Unlocking the Potential and Lessons of 3D Porous Electrodes in Living Biophotoelectrochemical Systems

Living biophotoelectrochemical systems are devices that 'wire' photosynthetic microorganisms (i.e., scalable and sustainable biocatalysts) to 3D-architectured electrodes to catalyse reactions for solar-power generation and fuel production using sunlight and water. Despite excellent progress over the last decade, large enhancements in solar-to-charge conversion efficiency are needed to enable real-world applications. One major challenge lies in optimising the bio-electrode interface, where the material and structure of the electrodes play a crucial role.<br/>State-of-the-art electrodes in this field are micro-pillar and inverse opal (IO) electrodes fabricated from indium-tin-oxide (ITO) nanoparticles.¹ Here, we provide important lessons for electrode design by tuning the pore sizes and homogeneity of IO-ITO electrodes, characterising their light management ability, surface morphology, electroactive surface area, cells wiring efficiency, and relating these to their biophotoelectrochemical performance.<br/>Our results indicate that the bare IO-ITO electrodes of different pore sizes (10-42 µm in diameter) managed light similarly and the larger pore-sized IO-ITO gave rise to the highest photocurrent output. Further attempts to boost light utilisation on these electrodes by adding a bio-mimicking reflective layer at the back of the electrode resulted in increased light reflection but did not influence the photocurrent output significantly, implying the light utilisation of the structure has been optimised.<br/>In conclusion, presented is the most comprehensive systematic study in the structure-activity relationship of electrode architecture to biophotoelectrochemcial output to our knowledge.<br/><br/><br/><br/>1. Chen, X.; Lawrence, J. M.; Wey, L. T.; Schertel, L.; Jing, Q.; Vignolini, S.; Howe, C. J.; Kar-Narayan, S.; Zhang, J. Z., 3D-printed hierarchical pillar array electrodes for high-performance semi-artificial photosynthesis. <i>Nat Mater </i><b>2022,</b> <i>21</i> (7), 811-818. DOI: 10.1038/s41563-022-01205-5