This chapter presents biophotoelectrochemical systems where one of nature's photosynthetic proteins, such as photosystem 1 (PS1), photosystem 2 (PS2), or bacterial reaction centers, are employed to create devices for technological applications. We use recent advances in biophotoelectrodes for energy conversion and sensing to illustrate the fundamental approaches in half-cell design and characterization. The aim is to guide electrochemists and photosynthetic researchers in the development of hybrid systems interfacing photosynthetic proteins with electrodes ranging from biosensors to biophotovoltaic cells. The first part gives an overview of the photosynthetic electron transfer chain with details on photosynthetic proteins and on the properties relevant for technological applications. The second part describes and critically discusses the main applications of biophotoelectrochemical cells based on photosynthetic proteins and exposes the respective requirement in electrode design. The following and final parts present the standard methodologies for the characterization of the biophotoelectrochemical half-cells with the main objectives of enhancing our mechanistic understanding of electron transfer, charge recombination, overpotential in photocurrent generation and protein degradation processes in devices, and thus open the perspectives for novel biophotoelectrochemical concepts and their rational optimization toward practical efficiencies.
Keywords: Bacterial reaction centers; Biophotoelectrochemical cells; Biophotovoltaics; Biosensors; Charge carrier; Charge recombination; Overpotential; Photocurrent; Photosystem 1; Photosystem 2; Water splitting.