Department of Physics, University of Trento , Via Sommarive 14 Povo, 38123 Trento, Italy.
Fondazione Bruno Kessler , Center of Materials and Microsystems, Via Sommarive 18, 38123 Trento, Italy.
ACS Appl Mater Interfaces. 2017 May 24;9(20):17517-17525. doi: 10.1021/acsami.6b16493. Epub 2017 May 15.
The interaction of the confined gas with solid surface immersed in water is a common theme of many important fields such as self-cleaning surface, gas storage, and sensing. For that reason, we investigated the gas-graphite interaction in the water medium. The graphite surface was prepared by mechanical exfoliation of highly oriented pyrolytic graphite (HOPG). The surface chemistry and morphology were studied by X-ray photoelectron spectroscopy, profilometry, and atomic force microscopy. The surface energy of HOPG was estimated by contact angle measurements using the Owens-Wendt method. The interaction of gases (Ar, He, H, N, and air) with graphite was studied by a captive bubble method, in which the gas bubble was in contact with the exfoliated graphite surface in water media. The experimental data were corroborated by molecular dynamics simulations and density functional theory calculations. The surface energy of HOPG equaled to 52.8 mJ/m and more of 95% of the surface energy was attributed to dispersion interactions. The results on gas-surface interaction indicated that HOPG surface had gasphilic behavior for helium and hydrogen, while gasphobic behavior for argon and nitrogen. The results showed that the variation of the gas contact angle was related to the balance between the gas-surface and gas-gas interaction potentials. For helium and hydrogen the gas-surface interaction was particularly high compared to gas-gas interaction and this promoted the favorable interaction with graphite surface.
被限制气体与沉浸在水中的固体表面的相互作用是许多重要领域的常见主题，例如自清洁表面、气体储存和传感。出于这个原因，我们研究了水介质中的气体-石墨相互作用。石墨表面通过高取向热解石墨（HOPG）的机械剥离来制备。通过 X 射线光电子能谱、轮廓仪和原子力显微镜研究了表面化学和形态。通过 Owens-Wendt 方法使用接触角测量来估计 HOPG 的表面能。通过俘获气泡法研究了气体（Ar、He、H、N 和空气）与石墨的相互作用，其中气泡与剥离石墨表面在水介质中接触。实验数据得到了分子动力学模拟和密度泛函理论计算的证实。HOPG 的表面能等于 52.8 mJ/m，超过 95%的表面能归因于色散相互作用。气体-表面相互作用的结果表明，HOPG 表面对氦气和氢气具有亲气性，而对氩气和氮气具有疏气性。结果表明，气体接触角的变化与气体-表面和气体-气体相互作用势能之间的平衡有关。对于氦气和氢气，气体-表面相互作用与气体-气体相互作用相比特别高，这促进了与石墨表面的有利相互作用。
