Intrusion/Extrusion of Water Into Organic Grafted SBA-15 Silica Materials for Energy Storage

Abstract

Mesoporous SBA-15 silica materials were grafted with trialkylsilyl compounds having short (C1) and long (C8) carbon chain and characterized by XRD, N2 physisorption analysis, 29Si MAS-NMR and contact angle (CA) measurements. A drastic enhancement of the hydrophobic property after grafting was observed by forced intrusion water; it occurred in two steps and with quite high intrusion pressures (mean values - 10 and - 15 MPa). The hydrophobic nature of both internal and external surface area was confirmed by 29Si MAS-NMR and CA measurements, respectively. After contact with water, materials displayed a partial hydrophobic behaviour with uncompleted spontaneous extrusion. The energies absorbed during water intrusion correspond to 4.3 and 6.1 J x g(-1) for C1 and C8 grafted species, respectively.

A Highly Stable Nonhysteretic {Cu2(tebpz) MOF+water} Molecular Spring

“…Such hysteresis allows the mechanical energy of a shock to be dissipated (the energy that the system absorbs on forced compression is much larger than the energy released on spontaneous decompression after the shock). Such systems are mostly represented by grafted silica gels+water/aqueous solutions and recently extension was made to MOFs+water/aqueous solution systems (MOF=metal–organic framework) . A scarce few works used an ionic liquid, ferromagnetic fluids, or glycerin and glycerol as nonwetting liquid.…”

“…On the other hand, many works, including prototype development and testing, are dedicated to HLS‐based shock absorbers based on water and grafted mesoporous silica . Such HLSs have pronounced hysteresis, which is beneficial for energy dissipation, and about two times greater accumulated energy on intrusion due to higher porosity.…”

“…Such porous heterogeneous lyophobic systems (HLSs) have some notable advantages for mechanical energy storage compared to conventional methods: high energy density, the possibility to accumulate mechanical energy at constant pressure, the ability to sustain unprecedented frequencies of charging/discharging, and the ability to be scaled down to nanosize, as in most cases the system is in the form of a suspension. Since the introduction of the HLS concept by Eroshenko, such systems have received considerable attention, and two main types thereof are considered to have desirable properties.…”

“…Despite growing interest in HLS properties, high‐pressure calorimetric measurements are still very rare, even though thermal effects on HLS compression/decompression are an essential part of their characterization for practical use and understanding of their operating mechanisms.…”

“…From the many reports on the energetic characteristics of HLSs, it is clear that those having a small hysteresis (suitable for energy storage) should be found among microporous systems . Such a search is complicated by the fact that there are no solid models to predict the values of the intrusion and extrusion pressures.…”