Pseudocapacitive Properties of Isostructural Oxides Sr2LaBMnO7 (B=Co, Fe)

Posted on 9 October 2023 by

Pseudocapacitive charge storage properties are demonstrated for two isostructural oxides, Sr₂LaFeMnO₇ and Sr₂LaCoMnO₇, showing promising energy density, power density and stability over repeated charge-discharge cycles.

Abstract

Pseudocapacitors promise to fill the gap between traditional capacitors and batteries by delivering reasonable energy densities and power densities. In this work, pseudocapacitive charge storage properties are demonstrated for two isostructural oxides, Sr₂LaFeMnO₇ and Sr₂LaCoMnO₇. These materials comprise spatially separated bilayer stacks of corner sharing BO₆ units (B=Fe, Co or Mn). The spaces between stacks accommodate the lanthanum and strontium ions, and the remaining empty spaces are available for oxide ion intercalation, leading to pseudocapacitive charge storage. Iodometric titrations indicate that these materials do not have oxygen-vacancies. Therefore, the oxide ion intercalation becomes possible due to their structural features and the availability of interstitial sites between the octahedral stacks. Electrochemical studies reveal that both materials show promising energy density and power density values. Further experiments through fabrication of a symmetric two-electrode cell indicate that these materials retain their pseudocapacitive performance over hundreds of galvanostatic charge-discharge cycles, with little degradation even after 1000 cycles.

Blatter Diradicals with a Spin Coupler at the N(1) Position

Posted on 9 October 2023 by nDominika Pomikło, nPiotr Kaszyńskin

Diradicals: Simple, modular and convergent access to diradicals with controllable S−T gap demonstrated with two examples.

Abstract

Reactions of a benzo[e][1,2,4]triazine with dilithiobenzenes lead to di-Blatter diradicals connected at the N(1) positions via a spin coupling unit, 1,4-phenylene or 1,3-phenylene. Electrochemical analysis in MeCN revealed four one-electron redox processes separated by 0.1–0.3 V in both diradicals. Variable temperature EPR measurements in polystyrene (PS) solid solutions gave the singlet-triplet energy gaps ΔE _S-T=2 J of −3.02(11) and −0.16(1) kcal mol⁻¹ for 1,4-phenylene and 1,3-phenylene derivatives, respectively. The latter negative value was attributed to conformational properties of the diradical in the PS solid solution. Results suggest a simple and efficient access to a family of stable Blatter diradicals with a controllable S−T gap through a judicious choice of the arylene coupling unit. DFT calculations indicate that the triplet state is stabilized by (het)arylenes with low LUMO.

Regulating the Innocuity of Urea Electro‐Oxidation via Cation‐mediated Adsorption

Posted on 9 October 2023 by

In the course of the UOR process, the presence of Li⁺ led to an increase in the Faradaic efficiency (FE) of the innocuous N₂ product from the standard value of ~15 % to 45 % compared with K⁺, while a decrease of the FEs of the over-oxidized NO_x ⁻ product from ~80 % to 46 %, indicating a more eco-friendly and sustainable process under the cation effect.

Abstract

Urea electrolysis is an emerging technology that bridges efficient wastewater treatment and hydrogen production with lower electricity costs. However, conventional Ni-based catalysts could easily overoxidize urea into the secondary contaminant NO_x ⁻, and enhancing the innocuity of urea electrolysis remains a grand challenge to be achieved. Herein, we tailored the electrode-electrolyte interface of an unconventional cation effect on the anodic oxidation of urea to regulate its activity and selectivity. Smaller cations of Li⁺ were discovered to increase the Faradaic efficiency (FE) of the innocuous N₂ product from the standard value of ~15 % to 45 %, while decreasing the FEs of the over-oxidized NO_x ⁻ product from ~80 % to 46 %, pointing to a more sustainable process. The kinetic and computational analysis revealed the dominant residence of cations on the outer Helmholtz layer, which forms the interactions with the surface adsorbates. The Li⁺ hydration shells and rigid hydrogen bonding network interact strongly with the adsorbed urea to decrease its adsorption energy and subjection to C−N cleavage, thereby directing it toward the N₂ pathway. This work emphasizes the tuning of the interactions within the electrode-electrolyte interface for enhancing the efficiency and sustainability of electrocatalytic processes.

High Formate Selectivity and Deactivation Mechanism of CuS Nanoparticles in CO2 Electrocatalytic Reduction Reaction

Posted on 9 October 2023 by

The obtained CuS nanoparticles is a good candidate for CO₂ electroreduction to formate with high FE (~98 %). The reconstruction of CuS with S loss in the form of H₂S, SO₂, and SO₄ ²⁻ during the reaction induces the degradation of the catalytic performance on CO₂ electroreduction to formate.

