Electrochemical reduction behavior of PO43– ions in molten CaCl2

This work focuses on the electrochemical reduction behavior of PO 4 3– ions in molten CaCl 2 at 1123 K, aiming to develop a next-generation process for producing white phosphorus (P 4 ) through electrolysis of dissolved PO 4 3– . Results from cyclic voltammetry indicate a shift for the electrochemical reduction of PO 4 3– from a reversible reaction to a quasi-reversible one as the potential scan rate increases. The detachment rate of P 4 gas was found to be higher at the graphite electrode compared to Mo and W electrodes. The apparent diffusion coefficient of PO 4 3– , determined from chronoamperometry and chronopotentiometry at a graphite electrode, ranges from 1.43 to 2.26 × 10 –4 cm 2 s –1 . Additionally, an increase in the concentration of O 2– was found to decrease the detachment rate of P 4 gas, likely due to changes in the melt's physical properties. However, the increase in O 2– up to 0.30 mol% does not significantly affect the diffusion of PO 4 3– . This study provides valuable insights into the electrochemistry of PO 4 3– in molten CaCl 2 and offers a theoretical guidance for the technology development of P 4 production through electrolysis.