Now, writing in Nature Energy, David Sinton, Edward Sargent and co-workers introduce a porous hydrophilic separator designed to replace conventional AEMs in CO electrolyzers. This separating component addresses critical limitations by enabling highly efficient ion transport while effectively suppressing gas crossover. The authors achieved optimized performance by systematically engineering the separator’s thickness, pore size and porosity, which reduced cell voltage and substantially improved energy efficiency. Further system gains were realized by replacing the precious iridium oxide anode catalyst with a nickel–iron–boride alternative and fine-tuning the operating temperature. The integrated approach delivered a high-performance electrolyzer that operates at lower full-cell voltage, with higher energy efficiency and improved single-pass carbon efficiency, all while maintaining stable performance over extended periods.
This study highlights the potential of microporous separators as promising alternatives to AEMs, which have been considered a key limiting factor for many electrochemical systems operating in alkaline environments. Indeed, around the same time and inspired by diaphragms in alkaline water electrolysis, an Article was published in Nature Communications by Feng Jiao and co-workers reporting on various low-cost commercial diaphragm materials as alternative separators in alkaline CO electrolyzers, also comparing favorably with AEMs. Notably, the Zirfon-based CO electrolyzer demonstrates comparable Faradaic efficiency for acetate with superior long-term stability, even under elevated temperatures, high alkaline electrolyte concentrations and when scaled up to a 100-cm2 cell area.
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