The conversion of CO2 to is an attractive possibility for lowering concentrations in Earth's atmosphere since its reduction can yield useful high-energy fuels. TiO2 nanowires have been previously highlighted as attractive catalysts for CO2 conversion. However, the mechanism of nanowire formation by APCVD methods is not well understood which limits their production in bulk. TiO2 nanowire growth experiments were performed using a novel phosphorus-doped seed particle method. Results show phosphorus doping enhances nanowire growth and may be applicable to other metal-oxide nanowire fabrication methods. Although there are current concerns for atmospheric concentrations of CO2, Earth's earliest atmosphere (~4.5 Ga ago) is thought to have been dominated by ~1-10 bar CO2. In equilibrium with Earth's ocean, the reduction of dissolved CO2 in an ancient ocean may have been the earliest pathway for the emergence of life.

Ancient alkaline hydrothermal vents, formed by serpentinization of the oceans crust are proposed to be dominated by iron sulfide catalysts that are capable of reducing CO2 toward organic synthesis. Yet, few laboratory experiments have been performed to simulate ancient hydrothermal conditions and test this theory for the earliest emergence of life. Iron sulfide precipitation experiments were performed and show species including mackinawite [FeIIS], proposed as a catalyst in CO2 reduction, which could line the interiors of ancient hydrothermal systems. Additionally, a hydrothermal reactor was assembled and new protocols developed for testing CO2 reduction under simulated ancient alkaline hydrothermal vent temperatures (120°C), pressures (~100 bar) and pH conditions. H2-rich hydrothermal simulants were mixed with CO2-rich ancient ocean simulants and allowed to react across ultramafic, and iron sulfide compositions.

The resulting mineral compositions and dissolved inorganic species suggest partial serpentinization is occurring during reactor experiments. Dissolved formate, a known intermediate of CO2 reduction to methane, was detected in the resulting solutions. These results suggest that the methods and protocols developed here are uniquely capable of testing the catalytic capability of hydrothermal systems. Since serpentinization can occur anywhere an ocean is in contact with the mineral olivine, these methods may be useful for understanding the alkaline hydrothermal vents that are suggested to exist on other planets in our solar system.