Improving Electrodeposition of Mg through an Open Circuit Potential Hold

We used in situ X-ray diffraction, XPS, SEM, and electrochemical methods to interrogate the mechanism of Mg electrodeposition from PhMgCl/AlCl₃ (APC) and EtMgCl electrolytes. An open circuit potential (OCP) pause following Mg deposition led to retained enhancement of Mg deposition and stripping kinetics along with lowered overpotentials for both. In situ X-ray diffraction demonstrated that the OCP pause led to a more polycrystalline deposit relative to that without the pause, while SEM presented micrographs that showed smaller deposits with an OCP hold. The improvement is attributed to an 'enhancement layer' that formed on the electrode during the OCP hold. Analysis of XPS data suggests that the 'enhancement layer' consists of Mg and Cl retained on the electrode surface, possibly following electrode depassivation.