Laser-Induced Methanol Decomposition for Ultrafast Hydrogen Production

Methanol (CH(3)OH) is a liquid hydrogen (H(2)) source that effectively releases H(2) and is convenient for transportation. Traditional thermocatalytic CH(3)OH reforming reaction is used to produce H(2), but this process needs to undergo high reaction temperature (e.g., 200 °C) along with a catalyst and a large amount of carbon dioxide (CO(2)) emission. Although photocatalysis and photothermal catalysis under mild conditions are proposed to replace the traditional thermal catalysis to produce H(2) from CH(3)OH, they still inevitably produce CO(2) emissions that are detrimental to carbon neutrality. Here, we, for the first time, report an ultrafast and highly selective production of H(2) without any catalysts and no CO(2) emission from CH(3)OH by laser bubbling in liquid (LBL) at room temperature and atmospheric pressure. We demonstrate that a super high H(2) 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 H(2) production from CH(3)OH to date. The energy conversion efficiency of laser light to H(2) 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 H(2) production upon LBL. Thermodynamically, the high temperature induced using laser in bubbles ensures fast and efficient release of H(2) from CH(3)OH 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 H(2) from CH(3)OH under normal conditions beyond catalytic chemistry.