An Electrochemical Ethylamine/Acetonitrile Redox Method for Ambient Hydrogen Storage

Hydrogen is an appealing energy carrier that can potentially replace conventional fossil fuels in the development of a clean, sustainable hydrogen economy, which would resolve environmental problems caused by the combustion of the non-renewable resources while also meeting the rising demand for energy. However, hydrogen storage has remained a major roadblock in the hydrogen economy development. As a matter of fact, the state-of-the-art methods fall short of the 2025 Department of Energy (DOE) onboard hydrogen storage target of 5.5 wt.% under 85 °C and 12 bars. Herein we report a new, electrochemical ethylamine/acetonitrile redox method for efficient, high-capacity hydrogen storage under completely ambient conditions. The amine/nitrile redox couple is selected due to their moderate chemical polarity and relatively simple hydrogenation and dehydrogenation pathways, which would aid reaction activation and reduce the energy barrier. Electrochemical potential provides the driving force in CH3CH2NH2 dehydrogenation under ambient conditions, rather than high temperature and pressure that are typically required to thermally drive an endothermic process. We demonstrate an effective, complete cycle of CH3CN hydrogenation to CH3CH2NH2 for hydrogen uptake and CH3CH2NH2 dehydrogenation to CH3CN for hydrogen release at low overpotentials, using commercial Pt black catalyst in an electrochemical cell. The studied CH3CH2NH2/CH3CN system has a theoretical H2 storage capacity of 8.9 wt.%, well surpassing the 5.5 wt.% DOE target. This study offers a new, effective hydrogen storage strategy that can be extended to many other amine/nitrile redox systems and would help advance the hydrogen economy development.