China 
Africa 
Explore chapters and articles related to this topic
Nanocatalysts from Biomass and for the Transformation of Biomass
Published in Vanesa Calvino-Casilda, Antonio José López-Peinado, Rosa María Martín-Aranda, Elena Pérez-Mayoral, Nanocatalysis, 2019
In the heterogeneously catalysed hydrogenation reactions, it is important to consider the phenomenon called “hydrogen spillover”, which consists of the dissociative adsorption of the hydrogen on a metal NP and the migration from its surface to the support surface, which can become catalytically active (Filikov and Myasoedov 1986). As a result, the hydrogenation rate is the sum of both reaction rates, on the metal surface and on the support surface. The support not only influences the dispersion of NPs but also on the hydrogen spillover, resulting in a beneficial or detrimental effect to the hydrogenation reaction. An example of the beneficial effect is the conversion of cellulose into sorbitol with a yield of 91.5% over a Pt nanocatalyst loaded on reduced graphene oxide (Pt/rGO) (Wang et al. 2014). The catalyst was prepared using ethylene glycol as a reductant agent under microwave irradiation, and the rGO led to a higher yield than other supports.
Modular Systems for Energy and Fuel Storage
Published in Yatish T. Shah, Modular Systems for Energy Usage Management, 2020
The mechanism of the increased performance and durability is hydrogen spillover and has been presented [191]. In this work, the use of the palladium-treated alloys for hydrogen source along with a new-type nickel–hydrogen battery and a PEM fuel cell was demonstrated. The objective of this work was to demonstrate a hydrogen storage module for an onboard electrical power source for micropower systems. In summary, the following conclusions are drawn from this study [177–192]:The palladium-treated intermetallic hydrogen storage alloys is compatible with the thin-film ink preparation process. The think-film inks made with the palladium-treated alloys can absorb hydrogen readily under atmospheric hydrogen.The contact with 26 wt% KOH solution slightly decreases the absorption rate in the first hydrogen absorption, but the absorption rate can be recovered after a few cycles of absorption and desorption.The thin-film ink can keep its structural integrity after 5,000 absorption/desorption cycles. The change of storage capacity with increasing the cycle number is determined by the property of the hydrogen storage alloy and the testing environment. With the existence of water vapor in the hydrogen, the degradation is accelerated.Both palladium-treated LaNi4.7Al0.3 and CaNi5 can be used as the hydrogen source for the microfabricated power systems. The current provided by these two alloys can be higher than the requirement of the microfabricated PEM fuel cell. The efficiency of hydrogen provided by LaNi4.7Al0.3 can be higher than 90% at room temperature.Due to the low pressure of the first plateau of CaNi5, not all the hydrogen in CaNi5 can be used by the fuel cell at room temperature. This leads to the low hydrogen efficiency of CaNi5 module compared to the LaNi4.7Al0.3 module.By monitoring the hydrogen pressure, the remaining amount of hydrogen can be determined. Hence the remaining power capacity of the fuel cell power system can be monitored.
A short review of nanographenes: structures, properties and applications
Published in Molecular Physics, 2018
Yafei Dai, Yi Liu, Kai Ding, Jinlong Yang
Hydrogen has attracted enormous research attention as a promising clean future energy resource. However, wide practical application of hydrogen as fuel requires that the storage of hydrogen can be processed more economically, conveniently and efficiently. Recently, increasing attention has been paid to the carbon materials (e.g. carbon nanotubes, carbon nanohorns, and activated carbons) due to its light mass density and high surface to volume ratio [92–95]. Among carbon materials, NGs with microporous are advantageous to store hydrogen due to its large surface area, large pore volume, low density, and tunable pore structure [96]. Hydrogen molecules are usually adsorbed physically on the surface of carbon materials. The hydrogen storage capacity of carbon materials is reported to be enhanced by the adsorption of metal nano particles such as Pt [97–101] or Ni [102]. The mechanism of this phenomenon is explained as follows: hydrogen molecules are dissociated on the surface of metal particles, and then atomic hydrogen moves to the carbon surface which is called hydrogen spillover. The hydrogen atoms keep diffusing on the carbon surface and chemisorbed reversibly or irreversibly [103], increasing the trap of atomic hydrogen on the carbon surface. Such atomic hydrogen storage is also added to the physisorption storage by molecular hydrogen, the total storage capacity of the carbon material increases. Therefore, the hydrogen storage capacity of the carbon material increases. Li et al. [104] and Ogawa et al. [92] investigated the metal atoms adsorption on the NGs and the adsorption of hydrogen atoms on NGs, respectively.