The catalytic methane decomposition is the leading method for COx-free hydrogen and carbon nanomaterial production. In the present study, calcium-silicate based bimetallic Ni-Fe catalysts have been prepared and used to decompose the methane content of the 'product gas' obtained in the biomass gasification process for increasing total hydrogen production. Al2O3 was used as secondary support on calcium silicate based support material where Ni or Ni-Fe were doped by co-impregnation technique. The activity of catalysts was examined for diluted 6% methane-nitrogen mixture in a tubular reactor at different temperatures between 600 degrees C and 800 degrees C under atmospheric pressure, and data were collected using a quadrupole mass spectrometer. Catalysts were characterized by XRD, SEM/EDS, TEM, XPS, ICP-MS, BET, TPR, and TGA techniques. The relation between structural and textural properties of catalysts and their catalytic activity has been investigated. Even though the crystal structure of catalysts had a significant effect on the activity, a direct relation between the BET surface area and the activity was not observed. The methane conversion increased by increasing temperature up to 700 degrees C. The highest methane conversion has been obtained as 69% at 700 degrees C with F3 catalyst which has the highest Fe addition, and the addition of Fe improved the stability of catalysts. Moreover, carbon nanotubes with different diameter were formed during methane decomposition reaction, and the addition of Fe increased the formation tendency. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.