3D Printing of Thylakoid-PEDOT:PSS Composite Electrode for Bio-Photoelectrochemical Cells

Thylakoid membranes (TMs) isolated from plant cells produce high-energy electrons by splitting water molecules using solar energy during photosynthesis. Since those photosynthetic electrons (PEs) can be harvested by oxidizing TMs, various approaches to attach TMs on electrodes have been investigated so far. Here, we propose embedding of TMs in the electrically conductive polymeric structure using 3D printing. A photosynthetic and electrically conductive ink based on a mixture ink of TMs and poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) was developed and 3D printed as lattice structures. This approach allows for more stable physical and electrochemical interfacing between TMs and the conductive polymer. Furthermore, free-form 3D structures, which can harvest PEs, can be constructed by 3D printing. 3D printing conditions for the TM/PEDOT:PSS inks were optimized, and 3D printed lattice electrodes with different geometries were analyzed in terms of light absorption and PE extraction. We found out that TM-embedded offset-stack lattice electrodes generated the highest PE current density of 70.6 μA/cm2. A bio-photoelectrochemical cell based on the TM-embedded offset-stack lattice generated a short-circuit current density of 0.57 mA/cm2 and a maximum power density of 101.7 μW/cm2.