Catalyst materials for a fuel cell stack

A fuel cell stack comprising:

• a first end region having a first number of fuel cell units, the first end region connected to a first reactant inlet, the first reactant inlet connected to a first reactant source configured to provide a first reactant to the fuel cell stack, the first reactant source being a hydrogen source, at least one of the first number of fuel cell units being a first fuel cell unit including a membrane electrode assembly (MEA) with a first catalyst material on either or both an anode and a cathode of the first fuel cell unit, the first catalyst material including a first catalyst composition;
• a second end region having a second number of fuel cell units, the second end region connected to a second reactant inlet, the second reactant inlet connected to a second reactant source configured to provide a second reactant to the fuel cell stack, the second reactant source being an oxygen source, at least one of the second number of fuel cell units being a second fuel cell unit including an MEA with a second catalyst material on either or both an anode and a cathode of the second fuel cell unit, the second catalyst material including a second catalyst composition;
• and
• a middle region having a third number of fuel cell units, the middle region situated between the first and the second end region, at least one of the third number of fuel cell units being a third fuel cell unit including an MEA with a third catalyst material on either or both an anode and a cathode of the third fuel cell unit, the third catalyst material including a third catalyst composition, the first catalyst material includes a first catalyst crystal facet distribution having a first catalytic activity and a first durability, the second catalyst material has a second catalyst crystal facet distribution having a second catalytic activity and a second durability, the third catalyst material has a third catalyst crystal facet distribution having a third catalytic activity and a third durability, the second catalytic activity is higher than the first and third catalytic activities, and the first and third durabilities are higher than the second durability.

A fuel cell stack comprising:

• a first end region having a first number of fuel cell units, the first end region connected to a first reactant inlet, the first reactant inlet connected to a first reactant source configured to provide a first reactant to the fuel cell stack, the first reactant source being a hydrogen source, at least one of the first number of fuel cell units being a first fuel cell unit including a membrane electrode assembly (MEA) with a first catalyst material on either or both an anode and a cathode of the first fuel cell unit, the first catalyst material including a first catalyst composition;
• a second end region having a second number of fuel cell units, the second end region connected to a second reactant inlet, the second reactant inlet connected to a second reactant source configured to provide a second reactant to the fuel cell stack, the second reactant source being an oxygen source, at least one of the second number of fuel cell units being a second fuel cell unit including an MEA with a second catalyst material on either or both an anode and a cathode of the second fuel cell unit, the second catalyst material including a second catalyst composition;
• and
• a middle region having a third number of fuel cell units, the middle region situated between the first and the second end region, at least one of the third number of fuel cell units being a third fuel cell unit including an MEA with a third catalyst material on either or both an anode and a cathode of the third fuel cell unit, the third catalyst material including a third catalyst composition, the first catalyst material having a first catalytic activity and a first durability, the second catalyst material having a second catalytic activity and a second durability, the third catalyst material having a third catalytic activity and a third durability, the second catalytic activity is higher than the first and third catalytic activities, and the first and third durabilities are higher than the second durability, the second catalyst material having a catalyst skin formed of pure Pt.