A laser-induced catalyst for the electrosynthesis of ammonia

Abstract

Electrocatalytic synthesis of ammonia is a sustainable, cost-effective alternative method for producing renewable electricity and can operate under milder conditions than the traditional Haber–Bosch method. We report direct laser-induced synthesis of copper nanocatalysts embedded in graphitic films for the synthesis of ammonia. Laser-induced metal-embedded graphene (m-LIG) offers many advantages, such as fast and simple synthesis, shape design of the electrodes, and direct printing on any substrate, including thermally sensitive plastics. Moreover, the one-step synthesis results in better integrity between the metal nanoparticles and the graphitic matrix, hence, leading to improved charge transfer and higher stability. Diffraction studies reveal the occurrence of metallic copper with the secondary phase of copper oxide. The phase of the copper nanoparticles can be tuned by controlling various laser parameters. Higher rates and efficiency of ammonia production are demonstrated by copper-embedded graphitic catalysts. The improved performances arise from the strong interaction between copper atoms and nitrogen molecules, which lowers the energy barrier for nitrogen activation. Moreover, the graphitic support stabilizes the copper atoms and enhances electron transfer, increasing active sites and selectivity for nitrogen reduction over competing reactions like hydrogen evolution; copper embedded laser-induced graphene (Cu-LIG) electrodes exhibit high ammonia production rates of 6378 mg cm⁻² h⁻¹ in a flow cell with a faradaic efficiency of approximately 80% at a current density of 280 mA cm⁻². Furthermore, the composite electrodes retain excellent prolonged stability even at a high current density of 120 mA cm⁻², maintaining an ammonia faradaic efficiency of around 40%, stable for at least 10 hours. This synthesis demonstrates an excellent rate of ammonia production, even at high current densities, establishing its strong potential for future technological applications.