Laser direct overall water splitting for H 2 and H 2 O 2 production

Abstract

Hydrogen (H 2 ) and hydrogen peroxide (H 2 O 2 ) play crucial roles as energy carriers and raw materials for industrial production. However, the current techniques for H 2 and H 2 O 2 production rely on complex catalysts and involve multiple intermediate steps. In this study, we present a straightforward, environmentally friendly, and highly efficient laser-induced conversion method for overall water splitting to simultaneously generate H 2 and H 2 O 2 at ambient conditions without any catalysts. The laser direct overall water splitting approach achieves an impressive light-to-hydrogen energy conversion efficiency of 2.1%, with H 2 production rates of 2.2 mmol/h and H 2 O 2 production rates of 65 µM/h in a limited reaction area (1 mm 2 ) within a short real reaction time (0.36 ms/h). Furthermore, we elucidate the underlying physics and chemistry behind the laser-induced water splitting to produce H 2 and H 2 O 2 . The laser-induced cavitation bubbles create an optimal microenvironment for water-splitting reactions because of the transient high temperatures (10 4 K) surpassing the chemical barrier required. Additionally, their rapid cooling rate (10 10 K/s) hinders reverse reactions and facilitates H 2 O 2 retention. Finally, upon bubble collapse, H 2 is released while H 2 O 2 remains dissolved in the water. Moreover, a preliminary amplification experiment demonstrates the potential industrial applications of this laser chemistry. These findings highlight that laser-based production of H 2 and H 2 O 2 from water holds promise as a straightforward, environmentally friendly, and efficient approach on an industrial scale beyond conventional chemical catalysis.