Abstract Biocarbon is a carbon-rich, porous material derived from biomass, and a promising electrode material for supercapacitors. Supercapacitors are fast-charging, long-lasting energy storage devices that have high power density and low energy density, relative to batteries. Many of the most recent efforts to raise the energy density of supercapacitors focus on increasing the gravimetric capacitance (F/g) of the electrode material. However, the electrodes in commercial supercapacitors are thin films ( 1 mm thick) may alleviate this limitation, but only if monoliths can be made electrically conductive and facilitate ion migration in electrolyte. Whilst electrode thickness inevitably raises the overall resistance, the extent to which resistance is raised depends on the structure of the pores. This is also the case with electrolyte transport, making the pore structure of a monolith a key factor in improving performance. We use electron deceleration with a scanning electron microscope, physisorption, and x-ray diffraction to better understand what wood structures may be retained in biocarbon, and what new structures may be created when transforming wood to biocarbon. The features in four biocarbon samples are studied: one commercial hard-wood biocarbon, and three in-house biocarbon made from poplar, black locust, and pine via a slow pyrolysis procedure. The macro features of wood (those >1 μm, such as vessels, rays tracheids and pits) are retained in all four biocarbon samples. However, the retention of submicron wood features (e.g. layered structures within cell wall) is determined by pyrolysis conditions. Fast heating retained some submicron morphological structures in the commercial biocarbon, while the slow pyrolysis biocarbons did not have any distinguishable submicron features. The physisorption data suggested that the distributions of mesopores (2–50 nm) varied between biocarbons. X-ray diffraction showed the graphite nano-crystallites in all four biocarbon samples, but with significant size variations. Further study is necessary to learn how to tune the distribution of pore sizes, in order to create biocarbons with desirable pore structures.

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确定将木材转化为生物碳时保留的结构

摘要 生物质碳是一种源自生物质的富含碳的多孔材料，是一种很有前景的超级电容器电极材料。超级电容器是快速充电、持久的储能设备，相对于电池而言，它具有高功率密度和低能量密度。许多最近提高超级电容器能量密度的努力都集中在增加电极材料的重量电容 (F/g) 上。然而，商用超级电容器中的电极是薄膜（1 毫米厚）可以缓解这种限制，但前提是可以使整体材料具有导电性并促进电解质中的离子迁移。虽然电极厚度不可避免地会增加总电阻，但电阻增加的程度取决于孔的结构。电解质运输也是如此，使整料的孔结构成为提高性能的关键因素。我们将电子减速与扫描电子显微镜、物理吸附和 X 射线衍射结合使用，以更好地了解生物碳中可能保留的木材结构，以及将木材转化为生物碳时可能产生的新结构。研究了四种生物碳样品的特征：一种是商用硬木生物碳，另一种是由杨树、刺槐和松树通过缓慢热解程序制成的内部生物碳。所有四种生物碳样品都保留了木材的宏观特征（那些 >1 μm，例如容器、射线管胞和凹坑）。然而，亚微米木材特征（例如细胞壁内的分层结构）的保留取决于热解条件。快速加热在商业生物碳中保留了一些亚微米形态结构，而缓慢热解生物碳没有任何可区分的亚微米特征。物理吸附数据表明中孔（2-50 nm）的分布在生物碳之间有所不同。X 射线衍射显示所有四种生物碳样品中都有石墨纳米微晶，但尺寸变化很大。需要进一步研究以了解如何调整孔径分布，以创建具有理想孔隙结构的生物碳。但尺寸变化很大。需要进一步研究以了解如何调整孔径分布，以创建具有理想孔隙结构的生物碳。但尺寸变化很大。需要进一步研究以了解如何调整孔径分布，以创建具有理想孔隙结构的生物碳。