High-purity hydrogen delivery for stationary and mobile applications using fuel cells is a subject of rapidly growing interest. As a consequence, the development of efficient storage technologies and processes for hydrogen supply is of primary importance. Promising hydrogen storage techniques rely on the reversibility and high selectivity of liquid organic hydrogen carriers (LOHCs), for example, methylcyclohexane, decalin, dibenzyltoluene, or dodecahydrocabazole. LOCHs have high gravimetric and volumetric hydrogen density, and they involve low risk and capital investment because they are largely compatible with the current transport infrastructure used for fossil fuels. A further advantage comes from the high purity (close to 100%) of the hydrogen generated by dehydrogenation, suitable to directly feed fuel cells without the need for bulky purification modules. Partial dehydrogenation (PDH) of liquid fuels has recently emerged as a transition technology for hydrogen delivery purposes. The principle is to extract from fossil fuels a small fraction of the available hydrogen, which can be used for fuel cell applications, while the dehydrogenated hydrocarbon mixture maintains suitable properties for its use as fuel. With this technology, the large energy demand of dehydrogenation processes can be satisfied by implementing a heat exchanger between the engine and the dehydrogenation reactor, overcoming one of the main constraints associated with the use of organic liquids as hydrogen carriers. This method qualifies itself as a transition technology toward more electrified transportations, in which the main propulsion is still obtained by fuel combustion, although the electrical utilities or auxiliary propulsion are powered by fuel cells. This paper provides a review of the effort that has been directed toward the utilization of organic liquids as hydrogen carriers, with particular focus on the design of the catalytic dehydrogenation process and on the recent approach of fuel partial dehydrogenation.

A proton conducting ceramic fuel cell (PCFC) operating at intermediate temperature has been developed that incorporates electrolyte and electrode materials prepared by flash combustion (yttrium‐doped barium cerate) and auto‐ignition (praseodymium nickelate) methods. The fuel cell components were assembled using an anode‐support approach, with the anode and proton ceramic layers prepared by co‐pressing and co‐firing, and subsequent deposition of the cathode by screen‐printing onto the proton ceramic surface. When the fuel cell was fed with moist hydrogen and air, a high Open Circuit Voltage (OCV > 1.1 V) was observed at T > 550 °C, which was stable for 300 h (end of test), indicating excellent gas‐tightness of the proton ceramic layer. The power density of the fuel cell increased with temperature of operation, providing more than 130 mW cm–2 at 650 °C. Symmetric cells incorporating Ni‐BCY10 cermet and BCY10 electrolyte on the one hand, and Pr2NiO4 + δ and BCY10 electrolyte on the other hand, were also characterised and area specific resistances of 0.06 Ω cm2 for the anode material and 1–2 Ω cm2 for the cathode material were obtained at 600 °C.

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The partial dehydrogenation of fuels like diesel or kerosene cuts to produce H 2 is an emerging idea of increasing interest. In the present work the study of the partial dehydrogenation of Jet A-1 fuel on PteSn/g-Al 2 O 3 based catalysts to produce H 2 to feed an on-board (aircraft) proton exchange membrane fuel cell is presented. Extensive physico-chemical characterization of 5% wt.Pt-1% wt.Sn/g-Al 2 O 3 and 5%wt.Pt-1%wt.Sn-1%wt.Na/g-Al 2 O 3 pelleted materials has been performed. A gradient of the active metals from the edge to the centre of the pellet has been observed. A higher concentration of Pt 0 has been detected on the outer part of the pellet than in the inner part, whereas Sn has been detected only on the external part of the pellet. The investigated materials are active as catalysts for the partial dehydrogenation of normal and desulfurised Jet A-1 kerosene fuel. The presence of sulfur compounds and coke deposition strongly affects the H 2 productivity which decreases rapidly with time on stream. The presence of a Na cation addition contributes to give the highest and most sustained H 2 production. The condensed outlet liquid stream retains the fuel properties in the range of the Jet A-1 kerosene fuel. These are encouraging preliminary results, inviting further research; coking and sulfur poisoning as well as identification of appropriate reaction conditions are the main challenges to be overcome in the immediate future.

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