Abstract

In this work, an effective methodology of analysis of thermal desorption spectra (TDS) of hydrogen in carbon materials was further developed and applied. The methodology makes it possible, from TDS data of one heating rate, to determine the activation energies and pre-exponential factors of the rate constants of desorption processes. The TDS data of Rajasekaran et al. for hydrogenated epitaxial graphenes with a diamond-like structure (as in graphane) were analyzed. Some new information was obtained about the states of hydrogen in such unusual structures. It was shown that about half of the hydrogen contained in the samples is localized in the interfacial regions (between graphene and the substrate), while the desorption of such hydrogen is limited by diffusion (with three activation energies (34 kJ/mol(H₂), 45 kJ/mol(H₂), and 68 kJ/mol(H₂)) of hydrogen molecules in these regions to the lateral surfaces of the samples. It was also shown that the rest of the hydrogen is localized on the top surface of the samples, while desorption of hydrogen atoms occurs with two activation energies and frequency factors (174 kJ/mol(H), 2 × 10¹³ s⁻¹, and 256 kJ/mol(H), 3 × 10¹⁸ s⁻¹); the obtained quantities are comparable to the related characteristics for graphane.

摘要

在这项工作中，进一步开发和应用了一种分析碳材料中氢的热解吸光谱 (TDS) 的有效方法。该方法可以从一种加热速率的 TDS 数据中确定解吸过程的速率常数的活化能和指前因子。Rajasekaran 等人的 TDS 数据。分析了具有类金刚石结构（如石墨烷）的氢化外延石墨烯。获得了一些关于这种不寻常结构中氢状态的新信息。结果表明，样品中大约一半的氢位于界面区域（石墨烯和衬底之间），而这种氢的解吸受到扩散的限制（具有三种活化能（34 kJ/mol(H ₂)、45 kJ/mol(H ₂ ) 和 68 kJ/mol(H ₂ )) 的氢分子在这些区域到样品的侧面。还表明，其余的氢位于样品的顶部表面，而氢原子的解吸发生在两个活化能和频率因子（174 kJ/mol(H)，2 × 10 ¹³ s ^-1，和 256 kJ/mol(H), 3 × 10 ¹⁸ s ^-1 )；获得的数量与石墨烷的相关特性相当。