Recent progress and perspectives of liquid organic hydrogen carrier electrochemistry for energy applications

Abstract

Amidst the global pursuit of clean and sustainable energy, the transition towards a hydrogen economy holds immense promise, yet is encumbered by significant storage challenges. Liquid organic hydrogen carrier (LOHC) electrochemistry emerges as a promising solution to enable efficient and sustainable hydrogen storage, meanwhile broadening the horizons of LOHCs for use as clean, renewable, and intense energy carriers to store and generate electricity. In this perspective, we embark on a review of recent trends and progress in LOHC redox electrochemistry, properties, and applications. We categorize electrochemically active, regenerable LOHCs into alcohols, amines, aromatic compounds, aminoxyl species, and others, based on their functional groups, with a keen emphasis on their electrochemical properties. Our examination of electrochemically redoxable LOHCs, with a particular focus on secondary alcohols such as isopropanol and cyclohexanol, primary amines such as ethylamine, aromatic compounds such as quinones, and aminoxyl species such as TEMPO, unveils their vast potential across diverse applications including ambient hydrogen storage, regenerative fuel cells for electricity generation, and rechargeable batteries and flow batteries for intensive electricity storage. Through this exploration, we discern promising avenues for advancing sustainable hydrogen and energy storage solutions by harnessing the diverse capabilities of different LOHC categories, thus paving the way towards a greener and more resilient energy landscape.