The effect of alkyl chain length on imidazole chloroaluminate ionic liquid/Pt(1 1 1) interface and aluminum deposition: A DFT-D3 study

Abstract

The structure, active sites, and adsorption mechanism of imidazole-based ionic liquids ([CnMIM]Al2Cl7) (n = 1, 2, 4, or 6) on the Pt(111) surface and their effects on aluminum electrodeposition were evaluated by first-principles approaches. The active sites of imidazolium ILs were on the cationic imidazole ring. The adsorption order was [HMIM]Al2Cl7 >[BMIM]Al2Cl7 >[EMIM]Al2Cl7 > [C1MIM]Al2Cl7. The electrostatic interaction, electrostatic induction, and the interfacial dipole effect made the ionic liquids with longer alkyl chain increase the coverage of cations on the Pt(111) surface as well as the number of charge transfers from ionic liquids to the Pt(111) surface, and decrease the distance between chlorine atoms and the Pt(111) surface. This is beneficial to suppress the dendrite formation during the electrochemical process and deposit aluminum in smaller sizes. These results will provide a basis for the selection of efficient ionic liquids of aluminum electrodeposition.