Haldar Sandip, Mukherjee Sankha, Singh Chandra Veer
Department of Materials Science and Engineering, University of Toronto Toronto ON M5S 3E4 Canada
Department of Mechanical and Industrial Engineering, University of Toronto Toronto ON M5S 3E4 Canada.
RSC Adv. 2018 Jun 6;8(37):20748-20757. doi: 10.1039/c7ra12512g. eCollection 2018 Jun 5.
Recently synthesized two-dimensional (2D) borophene possesses unique structural, mechanical, electrical and optical properties. Herein, we present a comprehensive study of H storage in alkali metal decorated and defect containing 2D borophene using density functional theory calculations. While the adsorption of H over pristine borophene was found to be weak with a binding energy of -0.045 eV per H, metal decoration and point defects enhanced the adsorption strength significantly. Interestingly, the magnitudes of binding energy for a single H molecule over Li, Na and Ca decorated borophene were found to increase up to -0.36, -0.34, and -0.12 eV per H, respectively. On the other hand, while the binding energy of one H molecule over the borophene substrate containing a single vacancy (SV) was only -0.063 eV per H, similar to that of phosphorene, the binding energy increased to an enormous -0.69 eV per H over borophene containing a double vacancy (DV). To gain further insight into the H adsorption process and identify sources of charge transfer, differential charge densities and projected density of states were calculated. Significant charge accumulation and depletion caused strong polarization of the H molecules. Finally, Na, Li and Ca decorated borophene yielded the gravimetric densities 9.0%, 6.8%, and 7.6%, respectively. The gravimetric density of the borophene containing a DV was found to be the highest, a staggering 9.2%, owing to increased interactions between DV borophene and the H molecules. These results suggest that borophene can be an effective substrate for H storage by carefully engineering it with metal decoration and point defects.
最近合成的二维硼烯具有独特的结构、机械、电学和光学性质。在此，我们使用密度泛函理论计算对碱金属修饰和含缺陷的二维硼烯中的氢存储进行了全面研究。虽然发现氢在原始硼烯上的吸附较弱，每个氢的结合能为-0.045 eV，但金属修饰和点缺陷显著增强了吸附强度。有趣的是，发现单个氢分子在锂、钠和钙修饰的硼烯上的结合能大小分别增加到每个氢-0.36、-0.34和-0.12 eV。另一方面，虽然一个氢分子在含有单个空位（SV）的硼烯基底上的结合能仅为每个氢-0.063 eV，与磷烯相似，但在含有双空位（DV）的硼烯上，结合能增加到每个氢-0.69 eV。为了进一步深入了解氢吸附过程并确定电荷转移的来源，计算了差分电荷密度和投影态密度。显著的电荷积累和耗尽导致氢分子强烈极化。最后，钠、锂和钙修饰的硼烯的重量密度分别为9.0%、6.8%和7.6%。发现含有双空位的硼烯的重量密度最高，达到惊人的9.2%，这是由于双空位硼烯与氢分子之间的相互作用增加。这些结果表明，通过用金属修饰和点缺陷对硼烯进行精心设计，它可以成为一种有效的氢存储基底。
