A pH-Switchable System for On-Demand Solar Hydrogen Production.

Artificial solar-to-fuel conversion is a pivotal pathway toward a sustainable energy future. Molecular hydrogen H₂, with its clean energy potential, emerges as a promising candidate to replace fossil fuels. Nevertheless, the intermittent nature of solar irradiation presents a formidable obstacle. Inspired by natural photosynthesis, a well-known three-component system is employed to decouple light absorption and hydrogen evolution. The system utilizes [Ru(bpy)₃]²⁺, triethanolamine, and methyl viologen to store solar energy as reduced viologen (MV^•+). By controlling pH, this stored energy can be efficiently released to produce hydrogen on demand. The system demonstrates superior efficiency compared to platinum-based catalysts, along with remarkable reversibility, cyclability, and stability. This work significantly advances solar-to-hydrogen conversion, providing a promising solution for the intermittent nature of solar energy and paving the way to a sustainable energy future.