Abstract

CO₂ electroreduction into liquid fuels is of broad interest and benefits reducing the energy crisis and environment burdens. CuS has been reported to be a desirable candidate for CO₂ electroreduction into formate; however, its formate selectivity and stability are still far from the demands of practical application. Herein, we report CuS nanoparticles exhibiting good Faradaic efficiency of formate (about 98 %) in CO₂ electroreduction and its deactivation mechanism during the reaction. The deactivation of CuS was found to be associated with the reconstruction and S loss of CuS, which deteriorates the Faradaic efficiency of formate. Combined with ionic and gas analyses, the S atom in CuS was lost in the form of H₂S, SO₂, and SO₄ ²⁻, followed by the reconstruction of CuS into copper oxides. Such a catalyst reconstruction facilitates electroreductions of CO₂ and H₂O, respectively, into CO and H₂, etc., resulting in the degradation of catalytical performance of CO₂ electroreduction into formate. This work reveals the important role of S loss and reconstruction of metal sulfide catalysts during the electroreduction reaction, which may benefit the further development of CuS-based electro-catalyst for CO₂ electroreduction.

Increasing Complexity in Adamantyl Thioethers Characterized by Rotational Spectroscopy

Posted on 9 October 2023 by

Oxygen or Sulfur: Three adamantyl thioethers are synthesized. Their structures and monohydrated complexes are characterized by rotational spectroscopy. Exchanging the oxygen atom by sulfur slightly distorts the molecular structure. Adducts with water are formed in a similar way with either the oxygen or the sulfur derivatives, highlighting the capability of sulfur to act as a good hydrogen bond acceptor in bulky structures of this type.

Abstract

We report on the synthesis and characterization using high-resolution rotational spectroscopy of three bulky thioethers that feature an adamantyl group connected to a sulfur atom. Detailed experimental and theoretical structures are provided and compared with the 1,1′-diadamantyl ether. In addition, we expand on previous findings concerning microsolvation of adamantyl derivatives by investigating the cluster formation between these thioethers and a water molecule. The investigation of such clusters provides valuable insights into the sulfur-centered hydrogen bonding in thioethers with increasing size and steric repulsion.

Amorphous TiO2 shells: an Essential Elastic Buffer Layer for High‐Performance Self‐Healing Eutectic GaSn Nano‐Droplet Room‐Temperature Liquid Metal Battery

Posted on 9 October 2023 by

The amorphous titanium dioxide is used to coat eGaSn nanodroplets (eGaSn NDs) to construct the core-shell structure of eGaSn@TiO₂ nanodroplets (eGaSn@TiO₂ NDs). The amorphous TiO₂ shell forms a stable SEI film, alleviates volume expansion, and provides electron/ion transport channels. The resulting eGaSn@TiO₂ NDs exhibit high capacities of 580, 540, 515, 485, 456 and 426 mAh g⁻¹ at 0.1, 0.2, 0.5, 1, 2 and 5 C, respectively. No obvious decay is observed in more than 500 cycles with a capacity of 455 mAh g⁻¹ at 1 C.

Abstract

Gallium-based alloy liquid metal batteries currently face limitations such as volume expansion, unstable solid electrolyte interface (SEI) film and substantial capacity decay. In this study, amorphous titanium dioxide is used to coat eutectic GaSn nanodroplets (eGaSn NDs) to construct the core-shell structure of eGaSn@TiO₂ nanodroplets (eGaSn@TiO₂ NDs). The amorphous TiO₂ shell (~6.5 nm) formed a stable SEI film, alleviated the volume expansion, and provided electron/ion transport channels to achieve excellent cycling performance and high specific capacity. The resulting eGaSn@TiO₂ NDs exhibited high capacities of 580, 540, 515, 485, 456 and 426 mAh g⁻¹ at 0.1, 0.2, 0.5, 1, 2 and 5 C, respectively. No significant decay was observed after more than 500 cycles with a capacity of 455 mAh g⁻¹ at 1 C. In situ X-ray diffraction (in situ XRD) was used to explore the lithiation mechanism of the eGaSn negative electrode during discharge. This study elucidates the design of advanced liquid alloy-based negative electrode materials for high-performance liquid metal batteries (LMBs).

Lead Adsorption by Fly Ash Geopolymer: Isotherm, Kinetic, and Thermodynamic Studies

Posted on 9 October 2023 by nMurali Pujari, nRohinikumar P, nSudharshan Reddy Manyam, nAdarsh Kumar Aryan

Adsorption is an effective method for removing heavy metals from water. Herein, a geopolymer synthesized from biomass fly ash was tested as an adsorbent for removing Pb from solution. The effects of contact time, pH, adsorbent dosage, and initial Pb concentration were tested. The results showed that this is a viable option for removing Pb from solution and reducing the accumulation of biomass fly ash.

