Transfer Redox Research Articles

Developing Terpyridine-Based Metal Complexes for Non-Aqueous Redox Flow Batteries

Redox flow batteries (RFBs) that utilize dissolved electroactive materials have shown great potential in storing intermittent solar and wind energy. The unique technological advantages of decoupled energy and power lead to high flexibility and scalability in RFB design, making it possible to satisfy a wide range of energy and power applications.[1,2] In traditional RFBs, inorganic transition-metal salts like all-vanadium, iron-chromium, and zinc-bromine RFBs are commonly used.[3,4] However, the narrow electrochemical stability window of water limits the attainable cell voltages in these aqueous systems. [5,6] To overcome these limitations, recent research has shifted towards non-aqueous RFBs (NARFBs) that use non-aqueous solvents, which can offer a wider electrochemical window up to 5 V.[7,8] Here, we introduce our research efforts on the design and synthesis of a series of terpyridine-based complexes of the first-row transition metals Cr, Mn, Fe, and Co for non-aqueous redox flow batteries (NARFBs). Electrochemical studies reveal that these complexes can undergo multi-electron transfer redox reactions. Notably, the Mn and Fe-based complexes exhibit both low negative redox potentials and high positive redox potential, enabling them to serve as a bipolar electrolyte for symmetric RFBs with a cell voltage of over 2 V. The assembled iron-based symmetric NARFB demonstrates a high cell voltage of 2.3 V, columbic efficiency of 97%, energy efficiency as high as 88%, and stable charge-discharge capacity retention of 60% after 160 cycles, corresponding to 99.75 % capacity retention per cycle. Figure 1

High performance phenothiazine-based battery materials achieved by synergistic steric blocking and extended conjugation

Phenothiazine derivatives, as sustainable cathode materials for batteries, show significant promise for large-scale electrical energy storage applications. However, the irreversibility of the sulfur redox active center severely limits their energy density and discharge voltage in rechargeable organic batteries. This study concentrates on identifying the potential side reactions that contribute to the irreversibility of phenothiazine-based materials. We propose a molecular design strategy that synergistically blocks the active site and extends the conjugation, markedly improving the electrochemical reversibility of these materials. Our findings reveal that phenothiazine derivatives can undergo two successive, one-electron redox reactions without interference from chemical bond rearrangement and reactive radicals. The assembled cells, utilizing lithium (Li) and sodium (Na) as anodes, display two distinct discharge plateaus at 3.3/3.9 V vs. Li+/Li and 3.1/3.7 V vs. Na+/Na, respectively, with nearly identical contributions from the nitrogen (N) and sulfur (S) redox centers. The phenothiazine derivatives designed via this strategy rank among the few phenothiazine-based organic electrode materials capable of achieving highly reversible, two-electron transfer redox reactions in organic batteries.

Efficient degradation of vulcanized natural rubber into liquid rubber by catalytic oxidation

Waste tire rubber based on natural rubber (NR) represents an abundant feedstock for the production of valuable products. This study investigated an efficient approach to convert NR vulcanizates into liquid rubber with the number-average molar masses of 1.3 × 104 g/mol. Compared to the anaerobic liquefaction at 300 °C for 3 min, NR vulcanizates were liquefied efficiently at 210 °C for 3 min by thermo-oxidative degradation catalyzed by manganese (II) stearate. The apparent activation energy of the NR degradation reaction decreased from 470.8 kJ/mol to 208.2 kJ/mol with catalysis, which was attributed to the formation of a coordination complex between catalysts and peroxides via the single-electron transfer redox reaction, leading to the catalytic oxidative degradation of NR vulcanizates. The main chain scission and crosslink scission occurred simultaneously during the degradation process, and the main chain scission was the primary catalytic oxidation reaction according to the Horikx theory. In addition, the obtained liquid rubber contained carbonyls, ether linkages, and sulfoxide groups, as proved by FTIR and 13CNMR . The catalytic oxidative degradation mechanism of NR vulcanizates was proposed based on the chemical structure of products and simulation results. The efficient method was proposed to highly facilitate the recycling and valorization of NR-based waste tire rubber.

