When generating hydrogen in a high-pressure catalytic reactor, what type of material should be used to prevent H2 embrittlement or corrosion?

The selection of a material is always at the discretion of the system designed and appropriate metallurgical experience knowledgeable about the process should be consulted as necessary.   316 stainless steel is one example of a material that is generally suitable for generation and containment of high-pressure hydrogen gas, but it is important to ensure stress levels in the piping and reactor structure are sufficiently low at the design pressure/temperature limits and within the allowable stress levels prescribed in ASME codes for pressure equipment and piping. As with any application, care must be taken in each specific application to address the required pressure, operating temperature, and potential contaminants, all of which could affect the material.