bluuebunny/crossref_metadata_2025 huggingface dataset:
Ternary Oxide Semiconductors and Alloys: Compositional Effects on Band Structure and Optoelectronic Properties
Authors: Rajeshwar Krishnan , Danladi Fahad , Meletis Efstathios , Rawat Abhishek
Published: February 2024

A new family of CuxCa1-xV2O6 (0 ≤ x ≤ 1) photoanodes were synthesized via time and energy-efficient solution combustion (SCS) method. The effect of introducing Cu in CaV2O6 on crystal structure, microstructure, and optical properties of the prepared CuxCa1-xV2O6 alloyss was investigated by powder x-ray diffraction (PXRD), scanning electron microscopy (SEM), diffuse reflectance (DRS), and Raman spectroscopy. PXRD patterns, SEM, and Raman results suggested that the polycrystalline powder samples were alloys of CuV2O6 and CaV2O6. DRS measurements showed a decrease in the optical bandgap with Cu mixing. The indirect bandgap decreased from 2.65 eV for CaV2O6 to 1.91 eV for CuV2O6. These experiments were corroborated with band structure calculations. In addition, the photoelectrochemical properties exhibited a strong dependence on the composition and revealed that all composites were n-type semiconductors. The photocurrent density of the composites was optimized by adjusting the Cu/Ca ratio in the prepared samples.
Viability of Solid Oxide Fuel Cell Vehicles with on-Board CO2 Capture
Authors: Barnett Scott A , Schmauss Travis Anthony
Published: February 2024

The viability of CO2-neutral transportation using hydrocarbon or alcohol fuels, in which the CO2 product is captured on-board the vehicle, is examined. Solid oxide fuel cells are proposed for energy conversion because they react fuels with pure oxygen, enabling on-board CO2 capture in a reasonable volume after compression to a moderate pressure of 250 bar; net storage volume is substantially less than of equivalent hydrogen tanks or batteries. During vehicle refueling, captured CO2 can be off-loaded and subsequently used in fuel production with renewable resources, or sequestered, thereby maintaining carbon-neutrality. Alternatively, these Carbon-Capture Fuel Cell Vehicles (CCFCVs) can be part of a CO2-negative pathway by using biofuels and sequestering the captured CO2. Storage volume and weight are analyzed for a range of vehicle types, comparing the proposed transportation platform with those of internal combustion, Li-ion battery, and hydrogen fuel cell vehicles (H2FCV); the results suggest that this is the best available option for long-range vehicles. The well-to-wheels efficiencies for fossil fuels and biomass-to-wheels efficiencies for biofuels are estimated using literature data. The results indicate that the CCFCV can yield efficiencies of ~ 40%, nearly twice that of the H2FCV, ~22%.
In Situ Investigation on Cl- Repellency Effect of Electrolyte Additive on NiOOH for Alkaline Sea Water Splitting
Authors: Ham Kahyun , Lim Ahyoun , Spanos Ioannis
Published: February 2024

Sea water splitting can produce green hydrogen by feeding abundant sea water directly without high-qualified water purification process. However, excess cation such as Mg2+ and Ca2+ in sea water absorbs on the cathode surface, and it causes the loss of active site and activity toward hydrogen evolution reaction. At the anode side, oxygen evolution reaction (OER) should be competed with chlorine evolution reaction due to huge amount of Cl- ion, so operating in high pH electrolyte at low overpotential has been suggested to increase the selectivity toward OER. To further inhibit the adsorption of Cl-, some researchers have suggested using anion additive such as PO4
3- and SO4
2- in the alkaline electrolyte, but both adsorption stability of additive anion and the interaction between anion and metal oxide catalyst are still needed to be studied.

In this study, we investigated the Cl- repellency effect of additive anion in the electrolyte to NiOOH catalyst, known as state-of-the-art OER catalyst, for alkaline sea water splitting. To observe the change in adsorbate species by additive anion, we tracked the mass change of the catalyst during the reaction through in situ electrochemical quartz crystal microbalance (EQCM). Furthermore, Cl- can change (degrade) the NiOOH structure by formation of metal-chloride complex. Through in situ Raman spectroscopy, we observed the structural stability of NiOOH in presence of anion additive as well as the adsorption stability of additive anion depending on the applied potential.
Activation of Commercial Stainless-Steel Electrodes for Highly Efficient and Stable Anion-Exchange Membrane Electrolysis
Authors: Jiang Tao , Aravind P.V. , Jayawardhana Bayu , Pescarmona Paolo P. , Kyriakou Vasileios
Published: February 2024

Commercial stainless steel (SS) is gaining interest as a promising electrode material to be widely used for green hydrogen production from alkaline water electrolysis. Herein, low-cost 304-type SS meshes (SM) were engineered through a simple 2-step activation process, i.e., chemical etching and electrochemical activation. The modified electrodes exhibited comparable hydrogen and oxygen evolution reaction properties with commercially, noble metal-based electrodes available. The modified stainless steel-based electrodes were assembled and tested in an AEM electrolyzer cell, which displays more than 300 mV-voltage drops compared to the bare stainless steel-based cells. The in-situ impedance spectroscopy revealed a significant decrease in the resistances due to interfacial contact, charge transfer, and mass transport. In addition, we identified nanocrystalline Fe-NiCr2O4 and nanocrystalline Ni(OH)2/Fe(OH)2 active species for SS used in hydrogen and oxygen evolution side respectively which could explain the significantly higher performance. In addition, we also developed an electrolyzer system to assess the long-term durability of our cell reactors in which our cells exhibited exceptional durability at 5.0 A (1.0 A cm-2) for 250 h. Our results exemplify that such an approach has the potential for upscaling and deployment in the next-generation, low-cost AEM electrolysis for green hydrogen production.
Electrocatalysts for High Temperature (100-200 ºC) and Pressure (45 bar) Alkaline Electrolysis
Authors: Leuaa Pradipkumar , Chatzichristodoulou Christodoulos
Published: February 2024

