Bridging Experiment and Modeling: Coupling CO2 Sequestration with White Hydrogen Production in Basaltic Rocks

Abstract Basaltic rocks, rich in divalent cations such as Ca²⁺, Fe²⁺, and Mg²⁺, have the potential to simultaneously sequester CO₂ and generate hydrogen through mineralization and serpentinization reactions. The objective of this study is to investigate the field-scale feasibility of coupled CO2 Sequestration with hydrogen generation in basaltic rocks. A numerical simulation model was developed, informed by experimental data from controlled CO₂-basalt interactions. Micro Gas Chromatography (MicroGC) and Inductively Coupled Plasma–Optical Emission Spectrometry (ICP-OES) were used to characterize the gas and liquid effluents. The numerical simulation model coupled flow, heat, and chemical reactions, and evaluated hydrogen generation, CO2 production, and siderite precipitation under varying conditions of mineral composition, pH, temperature, and CO₂ injection rates. MicroGC measurements indicate that at pH 6.5, increasing the temperature from 80 °C to 150 °C enhances H₂ generation, consistent with temperature-accelerated basalt dissolution and Fe²⁺-driven redox reactions. At 150 °C, shifting pH from 6.5 to 8.5 reduces H₂ but also markedly reduces free CO₂ in the produced gas, indicating greater CO2 sequestration. ICP-OES confirms enhanced release of Mg, Ca, Fe, and Si under lower pH and higher temperature, consistent with increased reactivity of olivine/pyroxene phases. The numerical model reproduced observed lab-experiment H₂:CO₂ trends and showed that (i) increased iron content in the basalt rocks both H₂ generation and siderite (FeCO₃) precipitation; (ii) higher CO₂ injection rates strongly favor carbonation but yield only modest H₂ gains; and (iii) temperature elevates cumulative H₂ while potentially redistributing carbonate mineral products. The results revealed a tunable trade-off: acidic, hotter conditions favor H₂ generation but leave more residual CO₂, whereas mildly alkaline conditions suppress H₂ yet improve CO₂ retention in the rocks. Optimizing pH–temperature–rate to maximize H₂ per unit of sequestered CO₂ provides an opportunity for co-producing geological hydrogen while achieving durable carbon storage in basalt. Future studies will focus on experimental validation, long-term reaction monitoring, and expanding the model to include other reactive silicate systems and flow geometries. Technoeconomic analyses would be relevant to further prove the viability of this concept.