Electroreduction of Al (III) and Controlled Synthesis of Aluminum Powders in Low‑Temperature Molten Salt

Abstract Conventional aluminum powder fabrication techniques such as ball milling and gas atomization suffer from wide particle‑size distribution, high energy consumption and impurity contamination, limiting their application in high‑end manufacturing. Low‑temperature molten‑salt electrolysis is a promising alternative, yet Al(III) electrochemical behavior and powder morphology control remain poorly understood. Herein, cyclic voltammetry, square‑wave voltammetry and chronopotentiometry were adopted to explore Al(III) electroreduction on tungsten electrodes in KCl‑LiCl‑AlCl3 melts at 375‑450 ℃. Al(III) undergoes a single‑step three‑electron quasi‑reversible reduction under diffusion control. Three Al‑Li intermetallic phases form via Li underpotential deposition. Al(III) diffusion coefficients range from 4.57×10-6 to 10.70×10-6 cm2 s-1 with an activation energy of 42.77 kJ mol-1, around half the value for high‑temperature halide melts. Galvanostatic electrolysis shows temperature modifies Al powder morphology from nanorods to microspheres. Uniform ~50 nm Al spherical nanoparticles free of Al‑Li alloys are obtained under optimized conditions. This work provides fundamental electrochemical data and technical support for controllable production of high‑performance aluminum powders.