Electrolytic hydrogen production is key in transitioning to a sustainable energy system, as it enables the production of sustainable fuels and chemicals from renewable electricity sources and a means to address their intermittent nature at the same time. Amongst the main electrolysis technologies, Alkaline Electrolysis (AE) is the most suitable for the hundreds of GW capacity that is required, as it relies only on abundant, low-cost materials, and has a proven record of reliability and scalability. However, AE suffers from poor efficiency and productivity. Increasing operating temperature and pressure offers a means to overcome this limitation [1, 2]. Nevertheless, electrodes with good long-term stability in the hot corrosive alkaline environment are required. Here, we report the performance of Co3O4 and NiMoOx coated nickel foam (NF) electrodes for the anode and cathode, respectively. The electrodes are tested from room temperature to 150 ºC at 45 bar pressure in 45 wt.% KOH. The Co3O4 coated NF (Co3O4/NF) anode performance is compared to that of commercial pristine NF and Inconel coated NF (Inconel/NF) electrodes. At room temperature the Inconel/NF electrode outperforms both the pristine NF as well as the Co3O4/NF electrodes. At 150 ºC and 45 bar pressure, the Co3O4/NF and Inconel/NF electrode perform quite similar. During the 108 h long-term stability test at 150 ºC and 45 bar, the Co3O4/NF electrode remains stable requiring an overpotential of ~185 mV at 500 mA.cm-2, whereas the overpotential of the Inconel/NF electrode increased from 178 mV to 209 mV after 84 h of operation at the same conditions. The structural and chemical evolution of these electrodes was explored by post-mortem scanning electron microscopy (SEM) in comparison to the fresh electrodes. The NiMoOx coated NF (NiMoOx/NF) cathode showed a low and stable overpotential (~130 mV) at the same conditions, similar to a precious metal coated nickel perforated plate electrode (~125 mV).

References

C. Chatzichristodoulou, F. Allebrod, and M. B. Mogensen, J. Electrochem.
Soc., 163, F3036–F3040 (2016).

F. Allebrod, C. Chatzichristodoulou, and M. B. Mogensen, J. Power Sources, 229, 22–31 (2013).
Luminescence and Excited State Dynamics of Tb1-XEuxAl3(BO3)4 (x=0.01-0.20)
Authors: Ceccon Leonardo , Ruggieri Silvia , Piccinelli Fabio , Bettinelli Marco
Published: February 2024

The room temperature luminescence spectra and emission decay curves of undoped and Eu3+-doped TbAl3(BO3)4 crystals, grown using the flux growth technique, are presented and discussed. The experimental results show that excitation of the Tb3+ excited states gives rise to 5D0 emission from the Eu3+ ion, and therefore non-radiative energy transfer involving the two ions is operative. Analysis of the experimental data indicates that the excitation of the Tb3+ donor ion gives rise to fast energy migration in the 5D4 level of the Tb3+ subset of cations, followed by the energy transfer process populating the 5D0 level of Eu3+. Upon increasing the Eu3+ acceptor concentration, the mainly green emission intensity and the decay time of the 5D4 level decrease, whilst the red emission of 5D0 becomes dominant. The experimental data are interpreted on the basis of the trigonal huntite-type structure of the double borate crystals under investigation.
UVC Emission Devices Based on Alternating Current Inorganic Electroluminescence Using Y2SiO5:Pr3+ Phosphors
Authors: Kang Taewook , Kim Sun Woog , Kim Jongsu
Published: February 2024

Ultraviolet C (UVC: 200-280 nm) lighting is urgently required for a number of sterilization applications such as water and air disinfection, food processing, and medical sterilization. Compared to other UVC emission sources, AC-driven inorganic phosphor electroluminescent (EL) devices are appealing due to their wide viewing angle, fast response time, low power consumption, high contrast, simple manufacture, and cost effectiveness. Although the luminance of inorganic phosphor EL devices is typically low, it is sufficient for most low-cost lighting and large-area display applications. In addition, inorganic phosphor EL devices have the advantage of emitting light without generating much heat.

In this study, UVC emission was demonstrated through EL devices using a UVC phosphor. Pr3+-doped Y2SiO5 (Y2SiO5:Pr3+) is used for UVC light, Y2SiO5:Pr3+ phosphor shows a broad UVC emission at 280 nm from the f-d transition of Pr3+ ions as well as a sharp red emission at 610 nm from the f-f transition of Pr3+ ions. The phosphors were synthesized in three types to fabricate EL devices. The Y2SiO5:Pr3+ powder, film, and nano-powder formed the phosphor layers of EL devices by screen printing, spin coating, and electrophoretic deposition, respectively. In order to emit UVC light, patterned gold was used for transparent electrodes of the devices instead of conventional indium tin oxide (ITO), which absorbs the UV region. The EL devices were demonstrated in two types: powder EL and electrolyte EL. The fabricated EL devices showed a wide range of UVC emission from 260 nm to 330 nm. Finally, luminescent and electrical analysis of each device was performed to analyze the characteristics.
Near-Infrared Emission of Ag+ Doped CuInSe2 Quantum Dots
Authors: Lin Chia-Ju , Chen Yuan , Chen Hsueh-Shih
Published: February 2024

