(3fw) Photocatalytic Gaseous CO2 Conversion Towards Terawatt Scale

Teaching Interests: Catalysis, Photoelectrochemistry, Electrochemistry, Fundamentals of Photovoltaics, Chemical Reaction Engineering, and Teaching Method (I received "Kaufman Teaching Certificate from MIT Teaching & Learning Lab)

Abstract Text:

The current state-of-the art system for CO₂ reduction reaction depends on an electrolyte because the corresponding reaction mechanisms are well-documented. However, this requires additional expensive procedures to initiate the reaction because CO₂ gas has to be dissolved into the electrolyte solution. Even after the CO2 dissolution process, CO2 tends to bubble out from the solution as pressure and temperature change. Moreover, under the liquid phase reaction system, reactant and product molecules are likely to be close to each other, which causes unwanted reverse or side reactions and thus degrades the overall CO₂ conversion efficiency. To overcome the current technical limitations, new gaseous CO₂ conversion systems, desirably using solar power, have to be designed and developed, and the new systems need to reach at least a 10 terawatt scale to have an impact on the global fuels market.

In a bid to realize this unprecedented level of CO₂ fixation using H₂O as electron source, we aim to adopt a scalable nanofabrication of leveraging microsphere lithography, dry etchings, and plasma-enhanced atomic layer deposition (ALD) into the seamless constructions for photocatalytic nanotube arrays, which are designed for gas-phase CO₂ reduction using sunlight and water. Specifically, such arrays should have a large number of ALD-grown core (Co₃O₄) - shell (SiO₂) nanotubes operating as independent photosynthetic units under ambient conditions. The SiO₂ nanoshell serves as a H+ transmitting and O₂ impermeable membrane to spatially separate H2O oxidation catalysis by Co₃O₄ inside the tube from CO₂ reduction catalysis by Cu, Ag, Fe, or Co nanoparticles outside the tube. This inherent product separation geometry allows to address long-standing scientific barriers of optimizing the combinations of photoactive materials (thermodynamic efficiency) and minimizing charge transfer losses and unwanted reactions (quantum efficiency) of artificial photosynthetic systems.