Investigation of electrochemical characteristics and nucleation mechanism of cerium influenced by F− in LiCl-KCl-CsCl melts

The present study investigated the influence of F− on the electrochemical characteristics and nucleation mechanism of cerium in LiCl-KCl-CsCl molten salts, a new electrolyte medium for pyroprocessing of spent nuclear fuel with lower melting point that reduces the temperature tolerance demand of operating equipment compared with LiCl-KCl melts. By employing different electrochemical techniques, the electrochemical reaction of Ce(III)/Ce in LiCl-KCl-CsCl melts containing F− was found to be a diffusion-controlled, electrochemical reversible and three electrons transfer redox reaction at 653 K (CCe(III) = 4.94 × 10−2 mol/kg). It was also discovered that exchange current density and the diffusion coefficient of Ce(III)/Ce dropped in the presence of F−, while shifting negatively the equilibrium potential and subsequently resulting in the change of thermodynamic characteristics. The electrodeposition mechanism of Ce was also studied, demonstrating that the nucleation mode of Ce successfully transformed into progressive nucleation when F− was added. The affected electrochemical characteristics and the mechanism of electrodeposition nucleation of Ce in LiCl-KCl-CsCl molten salts at lower temperatures were attributed to the stronger complex ion [CeCl5F]3− formed after the addition of F−, being illustrated by the mathematic analysis of the molten salt structure. The formation of complex ion [CeCl5F]3− provides a new solution to inhibit the dendrite growth issue in the pyroprocessing of spent nuclear fuel at lower temperatures.

Visible Light‐Induced Ru‐Catalyzed Directing‐Group‐Assisted C−H Activation of Arenes

AbstractRu‐catalyzed directing group assisted C−H functionalization of arenes remains one of the powerful tools for site selective organic synthesis. Previous thermos versions normally require high temperature, rendering low functional group tolerance. With the emergence of the photoredox chemistry, visible light mediated mild Ru‐catalyzed directed C−H activation, especially using [RuCl2(p‐cymene)]2 as catalyst, have recently been investigated. Meta, ortho, and para selectivity have been achieved owing to the different activation mode of ruthenium complex. Inner‐sphere electron transfer and outer‐sphere electron transfer redox processes were attributed to different reaction pathway. In this review, we will provide an overview on recent achievements in visible light mediated Ru‐catalyzed directed C−H activation of arenes.

Multivalent‐Ion Electrochromic Energy Saving and Storage Devices

AbstractElectrochromic devices (ECDs) show promising applications in various fields including energy‐saving smart windows, energy‐recycling batteries/supercapacitors, displays, thermal management, etc. Compared to monovalent cations (H+, Li+, Na+, and K+), multivalent‐ion carriers (Mg2+, Ca2+, Zn2+, and Al3+) can enable the ECDs with high optical contrast, high energy‐recycling capability, and attractive long‐term stability because of the multiple‐electron transfer redox. Additionally, Mg2+, Zn2+, and Al3+‐based ECDs assembled with metal anodes are exploited for applications in EC electronics, EC mirrors, flexible devices, etc. Attempts to develop multivalent‐ion ECDs can be traced to 2013. However, since 2017, the research activity in this field has surged in the world. Despite the fascinating achievements, there is still a long way from their maturity due to challenges related to the limited electrode materials and electrolytes, as well as the obscure multivalent‐ion redox mechanisms. This review aims to discuss 1) the EC mechanisms of electrode materials with multivalent ions, 2) the advantageous functionalities of multivalent‐ion ECDs, and 3) strategies developed for exploring electrode materials, electrolytes, and ECD structures. Additionally, future perspectives for remaining challenges and corresponding strategies for developing multivalent‐ion ECDs with designed functionalities are discussed.

