Enzyme-based photoelectrochemical systems for photobiocatalytic processes

With increasing energy demands and rising levels of CO2, methods for alternative energy sources are being explored. Bioelectrocatalysis and photoelectrocatalysis are emerging tools for the generation of electrical power or fuels. The natural photosynthesis apparatus utilizes light irradiation for the generation of fuels. Different methods to mimic the photosynthesis process have been developed, where enzymes or inorganic semiconductors were used. While photosystem I and photosystem II have ~100% quantum efficiency, stability issues and high isolation cost limits any further photosystem-based applications. In recent years, “photosynthesis-like” photoelectrochemical cells and photobioeletrochemcial cells were developed. These cells utilize semiconductors or enzymes for the generation of electrical power or fuels. Enzymes are “super-catalysts”, enabling high selectivity, fast turnover rates, and low activation barriers, while semiconductors can harness solar energy for the generation electron flux. By exploiting the advantages of both the enzymes and the semiconductors we can further design energy generating devices. Here we present the construction of photobioelectrochemical cells which utilize bilirubin oxidase from a thermophilic Bacillus pumilus and bilirubin oxidase from Myrothecium verrucaria with superior activity and stability at elevated temperatures.1 BOD was integrated into electrodes and utilized for bioelectrocatalytic oxygen reduction process. A polymer-based BOD entrapping technique was developed and tested in a systematic work. Obtained superior bioelectrocatalytic currents and different parameters that influence the directed or mediated electron transfer process will be presented and discussed. We further present an optimized photoanode based on BiVO4, which facilitates the oxidation of water into oxygen under light irradiation. Finally, we present the construction of BiVO4/BOD bias-free, donor-free photobioelectrochemcial cells that generate electrical power at neutral pH having light irradiation as the only required input.