Methane conversion using spark discharge-assisted laser-induced plasma (SD-LIP) with Pd catalyst: Non-oxidative hydrogen production

Abstract

Today, methane combustion gives rise to the tremendous release of carbon dioxide into the atmosphere. Finding an efficient method to convert methane into value-added compounds has attracted significant attention, along with mitigating greenhouse gas emissions. Here, the spark discharge-assisted laser-induced plasma (SD-LIP) is investigated in conjunction with the palladium (Pd) catalyst. In the proposed electro-photocatalyst reactor, a Q-switched Nd:YAG laser with a pulse duration of 10 ns- 120 mJ/pulse is utilized to ignite the spark discharge. Laser irradiation plays a pivotal role in inducing electric breakdown by injecting electrons and Pd nanoparticles into the electrode gap at atmospheric pressure. The results indicate that the electron density increases against the traditional spark discharge method. The breakdown voltage notably decreases due to the inverse Bremsstrahlung (IB) phenomenon, reducing specific energy input (SEI). Consequently, energy conversion efficiency (ECE) improves by 14 % having a very low SEI, ranging from 1 to 3 kJ/L. Furthermore, the novel reactor design of SD-LIP reveals the creation of heavier hydrocarbons (Iso-butane) in favor of slight coke formation. Laser decarbonization slows down catalytic deactivation through successive shots. In fact, SD-LIP gives rise to high efficiency in the methane conversion to hydrogen, where high carbon balance preservation (>97 %) is realized.