Copper-indium-selenide (CISe) quantum dots (QDs) are a class of appealing materials due to their near-infrared (NIR) photoluminescence (PL) and as a non-toxic alternative to lead and cadmium-based QDs. To improve the low photoluminescence quantum yield (PLQY) of CISe core QDs, the zinc sulfide (ZnS) shell was grown to passivate surface defect states on the CISe core. CISe/ZnS core-shell QDs were synthesized with tetrahedral structure and chalcopyrite phase, resulting in an emission wavelength of 992 nm and a PLQY of 90%. Additionally, Ag2+ was doped into the CISe core to redshift the emission wavelength. The combination of electrons in the conduction band and holes in the trap state formed by Ag2+ led to light emission and a red-shifted emission wavelength. By tuning the stoichiometry and shelling time, Ag-doped CISe/ZnS core-shell QDs were successfully synthesized with a PLQY of 18% at an emission wavelength of 1200 nm. This wavelength falls in the NIR-II range, characterized by minimum absorption, biological autofluorescence, reduced scattering, and deep tissue penetration. The tunable emission and high luminescent CISe QDs have great potential in biological labeling, sensing and optoelectronics applications.

Figure 1
Towards High-Quality Broad-Range Luminescence Thermometry - the Case of Pr3+-Activated Garnets
Authors: Zych Eugeniusz , Kulesza Dagmara , Bolek Paulina , Jedoń Joanna , Trojan-Piegza Joanna , Zeler Justyna
Published: February 2024

Accurate and sensitive remote temperature measurement over a wide range of temperatures, presumably 1000 degrees, is required in many existing and emerging applications. Novel and emerging technologies pose new requirements on the quality of temperature measuring, the resistance to disturbance by external electric and/or magnetic fields, spatial resolution, and the operating range of thermometers. Luminescence thermometry has the potential to become the technology of choice when classic methods become non-practical and/or do not offer the expected quality.

Designing a luminescence thermometer capable of measuring temperature reliably over, for example, 1000 degrees range is challenging, as managing luminescence processes in such a range is extremely difficult. Yet, wide-range luminescence thermometers are of interest in such fields as aviation, space, nuclear plant, and others. Fast, accurate, and credible measurements of quickly changing temperatures are critical in these areas.

In this presentation, we shall report on the thermometric competencies of a series of garnet phosphors, typically activated with Pr3+. We shall focus on the possibility of managing the physics related to energy flow between the excited levels of Pr3+ and thermal quenching of its three emissions resulting from the 5d®4f, 3PJ®3HJ and 1D2®3HJ transitions. Not only shall we demonstrate that the sensitivity of such sensors may be deliberately tuned to reach its maximum at temperatures where it is most needed, but we will also show that garnets nowadays may offer temperature measuring over a range of 800 degrees at least.

This research was supported by the Polish National Science Center (NCN) under the grant #UMO2018/29/B/ST5/00420.

Figure 1
Optimization of First-Principles Calculation Conditions for Ce3+ in Perovskite-Type Oxides
Authors: Hashimoto Hinaka , Ogasawara Kazuyoshi
Published: February 2024

The 4f-5d transition of Ce3+ in crystals is used in a variety of optical materials, including scintillators and phosphors. It also has the advantages that the wavelength can be controlled by the coordination environment and that Ce3+ is relatively inexpensive among rare earth elements. For the theoretical design of novel Ce3+-doped phosphors, prediction of 4f-5d transition energy by first-principles molecular orbital calculations using model clusters is effective. In general, increase of the cluster size improves the accuracy of calculations and reduces the difference between the experimental and calculated values while very large clusters have the disadvantage of requiring a huge amount of calculation time. Hence, understanding the cluster size dependence is important to determine the efficient and effective cluster size for the first-principles calculations.

In this study we focused on Ce3+-doped in YAlO3, and performed first-principles calculations of the 4f-5d transition energies for model clusters with different sizes. At first, the local structures around the Y3+ site of YAlO3 were cut out from the crystal structure. Then the central Y3+ ions of these clusters were replaced by Ce3+ ions. Then the transition energy of Ce3+ in YAlO3 was calculated by the relativistic discrete-variational Xα (DV-Xα) molecular orbital calculations using the Slater's transition state method. The detailed comparison of the results showed that for clusters larger than a certain size, the error between the experimental and calculated values became negligibly small. For comparison, the lattice relaxation was also taken into account by modifying the model clusters using two different methods: the method based on the Shannon's crystal radii and the structural optimization using the CASTEP code, and the results were compared in detail.
Probing the Recombination Process at the Intermixed Interface of a Solution-Processed Organic Light Emitting Diode By Impedance Spectroscopy
Authors: Kim Ji Soo , Kim Youn Sang , Kwon Soon-Hyung
Published: February 2024

Solution-processed organic light emitting diode (s-OLED) has garnered considerable research interest due to its cost-effectiveness, improved energy efficiency, and material-saving advantages over conventional vacuum deposition methods in OLED production. Recent studies have shown that the thermal annealing process of multilayered s-OLEDs induces intermixing at the interfaces of the layers and enhances the device performance [1,2]. However, the physical origin of the enhanced s-OLED performance by intermixing at the interfaces is poorly understood. To address this issue, we utilized electrical impedance spectroscopy (IS) to investigate the thermal-induced modifications of charge carrier dynamics in a bilayer s-OLED comprising an electron transporting layer (ETL) and an emission layer (EML). We separately assessed the conductance of the ETL and the charge carrier accumulation at the EML/ETL interface by the characteristic relaxation frequency and the plateau at a low frequency regime (20~100 Hz) extracted from the frequency-dependent capacitance spectra, respectively. The IS analysis revealed that improved charge transport in the ETL by thermal annealing process was mainly responsible for the performance enhancement, rather than intermixing at the EML/ETL interface. Notably, we found that annealing the s-OLEDs above the glass transition temperature (Tg) of the ETL, at which significant intermixing occurs, increased the magnitude of negative capacitance, indicating the increased rate of nonradiative trap-assisted recombination [3]. Accordingly, our IS analysis clarified that extended intermixing at the EML/ETL interface is rather detrimental to the performance of s-OLEDs. This study demonstrates that IS can serve as a powerful tool for accurately analyzing charge carrier dynamics in s-OLEDs by simultaneously probing charge transport, interfacial charge accumulation, and recombination processes, thereby providing valuable insights for optimizing s-OLED performance.

