[ electrolysis ]
Air 2O 2- → O 2
+ 4e
Anode
Electrolyte
O 2-
Electricity
Cathode
Hydrogen
2H 2
+ 2O 2 ← 2H 2 O + 4e Steam
On the anode side , often composed of nickel or other conductive materials , water molecules split into hydrogen ions ( H + ) and oxygen ions ( O 2− ). The hydrogen ions ( H + ) produced at the anode move through the solid oxide electrolyte to reach the cathode . This electrolyte material , Yttriastabilized zirconia ( YSZ ), offers excellent ionic conductivity across a wide range of temperatures while blocking the flow of electrons . It also keeps fuel and oxygen separate and retains water while ensuring structural stability .
For fuel-based electrodes , one standout material is nickel-doped Yttria-stabilized zirconia ( Ni-YSZ ) composite . This selection is driven by several key factors : its high porosity , which supports the smooth flow of reactants ; its exceptional electrocatalytic activity ; its ability to conduct both ions and electrons ( mixed ionic and electronic conductivity ); and its compatibility with the solid oxide electrolyte , preventing undesirable reactions with electrolyte materials . These qualities collectively contribute to the efficiency and reliability of solid oxide electrolyzers .
At the cathode , the hydrogen ions meet electrons from the external circuit to produce hydrogen gas ( H + ). Overall , the electrochemical process effectively breaks water down into its two constituent elements : hydrogen and oxygen .
In the electrode sandwich , other materials play a supporting role . For less demanding applications , the oxygen electrode uses strontium-doped lanthanum manganite ( LSM ) material , while more demanding situations call for Lanthanum strontium cobalt ferrite material .
Efficiency
SOECs set themselves apart from their counterparts , like PEM and alkaline electrolyzers , by operating at substantially higher temperatures , typically between 700 – 900 ° C . This temperature difference provides SOECs with a fundamental advantage – improved electrochemical efficiency .
These elevated temperatures translate to higher efficiency , a crucial factor in the pursuit of reducing the levelized cost of hydrogen ( LCOH ). Greater efficiency means producing
Hydrogen Tech World | Issue 12 | October 2023 17