Geometries of phthalocyanine (Pc) and metal (M = Cu, Fe, Zn, and Sn) Pc (MPc) adsorption on graphene have been studied using van der Waals density functional theory, which takes into account nonlocal correlation effects. The electronic properties were studied by the density functional theory. SnPc molecules energetically prefer to be adsorbed on the graphene surface with Sn-up conformation, which is different from the case of SnPc on the Ag(111) surface. For other MPcs, the centered metal atom remains within the plane of molecular backbone upon adsorbing on graphene surface. The adsorption of Pc and MPcs (M = Cu, Fe, Zn, and Sn) does not open the gap of graphene. Charges transfer slightly between the studied Pcs and graphene. The amount of charge transfer is the biggest, and the pattern of charge transfer is different for graphene−FePc.
The natural abundance of potassium in the earth's crust is 1000 times higher than that of lithium, so energy technologies built on potassium are more sustainable. Potassiumion batteries have attracted considerable attention because of their relatively low cost and high operating potential, but questions remain about the best anode material for such batteries. Here, we report first-principles computations based on density functional theory to investigate the performance of the UiO-66 metal− organic framework as an anode material for potassium-ion batteries; the goal is to provide a fundamental understanding of metal−organic framework (MOF)-based electrodes to guide the design and development of high-performance potassium-ion batteries. Our study includes the stability and electronic properties of potassiated structures and the mechanisms of potassium intercalation and diffusion in the framework. The results indicate that UiO-66 has a maximum specific capacity of 644 mAh/g as the anode of a potassium-ion battery. During potassiation, we observe charge transfer from potassium to carbon or oxygen of UiO-66 near the intercalated K. During K diffusion, the K migrates along the UiO-66 framework with a maximal migration energy barrier of 0.377 eV in the optimal pathway, which is much lower than the barriers for Li and Na diffusion in UiO-66. The diffusion coefficient of K in the anode is several orders of magnitude larger than those of Li and Na. This favors potassium ions over lithium ions or sodium ions when UiO-66 is the anode.
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