Hydrogen Production Based on Thylakoids Composite Hydrogel Beads with Improved Stability by ROS Scavenging Using Ceria Nanoparticles

Recently, studies for sustainable hydrogen production using photosynthesis are gaining attention. Thylakoid membranes (TMs), extracted from photosynthetic organisms, can serve as efficient systems for generating hydrogen, especially when combined with platinum nanoparticles (PtNP). However, reactive oxygen species (ROS), which are typically generated during the photosynthetic process and can damage the TM structure, limits hydrogen production stability of TMs. To address this issue, we developed a novel biohybrid bead system incorporating TM, PtNP, ceria nanoparticles (CeNP) and alginate, aiming to enhance the stability. In this system, alginate serves as an encapsulation matrix for both TM and CeNP. CeNP were included for their known ROS-scavenging properties, thus protecting TM from oxidative damage during prolonged light exposure. Initially, when PtNP were mixed directly with alginate before cross-linking, we observed a significant loss of PtNP catalytic activity due to interactions with calcium ions (Ca2+) used in the cross-linking process. To overcome this challenge, we implemented a two-step approach. First, the thylakoids were encapsulated with alginate and CeNP, and the cross-linking process was completed using 1.5 wt % of CaCl₂. Following this, the beads were immersed in a PtNP solution, allowing the PtNP to integrate into the specific site of thylakoid membrane without losing their catalytic properties. This approach ensured that the PtNP retained their ability to catalyze hydrogen production, which was verified through gas chromatography. Additionally, CeNP significantly enhanced the long-term stability of the system by scavenging ROS. TM composite hydrogel beads containing CeNP showed much higher stability and long-term hydrogen production compared to simple suspension of TM and PtNP without encapsulation. The ROS scavenging properties of CeNP were verified through H₂O₂ and superoxide dismutase assays, and stability of the system was verified through long-term hydrogen production comparison with suspension. This study highlights the potential of TM-based biohybrid system for hydrogen production with higher efficiency than conventional algae-based photosynthetic hydrogen production systems.



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