Catalytic hydrogen storage in liquid hydrogen carriers

Abstract

Hydrogen energy, often dubbed the “ultimate energy source”, boasts zero carbon emissions and no harmful by-products. Nevertheless, the storage and transportation of hydrogen remain significant hurdles for its commercialization and large-scale implementation. Liquid hydrogen carriers (LHC), such as cyclohexane, methylcyclohexane, N-heterocycles, methanol, and ammonia, have emerged as promising solutions in hydrogen energy conversion systems. The storage and release of hydrogen rely on molecular hydrogenation and dehydrogenation processes, which are heavily influenced by the presence of catalysts. As such, a thorough understanding of catalyst design and mechanism is essential to facilitate (de)hydrogenation reactions under milder conditions. In this review, we explore three prevalent LHC systems and the catalysts employed during (de)hydrogenation processes. While noble metal catalysts exhibit superior performance in catalytic hydrogen storage, non-noble metal catalysts have also made considerable advancements. Furthermore, some liquid organic molecules are close to commercialization, potentially providing new options for energy storage and transportation. This article aims to trigger interest in LHC research and inspire the development of innovative catalytic systems for the catalytic hydrogen storage process.’