One of the challenges of the next decades is the sufficient and sustainable supply of energy. In this respect advancements in hydrogen technology are of particular interest, since the generation of hydrogen from suitable starting materials, its storage and conversion to electrical energy is the prerequisite for the application of hydrogen as power source.
Surprisingly, the use of carbon dioxide for hydrogen storage has been largely neglected until to date. Based on the catalytic processes of formation and decomposition of formic acid a power supply system should be possible allowing in principle for a CO₂-neutral energy generation as depicted in the figure below.
In contrast to the established homogeneous hydrogenation of CO₂, the decomposition of formic acid kept almost disregarded. We could show for the first time the generation of significant amount of hydrogen from formic acid with the simple commercially available complex [RuCl₂(p-cymene)]₂.
Compared to previously known organic hydrogen generating systems the presented system allows to be run even at room temperature. At 26.5°C in the presence of 1.0 mol% [RuCl₂(p-cymene)]₂ approximately 110 mL of a 1:1 mixture containing hydrogen and carbon dioxide is generated per hour from 10 mL formic acid/NEt₃-adduct. We combined the hydrogen generation unit directly with a H₂/O₂ PEM fuel cell and used the energy produced by a small propeller for more than 48 hours.
The present work demonstrates that hydrogen can be produced on demand without the need of high temperature reforming processes. This possibility might be interesting for applications in portable electric devices.