Formation of highly concentrated hydrogen through methane decomposition over Pd-based alloy catalysts

Highly concentrated hydrogen and carbon nanofibers were produced through methane decomposition in a temperature range of 973–1123 K. Pd-based alloys containing Ni, Co, Rh, or Fe showed high catalytic activity and long life for methane decomposition at 973 K. In particular, Pd–Co/Al2O3 and Pd–Ni/Al2O3 showed the highest hydrogen yield at reaction temperatures above 973 K among all the catalysts tested. Highly concentrated hydrogen (>94 vol% >94 vol% ) was formed by methane decomposition over Pd–Co/Al2O3 at 1123 K. SEM images of catalysts [M/Al2O3 (M = Fe, Co, Ni, and Pd) and Pd–M/Al2O3 (M = Fe, Co, Ni, Cu, Ag, and Rh)] after methane decomposition showed the formation of carbons with fibrous structure. In addition, TEM images of Pd–Co/Al2O3 at the initial stage of reaction showed that Pd–Co alloy particles formed carbons from several facets, whereas Co or Pd metal particles formed carbon nanofibers from one facet. This would be one reason why Pd–Co alloy catalysts showed high activity and long life for methane decomposition at high temperatures.