Electrocapillary Metal Expulsion in Ga–Bi–Sn–Pb Liquid Alloy System

Electrocapillary metal expulsion has recently emerged as a promising low‐temperature approach for separating metals from liquid alloys. However, prior studies have been largely limited to binary and ternary systems in aqueous electrolytes, where selectivity is primarily governed by intrinsic surface‐energy differences of the constituent solute metals. Here, we extend this framework to a multicomponent quaternary Ga–Bi–Sn–Pb liquid alloy and demonstrate that electrolyte composition provides an additional parameter for controlling expulsion behavior. Under cathodic polarization of the liquid metal–electrolyte interface, electrocapillary charging reduces interfacial tension and promotes surface over‐enrichment (supersaturation), leading to interfacial instability and the expulsion of solute metals as nanoparticles. The expulsion sequence is governed by the combined effects of surface energy and excess Gibbs free energy, following the order Bi → Pb → Sn → Ga in non‐aqueous electrolytes. In contrast, aqueous electrolytes enable selective suppression of Pb expulsion and cation‐dependent control over Bi and Sn separation. By exploiting this electrolyte‐dependent behavior, two protocols are established: a single‐electrolyte approach for rapid preconcentration and a stepwise electrolyte‐switching strategy for high‐purity separation, yielding Bi (>98 wt.%), Sn (∼88–92 wt.%), and Pb (>95 wt.%). This work establishes electrocapillary refining as a low‐temperature tunable platform for selective metal recovery from multicomponent liquid alloys.