Releasing Hydrogen at High Pressures from Liquid Carriers: Aspects for the H₂Delivery to Fueling Stations

Abstract

Hydrogen fueling stations require multiple stages of compression to achieve the pressure needed to refuel hydrogen fuel cell electric vehicles at 700 bar. The physical compression equipment constitutes a large share of the total investment cost of hydrogen fueling stations. Hydrogen carriers, i.e., materials that carry either physisorbed or chemisorbed H2, provide an alternate approach to transport and deliver higher densities of hydrogen to the fueling station at lower pressures. Additionally, some liquid phase hydrogen carriers (LPHCs) are defined by thermodynamic properties that allow H2 release at elevated pressure, thus providing an opportunity to reduce the number of compressors at the fueling station. This study compares a series of LPHCs and evaluates the approach of using aqueous solutions of formic acid (FA) to deliver high volumetric densities of H2 to fueling stations and provide a first step of compression. While hydrogen release from most liquid carriers will provide hydrogen slightly above ambient pressure at high temperatures, hydrogen release from the decomposition of FA can provide hydrogen at pressures of several hundred bars at moderate temperatures. A challenge of formic acid is that the high pressure hydrogen is accompanied by 1 equivalent of carbon dioxide and thus requires subsequent separation and purification operations. Nevertheless, formic acid has the advantage of being liquid, which simplifies its handling and provides a continuous supply to a release unit. Furthermore, the energy demand for hydrogen release from FA is lower than for most alternative hydrogen carrier materials.

Size-Dependent Catalytic Cyclohexane Dehydrogenation with Platinum Nanoparticles on Nitrogen-Doped Carbon

“…Clean and renewable energy has been of great concern to cope with the current environmental pollution problems of nonrenewable fossil fuels. Hydrogen has been regarded as an ideal candidate of energy carrier for its high energy density, environment friendliness, and renewability. , However, the safe and high-density storage remains to be a great challenge for the utilization of hydrogen as a general energy source. − Liquid organic hydrogen carriers (LOHCs) have attracted much attention because of their high gravimetric hydrogen capacity and recyclability and easy transportation and storage using the existing infrastructures for fossil fuels. − Cyclohexane, with a high hydrogen storage density of 7.2 wt %, is regarded as an excellent LOHC. However, cyclohexane dehydrogenation to release hydrogen is endothermic and thus needs to be operated at high temperatures (around 300 °C) for adequate conversion.…”

A Precious Catalyst: Rhodium‐Catalyzed Formic Acid Dehydrogenation in Water

“…[3a], Together, these two reactions form the formic acid/carbon dioxide cycle as schematically shown in (Figure ). On this basis, hydrogen fuel stations could be realized as was proposed by Müller et al…”

Hydrogen technologies for energy storage: A perspective

“…Hydrogen carriers such as aqueous solutions of formic acid may provide an alternative approach for transport and delivery to fueling stations, where high pressures are needed to refuel fuel cell vehicles at 700 bar. 36 In recent years, HFTO has supported techno-economic analysis at Argonne National Laboratory to establish a baseline comparison between conventional compressed and liquid hydrogen delivery with several of these hydrogen carriers. Preliminary results have shown that methanol, a one-way carrier produced directly through the reaction between methane and steam, can be cost-competitive with compressed hydrogen delivery even when the carrier is transported several thousand kilometers by rail.…”