Molecular Dynamics Simulation of the Effect of GO Structure on the Interaction between Alkaline Solution and Ag/GO/C Composite Electrode

Abstract

A molecular model of the interaction between alkaline NaCl solution (Sol) and carbon-supported silver/graphene oxide (Ag/GO/C) composite electrode during oxygen reduction reaction was designed and constructed, and the Molecular dynamics (MD) simulation of the model was carried out. Based on the calculation and analysis of interaction energy (ΔE), diffusion coefficient (D) and radial distribution function (RDF), depending on the type and number of oxygen-containing functional groups of GO, the interaction law between alkaline solution and Ag/GO/C composite electrode was found out, and the interaction mechanism was revealed. The results showed that the interaction force between Sol and Ag/GO/C composite electrodes with 4 different GO structures (GO1, GO2, GO3 and GO4) is mutual attraction at 353 K. The interaction energy between the Sol and the Ag/GO2/C electrode is the highest in numerical terms, and the diffusion capacity of Na⁺ and Cl^– in the Sol is the weakest in the electrode system, indicating that the interaction between the Sol and the Ag/GO2/C electrode prevents the diffusion of solution molecules or ions on the surface of the electrode. The results of RDF showed that O₂, Na⁺ and Cl^– in solution within 3.5 Å have no obvious bonding effect with the electrode, while Sol has obvious bonding effect. When the interaction distance is 5–8 Å, O₂, Na⁺, Cl^–, Sol in the system and Ag atoms in different composite electrodes all have obvious non-bond interaction, indicating that Sol and the electrode are prone to bond interaction in the short-range region and non-bond interaction in the remote region, while O₂, Na⁺, Cl^–, and the electrode are only prone to non-bond interaction in the remote region. In other words, Ag/GO/C composite electrode has bonding and non-bonding effects in the formation of ORR system in alkaline NaCl solution, and it is mainly provided by non-bonding effects. When the number of –O–, –OH, –COOH in GO is 5 : 5 : 2 (GO2), that is, Ag/GO2/C composite electrode is most prone to ORR. This further proved that adding GO to the composite electrode can improve the catalytic performance of the electrode. These results are helpful to provide theoretical support for the research and development of electrodes in electrolytic chlor-alkali industry.