Hydrogen Gas Adsorption of the Triassic Chang 7 Shale Member in the Ordos Basin, China

The present study investigates the adsorption of hydrogen gas by the Triassic Chang 7 Shale Member in the Ordos Basin, China. The mineral composition, microscopic morphology, pore characteristics, hydrogen adsorption capacity, and factors influencing hydrogen adsorption were explored using X-ray diffraction (XRD), thin section observations, nitrogen adsorption, scanning electron microscopy (SEM), and high-pressure hydrogen adsorption experiments. Based on these integrated tools, it was revealed that the Chang 7 Shale Member primarily comprises organic matter (kerogen) and clay minerals (predominantly an illite/smectite-mixed layer [I/S]). Nitrogen adsorption-desorption curves indicated the presence of slit-shaped pores, cracks, and wedge-shaped structures. The adsorption of hydrogen by shale decreases with increasing temperature and increases with increasing pressure. This adsorption behaviour conforms to both the Freundlich and Langmuir equations; moreover, the Freundlich equation provides a better fit. Organic matter (kerogen) and clay minerals considerably influence hydrogen adsorption. The present research provides insights into the occurrence of hydrogen in shale, offering implications for the exploration of natural hydrogen gas.