Transforming Polymer Membranes for Better Hydrogen and CO2 Separation

July 23, 2024

TMA/water vapor exposures enlarge

A few TMA/water vapor exposures improves both molecular size-sieving and gas permeability of polybenzimidazole (PBI) membranes.

Scientific Achievement

CFN staff and collaborators showed that sequential exposures of polybenzimidazole membranes to trimethylaluminum and water vapor enhance H2 permeability (by 270%) and H2/CO2 selectivity (by 30%), improving utility for separations and blue H2 production.

Significance and Impact

This work demonstrates a scalable strategy to nanoengineer polymeric membranes for improved gas separation performance, crucial for clean H2 production and carbon capture.

Research Details

Atomic layer deposition (ALD) creates uniform sub-nanometer films on a variety of surfaces and nanopore walls and has been used to modify polymers to improve surface affinity towards specific molecules, solvent resistance, and barrier properties to gases and vapors. Here, for the first time, we demonstrate that few-cycle ALD can be used to engineer functional polymers at a sub-nanometer scale to improve both molecular size-sieving ability and, counterintuitively, gas permeability. Particularly, 1-cycle ALD treatment of polybenzimidazole (PBI) by sequential exposure to trimethylaluminum (TMA) and water vapor remarkably increases H2 permeability by 120%-270% and H2/CO2 selectivity by 30% at 35–200 ?C. The ALD not only deposits an AlOx layer on the surface but also enables the TMA to infiltrate and react with the bulk PBI to form an AlOx network, disrupting polymer chain packing and increasing chain rigidity. The membrane exhibits excellent stability when challenged with simulated syngas, overcoming the permeability/selectivity tradeoff for H2/CO2 separation. This study showcases a facile and scalable way of engineering polymeric membranes at a sub-nanometer level to improve molecular separation performance.

  • Enhanced membranes show excellent stability against high T and physical aging, surpassing the permeability/selectivity upper bound for H2/CO2
  • Process creates an AlOx network that disrupts polymer chain packing and increases rigidity.

Publication Reference

L. Hu, W.I. Lee, A. Subramanian, E. Deng, K. Kisslinger, S. Fan, V.T. Bui, Y. Ding, C.Y. Nam, H. Lin. “Few-cycle atomic layer deposition to nanoengineer polybenzimidazole for H2/CO2 separation”, Chemical Engineering Journal, 479, 147401 (2024).

DOI: 10.1016/j.cej.2023.147401
OSTI: https://www.osti.gov/biblio/2338136

Acknowledgment of Support

This work was funded by the U.S. Department of Energy (DOE) awards of DE-FE0031636 and DE-FE0032209. This research used the Materials Synthesis and Characterization and Electron Microscopy Facilities of the Center for Functional Nanomaterials, which is a U.S. DOE Office of Science User Facility, at Brookhaven National Laboratory under Contract No. DE-SC0012704.

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