College of Architecture and Environmental and National Engineering Research Center for Flue Gas Desulfurization, Sichuan University, Chengdu 610065, China.
Phys Chem Chem Phys. 2019 Feb 27;21(9):5133-5141. doi: 10.1039/c9cp00004f.
The selective adsorption of CO2 by alkali earth metal (AEM)-decorated double vacancy graphene (DVG) was investigated with the first principles method. It is found that Be, Ca, Sr and Ba can be anchored stably on the DVG (whereas Mg cannot), and the Ca-decorated sample (Ca_DVG) possesses the strongest CO2 adsorption with a heat release of -0.45 eV per CO2. Furthermore, the doping of oxygen atoms on Ca_DVG (denoted as Ca_PyODVG) can remarkably increase the adsorption energy to -0.74 eV per CO2. This considerable promotion is ascribed to a synergetic effect of Ca decoration and O doping, which boosts extra electrons to transfer from the Ca_PyODVG substrate to the adsorbed CO2 molecule via the Ca 3p-O 2s hybridization. Notably, the obtained Ca_PyODVG is demonstrated to have a more practical CO2 desorption temperature, as well as a broader window for the selective adsorption of CO2 over CH4 and H2. Our theoretical results imply that Ca_PyODVG should be a promising candidate for CO2 capture. Additionally, the adsorption energy of CO2 is linearly correlated to the work function of a substrate, which may be used to accelerate the experimental screening of promising adsorbents.
采用第一性原理方法研究了碱土金属（AEM）修饰的双空位石墨烯（DVG）对 CO2 的选择吸附。研究发现，Be、Ca、Sr 和 Ba 可以稳定地锚定在 DVG 上（而 Mg 不能），且 Ca 修饰的样品（Ca_DVG）对 CO2 的吸附最强，释放热为-0.45eV/CO2。此外，在 Ca_DVG 上掺杂氧原子（表示为 Ca_PyODVG）可以显著提高吸附能至-0.74eV/CO2。这种显著的促进作用归因于 Ca 修饰和 O 掺杂的协同效应，它通过 Ca 3p-O 2s 杂化促进额外的电子从 Ca_PyODVG 基底转移到吸附的 CO2 分子上。值得注意的是，得到的 Ca_PyODVG 具有更实用的 CO2 解吸温度，以及在 CO2 与 CH4 和 H2 的选择性吸附方面更宽的窗口。我们的理论结果表明，Ca_PyODVG 应该是 CO2 捕获的有前途的候选者。此外，CO2 的吸附能与基底的功函数呈线性相关，这可能用于加速有前途的吸附剂的实验筛选。
