Li原子和Ca原子修饰VO_(2)单层储氢性能的第一性原理研究

First-Principles Study on Hydrogen Storage Performance of Li-and Ca-Decorated VO_(2) Monolayer

具有高储氢容量和可逆储氢性能的新材料的开发对氢能的大规模利用至关重要。基于第一性原理计算,研究了Li原子和Ca原子单独修饰和共修饰VO_(2)单层体系的H 2分子存储性能。结果表明Li原子和Ca原子均能稳定结合在VO_(2)单层表面而不产生金属团簇。单个Li原子和Ca原子分别最多可稳定吸附3个和6个H 2分子,且H 2分子平均吸附能均大于0.20 eV/H 2。吸附体系差分电荷和态密度分析结果表明,氢分子的极化机制以及氢分子与金属原子间的轨道杂化作用是H 2分子在金属原子周围稳定吸附的主要原因。Li原子修饰体系的储氢质量密度随着Li原子覆盖度的增加而逐渐增加,而Ca原子修饰体系的储氢质量密度在低金属覆盖度时较高;Li/Ca共修饰体系的储氢质量密度有所增加,其储氢质量密度为5.00%(质量分数)。此外,考虑了不同温度和压强条件下储氢体系的稳定性。

The exploitation of new hydrogen storage materials with high-capacity and reversible performance could play a very important role in the large-scale utilization of hydrogen as an energy source.The hydrogen storage performances of Li and Ca atoms decorated as well as Li/Ca co-decorated VO_(2) monolayer system were comprehensively investigated based on first-principles calculations.The metal atoms are stably adsorbed on the surface of the VO_(2) monolayer without forming metal clusters.Three and six hydrogen molecules can be absorbed by a Li atom and Ca atom,respectively,and its average adsorption energy is larger than 0.20 eV/H 2.Charge density differences and density of states of H 2 adsorbed systems were analyzed,and the results reveal that both the polarization mechanism and orbital hybridization are responsible for the adsorption of hydrogen molecules.The hydrogen storage capacity of the Li-decorated system increases with the increase of Li coverage,while that of Ca-decorated system is high only in lower Ca coverage.Moreover,Li/Ca co-decoration can effectively increase the hydrogen storage capacity of the system,its hydrogen storage mass density is 5.00%(mass fraction).Finally,the influence of temperature and pressure on the stability of hydrogen adsorption system is studied.