Recent Advances in Reversible Liquid Organic Hydrogen Carrier Systems: From Hydrogen Carriers to Catalysts

Abstract

Liquid organic hydrogen carriers (LOHCs) have gained significant attention for large‐scale hydrogen storage due to their remarkable gravimetric hydrogen storage capacity (HSC) and compatibility with existing oil and gas transportation networks for long‐distance transport. However, the practical application of reversible LOHC systems has been constrained by the intrinsic thermodynamic properties of hydrogen carriers and the performances of associated catalysts in the (de)hydrogenation cycles. To overcome these challenges, thermodynamically favored carriers, high‐performance catalysts, and catalytic procedures need to be developed. Here, significant advances in recent years have been summarized, primarily centered on regular LOHC systems catalyzed by homogeneous and heterogeneous catalysts, including dehydrogenative aromatization of cycloalkanes to arenes and N‐heterocyclics to N‐heteroarenes, as well as reverse hydrogenation processes. Furthermore, with the development of metal complexes for dehydrogenative coupling, a new family of reversible LOHC systems based on alcohols is described that can release H2 under relatively mild conditions. Finally, views on the next steps and challenges in the field of LOHC technology are provided, emphasizing new resources for low‐cost hydrogen carriers, high‐performance catalysts, catalytic technologies, and application scenarios.This article is protected by copyright. All rights reserved

Promoting Catalytic Performance of Metal Hydrides for Reversible Hydrogen Storage in N-ethylcarbazole by Electronic Structure and Hydrogen Chemical Potential Tuning

“…Developing bifunctional hydrogen storage catalysts is beneficial for integrated and mobile applications of LOHCs and may also facilitate the invention of the so-called “chemical hydrogen batteries” . However, bifunctional catalysts for reversible hydrogen storage in carbazole-type LOHCs remain quite limited, and most of them are based on noble metals such as Pd, Ru, or Rh. ,− The only noble-metal-free bifunctional catalysts are two MH-based catalysts reported in our previous study. , The LaNi 5– x Al x nanoparticles are significantly more active than LaNi 5 nanoparticles and are particularly notable for their high hydrogenation activity at low temperatures of 130 °C compared to standard hydrogenation conditions of 150–180 °C . Recently, some interesting Ru-based one-way hydrogenation catalysts have been proven to be active under 100 °C, , but lowering the 12H-NEC dehydrogenation temperature below 180 °C is still challenging. , The comparison of catalytical performances of the current bifunctional catalysts for reversible hydrogen storage in NEC, low-temperature one-way hydrogenation catalysts, and Pd-based one-way dehydrogenation catalysts are listed in Table S4.…”

“…13,15 The LaNi 5−x Al x nanoparticles are significantly more active than LaNi 5 nanoparticles and are particularly notable for their high hydrogenation activity at low temperatures of 130 °C compared to standard hydrogenation conditions of 150−180 °C. 22 Recently, some interesting Ru-based one-way hydrogenation catalysts have been proven to be active under 100 °C, 35,36 but lowering the 12H-NEC dehydrogenation temperature below 180 °C is still challenging. 37,38 The comparison of catalytical performances of the current bifunctional catalysts for reversible hydrogen storage in NEC, low-temperature one-way hydrogenation catalysts, and Pd-based one-way dehydrogenation catalysts are listed in Table S4.…”

“…The NEC/12H-NEC couple is a model LOHC featured for moderated dehydrogenation temperature, which is highly promising for large-scale hydrogen storage and transport. 22 LaNi 5 is a classic hydrogen storage alloy, and it is known that its hydrogen storage properties and electronic structure can be tuned by metal doping. 23,24 It was confirmed in our previous studies that chemically synthesized LaNi 5 nanoparticles are active for both NEC hydrogenation and 12H-NEC dehydrogenation.…”

Floatable Termination-Vacant MXene Architecture for High-Performance and Cost-Effective Photothermal Dehydrogenation

“…4,5 This shows FA is more promising as a hydrogen carrier to avert the high risk in the hydrogen energy industry chain. 6,7 Efficient hydrogen release from FA is paramount for its hydrogen storage application. 7 Solar energy is predominantly harnessed as the driving force for FA dehydrogenation, relying on the fundamental principles of photothermal catalysis.…”

“…The stringent reaction conditions limit the application scope of methanol for hydrogen storage. Compared with methanol or other liquid hydrogen carriers, formic acid (FA) has a higher transportation safety rating and a lower activation temperature, enabling direct decomposition at a low-temperature range of 30–80 °C for on-demand hydrogen production. , This shows FA is more promising as a hydrogen carrier to avert the high risk in the hydrogen energy industry chain. , …”