[论文解读] Controlling Mixed Mo/MoS$_2$ Domains on Si by Molecular Beam Epitaxy for the Hydrogen Evolution Reaction

Eunseo Jeon, Vincent Masika Peheliwa+3 more|arXiv (Cornell University)|Jan 23, 2026

2D Materials and Applications被引用 0

一句话总结

论文展示了通过调控退火、循环次数和Mo/S比来在Si基底上通过分子束外延（MBE）实现MoS2的定制，以创建Mo-和MoS2富集区域，优化HER活性。

ABSTRACT

Molybdenum disulfide (MoS$_2$) is a prototypical layered transition-metal dichalcogenide whose electrocatalytic performance is governed by a delicate balance between crystallinity, defect density, and electronic conductivity. Here we report a systematic molecular beam epitaxy (MBE) study in which annealing temperature, deposition cycle number, and Mo/S thickness ratio were independently varied to control the structural and electronic properties of MoS$_2$ thin films. The successful epitaxial growth of atomically uniform MoS$_2$ directly on Si substrates enables strong interfacial coupling and efficient charge transfer, offering a viable route toward semiconductor-integrated catalytic architectures. X-ray diffraction, Raman spectroscopy, and X-ray absorption analyses reveal that higher annealing temperatures and excessive deposition cycles enhance crystallinity but reduce edge-site density and electrical conductivity, leading to diminished hydrogen evolution reaction (HER) activity. In contrast, intermediate cycle numbers and sulfur-deficient growth conditions yield heterostructures composed of MoS$_2$ with residual metallic Mo and sulfur vacancies, which activate otherwise inert basal planes while providing conductive pathways. These defect-engineered films deliver the best catalytic performance, achieving overpotentials as low as -0.33 V at -10 mA cm$^{-2}$, enlarged electrochemical surface area (ECSA) up to 8.0 cm$^2$, and mass-based turnover frequencies exceeding 23 mmol H$_2$ g$^{-1}$ s$^{-1}$, more than double those of stoichiometric counterparts. Our findings establish sulfur stoichiometry and growth kinetics as powerful levers to tune the interplay between structural order and catalytic activity in MBE-grown MoS$_2$ and point toward a broader strategy for engineering layered catalysts at the atomic scale.

研究动机与目标

• 了解退火温度、沉积循环次数与Mo/S厚度比对在Si上生长的MoS2结构与电子性质的影响。
• 研究界面耦合与电荷转移如何影响氢演化反应的催化性能。
• 识别缺陷工程策略（Mo残留、S空位）以激活基面并改善导电性。
• 评估硫化学计量与生长动力学如何调控晶体有序性与催化活性之间的平衡。

提出的方法

• 独立变化退火温度、沉积循环次数与Mo/S厚度比，对MoS2在Si上的MBE生长进行系统研究。
• 利用XRD、拉曼光谱以及X射线吸收分析等表征方法，将结构与性质相关联。
• 评估HER的电化学性能，包括超电势、电化学表面积（ECSA）和转化频率（TOF）。
• 分析晶体有序、边缘位点密度与导电性之间的权衡对催化活性的影响。

实验结果

研究问题

• RQ1 退火温度、沉积循环次数与Mo/S厚度比如何影响MoS2薄膜在Si上的晶体性和界面耦合？
• RQ2 硫化学计量和缺陷含量（如Mo残留、S空位）如何影响HER活性与导电性？
• RQ3 哪些生长条件能够在MoS2/Si异质结构中优化晶体有序性与催化缺陷工程之间的平衡？
• RQ4 混合Mo/MoS2区域是否能提高电荷转移并降低相对于理论MoS2的HER过电位？

主要发现

• 较高的退火温度和过多的沉积循环增加晶体有序性，但会降低边缘位点密度和导电性，从而降低HER活性。
• 中等循环次数和硫不足生长可得到带有残留金属Mo和S空位的异质结构，激活基面并提供导电通道。
• 经缺陷工程的MoS2薄膜在-10 mA cm^-2时的超电势可低至-0.33 V。
• 电化学表面积（ECSA）可达到8.0 cm^2，按质量计的 turnover frequency 超过23 mmol H2 g^-1 s^-1。
• 缺陷工程与硫化学计量成为调控MBE生长的MoS2/Si体系有序性与催化活性的关键手段。