Effect of Environmental Contaminants on the Interfacial Properties of Two-Dimensional Materials
Effect of Environmental Contaminants on the Interfacial Properties of Two-Dimensional Materials
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DOI：
10.1021/accountsmr.2c00114
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发表时间：
2022-09
影响因子：
14.6
通讯作者：
Fan Yang;G. Stando;Annette G Thompson;Dhruthi Gundurao;Lei Li;Haitao Liu
中科院分区：
文献类型：
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作者：
Fan Yang;G. Stando;Annette G Thompson;Dhruthi Gundurao;Lei Li;Haitao Liu
结论二维材料在加工和储存过程中，其表面会自发地与环境中的分子发生吸附和反应。这种效应虽然对二维材料的许多特性有重大影响，但在涉及它们的研究中并不总是得到承认和解释。该帐户总结了我们最近的工作，了解周围环境如何影响二维材料的特性及其缓解策略。我们在讨论中重点介绍了石墨烯和碳氢化合物，并结合其他2D材料以及水和氧气的研究进行了补充。当石墨烯和石墨暴露在空气和水中时，它们的表面会吸附环境中残留的碳氢化合物，通常在万亿分之一至十亿分之一的水平。碳氢化合物的吸附降低了石墨烯和石墨的表面能，并在它们和电解质之间形成了屏障。因此，石墨烯和石墨的润湿性和电化学性质可以通过仅仅暴露于周围环境而显著改变。这些变化可能非常显著，但根据当地环境的不同，变化很大：几个小时的空气暴露可以使石墨烯的水接触角增加40°，并使石墨的双层电容减少50%！原始石墨碳的高疏水性和差的电化学性能，曾经被认为是这些材料的固有特性，主要是由于无意的表面污染。对于许多其他2D材料，例如MoS 2、六方BN和云母，报道了相同类型的烃吸附。在云母的情况下，其本质上是高度离子的，烃的吸附破坏了其与离子液体的相互作用，并改变了离子液体在云母表面的自组装结构。同样，水也以几种方式影响石墨烯的表面性质。水蒸气可以与碳氢化合物竞争吸附到石墨烯表面上，从而降低碳氢化合物污染的速率。水可以插在石墨烯和它的一些支撑基底之间，改变它们的相互作用。最后，水通过促进O2/H2O氧化还原电对的电化学掺杂机制来增强O2对2D材料的掺杂，减少和逆转2D材料的表面污染可以大大提高材料和器件的性能。虽然完全停止污染仍然具有挑战性，但如上所述，高湿度环境显示出降低污染率。对于已经被空气中碳氢化合物污染的样品，通过在高真空、高温或轻度氧化环境中处理，可以部分恢复其表面性质。
ConspectusThe surface of 2D materials can spontaneously adsorb and react with molecules in the environment during their processing and storage. This effect, while having a significant impact on many properties of 2D materials, is not always recognized and accounted for in the research involving them. This Account summarizes our recent work in understanding how the ambient environment impacts the properties of 2D materials and its mitigation strategies. We highlight graphene and hydrocarbons in our discussion and complement it with selected studies involving other 2D materials as well as water and oxygen.When graphene and graphite are exposed to air and water, their surfaces adsorb the residue hydrocarbons, typically at part-per-trillion to part-per-billion levels, in the environment. The adsorption of hydrocarbons reduces the surface energy of graphene and graphite and creates a barrier between them and the electrolyte. As a result, the wettability and electrochemical properties of graphene and graphite can be significantly altered by mere exposure to the ambient environment. These changes can be very significant yet highly variable depending on the local environment: several hours of air exposure can increase the water contact angle of graphene by up to 40° and reduce the double-layer capacitance of graphite by up to 50%! The high hydrophobicity and poor electrochemical performance of pristine graphitic carbons, once believed to be intrinsic properties of these materials, are largely due to unintentional surface contamination. The same type of hydrocarbon adsorption was reported for many other 2D materials, such as MoS2, hexagonal BN, and mica. In the case of mica, which is highly ionic in nature, the adsorption of hydrocarbons disrupts its interaction with ionic liquid and alters the self-assembly structure of ionic liquid at the mica surface. Similarly, water also impacts the surface properties of graphene in several ways. Water vapor can compete with hydrocarbons for adsorption onto the surface of graphene, thus reducing the rate of hydrocarbon contamination. Water can intercalate between graphene and some of its supporting substrate, altering their interactions. Finally, water enhances the doping of 2D materials by O2by promoting an electrochemical doping mechanism involving the O2/H2O redox couple.Reducing and reversing the surface contamination of 2D materials can greatly enhance material and device performances. While completely stopping the contamination is still challenging, a high-humidity environment is shown to reduce the rate of contamination, as mentioned above. For samples already contaminated by airborne hydrocarbons, their surface properties can be partially restored by treatment in high-vacuum, high-temperature, or mildly oxidative environments.