Alleviating H2 embrittlement of Pd membrane in H2/CH4 coexisted system by carbon monoxide

Abstract

Pd based membrane played a crucial role in H₂ purification due to the unique permeation selectivity for H₂. Limited durability at low temperature was a main obstacle for the utilization of pure Pd membrane for H₂ purification in local, on-demand H₂ production. This research found that without further mixing of other metal, decoration of zeolite protection layer or in-situ modification of Pd based membranes, H₂ embrittlement could be alleviated by mixing small amount of CO in H₂/CH₄ coexisted system. The mechanism was probed via CO-TPD-MS test, gas adsorption analysis and density functional theory (DFT) simulations, revealing that CO competitively adsorbs on Pd active sites alongside CH₄, H₂O and H₂, forming a dynamically stabilized surface layer. Low temperature permeation stability improved by 300 ∼ 400 % compared to undoped systems. Loss of H₂ recovery rate had decreased by 75 ∼ 85 %. The saturated absorbed CO acted as a “armored” layer, which alleviated crystal phase transition caused by the mismatched dissolution and diffusion rate of H₂ on Pd bulk.