Abstract
Metal borohydrides have very high hydrogen densities but their poor thermodynamic and kinetic properties hinder their use as solid hydrogen stores. An interesting approach to improve their functionality is nano-sizing by confinement in mesoporous materials. In this respect, we used the 0.725 LiBH4–0.275 KBH4 eutectic mixture, and by exploiting its very low melting temperature (378 K) it was possible to successfully melt infiltrate the borohydrides in a mesoporous CMK-3 type carbon (pore diameter ~5 nm). The obtained carbon–borohydride composite appears to partially alleviate the irreversibility of the dehydrogenation reaction when compared with the bulk LiBH4-KBH4, and shows a constant hydrogen uptake of 2.5 wt%–3 wt% for at least five absorption–desorption cycles. Moreover, pore infiltration resulted in a drastic decrease of the decomposition temperature (more than 100 K) compared to the bulk eutectic mixture. The increased reversibility and the improved kinetics may be a combined result of several phenomena such as the catalytic action of the carbon surface, the nano-sizing of the borohydride particles or the reduction of irreversible side-reactions.
Highlights
Within the efforts to reduce CO2 emissions and introduce alternatives to fossil fuels, hydrogen appears as one of the most promising energy carriers
The CMK-3 type carbon was obtained through a nanocasting procedure, according to a modified version of the original synthesis method described by Ryoo et al [41] using 2D hexagonal SBA-15 silica (Claytec Inc, East Lansing, MI, USA) as a template
All diffraction peaks completely disappear in the case of the LiK/CMK-3 composite material, indicating the absence of crystalline borohydrides outside the pores of the carbon scaffold after infiltration
Summary
Within the efforts to reduce CO2 emissions and introduce alternatives to fossil fuels, hydrogen appears as one of the most promising energy carriers. Due to the possibility of achieving higher hydrogen density, storage in the solid state seems to be a highly advantageous option from different perspectives [5,6,7,8,9]. Among the various materials that have been considered for this purpose, metal borohydrides are interesting as hydrogen storage media [10,11]. For instance LiBH4 contains 18.5 wt% of hydrogen [12], while 13.8 wt% can be released by its decomposition to LiH, B and
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
