Evaluation of Porous Media Properties for the Performance of Sulfur-Depolarized Electrolysis

Sulfur-depolarized electrolysis (SDE) is an interesting alternative for H₂ production. Lower operational voltage (<1.2 V) and a valuable by-product offer an opportunity for economically competitive H₂ production in sectors where traditional processes are not feasible or competitive. However, given its incipient state in development, several questions are yet to be answered to achieve stable, competitive operation. A definitive reaction mechanism for the anodic sulfur oxidation reaction has not been defined and therefore optimal properties for the diffusion media have not been established. In this study, the influence of various commercial gas diffusion layers (GDLs) on SDE performance and acid generation was systematically investigated. The choice of GDL was found to have a decisive impact on overall cell performance, in some cases determining whether stable operation was achievable. By optimizing the diffusion layer, current densities of 1.3 A cm^-2 at 1.2 V were achieved, representing ≈30% improvement against state of the art. Based on observations during the study, a working hypothesis was proposed for the macroscale behavior of SDE during operation. These findings provide new insights into the anodic processes of SDE and identify critical parameters for developing efficient and durable electrochemical systems for low-voltage, economical hydrogen production.