Review: Hydrogen adsorption and storage through a spillover mechanism in palladium-integrated metal organic frameworks

Abstract

Hydrogen spillover, a mechanism involving the disassociation of molecular hydrogen on a metal catalyst and subsequent diffusion of atomic hydrogen to a support material, provides an effective approach for enhancing hydrogen adsorption and storage at ambient conditions. Among porous materials, metal organic frameworks (MOFs) stand out because of their large surface area, tunable porosity, and structural versatility. This review presents a comprehensive examination of hydrogen storage via the spillover mechanism in palladium integrated MOFs. These adsorbents demonstrate synergistic interactions between metal sites and MOF, contributing to improved hydrogen chemisorption and physisorption through spillover. Particular emphasis is placed on various Pd incorporation techniques, the influence of synthesis methods on spillover efficiency, and the physicochemical factors governing hydrogen uptake. The extent of hydrogen uptake depends strongly on the Pd loading, nanoparticle size, and the nature of the MOF support. Overloading of Pd often results in particle agglomeration, reducing the active surface area and thereby diminishing storage performance. Despite these advancements, challenges remain, particularly in achieving reproducible synthesis, optimizing Pd dispersion, and understanding the kinetics of spillover. The review highlights recent progress and critical challenges in developing Pd@MOF systems for practical hydrogen storage applications.