含有少量的中孔和大孔。活化3.5 h样品的吸氢量最大，达到3.28wt%。研究发现，吸氢量受比表面积和孔容等参数影响较大，77 K下不仅小于2 nm的微孔对活性炭吸氢行为贡献较大，中孔也有十分重要的影响。样品经硝酸氧化处理后，BET比表面积和总孔容均在一定程度上减小，而氢气吸附量也有所降低。

Texture and Hydrogen Adsorption of Activated Carbons Based on Hemp Stems

Hemp stems were used as raw materials and high-surface-area activated carbons were prepared through chemical activation with KOH as active agent in different activation times.The sample was treated with HNO_3 to study the effect of surface modification on adsorption capacity.The properties of the resulting samples were characterized by N2 adsorption-desorption techniques and FTIR.Hydrogen storage capacities at 77 K and 100 kPa were also determined.All samplesobtainhiigh surfaceareas(2435.93-3240.95m~2·g~(-1)and total pore vohmes(1.3-1.98 cm~3·g~(-1).Both of the surface area and total pore volumes increase with increasing activation time.As the activation time increase more than 3.5 h,both of the surface area and total pore volumes descend,which is due to the structure collapse.Pore size distributions were nearly similar and show multimodal dominated by micropores smaller than 2 nm with a small amount of meso/macropores.The maximum hydrogen uptake measured for the sample activated at 800℃ for 3.5 h reached 3.28wt％(in gravimetrie).Hydrogen adsorption is controlled mainly by textural properties such as surface area and pore volume.At 77 K.not only mieropores smaller than 2 nm but also mesopores contribute to the hydrogen adsorption.Treatment with HNO_3 lowered surface areas,total pore volumes and hydrogen adsorption capacities.