Metal-carbon composites have shown considerable hydrogen storage potential at room temperature. In the present work the behaviour of two different Pd amalgam doped carbon substrates, namely a carbogenic foam and a mildly oxidised ordered mesoporous carbon, are compared on the basis of their hydrogen sorption properties at 77 and 298 K and low pressures, aiming to investigate the effect of surface on the storage capacity. In both cases, the introduction of alloy nanoparticles leads to an improvement of the hydrogen uptake with respect to pure carbons. This effect is significant for the carbogenic foam however small for the ordered carbon. [...]
In this mini-review, selected contributions on the development of hydrogen storage systems based on small molecules using nanocatalysts for hydrogen generation will be described. The discussion is centered on the most applied compounds such as formic acid, metal hydrides, amine-boranes, alcohols, hydrocarbons, hydrazine and water. In addition, an overview of the most important aspects relating to the application of the metal nanoparticles in each reaction is also considered.
Electrochemical storage of hydrogen in activated carbon material has been investigated using different parameters of cathodic polarization. It has been proven that application of short galvanostatic pulses could be efficient for hydrogen storage in microporous carbon material. Charging current loads from 50 mA g−1 to 32 A g−1 have been used showing correlation between hydrogen capacity, time of charging and electrical efficiency. The anodic charge equivalent to electrooxidation of 1.0 wt% of hydrogen can be already reached after 90 s of cathodic polarization. Temperature effect has been also evaluated and a gradual increase of hydrogen capacity with a better pronounced oxidation plateau was obtained at higher temperatures. Reversible electrosorption of hydrogen is a useful reaction in supercapacitor performance and it might have a potential application for a negative electrode of supercapacitor as well as reversibly operating electrode in the secondary cell. [...]
The hydrogenation properties of magnesium hydride mechanically milled with iron fluorides (FeF2 and FeF3), were investigated by Temperature Programmed Desorption (TPD) and volumetric methods using a Sieverts-type apparatus, as prepared upon dehydrogenation and finally upon subsequent hydrogenation. The activation energy of hydrogen desorption (Ea), calculated from the Kissinger formula using TPD measurements obtained with different heating rates, showed significant decreases of Ea in comparison to that of milled MgH2 without any dopants. Moreover, the influence of these metal fluorides on the thermodynamics of the decomposition process was also examined. In the case of the FeF2 dopant, rehydrogenation following desorption caused the complete decomposition of the iron fluoride to BCC iron and the formation of a predominant MgH2 phase. In contrast to FeF2, the addition of FeF3 led to the formation of β-MgH2 as a major phase coexisting with Mg2FeH6 and MgF2 compounds. The presence of pure Fe in the MgH2+FeF2 composite, as opposed to MgH2+FeF3 containing Mg2FeH6 and MgF2, did not cause any significant influence on the sorption properties of MgH2. Moreover, the original material doped with FeF3 predominantly showed iron in the Mg2FeH6 compound, while the FeF2 dopant iron mostly showed the nearly pure BCC metallic phase [...]
Acceptorless dehydrogenation of alcohols has emerged as a powerful methodology for the valorization of biomass derived platform chemicals and building blocks. In this review we provide a short overview of the advantages and possible product outcomes of this method. The main focus will be devoted to the conversion of glycerol, which is the major waste product of biodiesel production, to lactic acid. While extensive research addresses the development of heterogeneous catalysts, recently new and highly active iridium and ruthenium complexes have also been reported. These novel homogeneous catalysts are even more active than the already reported heterogeneous systems and enable the direct conversion of glycerol into lactic acid and molecular hydrogen. While the product hydrogen might be used either as fuel or as reducing agent for other processes, lactic acid is a platform chemical widely employed by the polymer, pharmaceutical and food industries. The used catalytic methodology is atom-economic, waste-free and is uniquely suited for the efficient conversion of renewable resources.
JavaScript is turned off in your web browser. Turn it on to take full advantage of this site, then refresh the page.