rGO-Augmented Photosynthetic Biohybrid System for Biohydrogen Production: Regulatory Mechanisms and Wastewater Treatment Applications

Photosynthetic biohybrid system (PBS), which utilizes photoenergy to augment microbial metabolism, offers a promising route for efficient bioproduction and wastewater valorization. However, the existing PBS generally suffers from low bioproduction efficiency due to sluggish electron transfer at the semiconductor–microbe interface and inadequate stability for practical applications. In addition, well-defined culture media are exclusively used; thus, their potential for real wastewater treatment remains untapped. Herein, we address these challenges by using reduced graphene oxide (rGO) as a conductive bridge and protective layer to drastically augment the performance of a hydrogen-producing PBS, consisting of Shewanella oneidensis MR-1 cells and cadmium sulfide (CdS). The rGO layer, which encapsulates CdS and offers an abundant area for contact with bacterial cells, plays a critical role in boosting the separation and further delivery of photoexcited electrons to the cell surface. It also considerably reduces CdS photocorrosion by using excess photoelectrons to scavenge the photoinduced holes, thus improving bacterial viability. As a consequence, the rGO-augmented PBS exhibited a remarkable quantum efficiency of 22.8% for hydrogen production, which was 26 times higher than that of the rGO-free control under visible light. Superior hydrogen-producing efficiency and stability of the system for treating real aquaculture wastewater were also demonstrated. Our work may inspire technological innovations that synergize microbial and photocatalytic processes for sustainable bioproduction and/or wastewater valorization applications.