To achieve the necessary insights, suitable interrogation and measurement techniques are needed to detect what occurs on each electrode surface. High-speed video cameras have commonly been used as a non-invasive tool to monitor gas evolution on electrode surfaces. However, it is extremely difficult, if not physically impossible, to observe bubble generation in a zero-gap cell using a high-speed camera, even in the form of a boroscope. Therefore, it is necessary to develop other techniques that could be applied to the detection and characterization of bubble formation in water electrolysers.