Photo-Induced Hydrogen Production from Formic Acid Using a Palladium Catalyst

Liquid organic hydrogen carriers (LOHCs) are recognized as promising sustainable hydrogen (H2) carriers due to their high volumetric capacity and ability to store H2 at ambient conditions, eliminating the need for energy-intensive liquefaction or compression processes associated with H2 or ammonia gas. One of the main current drawbacks, however, is LOHCs’ high energy demand for H2 release. This work presents the photo-induced liberation of H2 from formic acid (FA) as a liquid H2 carrier, using visible light and well-established 5 wt% palladium nanoparticles supported over carbon (Pd/C). We show that low-power light-emitting diodes (LEDs) produced higher gas flow than their thermal baseline (35 °C), with 27.2 mL/min and 7.72 mL/min, respectively. Further, the rate of gas evolved with light intensity, catalyst loading, and the concentration of FA. Light-induced dehydrogenation shows similar deactivation as the known thermal mechanisms, such as the decreased Pd2+/Pd0 ratio and Pd nanoparticle agglomeration. Hence, these observations suggest a photothermal mechanism, whereby the LED provides heat efficiently absorbed by the Pd/C catalyst and enhanced by Pd’s ability to absorb light, thereby driving the FA dehydrogenation reaction at ambient conditions.