An Approach to Sustainable Hydrogen Generation From Stimulated Iron‐Rich Ultramafic Rock

Abstract Iron‐rich rocks undergoing oxidation in the presence of water are promising sources of geologic hydrogen (H 2 ). Yet, such reactions are often considered self‐limiting due to passivation and reduced permeability if volume expansion occurs. This study investigates hydrogen generation during a flow‐through experiment on fractured iron‐rich cores packed with proppants, simulating a stimulated subsurface environment. Hydrogen generation initially declined over time. Introducing a thermochemical fluid to accelerate the reaction via thermal enhancement did not yield measurable hydrogen gains. Subsequent acid treatment for 2 hr led to a 30‐fold increase in hydrogen generation, which was sustained for 144 hr before the onset of a decline. Post‐acidizing hydrogen generation remained larger than pre‐acidizing hydrogen. Post‐experiment characterizations confirmed the development of preferential flow paths, mineral precipitation along fracture surfaces, and fluid‐induced surface alteration. These results demonstrate that periodic chemical stimulation can significantly enhance and prolong hydrogen generation by reactivating mineral‐fluid interfaces.