Alkaline water electrolysis

From Wikipedia, the free encyclopedia
Jump to: navigation, search
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]
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 (KOH) or sodium hydroxide (NaOH). These electrodes are separated by a diaphragm, separating the product gases and transporting the hydroxide ions (H+) 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 contains various minerals, some of which are alkaline while others are 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 acidic or alkaline. The requirement is that there must be ions in the water to conduct electricity for the water electrolysis process to occur.[4][5]


  1. ^ a b c d e f g h i j k l m n Carmo, M; Fritz D; Mergel J; Stolten D (2013). "A comprehensive review on PEM water electrolysis". Journal of Hydrogen Energy. 38 (12): 4901. 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. 163 (11): F3197. 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.