Carbon black (CB) supported PtAg non-alloy bimetal catalysts were prepared by incipient wetness impregnation and evaluated for CO preferential oxidation in excess H2 (PROX). PtAg/CB catalysts exhibited an evident synergistic effect. The catalyst support selection is crucial to the synergistic effect. X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning TEM energy dispersive X-ray analysis (STEM-EDX) characterization indicates no alloy was formed over the PtAg/CB catalyst after activation in H2 at 500 °C for 2 h. However, temperature-programmed reduction (TPR) and XRD data evidenced strong interactions between platinum and silver, as a result of their simultaneous reduction and high temperature activation. The PtAg interactions result in high catalytic performance and the synergistic effects. This is another example of model catalyst research translating to real world catalysis. PtAg non-alloy catalysts may also be effective in eliminating or alleviating catalyst poisoning by CO-like intermediates in direct liquid fuel cells.