Carbon nanofiber (CNF) layers have been synthesized on flat fused silica and silicon substrates, as well as inside flow channels of silicon-technology based microreactors by thermal catalytic chemical vapor deposition of ethylene using nickel thin-film catalyst. These CNF layers are to be used as structured catalyst support. The influence of the ethylene concentration and addition of hydrogen to the carbon-containing gas on the morphology of CNF layers was studied. Very low amount of CNFs were produced at low ethylene concentrations (<25%) due to the restricted supply of carbon species. Addition of hydrogen during the CNF growth resulted in significant enhancement of the CNF-yield. producing thicker layers of CNFs and CNFs with smaller diameters. Channels containing silicon micropillars covered with these CNFs have a significantly enhanced surface-to-volume ratio compared to bare microreactor channels (3-4 orders of magnitude). Deposition of well-distributed platinum nanoparticles was carried out on these CNF layers, exemplifying their functionality as structured catalyst support to be used in microreactors. (C) 2010 Elsevier B.V. All rights reserved.