Preferential oxidation (PROX) of CO in H2 is the most efficient way to remove CO from practical reformate stream for PEM H2-O2 fuel cells. Over conventional Pt/Al2O3 catalyst, however, preferential oxidation of CO in H2 has been known to occur at temperatures above 150C, and the maximum CO conversion usually takes place at around 200C. In this study, the active reaction temperature window is enlarged to 25-200C over newly developed promoted catalysts compared with a narrow window at around 200C over the conventional Pt/Al2O3. A high void and tailorable sintered microfibrous carrier consisting of 5vol% 4 and 8 micron diameter Ni fibers is used to entrap 15vol% 150-250 micron diameter Al2O3 particulates. SEM images show the microstructures of the thin microfibrous entrapped alumina support particles. The alumina support particulates are uniformly entrapped into a well sinter-locked three-dimensional network of 4 and 8 micron Ni fibers. Cobalt and platinum are then dispersed onto the microfibrous entrapped alumina support particles by incipient-wetness impregnation method. The composite catalysts possess 80vol% voidage. At equivalent bed volumes, microfibrous entrapped catalysts achieve complete CO reduction (GC detection limit ~ 40 ppm CO) at 5 times higher gas hourly space velocity (GHSV) value compared with packed beds of 1-2mm catalyst particles demonstrating ultra-high contacting efficiency provided by the microfibrous entrapped catalysts. Hydrogen, oxygen, and carbon monoxide chemisorption, XRD, EDS, and TPR are performed to characterize the newly developed promoted Pt-Co/Al2O3 catalysts. The catalyst characterization studies reveal that nano-sized small Pt and Co particles are highly dispersed onto the entrapped micro-sized alumina support (220m2/g). The nano-dispersed nature of Pt and Co particles combined with the small support particulates (150-250 micron) promotes high contacting efficiency in the microfibrous entrapped catalysts compared with conventional packed beds of 1-2mm extrudates.