Heterogeneous Catalysts in N-Heterocycles and Aromatics as Liquid Organic Hydrogen Carriers (LOHCs): History, Present Status and Future

Abstract

The continuous decline of traditional fossil energy has cast the shadow of an energy crisis on human society. Hydrogen generated from renewable energy sources is considered as a promising energy carrier, which can effectively promote the energy transformation of traditional high-carbon fossil energy to low-carbon clean energy. Hydrogen storage technology plays a key role in realizing the application of hydrogen energy and liquid organic hydrogen carrier technology, with many advantages such as storing hydrogen efficiently and reversibly. High-performance and low-cost catalysts are the key to the large-scale application of liquid organic hydrogen carrier technology. In the past few decades, the catalyst field of organic liquid hydrogen carriers has continued to develop and has achieved some breakthroughs. In this review, we summarized recent significant progress in this field and discussed the optimization strategies of catalyst performance, including the properties of support and active metals, metal–support interaction and the combination and proportion of multi-metals. Moreover, the catalytic mechanism and future development direction were also discussed.

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.…”