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THRUST C:   Liquid Fuel Cascades

Hybrid Molecules and Materials Approaches to Cascade Photocatalysis

 

DOE PRIORITY RESEARCH OPPORTUNITIES (PROs) ADDRESSED: PRO-1, PRO-2, PRO-3, and PRO-4

THRUST INVESTIGATORS:
Atkin, Cahoon, Castellano, Concepcion, Dempsey, Dick, Ertem, Goldberg (Co-Lead), Grills, Hammes-Schiffer, Hazari, Holland, Jakubikova, Kanai, Lockett, Lopez, Maggard, Manbeck, Meyer, Miller (Co-Lead), Parsons, Polyansky, Rodriguez, Stach, Wang        

OVERVIEW:
The five-year goal of the Cascades Thrust is to develop design principles that enable the cooperative integrated photosynthesis of liquid fuels through multi-catalyst cascades

               Energetic Advantage of Cascade Catalysis

Despite impressive progress in the electrochemical generation of H2, HCO2H, and CO, the generation of liquid fuels with high activity and selectivity through artificial photosynthesis remains a central challenge. The Cascades Thrust introduces innovative strategies to address this problem, based on the guiding hypothesis that multiple catalysts can work synergistically to generate specific liquid fuels. This hypothesis is inspired by biological photosynthesis, in which different enzymes catalyze each step along the sequence of CO2 fixation, reduction, and homologation to carbohydrates and other biomass. Whether natural or artificial, photosynthesis of liquid fuels from CO2 requires at least 6 protons and 6 electrons delivered in a multi-step reaction sequence. Few synthetic catalysts can efficiently navigate so many redox reactions by themselves. By simplifying multi-proton/multi-electron transformations into shorter sequences carried out by multiple catalysts, each catalyst can be independently optimized to achieve the overall energy-storing reaction with minimal kinetic barriers.

Several key research questions will guide the team towards realizing the first liquid solar fuel cascades.

  • What are the basic structural paradigms for hybrid systems for multi-step cascade liquid fuel catalysis?
  • How can 2D surface patterning and 3D structural scaffolding provide the spatial control needed to overcome co-catalyst incompatibility and intermediate transport while enabling new reactivity?
  • How can kinetic studies of individual catalysts be paired with multi-scale dynamic simulations to develop design principles for cooperative cascade photosynthesis?