Permeabilidade seletiva de água e metanol através de filmes ultrafinos de rGO/Polímero: uma investigação computacional

Abstract

The search for clean and sustainable energy sources, driven by the growing energy demand and the problems caused by the use of fossil fuels, poses the challenge of developing technologies capable of replacing the polluting energy matrix (1). In this context, the Direct Methanol Fuel Cell (DMFC) stands out as an alternative, non-intermittent, and portable energy source, with low 𝐶𝑂2 emissions, no release of other polluting gases, and the ability to operate under conditions close to room temperature (2). Reduced graphene oxide (rGO) wrapped with poly(styrene sulfonate) (PSS) leads to the formation of a stable hybrid material (GPSS). This composite enables the fabrication of ultrathin films with promising barrier properties for DMFC applications, aiming to prevent methanol crossover poisoning, one of the major challenges of this technology (3). Experimental evidence shows that polymer electrolyte membranes of DMFCs coated with ultrathin GPSS-based films exhibit a significant reduction in methanol permeation and an increase in the cell’s power density. In this context, the objective of this work was to study the mechanism behind the methanol barrier provided by GPSS, which still allows the permeation of water and protons (4). To that end, classical Molecular Dynamics simulations were employed to investigate the structural and dynamic properties of GPSS at different polymer ionization fractions in a solvent composed of water, methanol, and hydronium. Regarding structural properties, the influence of the sulfonation fraction on the self-assembly of the layered film was discussed, including its effect on the PSS conformation and the distribution of rGO sheets, as well as the nature of the PSS–rGO interactions. As for the dynamic properties, the impact of GPSS structure on solvent diffusion was analyzed, and the mechanisms leading to the selective diffusion of methanol were elucidated.