Electrochemical reduction behavior of PO43- ions in molten CaCl2

This work focuses on the electrochemical reduction behavior of PO43- ions in molten CaCl2 at 1123 K, aiming to develop a next-generation process for producing white phosphorus (P-4) through electrolysis of dissolved PO43-. Results from cyclic voltammetry indicate a shift for the electrochemical reduction of PO43- 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 PO43-, determined from chronoamperometry and chronopotentiometry at a graphite electrode, ranges from 1.43 to 2.26 x 10(-4) cm(2) s(-1). Additionally, an increase in the concentration of O2- 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 O2- up to 0.30 mol% does not significantly affect the diffusion of PO43-. This study provides valuable insights into the electrochemistry of PO43- in molten CaCl2 and offers a theoretical guidance for the technology development of P-4 production through electrolysis.