A new catalyst that enables safe storage and transportation of hydrogen has been developed by researchers from the Brookhaven National Laboratory (BNL) at the U.S. Department of Energy.
The catalyst reversibly converts hydrogen and carbon dioxide (CO2) gas to and from a liquid formic acid at ambient pressure and temperature. The liquid can be shipped with the same type of infrastructure utilized to transport oil and gasoline. Hydrogen can be used as an alterative fuel, as it can be efficiently transformed into energy without generating greenhouse gases or toxic substances. However, the major problem is the storage and transportation of hydrogen. The issue can be addressed by using the new catalyst.
James Muckerman, a chemist at BNL and a co-author of the research, stated that when hydrogen release is required for fuel cell applications or others, the user can just turn over the ‘pH switch’ found on the catalyst in order to make the reaction run in a reverse way. In addition, the liquid solution can be directly utilized in formic-acid fuel cells, added Muckerman.
Yuichiro Himeda from the National Institute of Advanced Industrial Science and Technology (AIST) in Japan has been working on this kind of catalyst for several years. Himeda utilized iridium metal complexes that comprise aromatic diimine ligands with peripheral, pendent hydroxyl (OH) groups. Recently, he collaborated with BNL researchers, Etsuko Fujita, James Muckerman, and Jonathan Hull, to further advance the study. The team found that under appropriate conditions, the OH groups on the catalyst’s diimine ligand help hydrogen to react with CO2. The BNL team thought that it can enhance the reactivity by inserting the pendent bases close to the metal centers, instead of in peripheral positions. Finally, the group developed a new iridium metal catalyst that incorporates a novel ligand, synthesized by scientists at Scripps Research Institute.
Testing has shown that the catalyst offered a superior performance for storing and regenerating hydrogen under very mild conditions. This catalytic method may have an application in hydrogen fuel cells.