The accuracy of hydrogen sorption measurements on potential storage materials

The most common gas phase hydrogen sorption measurement techniques used for the characterisation of potential hydrogen storage materials are the volumetric, or manometric, and gravimetric methods and temperature-programmed desorption (TPD), also known as thermal desorption spectroscopy (TDS). In this article previous work relating to the accuracy of these measurements, including some comparative studies, is reviewed, together with some relevant standards and related guidelines. The potential sources of error in hydrogen sorption measurements performed volumetrically and gravimetrically are also discussed, together with some of those related to TPD. The issues covered include sample degassing procedures, hydrogen compressibility, gas purity and differences in helium and hydrogen leak rates.