Platinum nanoparticles (PtNPs) were synthesized on surface-activated carbon fibers with high thermal conductivity, and paper-structured composites were fabricated by a papermaking technique, using the PtNPs-supported carbon fibers and ceramic fibers as matrix materials. As-prepared materials, denoted paper-structured PtNPs catalyst. possessed a unique porous microstructure derived from entangled inorganic fiber networks on which PtNPs were well dispersed. in catalytic reduction of nitrogen oxides (NOx) in the presence of methane (CH4), both of which are model exhaust gas components of combustion engines, paper-structured PtNPs catalyst demonstrated excellent NOx and CH4 removal efficiency and rapid thermal responsiveness by comparison with the PtNPs-supported carbon fibers. commercial Pt catalyst powders and a monolithic Pt-loaded honeycomb. These features of the new catalyst material are thought to arise from synergistic effects of the highly active PtNPs in association with the unique paper-like microstructure, in promoting effective transfer of heat and reactants to the active sites of the Pt nanocatalysts. The paper-structured PtNPs catalyst with paper-like practical utility is expected to be a promising catalytic material for efficient NOx gas purification. (C) 2009 Elsevier B.V. All rights reserved.