Data on the diffusivity of hydrogen through rocks are published here. The studied rocks are related to storage formations, namely rock salt (salt caverns), sandstone (porous aquifer) and mudstone (cap rock). To quantify hydrogen diffusion rates in these rocks, a new experimental set up was build and tested to obtain break-through times and diffusion coefficients for dry and wet rock samples. The first data set is presented here. The main objectives of the study were (i) to verify the functionality and practicability of the experimental setup and (ii) to provide a first characterization of the H2 permeability of different rock types in context of hydrogen reservoirs.

The diffusion cell (FITOK, VACOM Company; Fig 1a, b) consists of two chambers, with the feed side filled with 2 vol% H2 in synthetic air and the permeate chamber filled with ambient air. In the permeate chamber, a hydrogen sensor was mounted on an SS PCB transmitter (EUROGAS Company) and the data connection was implemented via a pin port to a data logger (MEIER-NT Company) for online data monitoring and recording. The feed and permeate chamber comprise a volume of 0.2 L. They are connected by the sample-carrying through flange (Fig 1c) in which the sample is embedded with epoxy resin (ROTH Company).
The feed chamber was first purged for five minutes with a gas mixture of 2 vol% hydrogen in synthetic air (AIRLIQUIDE Company) at ambient pressure, through the feed gas inlet port and the feed gas outlet (Fig.1b). The permeate chamber contained ambient air and was equipped with a hydrogen sensor for the continuous measurement of hydrogen concentration in the permeate gas.