The effect of alkyl chain length on imidazole chloroaluminate ionic liquid/Pt(111) interface and aluminum deposition: A DFT-D3 study

The structure, active sites, and adsorption mechanism of imidazole-based ionic liquids ([CnMIM]Al2Cl7) (n = 1, 2, 4, or 6) on the Pt(1 1 1) 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(1 1 1) surface as well as the number of charge transfers from ionic liquids to the Pt(1 1 1) surface, and decrease the distance between chlorine atoms and the Pt(1 1 1) 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.

Automated summary

The structure, active sites, and adsorption mechanism of imidazole-based ionic liquids on the Pt(1 1 1) surface and their effects on aluminum electrodeposition were evaluated by first-principles approaches. The longer alkyl chain of the ionic liquids increased the coverage of cations on the Pt(1 1 1) surface and the number of charge transfers, and decreased the distance between chlorine atoms and the Pt(1 1 1) surface. This suppresses dendrite formation and promotes deposition of aluminum in smaller sizes. These results will aid in selecting efficient ionic liquids for aluminum electrodeposition.