Laser-Induced Methanol Decomposition for Ultrafast Hydrogen Production

Abstract

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.