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( OER ) takes place , oxidizing water into oxygen and generating protons ( H +). At the cathode , the hydrogen evolution reaction ( HER ) occurs , reducing protons to form hydrogen . The OER is crucial , as its kinetics are much slower than those of the HER , and the anode side is highly corrosive due to low pH , high potential , and oxygen generation . Industrial PEMWE usually operates under differential pressure from the cathode side to the anode side , resulting in additional stress at the CCM / PTL interface .
2 . Using thinner membranes . Current stateof-the-art is approximately 120 µ m , with future membranes moving toward 80 µ m and thinner . Thinner membranes reduce the electrochemical potential at a given current density , enabling higher current density in operation at a reasonable voltage . However , thin membranes are more prone to degradation , either from the electrochemical reaction or rough mechanical contact with the PTL .
Titanium PTLs play an important role in PEMWE , serving various functions . Not only do they transfer reactant water toward the catalyst layer , but they also facilitate good electrical conductivity between the bipolar plates and the catalyst layer . Titanium PTLs also remove heat from the electrochemical reaction and facilitate the removal of produced oxygen from the catalyst layer toward the bipolar plate . Additionally , they provide mechanical support to the CCM , especially under differential pressure . Titanium PTLs are designed to withstand harsh environments and offer corrosion-resistant properties . To support these functions , various PTL properties must be considered :
• Thickness
• Porosity
• Pore size distribution
• Surface roughness
• Mechanical stability and compressibility
• Electrical and thermal conductivity
• Permeability
Balancing these properties is challenging , and the interface between the PTL and the catalyst layer is crucial to ensuring high efficiency and long durability of PEMWE . The industry ’ s main target is to reduce the production cost of green hydrogen , wherein two clear trends are emerging :
1 . Reducing the iridium oxide loading at the anode ( a very scarce and expensive material ).
To address these trends , advanced PTLs are being developed with graded structures to :
• Optimize surface properties ( fine pore size distribution , thin and low porous layers ) to enhance catalyst utilization and provide a smooth contact for thin membranes , avoiding mechanical degradation .
• Optimize bulk properties ( mechanical compressibility , flow of water and gases ).
Ensuring the durability of PEMWE is crucial to maintaining low green hydrogen production costs . PTLs are coated with platinum , which provides good electrical contact with the catalyst layer and limits the oxidation / dissolution of titanium . The development of advanced coatings for titanium PTLs aims to reduce the amount of platinum used and explore alternative , cheaper coating materials .
Manufacturing challenges of PTLs
The production of PTLs for PEMWE systems involves several complex and demanding processes . These challenges must be addressed to ensure the high performance and durability of electrolyzers .
Material selection and processing are critical aspects of PTL manufacturing . Titanium is the preferred material for anode PTLs due to its corrosion resistance in harsh operating environments . However , processing titanium is challenging due to its high reactivity and the need for specialized equipment to handle the material .
Hydrogen Tech World | Issue 19 | December 2024 41