Finding a Path to CO2 Conversion on a Scale that Matters
Matthew Kanan
Associate Professor, Department of Chemistry
Director, TomKat Center for Sustainable Energy
Stanford University
Reversing the rise of CO2 in the atmosphere requires a massive transition from fossil to truly sustainable resources. At odds with this goal is the enormous and still growing demand for carbon-based products. The emissions problem cannot be solved without producing fuels and chemicals from CO2, H2O, and renewable energy. Decoupling carbon-based products from fossil resources could also improve global energy security. This talk will describe our research on (electro)chemical systems for sustainable chemical and fuel production. I will first discuss our work to improve the energy efficiency of electrochemical CO conversion, which can be paired with an upfront CO2-to-CO conversion technology to produce multi-carbon platform chemicals such as ethylene and alcohols. Using advances in cell designs and CO reduction catalysts, we have demonstrated lab-scale systems that enable high synthesis rates at unprecedented cell voltages. As a complementary approach to electrochemical conversions, we have been investigating simple acid-base chemistry to create new processes that turn CO2 into chemicals and fuels. In one application, we have developed systems that use alkali carbonate as a regenerable base for C–H carboxylation, resulting in CO2 insertion into C–H bonds with no reagent consumption or waste production. When applied to inedible biomass feedstocks, this chemistry provides a streamlined route to a critical monomer for high-volume, carbon-neutral plastics that outperform conventional materials. Extending this concept to fuel production, we have recently reported carbonate-based materials that are exceptionally active, selective, and robust catalysts for the reverse-water gas shift (RWGS) reaction. The combination of RWGS and Fischer-Tropsch catalysis is a highly attractive route to sustainable liquid fuels, but conventional RWGS catalysts must be operated at extreme temperatures to avoid competing methanation and coking reactions. Carbonate-based catalysts avoid these pitfalls, enabling RWGS at lower temperatures and thereby removing process design constraints for power-to-liquid fuel systems. The extreme simplicity of these catalyst materials also makes them well suited for the high-volume manufacturing that would be needed to produce sustainable liquid fuels on a meaningful scale.
