Understanding and Manipulating Rock-Water-Gas Interfaces in Ultramafic Rocks for Novel and Economically Relevant Reactions

Understanding and manipulating heterogeneous rock-water-gas interfaces are essential for discovering new methods of extracting critical minerals and controlling economically relevant reactions. Iron-rich ultramafic rocks in the subsurface are involved in chemical redox reactions, where iron is oxidized and electrons are transferred to reduce molecules such as water, producing hydrogen. This process, known as serpentinization, naturally produced significant amounts of hydrogen, first discovered in Mali during the 1980s. In addition, the interaction of water with these rocks produces percolated fluid with trace amounts of dissolved critical minerals such as Li, Co and Ni. However, 1) the complex and dynamic nature of the rock-water-gas interface during serpentinization, 2) factors affecting the thermodynamics and kinetics of the reaction, and 3) the optimization of the interface for high-yield and high-rate reactions are not yet fully understood. In this work, we combine computational and experimental methods to develop a chemical, mechanical, and electronic understanding of these reactions, aiming to create a generalizable framework. We explore how these processes can be tuned to produce economically valuable products such as hydrogen. Unlike the naturally occurring hydrogen discovered in Mali, we propose and demonstrate methods to stimulate and actively control the reaction kinetics for hydrogen production under subsurface conditions at rates and yields that are economically feasible if scaled, potentially meeting all our energy needs for the next 250,000 years.