Cationic Catalysis during the Discharge of Carbonate Anions in Molten Salts

Abstract

The paper presents a quantum-chemical model and experimental confirmation of cation catalysis mechanism during the cathodic discharge of carbonate anion in chloride melt. The model of cationized carbonate complex, which describes the effect of the acid-base properties of the melt on the electronic, energetic, structural, and electrochemical properties of the carbonate anion, was proposed. Cation-anion interaction between CO3 2- anion and the strongly polarizing cations (Li+, Ca2+, Mg2+) result either in the formation of cationized anions (metal complexes) or in anion dissociation. Dissociation of CO3 2- anions can occur directly or through an intermediate stage of formation of "short-lived" metal complexes. The changes in the electrochemical behavior of CO3 2- anion were studied by voltammetry by the sequential addition of cations with different polarizing (electrostatic) force to the Na,K,Rb|Cl eutectic. The potentiostatic electrolyses carried out in three electrolytes Na,K,Rb|Cl–Na2CO3–LiCl(CaCl2,MgCl2) at a same potential of -1.1 V against Ag/AgCl reference electrode gave a carbon powder.