Enhanced hydrogen storage in Ca-doped aluminum phosphide nanocages: A DFT study on alkali and alkaline earth metal dopants

Abstract

Hydrogen is a clean and sustainable alternative to fossil fuels, but its efficient storage remains a critical challenge. This study explores the hydrogen storage potential of alkali and alkaline earth metal-doped aluminum phosphide (Al12P12) nanocages using Density Functional Theory (DFT) at the B3LYP/6–31 G(dp) level. The adsorption energies, geometric structures, and electronic properties of Na, Li, K, Be, Mg, and Ca-doped Al12P12 nanocages were systematically investigated. Among these, Ca-doped Al12P12 nanocages exhibited the highest stability and most favorable hydrogen adsorption characteristics, with adsorption energies indicative of chemisorption. Molecular electrostatic potential (MEP) analysis revealed optimal hydrogen adsorption sites, while natural bond orbital (NBO) and HOMO-LUMO studies highlighted significant electronic structure changes upon hydrogen adsorption. The Ca-doped nanocage reduced the HOMO-LUMO energy gap from 3.39 eV to 1.47 eV, making it a promising candidate for hydrogen storage applications. These findings provide new insights into the design of metal-doped nanostructures for efficient hydrogen storage, contributing to the development of advanced energy storage systems.

Keywords

• Aluminum Phosphide nanocages
• Metal-doped nanostructures
• Density functional theory
• Hydrogen adsorption
• Ca-doped Al12P12 nanocage