[1] ACS Appl. Mater. Interfaces
2015, 7 (37), 20779–20785. https://doi.org/10.1021/acsami.5b05818.

[2] Advanced Materials Interfaces
2019, 6 (4), 1801627. https://doi.org/10.1002/admi.201801627.

[3] Phys. Rev. Lett.
2018, 120 (11), 116602. https://doi.org/10.1103/PhysRevLett.120.116602.

Figure caption. The capacitance at 20 Hz and current efficiency at 100 nit are plotted against the ratio of annealing temperature (T) to glass transition temperature (Tg) of ETL.

Figure 1
Spectro-Electrochemiluminescence Analysis of the Simultaneous Emission of Two Luminophores
Authors: Ibáñez David , González-García María Begoña , Hernández-Santos David , Fanjul Pablo
Published: February 2024

Electrochemiluminescence (ECL) is a powerful technique that combines the best features of electrochemistry and chemiluminescence in a single experiment. Its versatility, simplified optical set-up, low background signal and high sensitivity [1] allows the increase of new analytical applications. ECL signals are usually obtained from the excited states of a luminophore generated at the electrode surface during an electrochemical reaction due to the presence of a co-reactant. Particularly, resonance energy transfer (RET) mechanism is produced when at least two luminophores are present in solution, one luminophore acts as donor and the other one as acceptor [2]. In the absence of an external light source, donor luminophore emits light as consequence of its electrochemical excitation, part of this emission is absorbed by the acceptor to be excited and re-emits light.

Initially, ECL emission of two luminophores were separately analysed in this work: (1) luminol emission in presence of hydrogen peroxide as co-reactant shows one band from 350 to 600 nm (maximum at 420 nm) during its oxidation process at +0.20 V, while (2) ECL signal of Ru(bpy)3
2+ with tripropylamine as co-reactants displays one band at 620 nm at +0.95 V.

Furthermore, the simultaneous emission of luminol and Ru(bpy)3
2 (RET-ECL system) was analysed using a microspectrometer detector [3]. ECL spectra display three emission bands at 420, 510 and 620 nm. According to the previous experiments, bands at 420 and 510 nm should be associated with luminol due to its band emission is located from 350 to 600 nm, while band at 620 nm corresponds to Ru(bpy)3
2+. Nevertheless, Ru(bpy)3
2+ shows a characteristic absorption band at 450 nm, so minimum observed at this wavelength in the spectra is related to the Ru(bpy)3
2+ absorption. It demonstrates that bands at 420 and 510 nm are not really two bands, they form the characteristic band of luminol at 350-600 nm but is separated due to the characteristic absorption of Ru(bpy)3
2+ at 450 nm. Then, it is clear than Ru(bpy)3
2+ absorbs part of ECL emission of luminol before producing their own emission at more positive potentials. Spectro-electrochemiluminescence results demonstrates that the interaction between luminol and Ru(bpy)3
2+ is an important effect to be considered when ECL system is formed by these two luminophores.

References

[1] M.M. Richter, Chem. Rev. 104 (2004) 3003–3036.

[2] M.M.P.S. Neves, P. Bobes-Limenes, A. Pérez-Junquera, M.B. González-García, D. Hernández-Santos, P. Fanjul-Bolado, Anal. Bioanal. Chem. 408 (2016) 7121–7127.

[3] D. Ibáñez, M.B. González-García, D. Hernández-Santos, P. Fanjul-Bolado, Phys. Chem. Chem. Phys., 22 (2020) 18261-18264.
(Invited) Electroreductive C-S and C-O Bond Cleavage in Thioethers and Alcohols
Authors: Lundberg Helena
Published: February 2024

Alcohols and thioethers are highly prevalent in both natural and synthetic organic compounds but remain underexplored as starting materials in radical transformations. For this reason, new synthetic methods are highly desirable to unlock the potential of the compound classes. Here, electroreductive cleavage of C-S and C-O bonds in aryl alkyl thioethers and benzylic alcohols is described, along with mechanistic details. The reactions proceed via radical intermediates that, depending on the potential at which they form, may be trapped with electron deficient alkenes in Giese reactions. Alternatively, the open shell intermediates can undergo a radical-polar crossover to the corresponding anions with subsequent protonation or carboxylation to furnish alkanes or arylacetic acid products.

Figure 1
(Invited) Electrocatalytic Radical-Polar Crossover Hydrofunctionalization of Alkenes
Authors: Kim Hyunwoo
Published: February 2024

Due to the unique reactivity of open-shell intermediates, the development of catalytic transformations driven by single-electron transfer (SET) has been an area of intense research in organic chemistry. In particular, the employment of unconventional means of activation, including photoredox catalysis and electrocatalysis, has provided unique entry to single-electron reactivities and led to new solutions to challenging synthetic problems that are not readily addressed using existing tools.

