Scale-up potential of laser-driven chemical processes: A case study on hydrogen production using a femtosecond laser

• We propose a strategic scale-up approach for laser-driven H 2 production. • Laser filamentation disperses energy, enhancing H 2 production efficiency. • High pulse energy improves H 2 yield, but low repetition rate hinders filamentation. • A 20-mJ-class femtosecond laser yielded a 13 × higher H 2 production per pulse than a 0.5-mJ-laser. • A hybrid setup is proposed to combine cumulative effects with high-energy input. The scale-up of chemical reactions using femtosecond lasers remains an underexplored area, particularly in terms of strategies required for efficient and sustainable implementation. This study proposes a strategic approach to the large-scale application of femtosecond laser–driven chemical reactions, using H 2 production as a model system and defining scalability as H 2 yield per hour (mol h −1 ). The hydrogen generation process is initiated by multiphoton ionization of water, leading to plasma formation and radical generation, followed by subsequent recombination into H 2 . Through fundamental experimental investigations, we examined the impact of increased laser output on reaction efficiency and evaluated the role of nonlinear optical phenomena—specifically, laser filamentation—not merely as a propagation effect but as a controllable driver of chemical reactivity for scale-up. Spatial energy dispersion along the optical axis was analyzed, revealing that an extended laser filament serves as an effective energy reservoir, thereby enhancing H 2 production. Furthermore, our results show that lower repetition rates shorten filament length, reducing the effective interaction volume and limiting scalability. Under scaling conditions, H 2 production per pulse using a 20-mJ-class laser was enhanced by a factor of 13 compared to that achieved with a 0.5-mJ-class laser. These findings not only offer a scaling strategy but also provide mechanistic insights into femtosecond laser-driven photolysis and radical-mediated hydrogen evolution reaction.