We have developed a method for in-operando visualization of the interfacial pH during electrochemical reactions using electrochemically coupled laser scanning confocal microscopy (LSCM). We work with either addition of of pH fluorescent probes or synthesized pH nanosensors to spatio-temporally track the pH changes during the reaction. The approach allows us to monitor and quantify the dynamics of pH dependent reactions in 4D (three spatial dimensions plus time) and gain fundamental understanding on how imposed external forces (e.g. voltage) as well as electrode geometry affect the overall performance of the electrochemical process.