Photoelectrochemical cell has been considered as a promising candidate for realizing artificial photosynthesis mimicking the light and dark reactions in natural photosynthesis. Although the stability and sustainability are strong powers of the photoelectrochemical cell, an external applied bias is required to connect the water oxidation and biocatalytic reaction efficiently. In this thesis, photoelectrochemical tandem assemblies consist of a photoanode with water oxidation catalyst and a single-junction photovoltaic device were developed for unbiased photoelectrochemical biocatalytic conversion by regenerating the NADH cofactors.
Chapter 1 describes an unbiased photoelectrochemical tandem assembly of a photoanode with a water oxidation catalyst (FeOOH/BiVO4) and a photovoltaic device with a perovskite absorber to promote water oxidation and to provide sufficient voltage for cofactor-dependent biocatalytic reactions. The NADH cofactor was efficiently regenerated, and the successive biocatalysis by GDH was achieved without any external applied bias. Moreover, performances of the enzyme were significantly improved compared to previous research in terms of a turnover number and a turnover frequency. The results shows that the tandem configuration facilitates redox biocatalysis using solar light as the only energy source.
In chapter 2, a wireless photosynthetic device consist of a photoanode (FeOOH/BiVO4) and a CIGS solar cell to achieve autonomous reaction from water oxidation to biocatalysis was developed. For efficient and sustainable photoelectrochemical reaction, the stability to moisture and light is a key factor to operate in actual experimental and industrial conditions. In this point of view, the CIGS solar cell was introduced as a voltage supplier in the photovoltaic-photoanode tandem system. Only with a single-junction CIGS solar cell, the wireless photosynthetic device successfully regenerated the NADH cofactor and promote biocatalysis coupled with solar water oxidation.