Electrochemical Concepts A Practical Guide

Two platinum electrodes operate in a U-shaped electrochemical cell containing an acidic electrolyte. If approximately 1.8 V are applied between the two electrodes, current flows that produces both oxygen and hydrogen according to the following reactions  

The overvoltage (U- E°) is the driving force for the reaction to proceed at a desirable rate. However, it also causes an energy loss, which leads to heating of the cell. 

The electrochemical water decomposition reaction can be reversed according to 

---