Electro-Assisted Leaching of Platinum-Group Metals: Interfacial Electron Transfer, In Situ Oxidant Generation, Redox-Mediator Regeneration, and Process Integration—A Critical Review

Electro-assisted leaching of platinum-group metals (PGMs) is often described as applied current or enhanced extraction. Yet, these observations do not clarify whether charge transfers at the PGM surface or is first converted into a soluble oxidant. This critical review examines Pt, Pd, and Rh dissolution alongside selected Ru-related mechanistic evidence by organizing published studies into direct anodic attack, electrogenerated lixiviants, redox-mediator regeneration, and electrochemical potential control. It links electrochemical surface behavior to chloride complexation, oxidant speciation, feed accessibility, electrode design, mass transfer, parasitic reactions, and downstream recovery. Across these configurations, electrode potential, cell voltage, current density, and transferred charge vary; extraction yield alone cannot establish efficient electrical utilization. The proposed assessment therefore combines element-resolved recovery, oxidant utilization, Faradaic accounting, specific energy per unit of recovered metal, material balances, and reactor stability. Direct mechanistic evidence is distinguished from conventional chemical leaching comparisons and from downstream separation studies. The analysis identifies real-feed repeatability, Rh dissolution, chloride containment, electrode stability, and continuous operation as priority validation gaps. A closed-loop process is promising only when its improved selectivity and reagent recirculation outweigh electrical losses and additional separations.