HYDROGEN · Production and storage of hydrogen

Final Activity Report Summary - HYDROGEN (Production and storage of hydrogen)

Hydrogen production by electrolysis is an important technology for sustainable energy. The oxygen side is the bottleneck. The DTU have simulated the electrocatalysis at this side with computers. The efficiency is limited due the complexity of the reaction, which proceeds in 4 steps. The DTU obtained new insight into the use of metal ammines and borohydrides for hydrogen storage, enabling the prediction of crystal structures and new metal borohydrides and metal ammines with high storage capacity. Combining advanced computational and neutron scattering methods, the mechanisms for transport of ammonia in selected metal ammines were understood and rate limiting steps identified. Chalmers have studied how a well-known material (titanium dioxide, TiO2) absorbs (sun)light and how the absorbed energy can be stored by splitting water to form hydrogen. Analysing well-defined nanofabricated model surfaces showed that the conversion efficiency of TiO2 can be enhanced by functionalising it with noble metal nanoparticles. The mutual arrangement of the nanoparticles can be exploited to optimise the use of expensive metals. Chalmers have used a highly sensitive balance based on a quartz resonator to study the capability of metals to store hydrogen. Magnesium (Mg) is light and has a large capacity but it is difficult to release hydrogen from Mg. The addition of carbon to Mg alleviates this. The Oxford group proposed a mechanism for hydrogen release from sodium alanate using scandium and titanium as catalysts. The release proceeds via breaking of the bridge H-Al bond and subsequent formation of intermediate coordination compounds. The mechanism of hydrogen formation in electrolysis was studied by the UI with electronic structure calculations. The ordering of water molecules was studied with a new algorithm allowing long time simulations. An improvement to the density functional method for describing electronic systems was developed and implemented in software from the DTU node, and applied to help predict ways of improving oxides used in solar cells. The aim of EPFL's research is to store solar energy in hydrogen by splitting water. To convert energy in sunlight, materials like iron oxide need to be controlled at the nanoscale, in terms of morphology, chemical stability and photoactivity. Highly efficient electrodes based on these materials were demonstrated at the lab scale. Most promising solid hydrogen stores release hydrogen too slowly. To solve this problem using a molecular catalyst, WAR designed and developed transition metal based chemicals with improved hydrogen binding properties. Further development for practical use is now underway. SHELL's research focused on confining aluminum hydride particles to the cavities of metal-organic frameworks (MOFs). Shell prepared composites using dimethylethylamine alane as a precursor for aluminum hydride particles, which were loaded into the pores of the host material using solution infiltration. Two types of MOFs were impregnated with alane. These materials had different pore architectures and internal surface chemistry, leading to distinct encapsulated species. Examination of these systems showed the two materials to be stable, and loaded with alane nanoparticles. Leiden investigated how Ti metal facilitates hydrogen uptake in sodium alenate, a solid storage material. The degree to which different Ti coverages on Al surfaces of square symmetry promote dissociation of di-hydrogen was investigated. Leiden also investigated the light induced reaction by which water is split to form hydrogen. A method previously only applicable to electrochemical reactions was successfully generalised to enable its use to study photo-electrochemical half reactions. In a joint experimental and theoretical approach, Empa investigated the thermodynamic properties and the hydrogen sorption kinetics of borohydrides. The hydrogen mobility in the bulk of these compounds was studied to help develop new storage materials.

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