Irusta Yako, Morón-Navarrete Guillermo, González César
Departamento de Física de Materiales, Universidad Complutense de Madrid, E-28040 Madrid, Spain.
Instituto de Magnetismo Aplicado, UCM-ADIF, E-28230 Las Rozas de Madrid, Spain.
Nanotechnology. 2024 Jun 12;35(35). doi: 10.1088/1361-6528/ad50dd.
Motivated by the recent interest in the hydrogen energy, we have carried out a complete study of the catalytic activity of a defective molybdenum disulfide monolayer (MoS) by means of density functional theory (DFT) calculations. The MoSmonolayer is characterized by a nonreactive basal plane. In principle, its catalytic activity is concentrated at the edges, but an alternative way to increase such activity is obtained by creating active sites where the molecules can dissociate. These defects can be easily produced experimentally by different techniques. In our study, we have performed an atomic, energetic and electronic analysis of a hydrogen molecule adsorbed on a MoSmonolayer. In a first step, we have found that the Hmolecule remains physisorbed over both doped-free and Nb-doped MoSmonolayers, showing that the Nb atom does not increase the poor reactivity of the clean MoSlayer. Interestingly, our energetic results suggest that the vacancies will prefer to be formed close to the Nb atoms in the doped monolayer, but the small energy difference would allow the formation in non-doped like sites. Theoretically, we found out the conditions for the molecular dissociation on a S vacancy. In both cases, with and without Nb, the molecule should rotate from the original perpendicular position to an almost parallel orientation jumping an energetic barrier. After that, the atoms are separated binding to the Mo atoms around the missing S atom. Ourmolecular dynamics simulations show that for low pressure conditions (using one single molecule in the system) the Hprefers to desorb from the vacancy, while for larger pressures (when additional Hmolecules are added to the system) the molecule is finally dissociated on the vacancy. Our long simulations confirm the great stability of the structure with the two H atoms binding to the Mo atoms close to the vacancy. Finally, the inclusion of a third (or a fourth) H atom in the vacancy leads to the formation and desorption of a Hmolecule, leaving one (or two) atoms in the vacancy.
受近期对氢能的关注所推动，我们借助密度泛函理论（DFT）计算对缺陷二硫化钼单层（MoS）的催化活性进行了全面研究。MoS单层的特征在于其无反应性的基面。原则上，其催化活性集中在边缘，但增加这种活性的另一种方法是通过创建分子可解离的活性位点来实现。这些缺陷可以通过不同技术很容易地在实验中产生。在我们的研究中，我们对吸附在MoS单层上的氢分子进行了原子、能量和电子分析。第一步，我们发现氢分子在未掺杂和Nb掺杂的MoS单层上均保持物理吸附，这表明Nb原子并未增加清洁MoS层的低反应性。有趣的是，我们的能量结果表明，空位更倾向于在掺杂单层中的Nb原子附近形成，但能量差较小，这使得在未掺杂类似位点也可能形成。从理论上，我们找出了在硫空位上分子解离的条件。在有和没有Nb的两种情况下，分子都应从原来的垂直位置旋转到几乎平行的取向，跨越一个能量势垒。之后，原子分离并与缺失硫原子周围的钼原子结合。我们的分子动力学模拟表明，在低压条件下（系统中使用单个分子），氢更倾向于从空位解吸，而而而在较高压力下（当向系统中添加额外的氢分子时），分子最终会在空位上解离。我们的长时间模拟证实了两个氢原子与空位附近的钼原子结合时结构的高度稳定性。最后，在空位中引入第三个（或第四个）氢原子会导致氢分子的形成和解吸，空位中留下一个（或两个）原子。
