We employed a long Chronoamperometry (CA) study to measure the evolved oxygen during the water electrooxidation and methanol assisted water electrooxidation process. The leak proof three-electrode electrochemical setup was involved during the 6-hour CA experiment and the evolution of oxygen moles over time sampled in the head space of the closed electrochemical cell (1 ml of gas was taken) were collected and subjected to gas chromatograph in 30-minute interval. Figure (b) clearly demonstrate that the oxygen mole increased progressively throughout the reaction duration for both the process and a significant increase in the oxygen mole with time during methanol electrooxidation compared to water electrooxidation.