An Electrolysis-Distillation Approach for Producing Potassium Metal

Potassium (K) cannot be produced by molten-salt electrolysis due to its high vapor pressure and erosion of the graphite anode by K. To overcome this problem, a liquid tin (Sn) electrode was employed to enable the electrolysis by accommodating K in the form of K-Sn alloy that can be separated into K gas and Sn by a following distillation approach. The so-called electrolysis-distillation (ED) approach was conducted in molten K 2 CO 3 -KCl along with a nickel (Ni)-based inert oxygen-evolution anode at 150 to 700 mA/cm 2 at 700 °C. The K-Sn alloys were obtained with a current efficiency of >70 pct at 350 mA/cm 2 without harmful chlorine gas (Cl 2 ) generation, and the chemical diffusion coefficient of K in liquid Sn is ~ 5.21×10 −5 cm 2 /s. Moreover, the Ni-based alloy inert anode was stably served for over 100 hours. The vacuum distillation was conducted at 650 °C for 90 minutes to obtain K metal with a purity of 99.99 pct and a recovery rate of 93.5 pct. Therefore, the ED approach developed here is an efficient and clean route to produce K metal.