Photoelectrochemical pumping of enzymatic CO₂ reduction

Abstract

The need for renewable resources of carbon-based fuels and chemicals has focused on methods by which carbon dioxide could be utilized as the initial substrate. However, most of these methods have tended to be inefficient, both in terms of energy losses involved during CO₂ fixation and in the lack of specificity in the final products. We report here a novel approach for the fixation of CO₂ which combines a semiconductor photoelectrode (p-type indium phosphide, p-InP) with a biological catalyst (a formate dehydrogenase enzyme) to effect the first step, a two-electron reduction of CO₂ to formic acid. Photogenerated electrons in the semiconductor, which can be coupled to the enzyme through a mediator, can be produced with light of wavelengths shorter than 900 nm (>1.35eV) so that much of the energy of the solar spectrum could be captured for this process. The process is analogous to natural photosynthesis but has the potential to be more efficient at light collection and more specific in the production of reduced carbon species.