We disclose a general electrocatalytic hydrofunctionalization by utilizing a wide range of alkenes. The integration of the two involves an electrochemically instigated cobalt-hydride-catalyzed radical-polar crossover of alkenes that enable the generation of key cationic intermediates, which could readily be entrapped by challenging nucleophiles. We highlight the importance of precise control of the reaction potential by electrochemistry in conjunction with the decisive role of 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) as the co-solvent to obtain optimal and exclusive chemoselectivity.

In addition, we develope an electrocatalytic method for intramolecular hydroamination of allylic sulfonamides to access azetidines. The merger of cobalt catalysis and electricity enables regioselective generation of key carbocationic intermediates, which could directly undergo intramolecular C-N bond formation. The mechanistic investigations including electrochemical kinetic analysis suggest that the catalyst regeneration by nucleophilic cyclization is involved in the rate-determining step (RDS) of our electrochemical protocol and highlight the ability of electrochemistry in providing ideal means to mediate catalyst oxidation.
Enzymatic Bioelectrocatalysis for Organic Electrosynthesis
Authors: Minteer Shelley D.
Published: February 2024

Organic electrosynthesis has become a popular research area in the last decade due to a desire for more sustainable and greener organic synthesis methods. However, electrosynthesis frequently has challenges with selectivity. This talk will detail the design of bioelectrocatalytic systems for organic electrosynthesis with a focus on improving the selectivity and efficiency of electrosynthesis systems. Specifically, the talk will describe bioelectrocatalytic systems for C-H activation and chiral synthesis. It will discuss both materials design of electrodes and enzyme design for electrochemistry, but also discuss strategies for improving performance of bioelectroatalytic systems using bi-phasic electrochemical systems.
(Invited) Delivering Electrons and Protons to the Substrate in Molecularly-Based Reductive Electrocatalysis
Authors: Durin Gabriel , Lee Mi-Young , Kahl Christian , Weyhermüller Thomas , Han Chenhui , Zenner Johannes , Johny Jacob , Bordet Alexis , Kaeffer Nicolas , Leitner Walter
Published: February 2024

To steer away from fossil fuels the primary sourcing for goods and chemicals, combining renewable electricity with sustainable feedstocks in an electrochemical strategy is a formidable synthetic opportunity. In that frame, we investigate how molecular electrocatalysis can foster electrosynthetic conversions, in particular for organics reductions.[1]

Here, we will disclose that alkyne semihydrogenation, an important synthetic manifold, can be selectively electrocatalyzed by a simple molecular catalyst [Ni(bpy)3]2+, based on the earth-abundant metal nickel.[
2
] Our combined electrochemical, synthetic and computational investigations support that the catalytic cycle proceeds via the protonation of a nickelacyclopropene species and bypasses the need to generate a competent hydride.[3] As a proof-of-concept for molecular electrocatalytic alkyne semihydrogenation, this work opens a platform to develop original electrochemical routes for the hydrogenation/-functionalization of organics and small molecules.

We will also discuss the use of Pickering emulsion that separates organic substrates and aqueous electrolytes in different phases for electrocatalytic hydrogenation at the interface. We developed a hybrid design based on carbon nanotube-supported Pd nanoparticles that places at the interface and acts both as emulsion stabilizer and electrocatalyst. The system electrohydrogenates styrene into ethylbenzene with high faradaic efficiency (95.0%) and Pd specific current density (–148.1 mA·cm–2). Our system combines good solubility of the substrates, high conductivity, facile product isolation and applies to the transformation of various alkenes. This strategy may thus provide original solutions to the ECH of substrates having low water-solubility.[4]

References

[1] N. Kaeffer, W. Leitner, JACS Au,
2022, 2, 1266.

[2] M.-Y. Lee, C. Kahl, N. Kaeffer, W. Leitner, JACS Au,
2022, 2, 573.

[3] G. Durin, M.-Y. Lee, T. Weyhermüller, N. Kaeffer, W. Leitner, ChemRxiv, 10.26434/chemrxiv-2023-whtfd.

[4] C. Han, J. Zenner, J. Johny, N. Kaeffer, A. Bordet, W. Leitner, Nat. Catal., 2022
, 5, 1110.
(Keynote) Electrochemical and Mass Spectrometry Measurements of Nanometer Vesicles
Authors: Ewing Andrew G
Published: February 2024

We originally developed a tool to measure the chemical messenger contents of single nanometer vesicles starting with capillary electrophoretic separation, lysing and electrochemical detection. We called this flow vesicle impact cytometry (FVIEC). The method used a microfluidic device with sheath flow and electrode for detection. The next generation approaches led to static electrochemical measurements and mass spectrometry imaging of vesicular content. First, micro-/nano-electrochemical approaches have been developed to carry out quantitative measurements of intravesicular content and real-time monitoring of vesicle release dynamics. We have used stochastic vesicle impact electrochemical cytometry (VIEC) and intracellular VIEC (IVIEC) to provide a highly effective way to quantify the electroactive contents inside vesicles. This has allowed direct comparison of the quantity of molecules released by exocytosis to those in the vesicles. Partial release is observed across all cell types examined to date by the electrochemical methods and appears to be regulated.

