Solid hydrogen storage with palladium-graphene composites: Synthesis, characterization, and mechanistic insights

Abstract

Efficient and safe hydrogen storage is a pivotal challenge for the advancement of hydrogen energy technologies. To address this, the engineering of high-performance solid-state hydrogen storage materials through the loading of transition metals (TM) on carbon-based solids has gained considerable interest. However, the mechanics for TM such as Palladium that bolster hydrogen storage have not well addressed yet. This work presents hydrogen absorptions with metal Pd nanoparticles loaded on reduced graphene oxide (Pd-rGO), including material preparation, structural characterization, hydrogen storage performance, and quantum chemical mechanistic insights. A simple material synthesis strategy has been explored and Pd-rGO composites are successfully prepared with graphite powder as raw materials by an easy reduction-oxidation process. Then, Pd-rGO composites are characterized using X-ray diffraction, Fourier-transform infrared spectroscopy, Raman, transmission electron microscopy, and nitrogen adsorption-desorption isotherms methods to clarify the detailed structural characteristics of Pd-rGO with different loading amounts. It is found that Pd nanoparticles with an average particle size of 10 nm are uniformly dispersed on the surface of rGO. The materials have high defect severity and increased specific surface areas with Pd loading. The hydrogen adsorption capacity of Pd-rGO can be increased by 64 % compared with that without Pd loading due to the hydrogen spillover effect. In addition, the intensification mechanism of hydrogen storage of Pd-rGO composites is further understood by using density functional theory calculations and surface interaction analysis.