石墨烯吸附钙原子储氢的第一性原理平面波计算
Hydrogen storage of calcium atoms adsorbed on graphene: First-principles plane wave calculations
摘要：
基于第一性原理平面波计算，我们发现吸附在石墨烯上的Ca可以作为高容量的储氢介质，其可以通过在室温下操作来回收。Ca通过将其4s-电荷的一部分贡献给石墨烯的空$π^*$ -带而被化学吸附。最后，吸附的Ca原子带正电，半金属石墨烯变成金属状态。虽然在石墨烯上形成（4x 4）图案的每个吸附的Ca原子可以吸附多达5个H_2分子，但是通过将Ca吸附到石墨烯的两侧并且通过增加覆盖率以形成（2x2）图案，可以将储氢容量增加到8.4wt%。带电Ca原子之间的库仑排斥作用阻碍了Ca原子的成簇。
英文摘要：
Based on the first-principles plane wave calculations, we showed that Ca adsorbed on graphene can serve as a high-capacity hydrogen storage medium, which can be recycled by operations at room temperature. Ca is chemisorbed by donating part of its 4s-charge to the empty $π^*$-band of graphene. At the end adsorbed Ca atom becomes positively charged and the semi-metallic graphene change into a metallic state. While each of adsorbed Ca atoms forming the (4x4) pattern on the graphene can absorb up to five H_2 molecules, hydrogen storage capacity can be increased to 8.4 wt % by adsorbing Ca to both sides of graphene and by increasing the coverage to form the (2x2) pattern. Clustering of Ca atoms is hindered by the repulsive Coulomb interaction between charged Ca atoms.
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