Effect of Toluene on PEMFC Performance

Liquid organic hydrogen carriers (LOHCs) are promising means for hydrogen transportation. They are compatible with existing liquid fuel transport infrastructure and enable for efficient and safe hydrogen storage and transfer over long distances. Toluene and dibenzyltoluene are considered the two most promising LOHCs. Toluene is probably a contaminant found in hydrogen released from these LOHC liquids. The impact of hydrocarbon contaminants on automotive type fuel cells has been analyzed to a limited extent, and a few species only have specific limits (CO, CO₂, HCOOH, HCHO, CH₄). Currently, hydrocarbons are limited to a total of 2 ppm (methane basis) in the automotive hydrogen fuel standard, ISO 14687:2019. This may lead to strict impurity levels for species from LOHC, and therefore higher costs of hydrogen purification and quality assurance. This work presents contamination studies with toluene. The measurements were conducted using a PEMFC short stack with anode recirculation and with high fuel utilization (98%). The results show no effect or only a small contamination effect with up to 20 ppm toluene, and clear contamination with 50 ppm toluene. This supports the need for more studies so that a separate limit can be defined for toluene in future versions of the ISO 14687.