Electrochemical charged adsorbent for efficient <scp> CH ₄ </scp> / <scp> N ₂ </scp> separation

Abstract The efficient separation of CH 4 /N 2 represents a significant bottleneck in unconventional natural gas upgrading. Herein, we present an electrochemical charging strategy to prepare anion‐modified activated carbon fibre adsorbents (ACF‐NO 3 and ACF‐SO 4 ). Multiple characterizations confirm the successful enrichment of nitrate (NO 3 − ) and sulphate (SO 4 2− ) ions within the activated carbon fibre pores. Remarkably, the charged adsorbent ACF‐SO 4 exhibits outstanding performance with a high CH 4 adsorption capacity of 1.22 mmol · g −1 and an IAST CH 4 /N 2 selectivity of 6.08 at 298 K and 1 bar, significantly exceeding the ACF‐blank. Compared to the ACF‐blank, the higher isosteric heats of CH 4 adsorption on charged adsorbents indicate the stronger adsorption affinity between the adsorbents and CH 4 after charging. The different affinities with CH 4 and N 2 on the blank and charged ACF imply that the incorporated anions can act as additional adsorption sites and contribute significantly to the efficient CH 4 /N 2 separation. Breakthrough experiments demonstrate the excellent dynamic CH 4 /N 2 separation performance of the charged adsorbents. The static and dynamic cycling tests also confirm the exceptional stability of the charged adsorbents with their performance remaining unchanged. This electrochemical modification strategy provides valuable insights into designing adsorbents for gas adsorption and separation.