Abstract

The effectiveness of low-cost fly ash geopolymer (FAGP) adsorbents synthesized from biomass fly ash in lead removal from aqueous solution was studied. The synthesized FAGP was characterized by the Brunauer-Emmett-Teller method and energy dispersive spectroscopy. The adsorption experiments were performed in batch mode under various conditions, and the maximum removal efficiency and uptake were found at an optimum time of 120 min and pH 5. Adsorption isotherm studies confirmed that lead removal is best fitted by both Langmuir and Freundlich isotherms. A kinetic analysis showed that pseudo-second-order kinetics governs lead adsorption. Lead adsorption was determined to be an endothermic, spontaneous process through thermodynamic analysis.

Fluorescence and Phosphorescence Energy Transfer in Cucurbituril‐Based Supramolecular Systems

Posted on 9 October 2023 by nDaria V. Berdnikova, nEkaterina Y. Chernikovan

In this Review, we highlight cucurbituril-based host–guest assemblies demonstrating fluorescence (singlet–singlet, FRET) and phosphorescence (triplet–singlet, TS-FRET) resonance energy transfer. We overview the achievements and challenges as well as discuss current and future applications of the cucurbituril-based energy transfer systems.

Abstract

Supramolecular systems demonstrating resonance energy transfer have recently became a topical area on the borderline of supramolecular chemistry, photochemistry, photophysics and biology. The modularity of supramolecular interactions is a prerequisite for fine tuning of optical properties, which is difficult to achieve by other means. As a component of such systems, cucurbit[n]uril (CB[n]) macrocycles can play a wide spectrum of roles from anchoring of FRET pairs and modulation of the optical output to providing biocompatibility of FRET stains for cell imaging. The aim of this Review is to outline the development of the CB[n]-based systems with fluorescence (FRET) and phosphorescence (TS-FRET) energy transfer and to highlight achievements, challenges and perspectives of this fascinating combination of a classical photophysical process and a classical supramolecular host. Particular attention in this Review is given to the current and potential applications of the reviewed systems.

The Cellular Environment Guides Self‐Assembly and Structural Conformations of Microtubule‐Associated Protein Tau (MAPT)

Posted on 9 October 2023 by nKelly M. Montgomery, nAvi J. Samelson, nJason E. Gestwickin

Abstract

In neurodegenerative tauopathies, such as Alzheimer's disease (AD), microtubule-associated protein tau (MAPT/tau) transitions from a soluble form to insoluble, filamentous lesions inside affected neurons. During this process, tau adopts a range of physical configurations: from misfolded monomers to higher-order oligomers and fibrils. Tau aggregation is also associated with changes in post-translational modifications (PTMs), such as ubiquitination, oxidation, glycation, hyper-phosphorylation and acetylation, which collectively produce an impressive range of possible tau proteoforms. Many of these tau proteoforms are highly cationic and unlikely to self-assemble without neutralization of their charges. Indeed, tau fibrils from patients contain anionic biomacromolecules and bound proteins, suggesting that cytosolic components contribute to fibrilligenesis. Here, we review what is known about how the cytosol impacts tau's aggregation pathways. We also speculate that the composition of each brain region (e. g., redox state, tau proteoforms, levels of permissive polyanions, etc.) might play an active role in shaping the structure of the resulting tau fibrils. Although much remains to be discovered, a greater understanding of the role of the cytosol on tau self-assembly might lead to identification of new therapeutic targets.

BiVO4 Heterojunctions as Efficient Photoanodes for Photoelectrochemical Water Oxidation

Posted on 9 October 2023 by nDongqing He, nQi Wang, nWeijun Zhang, nXiaodong Liu, nXianghong Cuin

This Review provides an overview on recent research on BiVO₄ heterojunction photoanodes for photoelectrochemical water oxidation reactions, including interface junction formation (Type I/Type II heterojunctions, p–n heterojunctions, Z-scheme and S-scheme heterojunctions) and surface functional junction formation (incorporating metal(oxy) hydroxides/metal oxides, functional interlayer structures, MOF/COF-based cocatalysts, molecular metal complexes, and protective layers).heterojunctioninterfacephotocatalysisphotoelectrodevanadateswater splitting

Abstract

Photoelectrochemical (PEC) water splitting has attracted strong interest as sustainable technology by converting solar energy into hydrogen. The semiconductor photoelectrodes play an important role to increase the solar-to-hydrogen conversion efficiency. Bismuth vanadate (BiVO₄) is an excellent candidate as a photoanode material for PEC water oxidation because of its visible light absorption, suitable band edge location, high stability and low cost. However, BiVO₄ alone may undergo short carrier diffusion length, rapid recombination of photo-induced charge carriers and photocorrosion. The heterojunction strategy established by combining two or more materials has provided an outstanding technique to address these issues. This Review focuses on recent important works with respect to BiVO₄ heterojunction photoanodes for PEC water oxidation reactions, including interface junction and surface functional junction formation. Additionally, challenges faced and prospects for future research on BiVO₄ heterojunction photoanodes in the field of solar-to-hydrogen conversion are proposed.