rGO-Augmented\nPhotosynthetic Biohybrid System for\nBiohydrogen Production: Regulatory Mechanisms and Wastewater Treatment\nApplications

Photosynthetic biohybrid system (PBS),\nwhich utilizes\nphotoenergy\nto augment microbial metabolism, offers a promising route for efficient\nbioproduction and wastewater valorization. However, the existing PBS\ngenerally suffers from low bioproduction efficiency due to sluggish\nelectron transfer at the semiconductor–microbe interface and\ninadequate stability for practical applications. In addition, well-defined\nculture media are exclusively used; thus, their potential for real\nwastewater treatment remains untapped. Herein, we address these challenges\nby using reduced graphene oxide (rGO) as a conductive bridge and protective\nlayer to drastically augment the performance of a hydrogen-producing\nPBS, consisting of Shewanella oneidensis MR-1 cells and cadmium sulfide (CdS). The rGO layer, which encapsulates\nCdS and offers an abundant area for contact with bacterial cells,\nplays a critical role in boosting the separation and further delivery\nof photoexcited electrons to the cell surface. It also considerably\nreduces CdS photocorrosion by using excess photoelectrons to scavenge\nthe photoinduced holes, thus improving bacterial viability. As a consequence,\nthe rGO-augmented PBS exhibited a remarkable quantum efficiency of\n22.8%\nfor hydrogen production, which was 26 times higher than that of the\nrGO-free control under visible light. Superior hydrogen-producing\nefficiency and stability of the system for treating real aquaculture\nwastewater were also demonstrated. Our work may inspire technological\ninnovations that synergize microbial and photocatalytic processes\nfor sustainable bioproduction and/or wastewater valorization applications.