Accelerating Hydrogen Production through Serpentinization: A Batch Reactor Experimental Study

ABSTRACT: The energy industry is currently facing significant demand in subsurface energy exploration and extraction to realize energy transition. Natural geological hydrogen produced through serpentinization has immense potential as an efficient clean energy source to support this transition. Previous research indicates that hydrogen generation via serpentinization is primarily influenced by factors such as fluid pH, silica activity, specific surface area (SSA), and Fe2+/Fe3+ ratio. However, studies have yielded conflicting results regarding which accelerators (or key factors) enhance hydrogen production. These discrepancies may stem from variations in experimental setups, inconsistent parameter settings, and potential contamination from laboratory equipment, all of which contribute to significant uncertainties and potential inaccuracies in factor screening. In the current study, we use a Dickson-style rocking autoclave, equipped with flexible gold reaction cells and titanium fittings, for batch reactions, to collect sequential gas samples for quantifying produced hydrogen. Specifically, San Carlos olivine minerals are reacted with a base fluid (pH =12.5) under conditions of 230 °C and 32 MPa. Hydrogen quantification is performed using a modified Thermal Conversion/Elemental Analyzer coupled with an Isotope Ratio Mass Spectrometer (TC/EA-IRMS) system, validated with a known gas mixture. In addition, Brunauer-Emmett-Teller (BET) measurement is applied to establish the correlation between grain size and SSA of the San Carlos olivine. Insights gained from these batch experiments will inform the design of subsequent flow-through experiment, aimed at simulating in-situ geological hydrogen production, which is essential for enhancing hydrogen generation and optimizing geological site screening.