Here we show decoupled water electrolysis concept, where hydrogen evolution and oxygen evolution are spatially and temporally separated using a charge storage (CS) electrode as a red-ox mediator. In intercalation step (Figure 1) the negative terminal of power supply is connected to the CS electrode and the positive terminal to the Pt electrode. At a certain potential, the OER starts on the Pt electrode (2H2O → 4H+ + 4e- + O2) and H+ intercalation takes place on the CS electrode. During the intercalation step O2 gas is released in the cell. In step deintercalation step the polarity of the power source is reversed and at a certain potential, hydrogen evolution reaction takes place on the Pt electrode (2H+ + 2e- → H2) and H deintercalation reaction on the CS electrode. During the deintercalation step, H2 gas is released in the cell and this is highly efficient step for H2 production.