Design of $CO_2$-Reductive Copper Oxide-Based Photobiocathodes

Abstract

Green plants convert sunlight into high-energy chemicals by coupling solar-driven water oxidation in the Z-scheme and $CO_2$ fixation in the Calvin cycle. In this study, formate dehydrogenase from Clostridium ljungdahlii (ClFDH) is interfaced with a $TiO_2$-coated $CuFeO_2$ and $CuO$ mixed (ClFDH–$TiO_2$|CFO) electrode. In this biohybrid photocathode, the $TiO_2$ layer enhances the photoelectrochemical (PEC) stability of the labile CFO photocathode and facilitates the transfer of photoexcited electrons from the CFO to ClFDH. Furthermore, inspired by the natural photosynthetic scheme, the photobiocathode is combined with a water-oxidizing, $FeOOH$-coated $BiVO_4$ ($FeOOH$|$BiVO_4$) photoanode to assemble a wireless Z-scheme biocatalytic PEC device as a semi-artificial leaf. The leaf-like structure effects a bias-free biocatalytic $CO_2$-to-formate conversion under visible light. Its rate of formate production is 2.45 times faster than that without ClFDH. This work is the first example of a wireless solar-driven semi-biological PEC system for $CO_2$ reduction that uses water as an electron feedstock.