Measuring Total Sulphur Amount Fraction at picomol/mol in Hydrogen Fuel: New Results from cryo-GC-SCD Analytical Method

Fuel cell electric vehicles are expanding quickly from light-duty to heavy-duty applications such as buses or trucks. Hydrogen fuel quality needs to comply with ISO14687:2019 to avoid any improper performance of the vehicles. Total sulphur is one of the most impactful contaminants to a fuel cell system and has a threshold of 4 nmol/mol. Most analytical methods provide a limit of detection (LOD) of 1 nmol/mol for total sulphur in hydrogen. Total sulphur is often not quantified and reported as below LOD due to lack of sensitivity. A new analytical method using cryo-focussing gas chromatography with sulphur chemiluminescence detector (cryo-GC-SCD) was developed for picomol/mol analysis of total sulphur. The method achieved linearity between 150-16,000 picomol/mol, validated against NPL reference materials, and relative expanded uncertainty of 21% (k = 2). Samples from 11 hydrogen refuelling stations (HRS) were analysed using this method. The total sulphur amount fraction for all the HRSs was more than 10 times lower than the actual ISO14687:2019 threshold with highest value around 290 picomol/mol. The study demonstrated that the cryo-GC-SCD method can measure total sulphur at picomol/mol in hydrogen fuel. Additionally, it provided the first results on sulphur compound stability in an aluminium gas cylinder for which further study is needed.