Hydrogen purity requirement for fuel cell vehicles and infrastructure?

• A. Hydrogen must meet moderate purity standards around 95%.
• B. Hydrogen can be any purity as long as the recipient tolerates impurities.
• C. Hydrogen must meet high purity standards (often ~99.9%+ with low contaminants); affects compression, filtration, and materials in distribution systems.
• D. Purity only matters for storage, not distribution.

Answer: (C)

Hydrogen purity is crucial because fuel cells are extremely sensitive to impurities. Even trace amounts of certain contaminants can poison the catalysts, reduce performance, and shorten the system’s life. The best answer reflects that hydrogen must meet high purity standards, typically around 99.9% or higher, with very low levels of contaminants such as carbon monoxide, sulfur compounds, ammonia, halogens, and particulates. Keeping purity high is essential not only for the fuel cell stack itself but also for the components that handle and transport hydrogen—compressors, filters, seals, and materials in the distribution network—since impurities can cause corrosion, catalyst poisoning, membrane degradation, or mechanical fouling. The other ideas fall short because moderate purity is usually not sufficient for PEM and other sensitive fuel cell technologies, assuming any tolerance of impurities is unsafe given performance variability and aging, and because purity concerns apply to both storage and distribution, not just storage.