Research Projects

Although hydrogen offers significant advantages as an energy carrier, challenges exist in its storage which limits its widespread adoption. Among various systems investigated for H₂ storage, chemical hydrogen storage is an attractive prospect. This involves storing H₂ in systems such as metal hydrides, NH₃, or liquid organic hydrogen carriers (LOHCs). While these and other materials pose challenges related to thermodynamics and kinetics, LOHCs have been the focus of current research interest. This is due to their ability to meet the present targets, e.g., energy density, cost, charging/discharging rates, reversibility, environmental safety, 5.5 wt% storage capacity and compatibility with the existing infrastructure for storage and transportation, which will enable their efficient implementation for applications. LOHCs are a pair of organic compounds capable of effectively carrying and releasing H₂ in their hydrogen rich/lean forms. Hydrogen is typically released from its rich form, a cyclic hydrocarbon or heterocyclic compound via a dehydrogenation reaction. The H₂ lean form, typically an aromatic or heteroaromatic compound, could be put back in the cycle via a hydrogenation reaction. Implementation of LOHCs as hydrogen storage or carrier materials is still in its infancy. Challenges exist in the design and development of catalysts that are capable of facilitating reversible dehydrogenation/hydrogenation reactions of LOHCs under mild conditions, ensuring efficiency and stability, ensuring efficiency and stability. Among the LOHCs explored, methyl cyclohexane, H-18-dibenzyltoluene, and some nitrogen heterocycles, such as 1,2,3,4-tetrahydroquinoline and carbazole-based systems have garnered significant interest due to their high H₂ storage capacities, good stability and compatibility with the existing gasoline infrastructure, and offer efficient storage and transport of hydrogen. There has been no research activity to design and develop heterogeneous hybrid catalytic systems incorporated with a dehydrogenation catalyst and a hydrogenation catalyst that work in tandem and thus close the cycle. In addition, bimetallic catalytic systems of the type, precious metal + a less precious/non-precious metal which work in a synergistic manner are scarcely explored for reversible H₂ storage in LOHCs. A rational synthesis considering tuning the d-band center of the constituent metals in order to realize desired catalytic activity, remains unexplored. Additionally, heterogenized homogeneous catalysts which offer advantages over their homogeneous or heterogeneous counterparts, in particular for dehydrogenation of LOHCs, largely remain unexplored. Demonstration of reversible hydrogen storage in practically important LOHCs such as methyl cyclohexane, H-18-dibenzyltoluene, and 1,2,3,4-tetrahydroquinoline using such catalysts remain unexplored. Further, there has been no effort to explore the viability of scale up of several of these systems. The proposed project aims to address these gaps. In particular, design and development of heterogeneous hybrid catalysts possessing both, dehydrogenation and hydrogenation catalysts which work in tandem, are planned for study. Heterogenization of a homogeneous dehydrogenation catalyst and a bimetallic catalyst comprised of a precious metal and a less precious/non-precious metal-based catalyst for hydrogenation supported on a single support for tandem catalysis are also planned for study. Scale up of the systems that show promise for applications, is also planned. The proposed project involves supporting (a) bimetallic catalysts (“one catalyst does both”) and (b) hybrid catalyst comprised of homogeneous dehydrogenation catalyst and heterogeneous hydrogenation catalyst on suitable supports. Both, bimetallic catalyst and also the hybrid catalyst will be evaluated for reversible hydrogen storage in LOHCs. These new generation catalysts will bring in a paradigm shift in our efforts to shift to a hydrogen economy.