Nano-palladium dispersed double-shelled carbon hollow nanostructures: a novel approach to store hydrogen

Abstract

Double-shelled carbon hollow (DSCH) nanostructures are promising candidates for hydrogen storage applications due to their tailored hierarchical morphology. This work proposes a novel approach to enhance the hydrogen storage performance by taking advantage of the nanoarchitecture construction and nanoconfinement strategies, wherein the storage of atomic and molecular forms of hydrogen is demonstrated under near-ambient conditions. Ultrafine catalytic Pd nanoparticles confined within double-shelled carbon were harnessed to promote the effective spillover mechanism and improve the hydrogen sorption–desorption cycle performance. The phases, morphology, size and distribution of nanoparticles in DSCH were studied using X-ray diffraction, scanning and transmission electron microscopy. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy provided information on the functional groups and surface composition. Benefitting from the unique structure and interconnected hierarchical pores, DSCH nanostructures showed a storage capacity of 0.78 wt% at 298 K and 20 atm H₂ pressure. The hydrogen storage in DSCH was ascribed to (i) adsorption of molecular hydrogen on the carbon surface, (ii) chemisorption of atomic hydrogen induced by the spillover mechanism, (iii) formation of metal hydride and (iv) free molecular hydrogen in the inner hollow core. The palladium nanoparticles were found to play a dual role, i.e. as a catalyst for the spillover mechanism and as a sorbent to absorb hydrogen. Overall, the hierarchical porous nanohybrids showed good cycling stability and enhanced spillover efficiency due to the presence of non-agglomerated and well-dispersed metal nanoparticles.