“One-dot” differential electrochemistry mass spectrometry (ODEMS) system was constructed by using a pin-hole covered with a Teflon film as gas inlet, thus leading to a high signal-to-noise ratio. The electrocatalytic activity of Pt/C and Pt-Ir/C electrocatalysts for the ethanol oxidation reaction (EOR) was investigated by potentiostatic techniques by ODEMS system. The 20 wt% electrocatalysts were synthesized by a modified polyol method and physically characterized by different techniques, including X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). The chronoamperometry study shows that, although the ethanol oxidation starts at lower potential on Pt-Ir/C, the kinetics of the reaction is faster on Pt/C. The CO₂ current efficiency (CCE) was also determined on both electrocatalysts after calibration of the m/z= 44 signal: the CCE value can reach up to 21% on Pt-Ir/C at room temperature, compared to ca. 6% on Pt/C.