More recently, we have used mass spectrometry imaging with NanoSIMS as a complimentary approach to image the neurotransmitter dopamine across the internal volume of these incredibly small vesicular structures. We have developed standards to carry out quantitative NanoSIMS and subsequently used it to quantify the chemical contents across the nanometer structure of vesicles. We then used NanoSIMS imaging of dopamine inside and drug into vesicles to quantify the fraction of messenger and demonstrate drug entry during exocytosis providing definitive evidence of partial release and a means to introduce drug into cells.
Investigating Enzyme-Based Electrode Processes Using Electrochemical Impedance Spectroscopy and Distribution of Relaxation Time Analysis
Authors: Torrigino Federica , Herkendell Katharina
Published: February 2024

Enzymatic fuel cells (EFCs) are an emerging class of electrochemical devices that have the potential to harness renewable energy sources by converting the chemical energy of an organic substrate into electrical energy. Enzymes are responsible in an EFC for highly selective and efficient electrode processes under typically mild ambient conditions, such as the oxidation reaction at the anode and the reduction reaction at the cathode 1. In addition to more conventional techniques, electrochemical impedance spectroscopy (EIS) can be employed to characterize such systems. Electrochemical behavior of enzymatic electrodes, such as enzyme reaction kinetics, substrate mass transport, and electrode stability, can be studied by measuring the system's impedance over a wide frequency range and then performing a precise post-process analysis based on the distribution of relaxation time (DRT). DRT analysis is rarely used to interpret EIS spectra within the EFCs research field, despite the fact that it is widely acknowledged as relevant for properly understanding the EIS potential to improve power density in fuel cells 2,3. Glucose oxidase (GOx) and bilirubin oxidase (BOD) were immobilized on multi-walled carbon nanotubes (MWCNTs) to catalyze the bioelectrocatalytic oxidation of glucose at the anode and the bioelectrocatalytic reduction of oxygen at the cathode, respectively. This study presents a promising approach for the investigation of enzyme-based anodic and cathodic processes by measuring them with EIS and then interpreting the results with DRT analysis, as depicted in Figure 1. By varying different operating parameters, such as the enzymatic loading on the electrode surface or electrolyte conditions, this method can be used to identify three primary relaxation processes occurring at both electrodes. At the interface between the electrolyte and the electrode, it is possible to conclude that high-frequency processes are accountable for ionic conduction, intermediate-frequency processes are accountable for charge transfer, and low-frequency processes are accountable for oxygen surface exchange and diffusion.This method provides access to preliminary fundamental information about enzymatic bioelectrode processes, which can be used to optimize biofuel cell construction and compositions and increase their power output.

Figure 1. Schematic representation of the characterization method used to characterize a GOx-CNT-modified anode consisting of EIS measurements and subsequent DRT analysis. Concentration of glucose 175 mM in 0.1 M HEPES Buffer, pH 7; EIS parameters: 20 mV sinusoidal excitation, 0.1 Hz-100 kHz.

References

K. Herkendell, A. Stemmer and R. Tel-Vered, Nano Res.,
12(4), 767–775 (2019).

H. Wang, X. Long, Y. Sun, D. Wang, Z. Wang, H. Meng, C. Jiang, W. Dong and N. Lu, Frontiers in microbiology,
13, 973501 (2022).

F. Ciucci, Current Opinion in Electrochemistry,
13, 132–139 (2019).

Figure 1
Low-Cost Platforms for Point-of-Use Sensors
Authors: Furst Ariel L
Published: February 2024

Electrochemical biosensors are promising for sensing in low-resource settings because they are easy use and low-cost. Disposable screen-printed electrodes are popular for biosensing applications, but the dopants in the ink used for gold electrode production can interfere with electrode modification and sensing. We have developed an alternative disposable electrode made from high-quality gold leaf. We compared the topology and performance of three different disposable gold electrodes: our gold leaf electrodes and two commercial screen-printed versions. Our electrodes consistently outperformed commercial electrodes for biosensing, and we have further expanded these electrodes for the detection of infectious disease. In contrast, carbon screen-printed electrodes tend to be lower cost and higher quality than their gold counterparts. However, chemistry to modify them with biomolecules remains more challenging than self-assembly on gold. We have therefore developed new chemistries to enable the facile modification of these electrodes with biomolecules and have successfully applied these modified electrodes for environmental sensing. Together, these works demonstrate the importance of fundamental advances in platform design to enable improved technologies.
Electron Uptake from Solid Electrodes Regulates the More Efficient Conversion of CO2 to Polyhydroxybutyrate with Rhodobacter Spaeroides
Authors: Li Shuwei , Kim Minsoo , Kong Da Seul , Kim Eunseo , Park Eun Joo , Park Won Gyeong , Kim Jung Rae
Published: February 2024

The recent climate crisis has accelerated studies on mitigating the atmospheric CO2 level. Microbial electrosynthesis (MES) is highlighted as a promising strategy for CO2 conversion to useful chemicals. This study examined electrode-driven polyhydroxybutyrate (PHB) production from CO2 in Rhodobacter sphaeroides. The electron uptake and regulation of metabolic pathways differed in electrode-associated and suspended R. sphaeroides cells. The electrode-associated cells produced PHB at concentrations reaching 23.50 ± 2.8% of the dry cell weight (DCW). These results reveal a means for CO2 upcycling to polymeric substances and provide novel insights into the genetic regulation of electrode-associated cells in MES.
Real-Time Mass Spectrometry for Simultaneous Monitoring of Electrode Dissolution and Reaction Product Distribution during Organic Electrosynthesis
Authors: Nikolaienko Pavlo , Ranninger Johanna , Berkes Balázs B. , Mayrhofer Karl J. J.
Published: February 2024

An organic electrosynthesis is an emerging tool for modern chemical manufacturing fitting the environmental and sustainability agenda. It utilizes polarized electrode surfaces as “traceless” oxidants or reductants, whereas its heterogeneous nature and exceptional tunability enable easy access to radical intermediates and novel mechanistic pathways. In the line of further energy input improvement, there is a growing demand for appropriate catalytic materials devoted to organic molecule transformations, for which the activity and selectivity have so far been most studied. Although the investigation of electrodes’ and electrocatalysts’ stability in the field of electrochemical energy conversion is well-established, there is still a lack of attention to the symmetrical studies for organic electrosynthesis. Nevertheless, electrode material losses shorten the reactor’s lifetime and can cause metal cathodic re-depositions, severely altering reaction product selectivity and final product contaminations. Although some reports on the ex-cell metal dissolution analysis are available, no information about its mechanism can be gained in such a way. To highlight the issue numerically, an analytical method to characterize rates and mechanisms of catalyst dissolution within a real-time response-enabled potential-, temperature-, or time-resolved parametrization of the electrocatalyst is highly demanded.

