Methane Pyrolysis with a Molten Cu–Bi Alloy Catalyst

Clarke Palmer, Maryam Tarazkar, Henrik Høgh Kristoffersen, John Gelinas, Michael J. Gordon, Eric W. McFarland, Horia Metiu*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Current methods of hydrogen productionfrom methane generate more than 5 kg of CO2 for every 1 kg of hydrogen. Methane pyrolysison conventional solid heterogeneous catalysts produces hydrogen without CO2, but the carbon coproduct poisons the catalyst. This can be avoided by using a molten metal alloy catalyst. We present here a study of methane pyrolysis using mixtures of molten Cu–Bialloys as the catalyst. We find that molten Cu–Bi is an active catalyst, even though pure molten Bi and Cu are not. Surface tension measurements and constant-temperature ab initio molecular dynamics simulations indicate that the surface is enriched in Bi and that the catalytic activity is correlated with the concentration of Bi at the surface. Bader charge analysis indicates that bismuth donates charge to copper. In the most stable configuration of dissociated methane on these liquid surfaces, CH3 binds to a bismuth surface atom and H to Cu. The energy barriers for the dissociative adsorption of methane, calculated using the nudged elastic band (NEB) method, are between 2.5 and 2.6 eV, depending on the binding site on the surface of the Cu45Bi55 alloy. The computed barriersare in rough agreement with the experimental apparent activation energy of 2.3 eV.
Original languageEnglish
JournalACS Catalysis
Volume9
Pages (from-to)8337-8345
Number of pages9
ISSN2155-5435
DOIs
Publication statusPublished - 2019

Keywords

  • Methane
  • Pyrolysis
  • Hydrogen
  • Coking
  • Ab initio molecular dynamics
  • Surface tension
  • Bismuth/copper
  • Molten alloy

Cite this

Palmer, C., Tarazkar, M., Kristoffersen, H. H., Gelinas, J., Gordon, M. J., McFarland, E. W., & Metiu, H. (2019). Methane Pyrolysis with a Molten Cu–Bi Alloy Catalyst. ACS Catalysis, 9, 8337-8345. https://doi.org/10.1021/acscatal.9b01833