The adsorption behavior of shale on H₂ and cushion gas (CH₄) is an important factor affecting the

utilization efficiency and storage capacity of H₂ in shale reservoirs. To investigate the adsorption mechanisms and the differential adsorption characteristics of H₂ and CH₄ on shale, the high-temperature (303.15–363.15 K) and high-pressure (~18 MPa) adsorption experiments were conducted, and a modified Dubinin-Radushkevich -

Brunauer-Emmett-Teller (DR-BET) adsorption model was developed and validated to assess its predictive capability regarding the adsorption capacities of shale under varying temperature-pressure conditions. Results

indicate that the shale samples consistently exhibit a greater adsorption capacity for CH₄ than for H₂, indicating a distinct adsorption advantage for CH₄. The adsorption of H₂ by shale is governed by multi-layer adsorption, while the CH₄ adsorption exhibits a shift in the dominant adsorption mechanism from micropore filling at low pressures (<8 MPa) to meso-macropore bilayer adsorption at high pressures (>8 MPa). The evaluation method of selective adsorption of CH₄ and H₂ by shale considering the micropores and meso-macropores was established, demonstrating that the micropores exhibit a significantly stronger CH₄ adsorption affinity than the meso-macropores. The modified DR-BET model predictions across burial depths (1,000–6,000 m) revealed fundamentally different adsorption trends between CH₄ and H₂, with the CH₄/H₂ adsorption ratio progressively decreasing as burial depth increases, thereby confirming the diminished adsorption advantage for CH₄ at greater depths. For practical hydrogen storage implementation, a scientifically defensible depth range should be established through the comprehensive optimization of both hydrogen utilization efficiency and storage capacity. This research provides theoretical foundations for the advancement of underground hydrogen storage in shale reservoirs.