Herein we present a system to study organic electrosynthetic protocols under dynamic operations to quantitatively monitor the electrode dissolution aligned with reaction products during organic molecules transformations. The instrument comprises an electrochemical flow cell (EFC) with exchangeable working electrodes, the outlet of which is interfaced with an online quadrupole mass spectrometer (OQMS) for the analysis of extracted by solid membrane gaseous products and an inductively coupled plasma mass spectrometer (ICP-MS) for the detection of dissolved metals. The system is exemplified by a benchmark Kolbe electrolysis over platinum Pt anode, commonly considered a stable and inert electrode material. Based on the literature, methanol has been used as a solvent of choice, while partially neutralized acetic acids with different bases were studied as objects. The methodology shed some light on understanding the role of platinum oxide formation on the electrode surface and can be used to study time- and potential-resolved catalyst stability and the possibility for dissolved transition metal-catalyzed electroorganic transformations.
(Invited) Electrochemical Synthesis of Chelation-Stabilized Organo-Λ
3-Bromanes
Authors: Sokolovs Igors , Suna Edgars , Francke Robert
Published: February 2024

The chemistry of hypervalent halogen species has made enormous progress over the last few decades, and hypervalent iodine(III) compounds have become common reagents in nowadays organic synthesis. The related isoelectronic hypervalent bromine(III) species feature superior reactivity to the I(III) counterparts due to the higher oxidizing ability, stronger electrophilicity and better leaving group ability (nucleofugality) of the bromanyl moiety. However, the hypervalent bromine chemistry appears to be significantly less developed than that of the iodine(III) compounds. This notable imbalance appears to be due to the relatively low stability and high oxidizing power of bromine(III) reagents, resulting in reactivity that is difficult to control. Furthermore, there is a clear shortage of simple method for the synthesis of bromine (III) species, but known methods often require handling of the highly toxic and corrosive BrF3 precursor. In this context, we have proposed the electrochemical generation of chelation-stabilized hypervalent bromine(III) compounds as a possible solution to the above problems. This presentation will give an overview of our current progress in this field.
Peroxodicarbonate as Versatile Green Oxidizer
Authors: Waldvogel Siegfried R
Published: February 2024

The electrochemical conversion of aqueous carbonate solutions at boron-doped diamond anodes provides access to an unique oxidizer. The key aspects for a highly efficient electrosynthesis requires a splendid heat dissipation and high concentration of the alkali carbonates. With reaching almost molar concentrations of peroxodicarbonates a novel reactivity is achieved.[1]

This green reagent allows direct epoxidation, S- and N-oxidations, oxidative deborolations and many more useful transformations including the selective Kraft lignin oxidation.[2-4]

References:

[1] A.-K. Seitz, P. J. Kohlpaintner, T. van Lingen, M. Dyga, F. Sprang, M. Zirbes, S. R. Waldvogel, L. J. Gooßen, Angew. Chem. Int. Ed.
2022, 61, e202117563.

[2] A.-K. Seitz, T. van Lingen, M. Dyga, P. J. Kohlpaintner, S. R. Waldvogel, L. Gooßen, Synlett
2022, 33, 1527–1531.

[3] M. Zirbes, T. Graßl, R. Neuber, S. R. Waldvogel, Angew.
Chem. Int. Ed.
2023, 62, e202219217.

[4] P. J. Kohlpaintner, L. Marquart, L. J. Gooßen, S. R. Waldvogel, Eur. J. Org. Chem.
2023, e202300220.
Catalytic Electricity Promoted Electrochemical Synthesis
Authors: Sato Eisuke , Fujii Mayu , Yoshida Haruka , Suga Seiji
Published: February 2024

Direct electron transfer from organic compounds has been used as a powerful catalyst to promote various chemical transformations. In particular, electrochemical organic synthesis enables both hole-catalyzed (anodic oxidation) and electron-catalyzed (cathodic reduction) transformations. We will present the catalytic cathodic reduction-promoted reactions and the application of an electrochemical flow reactor, which allows efficient transformations. Trimethylsilylcyanide (TMSCN), for example, could be reduced on a cathode, and the corresponding radical anion reacted with carbonyl compounds or imines. The addition reaction only required a small amount of electricity, and the catalytic transformation was achieved.

In addition, the machine learning-assisted conditions optimization of the electrochemical flow synthesis has also been demonstrated. Gaussian process regression (GPR) could illustrate the relationships between the conditions and the reactivities on counter maps. The counter maps suggest that achieve a good yield or time-scale yield of the desired compounds.
Facile Synthesis of Nitrogen Cation-Doped Polycyclic Aromatic Hydrocarbons by Anodic Intramolecular Pyridination
Authors: Inagi Shinsuke , Ohno Yushi , Ando Shogo , Furusho Daisuke , Tomita Ikuyoshi
Published: February 2024

The bottom-up synthesis of heteroatom-doped polycyclic aromatic hydrocarbons (PAHs) has attracted attention in the development of models of doped graphene. Among PAHs, nitrogen-cation (N
+)-doped PAHs are known to exhibit superior optoelectronic functionalities; however, practical methods for synthesizing N
+-doped PAHs are limited and challenging [1]. In our previous study, the SNAr reaction was used for the intramolecular cyclization of phenylpyridine derivatives possessing an electron-deficient perfluoroaryl moiety to give the corresponding N
+-doped triphenylene in high yields under moderate conditions without the use of a transition-metal catalyst [2,3]. However, one of the challenges in the synthesis of N
+-doped PAHs via the SNAr reaction is poor functional-group tolerance.

