Alkaline water electrolysis

Alkaline water electrolysis
Typical Materials
Type of Electrolysis: Alkaline Water Electrolysis
Style of membrane/diaphragm: NiO
Bipolar/separator plate material: Stainless steel
Catalyst material on the anode: Ni/Co/Fe
Catalyst material on the cathode: Ni/C-Pt
Anode PTL material: Ti/Ni/zirconium
Cathode PTL material: Stainless steel mesh
State-of-the-art Operating Ranges
Cell temperature: 60-80C [1]
Stack pressure: <30 bar [1]
Cell area: < 4 m2 [1]
Current density: 0.2-0.4 A/cm2 [1]
Cell voltage: 1.8-2.40 V [1]
Power density: to 1.0 W/cm2 [1]
Part-load range: 20-40% [1]
Spec. energy consumption stack: 4.2-5.9 kWh/Nm3 [1]
Spec. energy consumption system: 4.5-7.0 kWh/Nm3 [1]
Cell voltage efficiency: 52-69% [1]
System hydrogen production rate: <760 Nm3/h [1]
Lifetime stack: <90,000 h [1]
Acceptable degradation rate: <3 µV/h [1]
System Lifetime: 20-30 a [1]

Alkaline water electrolysis has a long history in the chemical industry. It is a type of electrolyzer that is characterized by having two electrodes operating in a liquid alkaline electrolyte solution of potassium hydroxide or sodium hydroxide. These electrodes are separated by a diaphragm, separating the product gases and transporting the hydroxide ions from one electrode to the other.[1][2] A recent comparison showed that state-of-the-art nickel based water electrolyzers with alkaline electrolytes lead to competitive or even better efficiencies than acidic polymer electrolyte membrane water electrolysis with platinum group metal based electrocatalysts.[3]

Electrolysis requires minerals to be present in solution, tap, well, and ground water contain various minerals which are both alkaline and acidic. Water above a pH of 7.0 is considered alkaline, below 7.0 it is acidic. Electrolysis can occur only if the water is acid or alkaline, the requirement is that there are ions in the water to conduct electricity for the water electrolysis process to occur.[4][5]

References

  1. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Carmo, M; Fritz D; Mergel J; Stolten D (2013). "A comprehensive review on PEM water electrolysis". Journal of Hydrogen Energy. doi:10.1016/j.ijhydene.2013.01.151.
  2. ↑ "Alkaline Water Electrolysis" (PDF). Energy Carriers and Conversion Systems. Retrieved 19 October 2014.
  3. ↑ Schalenbach, M; Tjarks G; Carmo M; Lueke W; Mueller M; Stolten D (2016). "Acidic or Alkaline? Towards a New Perspective on the Efficiency of Water Electrolysis". Journal of The Electrochemical Society. doi:10.1149/2.0271611jes.
  4. ↑ "USGS Water Science School". Retrieved 14 October 2014.
  5. ↑ "Argonne National Laboratory Newton Ask a Scientist". Retrieved 14 October 2014.
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