Kappa-carrageenan-assisted synthesis of WO₃ nanosheets as 2D photocatalysts for visible-light-driven hydrogen production.

The use of non-noble photocatalysts for molecular hydrogen generation through water splitting is increasingly valued, with WO₃ emerging as a highly efficient catalyst for the Hydrogen Evolution Reaction (HER). Its crystallographic phases and morphologies can be tailored by modifying polysaccharides and adjusting synthesis parameters during hydrothermal processes. In this study, kappa-carrageenan (κ-CGN) was utilized as a stabilizer for the green synthesis of WO₃, influencing its shape and size. Transmission electron microscopy (TEM) revealed a network of interconnected channels, highlighting the structural role of κ-carrageenan. Hydrogen production tests were conducted in a water-ethanol solution using standalone WO₃. The 0.5 wt% WO₃ photocatalyst achieved a hydrogen production rate of 45.56 mmol·h-1/g catalyst, significantly higher than the 10.92 mmol·h-1/g catalyst from photolysis. The catalytic activity peaked at 1.0 wt% with a rate of 51.85 mmol·h-1/g catalyst, although efficiency declined at higher concentrations (3.0 and 5.0 wt%). The photocatalyst remained stable over two days of testing. WO₃ nanosheets effectively direct high-energy electrons to catalytic sites, minimizing energy loss. This research demonstrates the potential for optimizing WO₃ morphology at the molecular level to enhance interfacial active sites for scalable hydrogen production.