Generating H₂ during the CO₂ sequestration in basalt formations

This work demonstrates the potential of generating H₂ and geologically storing CO₂ simultaneously in basalt formations. Basalt is able to produce H₂ in CO₂-saturated water at a rate of 46.68 ppm d⁻¹ under 25 °C, with generation rates leveling off after 6 days. At the reaction temperature of 60 °C, the cumulative hydrogen production of basalt for 5 days reaches 11,960 ppm, and its daily hydrogen production rate is more than 51 times that of 25 °C. The CO₂-acidified experiment produced the most H₂, presumably due to the pH buffering of the CO₂ system. The water–solid reaction interface provided by basalt is essential for H₂ production. Scanning electron microscopy (SEM) results show that substantial nano-sized mineral precipitate formed on the basalt surfaces. Electronic microprobe results (EMPA) show that carbonate minerals are formed after the reaction of basalt with CO₂ and water under ambient temperature conditions. Thermogravimetric analysis (TG) results show a mineral carbonation efficiency of 4.17% in 3 months. The present experimental results demonstrate the technological feasibility of producing hydrogen for the energy transition while storing CO₂ geologically, thus mitigating anthropogenic emissions of a greenhouse gas and also creating revenue for CCS.