标题： 高度氢化单层石墨烯在超高真空和空气中的稳定性 显示英文标题

标题： Stability of Highly Hydrogenated Monolayer Graphene in Ultra-High Vacuum and in Air

摘要： 氢化单层石墨烯的稳定性通过X射线光电子能谱(XPS)在两种不同环境条件下进行了研究：超高真空(UHV)和常压环境。研究通过测量两种氢化样品的C 1s线型演化来进行，其中一个样品保存在UHV腔室中，另一个样品逐步暴露于空气中。 特别是，C 1s芯级谱中的$sp^3$相对强度，由面积比$\frac{sp^3}{sp^2+sp^3}$表示，被用作氢化程度的标志，并且在UHV中四个月后变化了(4 $\pm$ 2)$\%$。因此，发现氢化单层石墨烯具有长期稳定性，这表明只要保持在真空中，这种材料可以作为氢（或氚）存储的良好候选材料。 另一方面，暴露在空气中的样品的C 1s谱显示出显著氧化。碳氧化物的快速增长至饱和状态的时间常数$\tau$为1.8 $\pm$ 0.2小时。 最后，发现将氧化样品重新暴露于原子氢是一种有效的恢复氢化石墨烯的方法。这一过程通过进行XPS和电子能量损失谱学研究，后者用于观察CH伸缩模式作为重新氢化的直接迹象。 显示英文摘要

摘要： The stability of hydrogenated monolayer graphene was investigated via X-ray photoemission spectroscopy (XPS) for two different environmental conditions: ultra-high vacuum (UHV) and ambient pressure. The study is carried out by measuring the C 1s line shape evolution for two hydrogenated samples one kept in the UHV chamber and the other progressively exposed to air. In particular, the $sp^3$ relative intensity in the C 1s core-level spectrum, represented by the area ratio $\frac{sp^3}{sp^2+sp^3}$, was used as a marker for the hydrogenation-level and it resulted to vary by (4 $\pm$ 2)$\%$ in UHV after four months. Thus, a long-term stability of hydrogenated monolayer graphene was found, that indicates this material as a good candidate for hydrogen (or tritium) storage as long as it is kept in vacuum. On the other hand, the C 1s spectrum of the sample exposed to air shows a significant oxidation. A rapid growth up to saturation of the carbon oxides was observed with a time constant $\tau$ = 1.8 $\pm$ 0.2 hours. Finally, the re-exposure of the oxidised sample to atomic hydrogen was found to be an effective method for the recovery of hydrogenated graphene. This process was studied by carrying out both XPS and electron energy loss spectroscopy, the latter exploited to observe the CH stretching mode as a direct footprint of re-hydrogenation.