Aqueous Carbon Under Nanoconfinement at High-Pressure and High-Temperature Conditions

The carbon cycle in deep Earth greatly influences the carbon budget near the Earth’s surface. Aqueous fluids play an important role in the carbon transport in Earth’s crust and upper mantle. In deep Earth, water does not exist alone, and is largely stored within minerals, e.g. silicates. Here, we applied first-principles molecular dynamics simulations to study aqueous carbon solutions under nanoconfinement at high-pressure and high-temperature conditions, as found in Earth’s upper mantle. We compared the confinement effects by graphene layers and silica slabs. We found that CO₂(aq) dissociates more in water under confinement than in the bulk solution. The reactions at the SiO₂ interfaces also considerably affect the chemical equilibrium of CO₂(aq). We will discuss possible implications for the carbon transport in deep Earth.