How does palladium absorb hydrogen and how does this change the metal?

Under suitable conditions, such as 80 °C (176 °F) and 1 atmosphere of pressure, palladium can absorb more than 900 times its own volume of hydrogen.1

This absorption process significantly alters the physical properties of the metal:

• Structural changes: The metal expands as it forms a metallic or alloylike hydride.1
• Mechanical properties: Palladium becomes harder, stronger, and less ductile.1
• Physical properties: Both the electrical conductivity and magnetic susceptibility of the metal decrease.1

The hydrogen absorbed by the palladium can be removed by increasing the temperature or reducing the pressure. Because hydrogen passes through the metal rapidly at high temperatures, heated palladium is often utilized as a semipermeable membrane for hydrogen purification or to regulate the flow of hydrogen in closed systems.1