Photoelectrochemical platforms for solar water oxidation and biocatalytic photosynthesis

Abstract

Green plants operate elaborate photosystems in a beautiful harmony to convert sunlight into chemical energy with an unparalleled quantum yield, through photoinduced electron transfer. Inspired by the natural photosynthetic scheme, many efforts have been made to construct artificial photosynthetic platforms for improvement of human-made energy devices. In this thesis, the design strategies are addressed for successful implementation of photoelectrochemical platforms for solar water oxidation and biocatalytic photosynthesis.

Chapter 1 and 2 demonstrates an application of the quinone-based hybrid material in the field of solar-to-chemical conversion. Based on unique features of quinone, such as its inherent redox properties, the synthesis of polynorepinephrine-functionalized, reduced graphene oxide film is described, as a mimic of quinone acceptors in photosystem II to enhance the efficiency of solar water oxidation. The results show that the construction of a quinone-based cascaded electron transfer pathway should provide more opportunities for implementing efficient artificial photosynthetic systems

Chapter 3 describes the utilization of amorphous carbon nitride (ACN) for photochemical NADH regeneration and redox enzymatic synthesis under visible light, mimicking photosystem II. ACN was synthesized through thermal decomposition of graphitic carbon nitride. The change of microstructure leads to the higher photocatalytic activity of ACN with extended visible light absorption and less charge recombination. The results suggest that robust ACN can efficiently provide light-powered electrons to be channeled into redox biocatalytic cycles.

In Chapter 4 and 5, the construction of biomimetic photoelectrochemical cells (PECs) is presented for implementation of the integrated full photosynthetic cycle. In the PEC systems, the electrons are extracted from water oxidation at photoanodes. Then, sequential electron transfer to their counterparts and further to redox enzymes lead to the effective production of value-added organic chemicals. The PECs are configured with i) 3-jn-Si/ITO/CoPi photoanode and H-SiNW photocathode and ii) a FeOOH/$BiVO_4$ photoanode and a CNT/g-$C3N_4$ cathode. The detailed electron generation and transfer mechanisms are also discussed.