Inspired by work using in situ Raman to observe of the pH gradient near the GDE electrode of CO2 Reduction in alkaline electrolyte 47 , we analysis the local surface pH on the surface of the copper nanoparticle. The local pH could determine by the ratio of 𝐶𝑂 /𝐻𝐶𝑂 . During our in situ Raman experiment, the distance between the immersion objective and the catalysts remains constant. Therefore, we can use the peak intensity of 𝐶𝑂 and 𝐻𝐶𝑂 to roughly determine the surface pH in different electrolysis conditions. We can observe the peak intensity of 𝐶𝑂 decreasing, while the peak intensity of 𝐻𝐶𝑂 is increasing, which indicates that the surface pH will increase with different anodic pulsed potentials. Also, since in the oxidation process, the surface *OH could react with the NH3 to form some NH2 or NH , this means the consumption of OH -during pulsed condition might occur faster than the without NH3 condition. This may help explain why under 1M KOH and 1M NH4OH electrolyte composition, the reaction has higher ethanol selectivity than the 1M KOH, 1.5 M NH4OH. The increase of bicarbonate concentration may also increase the selectivity for CH4 48 .