First-principles studies of imidazolium chloroaluminate ionic liquids with different substitutions on the Pt(111) surface

The electrolyte/electrode interface is vital for aluminum electrodeposition, and is directly linked by the slight change of an imidazolium cation. The effect of functional groups substitution on the reactivity and adsorption behavior of methyl-imidazole heptachloride aluminum ILs such as 1-hydrogen-3-methylimidazole heptachloride aluminum ([H1MIM]Al2Cl7), 1-allyl-3-methylimidazole heptachloride aluminum ([AMIM]Al2Cl7), 1-Propyl-3methylimidazole heptachloride aluminum ([C3MIM]Al2Cl7) and 1-methoxyethyl-3-methylimidazole heptachloride aluminum ([MoeMIM]Al2Cl7) on the Pt(111) surface were revealed by first-principles methods. The active centers of [H1MIM]Al2Cl7 and [C3MIM]Al2Cl7 are distributed on the imidazole ring and the Cl atoms of the anion, while the active centers of [AMIM]Al2Cl7 and [MoeMIM]Al2Cl7 are distributed on the imidazole ring, the C or O atoms in the alkyl chain, and the Cl atoms of the anion. Moreover, the imidazole ring of [AMIM]Al2Cl7 has the minimum surface maximum value of electrostatic potential. It suggested that the imidazolium rings of these four ionic liquids (ILs) tend to adsorb on the Pt(111) surface in a flat-lying orientation, and that [AMIM]Al2Cl7 more easily adsorbs on the surface. The distances between the Cl atoms of Al2Cl7- and the Pt (111) surface decrease, indicating that the Al2Cl7- of [AMIM]Al2Cl7 can easily penetrate the electric double layer and move to the cathode surface to be discharged, which speeds up the nucleation rate. Additionally, [C3MIM]+, [AMIM]+, and [MoeMIM]+ have stronger interaction with the surfaces and larger volumes than [H1MIM]+, causing them to flatten the electrode surface and refine the grains during aluminum deposition. The results of adsorption calculations are found to be consistent with both the previous predictions and the experimental deposition effect of [AMIM]Al2Cl7 and [H1MIM]Al2Cl7 on the Pt electrode.

Automated summary

The study investigated the impact of functional group substitution on the reactivity and adsorption behavior of aluminum ILs on the Pt surface using first-principles methods. It was found that certain imidazolium ILs tend to adsorb on the Pt surface, aiding in the deposition of aluminum.