Chapter 8: Hybrid Biological–Inorganic Systems for CO₂ Conversion to Fuels

Photosynthesis provides guidelines to convert CO₂ into fuels and other valuable carbon products. However, the storage of solar light in natural photosynthesis is largely sacrificed to maintain a wide range of reproductive and living processes. Artificial photosynthesis can overcome these energy storage limitations. A promising artificial photosynthetic approach is to use inorganic systems to replace the solar energy expending processes of natural photosynthesis and to integrate this renewable energy conversion with the carbon fixation processes of biological organisms to produce carbon fuels. These hybrid biological–inorganic (HBI) systems can achieve solar-to-product efficiencies that far exceed the energy storage efficiencies of natural photosynthesis. In this chapter, three different types of HBI systems are categorized by their electron source: direct H₂, indirect H₂ (organic-mediated) and electron-transfer (direct and redox-mediated). The mechanisms and energetics of the carbon fixation pathways of these three HBI systems are presented together with an accurate energy efficiency metric that allows different HBI systems to be directly compared.