Quantum capacitances of alkaline-earth metals: Be, Ca, and Mg integrated on Al₁₂N₁₂ and Al₁₂P₁₂ nanostructured—insight from DFT approach

In this study, the quantum capacitance (C_Q) of aluminum nitride (Al₁₂N₁₂) and aluminum phosphide (Al₁₂P₁₂) have been investigated to explore the effects of Be, Ca, and Mg alkali-earth metals doping on the electronic properties, structural ability, and quantum capacitance of Al₁₂N₁₂@Be, Al₁₂N₁₂@Mg, Al₁₂N₁₂@Ca, Al₁₂P₁₂@Be, Al₁₂P₁₂@Mg, and Al₁₂P₁₂@Ca nanostructured using density functional theory (DFT) computation at the ωB97XD/6-311+G(d, p) level of theory. Detailed investigation into the electronic properties showed that Al₁₂N₁₂@Be and Al₁₂P₁₂@Be with value 6.95 and 6.17 eV possessed greater energy gap. Al₁₂N₁₂@Be and Al₁₂P₁₂@Ca possessed higher second-order stabilization energy with values 245.15 and 372.9 kJ/mol, respectively. Investigation into the quantum capacitance showed the maximum quantum capacitance with respect to Al₁₂N₁₂ surface is observed in Al₁₂N₁₂@Be with C_Q value of 193.20 μF/cm², and with respect to Al₁₂N₁₂, it is observed in Al₁₂P₁₂@Ca with C_Q value of 107.14 μF/cm². The trend of results obtained, can be seen to provide an effective and simple new idea for the design of Al₁₂N₁₂ and Al₁₂P₁₂-based supercapacitors that possess high energy density and storage ability. Graphical abstract: [Figure not available: see fulltext.]