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.
가시 광선의 효율적인 이용은 태양에너지를 화학에너지로 변환하는 인공광합성 과정에서 중요한 문제로 대두되어 왔다. 현재까지의 연구에서, 단일 광흡수 물질은 전도대와 가전자대, 그리고 그 사이의 에너지 갭의 한계로 가시광선을 효율적으로 이용하지 못하며, 이를 해결하기 위해 두 가지 광흡수 층의 상보적인 흡수가 필수적이다. 본 논문에서는 광전지-광양극 탠덤구조를 이용한 지속가능하고 효율적인 생체촉매 기반 인공광합성 시스템 개발을 위한 연구를 다루었다. 구체적으로, 수산화철 촉매가 코팅된 비스무스바나듐산화물 광양극과 페로브스카이트 태양전지를 탠덤구조로 배열하고 탄소나노튜브 필름 전극을 이용하여 외부 인가 전압 없이 성공적으로 광전기화학 산화환원 촉매 반응이 이루어지도록 하였다. 또한 불안정한 페로브스카이트 태양전지를 구리인듐갈륨셀레늄 태양전지로 대체하여 더욱 안정적으로 작동하는 광전지-광양극 탠덤구조를 만드는 데에 성공하였다. 이를 이용하여 빛만을 이용해 자체적으로 작동하는 무선 인공광합성 디바이스를 제작하는 데에 성공함으로써 효율적이고 지속가능한 생채촉매 반응 플랫폼을 개발하였다.
