Pyrazolium Phase‐Change Materials for Solar‐Thermal Energy Storage

Here, we present an investigation of the thermochemistry of proton uptake in acetonitrile across three charge states of a polyoxovanadate-alkoxide (POV-alkoxide) cluster, [V 6 O 7 (OMe) 12 ] n ( n = 2–, 1–, and 0). The vanadium oxide assembly studied features bridging sites saturated by methoxide ligands, isolating protonation to terminal vanadyl moieties. Exposure of [V 6 O 7 (OMe) 12 ] n to organic acids of appropriate strength results in the protonation of a terminal V=O bond, generating the transient hydroxide-substituted POV-alkoxide cluster [V 6 O 6 (OH)(OMe) 12 ] n +1 . Evidence for this intermediate proved elusive in our initial report, but here we present the isolation of a divalent anionic cluster that features hydrogen bonding to dimethylammonium at the terminal oxo site. Degradation of the protonated species results in the formation of equimolar quantities of one-electron-oxidized and oxygen-atom-efficient complexes, [V 6 O 7 (OMe) 12 ] n +1 and [V 6 O 6 (OMe) 12 ] n +1 . While analogous reactivity was observed across the three charge states of the cluster, a dependence on the acid strength was observed, suggesting that the oxidation state of the vanadium oxide assembly influences the basicity of the cluster surface. Spectroscopic investigations reveal sigmoidal relationships between the acid strength and cluster conversion across the redox series, allowing for determination of the proton affinity of the surface of the cluster in all three charge states. The fully reduced cluster is found to be the most basic, with higher oxidation states of the assembly possessing substantially reduced proton affinities (∼7 p K a units per electron). These results further our understanding of the site-specific reactivity of terminal M=O bonds with protons in an organic solvent, revealing design criteria for engineering functional surfaces of metal oxide materials of relevance to energy storage and conversion.

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“…For previously reported acids, the referenced NMR data are noted in Table S1 . 51 , 54 , 76 , 79 − 83 …”

Section: Methodsmentioning

confidence: 99%

Charge-State Dependence of Proton Uptake in Polyoxovanadate-alkoxide Clusters

2022

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“…16-17, 20-21, 28 Our group has recently described a family of pyrazolium salts as phase change materials. 29 Organic salts are usually non-flammable, chemically and thermally stable, and relatively non-volatile with good heat transfer properties. 30 a) b)…”

Section: Introductionmentioning

confidence: 99%

Role of Hydrogen Bonding in Phase Change Materials

Matuszek

Vijayaraghavan

Kar

et al. 2019

Crystal Growth & Design

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Phase change materials (PCMs) which melt in the temperature range of 100-230 °C, are a promising alternative for the storage of thermal energy. In this range, large amounts of energy available from solar-thermal, or other forms of renewable heat, can be stored and applied to domestic or industrial processes, or to an Organic Rankine Cycle (ORC) engine to generate electricity. The amount of energy absorbed is related to the latent heat of fusion (ΔH f) and is often connected to the extent of hydrogen bonding in the PCM. Herein, we report fundamental studies, including crystal structure and Hirshfeld surface analysis, of a family of guanidinium organic salts that exhibit high values of ΔH f , demonstrating that the presence and strength of H-bonds between ions plays a key role in this property. File list (3) download file view on ChemRxiv Manuscript.pdf (865.17 KiB) download file view on ChemRxiv Supplementary information.pdf (3.39 MiB)

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“…Phase-change heat-transfer technology has a wide range of applications in the fields of energy saving, [1][2][3][4] petrochemical engineering, [5,6] and desalination. [7][8][9][10] The application scenarios and needs of phase-change heat transfer are always changing and research into its enhancement has never stopped.…”

Section: Introductionmentioning

confidence: 99%

Enhanced Phase‐Change Heat Transfer by Surface Wettability Control

et al. 2022

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The phase-change heat-transfer coefficient can be improved by several orders of magnitude through the design of micronanostructures on typical surfaces. However, with the rapid development of intelligent and integrated devices, there is an increasing desire to regulate the heat exchange form of the surface to adapt to various environmental requirements. This study concerns the design of a carbon nanotube array-based phase-change heat-transfer surface, which can switch its wettability between superhydrophobicity and superhydrophilicity. By installing this surface on a device that integrates boiling heat transfer and condensation heat transfer, the device can independently adjust the surface wettability for different heattransfer requirements. As a result, this surface can enhance condensation heat-transfer coefficient over 90 % in the superhydrophobic state and enhance the boiling heat-transfer coefficient over 41 % in the superhydrophilic state. Surfaces with controllable wettability can aid development of a new generation of smart control technologies to actively regulate system and device temperatures.

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Pyrazolium Phase‐Change Materials for Solar‐Thermal Energy Storage

Cited by 37 publications

References 28 publications

Charge-State Dependence of Proton Uptake in Polyoxovanadate-alkoxide Clusters

Charge-State Dependence of Proton Uptake in Polyoxovanadate-alkoxide Clusters

Role of Hydrogen Bonding in Phase Change Materials

Enhanced Phase‐Change Heat Transfer by Surface Wettability Control

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