We fabricated three different Pt/alumina catalysts for micro-thermoelectric hydrogen sensor (micro-THS). In the three Pt/alumina catalysts, two were prepared by impregnation of a commercial alumina with an aqueous solution of platinum (IV) chloride pentahydrate, and the third was prepared by impregnation of commercial alumina and nano-Pt with isobornyl acetate solution. To fabricate the micro-THS, the three Pt/alumina catalysts were integrated on thin membrane of the micro-THS, and its hydrogen sensing properties were investigated. The micro-THS with nano-Pt loaded alumina catalyst showed better sensing performance than those with Pt/alumina catalysts prepared by an aqueous solution of platinum (IV) chloride pentahydrate, because of effectively dispersed nano-Pt metal grain on the surface alumina grain observed by TEM. Its voltage signal was 15.7 mV for hydrogen concentration of 1% in dry air at catalyst temperature of 100 degrees C. (c) 2006 Springer Science + Business Media, Inc.