Afzalalghom Aliyeh, Beitollahi Ali, Mirkazemi Seyed Mohammad, Maleki Mahdi, Sarpoolaky Hossein
School of Metallurgy & Materials Engineering, Iran University of Science and Technology (IUST), Narmak, Tehran, 16846, Iran.
Small. 2024 May;20(22):e2308082. doi: 10.1002/smll.202308082. Epub 2024 Jan 22.
Graphitizability of organic precursors is the topic of numerous investigations due to the wide applications of graphitic materials in the industry and emerging technologies of supercapacitors, batteries, etc. Most polymers, such as polydivinyl benzene (PDVB) are classified as non-graphitizings that do not convert to Graphite even after heating to 3000℃. Here, for the first time, the development of graphitic structure in the hierarchal porous sulfonated-PDVB microspheres without employing specific equipment or additives like metal catalysts, organic ingredients, or graphite particles, at 1100°C is reported. The abnormal additive-free graphitic structure formation is confirmed by Raman spectroscopy (I/I = 0.87), high-resolution transmission electron microscopy (HRTEM), and selected area diffraction patterns (SAED), as well as x-ray diffraction patterns (XRD), while preservation of aromatic compounds from the carbonization is detected by Fourier transform infrared (FTIR) analysis. Polymer evolution from room temperature to 1100°C is also studied by FTIR, Raman spectroscopy, and XRD techniques. Based on the obtained results, it is suggested that the hierarchal and complicated ink-bottle pore network with a high surface area besides super micropores in the sulfonated-PDVB microspheres has served as nano-sized reaction media. These pores, hereafter referred as "dynamic nanoreactors", are expected to have confined the in-situ produced thermal decomposition products containing broken bond benzene rings, while changing dimensionally and structurally during the designed carbonization regime. This confinement has led to the benzene rings fusion at 250°C, a remarkable extension of them at 450°C, their growth to graphene sheets at 900°C and finally, the stacking of curved graphene layers at 1100°C. The results of this research put stress on the capability of nanopores as nanoreactors to facilitate reactions of decomposition products at low temperatures and ambient pressures to form stacked layers of graphene; A transformation that normally requires catalysts and very high pressures for only specific polyaromatic hydrocarbons.
由于石墨材料在工业以及超级电容器、电池等新兴技术中的广泛应用，有机前驱体的石墨化成为众多研究的主题。大多数聚合物，如聚二乙烯基苯（PDVB），被归类为非石墨化聚合物，即使加热到3000℃也不会转化为石墨。在此，首次报道了在1100℃下，无需使用特定设备或添加剂（如金属催化剂、有机成分或石墨颗粒），在分级多孔磺化PDVB微球中形成石墨结构。通过拉曼光谱（I/I = 0.87）、高分辨率透射电子显微镜（HRTEM）、选区衍射图案（SAED）以及X射线衍射图案（XRD）证实了无添加剂异常石墨结构的形成，同时通过傅里叶变换红外（FTIR）分析检测到碳化过程中芳香化合物的保留。还通过FTIR、拉曼光谱和XRD技术研究了聚合物从室温到1100℃的演变。基于所得结果，表明磺化PDVB微球中除了超微孔之外具有高表面积的分级且复杂的墨水瓶状孔网络充当了纳米级反应介质。这些孔，以下称为“动态纳米反应器”，预计在设计的碳化过程中，在尺寸和结构发生变化时，限制了原位产生的含有断键苯环的热分解产物。这种限制导致苯环在250℃时融合，在450℃时显著扩展，在900℃时生长为石墨烯片，最终在1100℃时弯曲的石墨烯层堆叠。这项研究结果强调了纳米孔作为纳米反应器在促进分解产物在低温和常压下反应以形成石墨烯堆叠层方面的能力；这种转变通常仅针对特定多环芳烃需要催化剂和非常高的压力。
