Biogeochemical Control of Hydrogen–Iron Minerals Interfacial Chemistry in Subsurface Energy Systems

Abstract

Microbial processes are increasingly recognized as critical modifiers of solid–fluid interfaces in subsurface systems; however, their role in hydrogen–mineral interfacial chemistry remains poorly constrained. Here, we demonstrate that microbial colonization fundamentally reprograms the interfacial behavior of iron-bearing minerals, overriding intrinsic pressure–temperature controls. Using pyrite (FeS2) and hematite (Fe2O3) as representative substrates, we integrated high-pressure/high-temperature experiments (1–12 MPa, 25–50 °C) with multiscale surface and geochemical analyses, including contact-angle measurements, XPS, ICP–OES, SEM–EDS, and AFM. Abiotic systems exhibit pressure-enhanced hydrophobicity and temperature-driven hydrophilicity; however, microbial colonization overrode both effects, driving the minerals toward strongly hydrophilic states. These biological transformations are governed by coupled biogeochemical mechanisms, including Fe–S redox transformations, ion redistribution, mineral dissolution, extracellular polymeric substance (EPS) adsorption, and nanoscale surface roughening associated with biofilm formation. Collectively, these processes alter surface chemistry and topography, producing emergent wettability states that cannot be predicted from abiotic conditions alone. Our findings establish microbial activity as a dominant control on hydrogen–mineral interfacial behavior, with direct implications for hydrogen storage efficiency, reactive transport, and the design of sustainable subsurface energy systems.