Molecular Dynamics Simulation of the Interaction between Alkaline NaCl Solution and Carbon-Supported Composite Electrodes

Abstract

Using carbon-supported (M/C, M = Ag, MnO, MnO₂, Mn₃O₄ and Pd) composite electrodes as the oxygen depolarized cathode (ODC) for chlor-alkali electrolysis, the energy consumption can be greatly reduced. However, the electrode stability and mass transfer process caused by the interaction between the ODC and the electrolyte solution are not very ideal, resulting in low efficiency of the electroreduction reaction, and its mechanism is still unclear. In this work, the interaction model of ORR of M/C electrodes in alkaline NaCl solution (ANS) were constructed, and MD simulation of the models were carried out. Based on the calculation and analysis of the interaction energy, diffusion coefficient and radial distribution function, the interaction law between the carbon-supported composite electrode and ANS was found out, and the interaction mechanism was revealed. The results showed that the interaction between O₂ in ANS and different M/C electrodes is mutually attractive at 353 K, and the order is Ag/C > Pd/C > MnO/C > MnO₂/C >Mn₃O₄/C. The change law of diffusion coefficients of O₂ in different M/C composite electrode systems is consistent with that of the interaction energy, but the ANS is opposite. O₂ molecule needs to break through the interaction between ANS and M/C composite electrode to interact with the composite electrode. The results of RDF illustrated that it is difficult for O₂ molecule to bond with the active component M in different M/C electrodes in the short-range region, but they form non-bonding interaction in the remote region. On the other hand, ANS and the active component M of different M/C electrodes have bond interaction in the short-range region, and non-bond interaction is greater than bond interaction in the remote region. These results provide theoretical basis for further research and development of electrode materials in chlor-alkali electrolysis industry.