Quantum Chemical Predictions for Alkaline Earth (AE)-Doped Graphene: A Density Functional Theory (DFT) Based Investigation for a Novel Class of Carbon-Based Two-Dimensional Nanomaterials Toward Electrochemical, Catalytic and Electronic Applications

Abstract

Graphene doping is a known route towards increasing the reactivity of graphene, particularly for the oxygen reduction reaction in fuel cells and metal-air batteries. The most prominent dopants in graphene for ORR are non-metals near to carbon in the periodic table. While alkaline-earth elements, such as beryllium, magnesium, calcium, strontium and barium are relatively abundant in the Earth’s crust, graphenes modified with these elements have not been fully explored. Graphene systems, which were substitutionally doped with alkaline-earth elements, were investigated through density functional theory (DFT) calculations to elucidate its energetics and electronic properties. A localized ionic bonding between alkaline-earth elements and the graphene substrate was observed, with greater charge transfer as inferred by Bader analysis for Be and Mg. The localized nature of the charge transfer from the dopant to the adjoining carbon atoms in the substrate is a novel property of AE-doped graphene. Semi-metallic properties due to strongly localized states near the Fermi level have been observed for all AE-doped graphenes except for Be. For Be, p-type semiconductor properties were observed consistent with previous studies on Be doped graphene. This will provide the groundwork for further study towards the use of alkaline-earth metal dopants in an alternative precious-metal free cathode material for metal-air battery and fuel cell applications. The basic and exploratory nature of this scientific study is also expected to open a path towards other emergent applications for the catalysis of other reactions, as well as in electronics and other domains. Observable trends between different alkaline-earth doped graphenes have also been investigated. Figure 1