Safe and sustainable hydrogen production using Liquid Organic Hydrogen Carriers (LOHCs)
In the definition of a carbon-neutral energy system and chemical production, the use of hydrogen plays a pivotal role. However, considering the risks associated with its storage and transport under cryogenic conditions and/or at high pressure, the employment of low pressures alternatives is urgent. LOHCs represents a safe and efficient option. This contribution will discuss the use of LOHCs as energy and hydrogen carriers as well as their application in biomass valorization reactions to produce value-added compounds. In this context, the attention will focus on formic acid and small alcohols that are a renewable H-source promising in relevant chemical transformations.
The high energy content per unit of mass of molecular hydrogen (120 MJ kg-1 or 33.3 kWh kg-1) makes it key for shifting towards a decarbonized energy system and industrial chemical production. However, most worldwide H2 production occurs via hydrocarbon steam reforming (45–65 Mt/year), and this process is associated with a high CO2 footprint, though cost-effective (1). Even if, in principle, it is possible to combine a sequestration and storage technology of the co-produced CO2 with the reforming reaction, this strategy is viable only for large-scale production. Therefore, the research for green hydrogen production is becoming ever more urgent in the context of a zero-carbon energy system.
Water electrolysis enables hydrogen production with high purity (> 99.5%) without the co-generation of gas emissions; however, this is a high energy-intensive process, which makes its utilization economically unfavourable for large-scale production.
Moreover, being the lightest molecule, H2 has a very low density and this constitutes a critical aspect of its storage and transportation (1,2). To increase the energy density per unit volu ...