Effects of anode materials in electricity generation of microalgal-biophotovoltaic system - part I: Natural biofilm from floating microalgal aggregation

A biophotovoltaic (BPV) system is an emerging photo-bio-electrochemical technology that promises bioelectricity generation through the photosynthesis of exoelectrogenic microorganisms. An algal pool or floating photobioreactor with algae cultivation medium is a potential electron source for sustainable operation of such BPV device. Therefore, bioelectricity generation from algae cultivation medium should be studied to demonstrate this value-added feature. In natural conditions, self-aggregated microalgae form biofilms on the medium surface. One technical concern is that previous studies emphasized the role of anode materials and biofilm formation for the enhancement of electron transmission in BPV device, whereas cell performance by free-floating microalgae medium and natural biofilm still has research value. Hence, cell performance under different anode materials is a crucial decision-making factor of the system with a natural biofilm. In this paper, the experiment was repeated three times to investigate the bioelectrical power generation of BPV device in natural conditions from using three different anode materials, namely graphite, indium tin oxide (ITO)-coated glass, and ITO-coated plastic. In the experiments, BPV devices with ITO anode experienced power overshoot problems by the use of natural floating Spirulina (Arthrospira) platensis aggregation. ITO-coated glass- and plastic-based BPV devices produced maximum power densities of 0.118 mW/m² and 0.215 mW/m², respectively. The findings are expected to contribute to further understanding on the correlation of these parameters with regards to power generation by BPV device.