Electrochemically controlled energy release from a norbornadiene-based solar thermal fuel: increasing the reversibility to 99.8% using HOPG as the electrode material

Waidhas, Fabian; Jevric, Martyn; Bosch, Michael; Yang, Tian; Franz, Evanie; Liu, Zhi; Bachmann, Julien; Moth‐Poulsen, Kasper; Brummel, Olaf; Libuda, Jörg

doi:10.1039/d0ta00377h

Cited by 27 publications

(50 citation statements)

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“…At highly oriented pyrolytic graphite (HOPG) electrodes, reversibility of up to 99.8% was achieved. 115 Electrocatalytically triggered Z to E back-conversion of AZOs has also been demonstrated via reductive radical cascade. By inducing electron transfer, the resulting Z dÀ to E dÀ AZO isomerizes 10 13 times faster on the radical anion potential energy surface than normal Z to E conversion.…”

Section: Controlling Energy Releasementioning

confidence: 99%

Storing energy with molecular photoisomers

Wang

Erhart

et al. 2021

Joule

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Section: Controlling Energy Releasementioning

confidence: 99%

Storing energy with molecular photoisomers

Wang

Erhart

et al. 2021

Joule

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107

162

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“…In a recently reported setup, a high-power UV photon source was implemented into an electrochemical IRRAS setup . The method was successfully applied to probe the photoconversion of norbornadiene to quadricyclane both in the liquid phase , and on ordered oxide-based hybrid materials …”

Section: Introductionmentioning

confidence: 99%

Photoconversion of 2-Propanol on Rutile Titania: A Combined Liquid-Phase and Surface Science Study

et al. 2021

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A fundamental reaction in industries for producing aldehydes and ketones is the partial oxidation of alcohols. As a model reaction, we investigated the photo-oxidation of 2-propanol on rutile titania, which is a promising chemically nontoxic photocatalyst. Photochemical infrared reflection absorption spectroscopy (PC-IRRAS) was used to study the reaction on powder catalysts in the liquid phase (neat liquid and dissolved in dichloromethane). We compare these results with polarized Fourier transform (FT)-IRRAS and temperature-programmed desorption (TPD) experiments on rutile TiO2(110) single crystals in ultrahigh vacuum (UHV). Our in situ liquid-phase experiments showed that 2-propanol converts into acetone on rutile powders, which is in accordance with previous ex situ studies. Mass transport limitations are the key to avoid total oxidation. However, the yield of acetone is limited. We identified water formed as a byproduct and suspected that water might block the active sites. To elucidate possible reaction mechanisms, further experiments were performed on rutile TiO2(110) single crystals in the presence and absence of oxygen and UV irradiation under UHV conditions. Here, we obtained further insights into the elementary steps of the different 2-propanol reactions. We demonstrated that acetone desorbs from a diolate species, which forms in the presence of oxygen under UV irradiation at temperatures around 200 K. Furthermore, propane was identified for the first time as a new thermally activated deoxygenation product besides the simultaneously formed, formally reported, propene. Propene formation is quenched by UV irradiation. Active site blocking by water is confirmed by TPD and polarized FT-IRRAS measurements.

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“…Alternative triggering methods to return to the thermodynamically stable state include thermal activation and metal–oxide-driven catalysis, ,, typically utilized for azoarenes and norbornadienes, respectively. Thermal reversion typically requires substantial energy input to overcome the activation barriers for the azoarene Z to E isomerization in the range of 100–133 kJ/mol (Δ H ‡ ) ,,, and high-temperature conditions ranging from 70 to 120 °C depending on the structure of the photoswitch. , Alternatively, the use of chemical and photoredox catalysis to trigger Z to E isomerization has emerged as another tool to lower the activation energy, , largely focused on the norbornadiene derivatives. − Thus, investigations into alternative stimuli to induce Z to E switching may further expand the opportunities − available to the azoarenes and increase the efficiency of triggered heat release …”

Section: Introductionmentioning

confidence: 99%

Efficient Electrocatalytic Switching of Azoheteroarenes in the Condensed Phases

et al. 2021

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Azo-based photoswitches have shown promise as molecular solar−thermal (MOST) materials due to their ability to store energy in their metastable Z isomeric form. The energy is then released, in the form of heat, upon photoisomerization to the thermodynamically stable E form. However, obtaining a high energy density and recovering the stored energy with high efficiency requires the materials to be employed in the condensed phase and display a high degree of Z to E switching, both of which are challenging to engineer. Here, we show that arylazopyrazole motifs undergo efficient redoxinduced Z to E switching in both the solution and the condensed phase to a higher completeness of switching than achieved photochemically. This redox-initiated pathway lowers the barrier of Z to E isomerization by 27 kJ/mol, while in the condensed phase, the efficiency of electrochemical switching is improved by over an order of magnitude relative to that in the solution state. The influence of the photoswitch's phase, electrical conductivity, and viscosity on the electrochemical switching in the condensed phase is reported, culminating in a set of design rules to facilitate further investigations. We anticipate the use of an alternative stimulus to light will facilitate the application of MOST materials in situations where phototriggered heat release is unachievable or inefficient, e.g., indoor or at night. Furthermore, exploiting the electrocatalytic mechanism, whereby a catalytic amount of charge triggers Z to E switching via a redox process, bypasses the need for fine tuning of the photoswitching chromophore to achieve complete Z to E switching, thus providing an alternative approach to photoswitch molecular design.

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Electrochemically controlled energy release from a norbornadiene-based solar thermal fuel: increasing the reversibility to 99.8% using HOPG as the electrode material

Abstract: Solar energy conversion using molecular photoswitches holds great potential to store energy from sunlight in the form of chemical energy in a process that can be easily implemented in a direct solar energy storage device.

Cited by 27 publications

References 50 publications

Storing energy with molecular photoisomers

Storing energy with molecular photoisomers

Photoconversion of 2-Propanol on Rutile Titania: A Combined Liquid-Phase and Surface Science Study

Efficient Electrocatalytic Switching of Azoheteroarenes in the Condensed Phases

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