Optimizing Ionic-Electronic Pathways Via Bioinspired Self-Polymerized Dopamine in All-Solid-State Composite Cathode

The research of all-solid-state batteries (ASSBs) has been the principal emphasis in recent years. By utilizing the capabilities of advanced materials science and innovative engineering, ASSBs have the potential to revolutionize industries as diverse as consumer electronics, electric vehicles, aviation, and renewable energy. Solid-state batteries with their outstanding energy density, fast charging capabilities, and resistance to thermal runaway are anticipated to revolutionize the future of energy storage and allow a new era of eco-friendly, high-performance applications.Nonetheless, the point-of-contact resistance of ASSBs is high owing to the diverse chemical and physical characteristics of the individual solid components and the nature of solid-solid contact. To further enhance the electrochemical performance of ASSBs, especially their high-rate capabilities, it is crucial to raise the electronic conductivity of the cathode composites. Improving the electrical conductivity of electrodes to achieve high-rate capacity requires the addition of carbon. Utilizing common carbon materials, such as vapor-grown carbon fibers (VGCF), enables homogeneous current distribution in the cathode layer. Nevertheless, the use of carbon additives in sulfide-based ASSBs is inhibited by significant challenges. Carbon additives provide enough electronic percolation pathways in the composite cathodes, speeding the decomposition of sulfide SSEs during the charging process. Consequently, even with minimal amounts of carbon additives, rapid deterioration of sulfide SSEs continues to occur at the electrolyte/carbon interface, causing severe side reactions and the creation of an unfavorable interfacial layer between the carbon additives and SSEs.To achieve high cycle performance, ASSBs included conductive agents in the composite cathode to promote solid contact between the active material and sulfide solid electrolyte Li6PS5Cl; nevertheless, a significant side reaction was observed between the conductive agents and solid electrolyte. To prevent a substantial side reaction and achieve improved electrochemical performance with high-rate capacity, self-polymerized dopamine (PDA) thin film was coated on the VGCF’s surface in this investigation. Dopamine hydrochloride would be oxidized and self-polymerized into polydopamine under alkaline environments (pH 8.5) without the necessity for severe reaction conditions, sophisticated equipment, costly catalysts, or hazardous organic solvents.During the electrochemical test, the improved lithium conductivity of polydopamine-coated VGCFs after cycling at 0.1 C-rate was confirmed by galvanostatic intermittent titration technique (GITT) data and electronic-blocking cells. After polydopamine coating, the electrochemical performance of VGCFs dramatically improved with better reaction reversibility, enhanced specific capacity with high C-rate, and extended cycle life, as evidenced by polydopamine-coated VGCFs achieving ~165.5 mAh.g-1 after 100 cycles, compared to ~118.7 mAh.g-1 for unmodified VGCFs. Owing to the presence of two-electron transfer redox processes per benzoquinone skeleton, which reduced to catecholate and coordinate with lithium-ion, polydopamine facilitated a shorter ion diffusion path for a more rapid and straightforward reduction reaction even if compare with non-VGCFs composite cathode.In composite cathode, electronegative elements with lone-pair electrons, such as O (oxygen functional groups on VGCFs), react with electrophilic species, such as P5+ in Li6PS5Cl (PS4 3-), resulting in the formation of P-O bonding through nucleophilic reaction on oxygen-substituted thiophosphate and thioethers. In addition, the S atom of PS4 3- can attack the electrophilic C atom in the carbonyl group on the surface of VGCFs. Intense interactions between P5+ and the electronegative element O, as well as S2 and the electrophilic atom C, thus damage the crystal structure of SSEs and contribute to the reduction in the specific capacity of the composite cathode. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy were then utilized to confirm the existence of by-products such as P-S-P, S-S, Li2S, and P-O; the presence of polydopamine demonstrated its ability to minimize side reactions and preserve the solid-state electrolyte.In addition, polydopamine's excellent adhesive capabilities enable it to build a stable and homogenous coating on the VGCF's surface. This coating may enhance the adherence of the conductive agents to the electrode's components. As polydopamine-coated VGCFs exhibited low and homogeneous resistivity in the cathode's elements, scanning spreading resistance microscopy (SSRM) was used to highlight the enhancement of particle distribution to optimize the ionic and electronic pathways.This study examines, in summary, the effect of a polydopamine coating layer on the conductivity of solid-state battery conductive agents. Even though polydopamine is recognized for its insulating characteristic, it may also display strong electrical conductivity and adhesion under certain conditions. Thus, we observed that VGCFs coated with a suitable PDA thin film eliminate unneeded kinetic energy for side reactions and improve the ionic-electronic route in composite electrodes. The discovered principles and mechanism of polydopamine coated on conductive agents are applicable to a polymer manufacturing method or modification that is coated on conductive agents, therefore enhancing the electrochemical performance of ASSBs. Figure 1

