Hydrogen is a clean fuel that can potentially revolutionize the energy supply chain and decarbonize fuel consumption. However, a key hurdle that needs to be overcome before a full‐scale hydrogen economy can be established is hydrogen storage which is currently the main limitation. Here, we propose that hydrogen gas can be stored in underground coal seams, where it adsorbs on the coal surface. However, currently, no hard data related to such a procedure exists. We, therefore, demonstrate experimentally that significant amounts of hydrogen gas can be stored via this route. Hydrogen adsorption capacities reached 0.6 moles H₂/kg of coal at 14.3 MPa, and adsorption capacity initially increased strongly with pressure (up to ∼4 MPa) and then plateaued out, while temperature only had a very minor influence. This study provides fundamental data for hydrogen storage in coal seams, and thus aids in the industrial implementation of a hydrogen supply chain.

Hydrogen is a clean fuel which has the potential to drastically decarbonize the energy supply chain. However, hydrogen storage is currently a key challenge; one solution to this problem is hydrogen geo‐storage, with which very large quantities of H₂ can be stored economically. Possible target formations are deep coal seams, and coal permeability is a key parameter which determines how fast H₂ can be injected and withdrawn again. However, it is well known that gas injection into coal can lead to coal swelling, which drastically reduces permeability. We thus injected H₂ gas into a coal core and measured dynamic permeability, while imaging the core via x‐ray micro‐tomography at reservoir conditions. Importantly, no changes in coal cleat morphology or permeability were observed. We conclude that H₂ geo‐storage in deep coal seams is feasible from a fundamental petro‐physical perspective; this work thus aids in the large‐scale implementation of a hydrogen economy.

MIL-96(Al)–Ca1 shows the highest CO₂ adsorption capacity; while MIL-96(Al)–Ca4 displays a distinguished morphology with the highest selectivity of CO₂/N₂.

Wettability is one of the main parameters controlling CO₂ injectivity and the movement of CO₂ plume during geological CO₂ sequestration. Despite significant research efforts, there is still a high uncertainty associated with the wettability of CO₂/brine/rock systems and how they evolve with CO₂ exposure. This study, therefore, aims to measure the contact angle of sandstone samples with varying clay content before and after laboratory core flooding at different reservoir pressures, of 10 MPa and 15 MPa, and a temperature of 323 K. The samples’ microstructural changes are also assessed to investigate any potential alteration in the samples’ structure due to carbonated water exposure. The results show that the advancing and receding contact angles increased with the increasing pressure for both the Berea and Bandera Gray samples. Moreover, the results indicate that Bandera Gray sandstone has a higher contact angle. The sandstones also turn slightly more hydrophobic after core flooding, indicating that the sandstones become more CO₂-wet after CO₂ injection. These results suggest that CO₂ flooding leads to an increase in the CO₂-wettability of sandstone, and thus an increase in vertical CO₂ plume migration and solubility trapping, and a reduction in the residual trapping capacity, especially when extrapolated to more prolonged field-scale injection and exposure times.