Here, a facile and selective synthesis method for N
+-doped PAHs has been established via anodic intramolecular cyclization, inspired by the Yoshida’s protocol for C–H amination without a transition-metal catalyst or an oxidant [4]. The reaction mechanism, in particular the reaction selectivity, was elucidated using density functional theory (DFT) calculations. The N
+-doped PAH products were found to have a donor–acceptor structure composed of an arene moiety and a pyridinium moiety, as evidenced by DFT calculations, UV–vis analysis, and electrochemical measurements. The proposed intramolecular anodic pyridination is a practical strategy for the late-stage introduction of N+ into π-electron systems and broadens the scope of molecular design of N
+-doped PAHs.

References:

J. Liu, X. Feng, Synlett
2020, 31, 211–222

Y. Asanuma, H. Eguchi, H. Nishiyama, I. Tomita, S. Inagi, Org. Lett.
2017, 19, 1824–1827

N. Shida, H. Nishimi, Y. Asanuma, I. Tomita, S. Inagi, Polym.
J.
2020, 52, 1401–1406.

T. Morofuji, A. Shimizu, J. Yoshida, J. Am. Chem. Soc., 2013, 135, 5000–5003.

Figure 1
Fast Fourier-Transform Impedance Spectroscopy Applied to Electrochemical Sensors
Authors: Sepunaru Lior , Roehrich Brian , Leung Kaylyn , Gerson Julian , Kippin Tod , Plaxco Kevin
Published: February 2024

We show that using fast Fourier transform electrochemical impedance spectroscopy (FFT-EIS) to interrogate electrochemical aptamer-based biosensors leads to improved (here better than 2 s) time resolution and calibration-free operation, even when such sensors are deployed in vivo. Because this approach uses the heterogeneous electron transfer rate constant as a means of monitoring target concentration, rather than absolute current, it is independent of both sensor-to-sensor fabrication variation and the drift arising due to fouling in biological fluids, rendering the technique suitable for performing calibration-free in vivo measurements. To showcase these benefits, we demonstrate the approach’s ability to perform real-time molecular measurements in the veins of living rats.
Electrochemical Reduction of C-O Bonds
Authors: Villo Piret , Lill Malin , Alsaman Zainab , Soto Kronberg Adrian , Chu Victoria , Ahumada Guillermo , Agarwala Hemlata , Ahlquist Mårten , Lundberg Helena
Published: February 2024

Reductive activation and transformation of C-O bonds in alcohols have been a challenge for many decades, yet is still considered an important step in the process of converting biomass into biofuel and chemicals. The challenge arises from the cleavage of the carbon-oxygen bond which generally requires forcing conditions and is reflected in the high bond dissociation energy compared to other polarised sigma bonds.[1] Our project focuses on electroreductive cleavage of alcohols in the presence of a hydrogen donor in an undivided cell with up to 95% of the corresponding alkane. C-O transformation is also accomplished through carboxylation with carbon dioxide, resulting in yield up to 43%.[2]

[1] Villo, P.; Shatskiy, A.; Kärkäs, M. D.; Lundberg, H. Electrosynthetic C−O Bond Activation in Alcohols and Alcohol Derivatives. Angewandte Chemie International Edition
2023, 62 (4), e202211952. https://doi.org/10.1002/anie.202211952.

[2] Villo, P.; Lill, M.; Alsaman, Z.; Kronberg, A. S.; Chu, V.; Ahumada, G.; Agarwala, H.; Ahlquist, M.; Lundberg, H. Electroreductive Deoxygenative C–H and C–C Bond Formation from Non-Derivatized Alcohols Fueled by Borohydride Oxidation. ChemRxiv August 2, 2023. https://doi.org/10.26434/chemrxiv-2023-tw9l1-v2.

Figure 1
Tetrabutylammonium Borohydride: A Sacrificial Reductant in Organic Electrosynthesis
Authors: Ahumada Guillermo , Lill Malin , Kuzmin Julius , Goossens Ellymay , Steffensen Astrid , Lundberg Helena
Published: February 2024

In this work, tetrabutylammonium borohydride (TBAB) is investigated as a terminal reductant in reductive organic electrosynthesis as replacement for sacrificial anodes. Sacrificial anodes are typically based on easily oxidized metals, such as Mg, Zn, or Al, and are consumed during the reaction, resulting in stoichiometric metal waste. In contrast, oxidation of TBAB enables the use of inert anodes and results in anodic H2 formation, effectively serving as the inverse of cathodic proton reduction. Our results indicate that TBAB oxidation at carbon-based electrodes can replace the use of sacrificial anodes in several organic electrosynthetic reactions, including Birch reduction, hydrodesulfurization of thioethers, hydrodeoxygenation of alcohols1, and cross-electrophile couplings.

References

Villo, P.; Lill, M.; Alsaman, Z.; Soto Kronberg, A.; Chu, V.; Ahumada, G.; Agarwala, H.; Ahlquist, M.; Lundberg, H. Electroreductive Deoxygenative C–H and C–C Bond Formation from Non-Derivatized Alcohols Fueled by Borohydride Oxidation. ChemElectroChem. 2023, accepted for publication (a previous version can be found in ChemRxiv, DOI: 10.26434/chemrxiv-2023-tw9l1-v2.)

Figure 1