Advances in CO2 circulation hydrogen carriers and catalytic processes

Hydrogen serves as a renewable, clean energy carrier, and the critical development of technologies for safer and simpler storage and transportation is imperative for addressing global warming. There is also a growing demand for efforts to capture and utilize CO2 to tackle similar issues. Consequently, considerable attention has been drawn to carriers that chemically store hydrogen. Hydrogen can be stored and released through hydrogenation and dehydrogenation. Notably, the storage and release of hydrogen via CO2 hydrogenation and subsequent dehydrogenation of its hydrogenation product could potentially bolster the future hydrogen economy, rendering it an appealing option as a CO2 circulation hydrogen carrier (CCHC). To leverage CCHC for various applications, a catalytic process enabling the reversible storage and release of hydrogen is essential. This review focuses on CCHC candidates, such as methanol (MeOH), dimethyl ether (DME), and formic acid (FA), summarizing recent catalytic approaches for hydrogen production through pivotal dehydrogenation processes within the CCHC cycle.