Enhanced O₂ selectivity of carbon molecular sieves by electrochemical oxidation for air separation

We propose a novel method for synthesizing carbon molecular sieves (CMS) with enhanced performance for O₂ separation from air using flow-type electrochemical oxidation (F-ECO). The F-ECO process introduces oxygen-containing functional groups (OCFGs) at pore entrances of activated carbon (AC), creating an ultrathin layer that works as an energy barrier for improving O₂ selectivity. The parameters for the F-ECO process were optimized using an experimental design method. The microstructure and surface species of the F-ECO-treated AC samples were characterized using X-ray photoelectron spectroscopy and gas adsorption measurements. The F-ECO treatment slightly reduced micropore volume but dramatically increased the O₂ dynamic selection coefficient of AC, indicating improved N₂/O₂ separation. The optimal F-ECO conditions produced a CMS with O₂ selectivity comparable to the CMS provided by conventional methods in industry, along with a faster O₂ adsorption rate while minimizing the decrease in effective O₂ adsorbed amount. This performance was achieved by carefully controlling the surface oxidation proposed by the experimental design method based on Bayesian optimization. The results demonstrate the potential of this approach for developing energy-efficient O₂ enrichment technologies.