Figure 6. Low-cost hydrogen sensor (left); the sensitivity can be regulated via the potentiometer (colored in blue with gray screw); simplified hydrogen concentration measurement (right)

From

Hydrogen Evolution Reaction with Sunlight for School Chemistry Education

Malte Petersen, Paul Worliczek, Johannes B. Max, Afshin Nabiyan, Manuel Wejner, Jonas Eichhorn, Carsten Streb, Felix H. Schacher, Timm Wilke

World Journal of Chemical Education. 2021, 9(4), 190-196 doi:10.12691/wjce-9-4-12