瞬时离子释放扩散模型及熔盐电解固态WS<sub>2</sub>制备纳米W的液相扩散研究

Abstract

Over the past few years, preparation of metals by molten salt electrolysis of solid metal oxide (or sulfide) cathodes has attracted numerous interests from both academic and industrial communities. According to the three-phase interlines theories, diffusion of O2- (or S2-) ions should play an important role in the solid cathode process, however, it has seldom been studied due to the absence of both convenient theoretical and experimental methods. In this work, we introduced an instantaneous ion release diffusion model (IIRD Model) for porous electrodes as theoretical base, and fabricated mini porous electrodes by filling WS2/W mixture into the cylindrical cavities in a Mo foil substrate and performed double potential operations to study the liquid diffusion of S2- ions in the solid sulfide cathode in the equi-molar NaCl-KCl melts. The experimental results were in good accord with the theoretical equation. By curve fitting, the diffusion coefficient of S2- ions in the electrolysis generated porous W layer was evaluated as 9.2×10-6 cm2/s at 973 K, with the diffusion activation energy of about 53.4 kJ/mol. The study indicates that electrochemical reduction of WS2 to nanometer W can be achieved very quickly, and the electrolysis of solid WS2 cathode should be rate determined by the liquid diffusion of S2- ions in the generated porous W layer.