Laser-Induced Methanol Decomposition for Ultrafast Hydrogen Production

Methanol (CH₃OH) is a liquid hydrogen (H₂) source that effectively releases H₂ and is convenient for transportation. Traditional thermocatalytic CH₃OH reforming reaction is used to produce H₂, but this process needs to undergo high reaction temperature (e.g., 200 °C) along with a catalyst and a large amount of carbon dioxide (CO₂) emission. Although photocatalysis and photothermal catalysis under mild conditions are proposed to replace the traditional thermal catalysis to produce H₂ from CH₃OH, they still inevitably produce CO₂ emissions that are detrimental to carbon neutrality. Here, we, for the first time, report an ultrafast and highly selective production of H₂ without any catalysts and no CO₂ emission from CH₃OH by laser bubbling in liquid (LBL) at room temperature and atmospheric pressure. We demonstrate that a super high H₂ yield rate of 33.41 mmol·h^-1 with 94.26% selectivity is achieved upon the laser-driven process. This yield is 3 orders of magnitude higher than the best value reported for photocatalytic and photothermal catalytic H₂ production from CH₃OH to date. The energy conversion efficiency of laser light to H₂ and CO can be up to 8.5%. We also establish that the far from thermodynamic equilibrium state with high temperature inside the laser-induced bubble and the kinetic process of rapid quenching of bubbles play crucial roles in H₂ production upon LBL. Thermodynamically, the high temperature induced using laser in bubbles ensures fast and efficient release of H₂ from CH₃OH decomposition. Kinetically, rapidly quenching of laser-induced bubbles can inhibit reverse reaction and can keep the products in the initial stage, which guarantees high selectivity. This study presents a laser-driven ultrafast and highly selective production of H₂ from CH₃OH under normal conditions beyond catalytic chemistry.