Galvanic operation of RED for electricity production has been demonstrated, but electrical power density and limiting current density are typically less than 0.2 W/m2 and 10 A/m2 . Here, we propose to produce hydrogen with a RED cell, through operating in an electrolytic mode. This multiple membrane electrolysis process is partially driven by the membranes through their “Donnan-potential”, and partially driven by additional electrical energy input [3-6]. By pushing the RED cell into the electrolytic region, high current density needed for hydrogen production, can be achieved.
Here, hydrogen production using an electrolytic RED is evaluated with a varying number of cell pairs (1 to 10) and with acidic, neutral and basic electrolytes at a fixed 10 mA/cm2. Under neutral conditions, the resulting voltage obtained from the RED cell decreased from 2.1± 0.1 V to 1.2±0.2 as the number of cell pairs increased from 1 to 10. In addition, the energy conversion efficiency of the system decreased due to the increase in mixing energy (ΔGmix.) from 130.6 J to 1203.2 J at higher cell pairs. When the cell was operated with an acidic cathode and basic anode, the applied voltage and energy consumption decreased by 45% compared to neutral pH. In addition, the current density achieved was 4x greater at a voltage 1 cell pair. The hydrogen to electrical energy ratio increased from to 100% at 2 mA/cm2 when the number of cell pairs increased from 1 to 10 with neutral electrolytes. This ratio increased by 3x under acid-base electrolytes.
- Logan, B.E. and M. Elimelech. Nature, 2012. 488(7411): p. 313-319.
- Zhu, X., He, W., & Logan, B. E. (2015). Reducing pumping energy by using different flow rates of high and low concentration solutions in reverse electrodialysis cells. Journal of Membrane Science, 486, 215-221.
- Hatzell, M.C., I. Ivanov, R.D. Cusick, X. Zhu, and B.E. Logan. Physical Chemistry Chemical Physics, 2014. 16(4): p. 1632-1638.
- Nazemi, M., Zhang J., Hatzell M.C., “Harvesting Natural Salinity Gradient Energy for Hydrogen Production through Reverse Electrodialysis (RED) Power Generation”, J. Electrochem. En. Conv. Stor., 2017; DOI: 10.1115/1.4035835.
- Hatzell, M.C., X. Zhu, and B.E. Logan. ACS Sustainable Chemistry & Engineering, 2014. 2(9): p. 2211-2216.
- Nazemi, M., Padgett, J., and Hatzell, M.C. (2017). Acid/Base Multi‐Ion Exchange Membrane‐Based Electrolysis System for Water Splitting. Energy Technology.