Aluminum Nanoplatelet Electrodeposition in AlCl3–1-Ethyl-3-Methylimidazolium Chloride–Urea Melts

Abstract

The electrodeposition behavior of Al nanoplatelets, which are two-dimensional Al metal thin layer deposits, was investigated in five types of Lewis acidic 60–x–(40−x) [0 ≤ x ≤ 40] mol% AlCl3–1-ethyl-3-methylimidazolium chloride ([C2mim]Cl)–urea room-temperature melts. Al nanoplatelets were obtained in 60–10–30 and 60–0–40 mol% AlCl3–[C2mim]Cl–urea melts. X-ray diffraction measurements revealed that these Al nanoplatelets were oriented in the 111 direction. The formation of this anomalous Al nanoplatelets was analyzed using the operando digital microscope observation technique with our original air-tight electrochemical cell. We succeeded in video recording of the entire formation of Al nanoplatelets in the 60–0–40 mol% AlCl3–[C2mim]Cl–urea melt. Considering these results and electrode reactions involved in the Al deposition process, the electrodeposition behavior of the Al nanoplatelet formation could be attributed to the adequate quantities of free urea molecules generated during the electrode reaction and their specific adsorption onto the (111) Al crystal plane. The applied current density was an important key factor for the electrodeposition of the Al nanoplatelets in the AlCl3–[C2mim]Cl–urea melt. Al nanoplatelets were produced at low applied current densities smaller than −5.0 mA cm−2. The Al nanoplatelets became larger at lower applied current densities.