Iron mobility in subduction zone fluids at forearc depths and implications for mantle redox heterogeneity

The mobility of redox sensitive elements such as iron, carbon and sulfur in subduction zone fluids is important for redox transfer between the subducting slab and mantle wedge. However, the speciation of Fe during its mobility in subduction zone fluids at forearc depths is still unclear. Here, we studied the Fe isotope compositions of high-pressure (HP) fluid-metasomatized rocks (Mg-rich leucophyllite and gneiss, which is mineralogically transitional between leucophyllite and metagranite) from the Eastern Alps and found evidence for two distinct types of Fe species during Fe mobility in subduction zone fluids. The protolith of both types of rocks is metagranite, which shows δ56Fe values of 0.12–0.25‰. Compared to the metagranite, the transitional gneiss shows slightly higher Fe2O3t contents, lower Fe3+/∑Fe ratios and significantly lower δ56Fe values of −0.03–0.16‰, whereas the leucophyllite exhibits much lower Fe2O3t contents, comparable or slightly lower Fe3+/∑Fe ratios and generally higher δ56Fe values of up to 0.55‰. These observations indicate that the granitic protolith has experienced two types of fluid metasomatism. Combined with previous results, we infer the mobility of Fe in subduction zone fluids at forearc depths via two kinds of Fe species, Fe2+-(CO3), and Fe2+-(HS) or Fe2+-Cl. The Fe mobility was dominant in the form of the Fe2+-(CO3) complex in a carbonate-rich fluid during the formation of transitional gneiss, consistent with reported radiogenic Sr and isotopically light Mg isotope compositions, whereas Fe loss in the form of Fe2+-(HS) or Fe2+-Cl complexes via dissolution of biotite and phlogopite can account for the formation of leucophyllites. According to the tectonic evolution of the Eastern Alps, both types of fluids possibly originated from the dehydration of the sediment-serpentinite mélange produced by the subducting oceanic slab of the Alpine Penninic unit. The diversity of ferrous iron species in the subduction zone fluids at forearc depths probably reflects the variation in the redox properties of fluids derived from carbonate-rich sediment and serpentinite under such conditions. Our results provide an excellent example of tracing Fe mobility with distinct Fe species in subduction zone fluids.

A hexaazatriphenylene‐based porous organic polymer for high performance supercapacitor

AbstractPorous organic polymers (POPs) with high physiochemical stability and pseudocapacitive activity are crucial for supercapacitors with high specific capacitance and long cycle life. We report herein a hexaazatrinaphthylene‐based POP (HPOP‐1) for high‐performance supercapacitor by introducing redox‐active hexaazatrinaphthylene (HATN) moiety through Sonogashira–Hagihara coupling reaction. HATN moiety can undergo a proton‐induced electron transfer redox reaction, which endows HPOP‐1 with high pseudocapacitive activity. As electrode materials for supercapacitor application, HPOP‐1 exhibits high specific capacitance (667 F g−1 at 0.5 A g−1) and long‐term cyclic stability (90% capacitance retention after 10,000 cycles at 5 A g−1) in a three‐electrode system with 1 M H2SO4 as the electrolyte. In addition, HPOP‐1 also exhibits a specific capacitance of 376 F g−1 at 0.5 A g−1 in 1 M KOH electrolyte. An asymmetric supercapacitor was further fabricated with HPOP‐1 as negative electrode and rGO as positive electrode, respectively. The device delivers a specific capacitance of 63 F g−1 at 0.5 A g−1 and a rate performance of 37 F g−1 at 5 A g−1. Our work provides a facile approach for the design and preparation of pseudocapacitive POPs with high specific capacitance and long cycle life.

