National Renewable Energy Laboratory, Golden, Colorado 80401, USA.
J Chem Phys. 2013 Jul 28;139(4):044709. doi: 10.1063/1.4816365.
When compressive strain is applied to a single-layered material, the layer generally ripples along the third dimension to release the strain energy. In contrast, such a rippling effect is not favored when it is under tensile strain. Here, using first-principles density-functional calculations, we show that molecular adsorption on boron-doped graphene (BG) can be largely tuned by exploiting the rippling effect of the strained graphene. Under tensile strain, the adsorption energy of K2CO3, NO2, and NH3 on BG, for which the molecular adsorption is a chemisorption characterized by a covalent B-molecule bond, exhibits a superlinear dependence on the applied strain. In contrast, when microscopic ripples are present in the BG under compressive strain, the adsorption strength is significantly enhanced with increasing the strain. Such a nonlinear and asymmetric effect of strain on the molecular adsorption is a characteristic of two-dimensional systems, because a general elastic theory of molecular adsorption on three-dimensional systems gives a linear and symmetric strain effect on the adsorption strength. We provide the underlying mechanism of the anomalous strain effect on the chemical molecular adsorption on BG, in which the microscopic rippling of the graphene and the creation of the π-dangling bond state near the Dirac point play an important role. Our finding can be used to modify chemical reactivity of graphene with a wide range of application.
当压缩应变施加到单层材料上时，该层通常会沿第三维卷曲以释放应变能。相比之下，当处于拉伸应变时，这种卷曲效应不受青睐。在这里，我们使用第一性原理密度泛函计算表明，通过利用应变石墨烯的卷曲效应，可以在很大程度上调节硼掺杂石墨烯（BG）上的分子吸附。在拉伸应变下，BG 上的 K2CO3、NO2 和 NH3 的吸附能，其分子吸附是由共价 B-分子键表征的化学吸附，表现出对施加应变的超线性依赖性。相比之下，当 BG 中存在微观卷曲时，随着应变的增加，吸附强度显著增强。这种应变对分子吸附的非线性和不对称效应是二维系统的特征，因为三维系统上分子吸附的一般弹性理论对吸附强度的应变效应是线性和对称的。我们提供了 BG 上化学分子吸附异常应变效应的潜在机制，其中石墨烯的微观卷曲和狄拉克点附近的π悬空键状态的产生起着重要作用。我们的发现可用于修饰具有广泛应用的石墨烯的化学反应性。
