Impact of Water Flow Rate on Current Efficiency in Solid Polymer Water Electrolyzer Under 2 MPa Condition

When solid polymer water electrolyzer is operated under high pressure conditions, large pressure difference forms between anode and cathode, causing crossover of produced gas, especially for hydrogen gas, and reducing its current efficiency. Supplying water into cathode channel, in addition to anode, is a countermeasure to decrease the crossover, because the water flow improves to drain the hydrogen gas outside of cell, leading to suppression of the crossover and increase of the efficiency. This countermeasure for the crossover is investigated by SPWE operation under 2 MPa condition with visualization of hydrogen bubbles in the SPWE. The investigation revealed that supplying water into cathode channel increased the efficiency within several percent under 0.33 A/cm2. Enhanced detachment of hydrogen bubbles from the surface of current supplier, which was confirmed by the visualization, increased the efficiency.