Developing terpyridine-based metal complexes for non-aqueous redox flow batteries

This paper describes the design and synthesis of a series of terpyridine-based complexes of the first-row transition metals Cr, Mn, Fe, and Co for non-aqueous redox flow batteries (NARFBs). Electrochemical studies reveal that these complexes can undergo multi-electron transfer redox reactions. In particular, the Mn and Fe-based complexes exhibit both low negative redox potentials and high positive redox potential, permitting them to serve as a bipolar electrolyte for symmetric RFBs with a cell voltage of more than 2 V. The solubility of these complexes can be effectively improved by incorporating a polyether substituent on the terpyridine ligand and counter anion optimization. The iron complex [Fe(tpy-O(CH2CH2O)3CH3)2][TFSI]2 shows a high solubility of 0.76 M in MeCN. The fabricated iron-based symmetric NARFB demonstrates a superior battery performance with a high cell voltage of 2.3 V, columbic efficiency of 97%, energy efficiency as high as 88%, and stable charge-discharge capacity retention of 60% after 160 cycles, corresponding to 99.75 % capacity retention per cycle. The post-cycling cyclic voltammetry (CV), UV-Vis, and 1H-NMR characterizations indicate only minor chemical decomposition of the cycled complex, confirming its good charging-discharging stability.

Reversible Redox-Dependent Conformational Switch of the C-Terminal α-Helical Lid of Human Hsp70 Observed by In-Cell NMR.

Glutathionylation of human stress-inducible Hsp70 (hHsp70) under oxidative stress conditions has been suggested to act as an on/off switch of hHsp70 chaperone activity and thus transfer redox signals to hHsp70 clients through a change in conformation. The mechanism of this switch involves unfolding of the C-terminal α-helical lid, SBDα, upon glutathionylation, which then binds to and blocks the hHsp70 substrate-binding site. This process is reversible and redox-regulated and has been demonstrated for purified protein in solution. Here, we found that this redox-regulated reversible process also occurs in the cellular environment. Using Escherichia coli as a model system, in-cell NMR data clearly indicate that hHsp70 SBDα undergoes a conformational transition from ordered to disordered after diamide stimulation. The disordered SBDα could spontaneously recover back to the helix bundle conformation over time. This oxidative-stress induced process also occurred in cell lysate, with a similar unfolding rate as in cells, but the refolding rate was significantly slower in cell lysate. Increased temperature accelerates this process. Under heat stress alone, unfolding of the SBDα could not be detected in cells. Our in-cell NMR results provide direct support for the molecular switch model of hHsp70 redox regulation and also demonstrate the power of in-cell NMR for real-time study of protein structures during biological processes in living cells.

The “Ex-cell” approach to organic electrosynthesis

The “ex-cell” approach to organic electrosynthesis has enabled important progression to be made in numerous systems. Separating out the electrochemical step from the subsequent chemical step means that substrate scopes can be expanded and a broader scope of reagents are more easily prepared. Moieties can be included that otherwise readily undergo single-electron transfer redox events at the electrode surface. We detail several examples of this, including those based on the ex-cell synthesis and use of bases, cations and hypervalent iodine reagents, among others.

Gold nanoclusters: Photophysical properties and photocatalytic applications.

Atomically precise gold nanoclusters (Au NCs) have high specific surface area and abundant unsaturated active sites. Traditionally, Au NCs are employed as thermocatalysts for multielectron transfer redox catalysis. Meanwhile, Au NCs also exhibit discrete energy levels, tunable photophysical and electrochemical properties, including visible to near infrared absorption, microsecond long-lived excited-state lifetime, and redox chemistry. In recent years, Au NCs are increasingly employed as visible to near infrared photocatalysts for their high photocatalytic activity and unique selectivity. This review focuses on the photophysical properties of a variety of Au NCs and their employment as photocatalysts in photocatalytic reactions and related applications including solar energy conversion and photodynamic therapies.

Electro–Oxidation of Nitroxide Radicals: Adsorption–Mediated Charge Transfer Probed Using SERS and Potentiometry

Organic compounds containing nitroxide radicals such as 4–hydroxy–2,2,6,6–tetramethylpiperidine–1–oxyl (4–hydroxy–TEMPO) are redox–active and are of interest for potential applications in redox flow batteries. The mechanisms governing charge–transfer reactions of such compounds are not well understood. Specifically, the anodic charge transfer coefficient (α a) corresponding to the electro–oxidation of 4–hydroxy–TEMPO in an aqueous medium is ∼0.9, i.e., α a deviates considerably from the expected value (0.5) for a symmetric single–step one–electron transfer redox reaction. In a previous publication (J. Electrochem. Soc., 2020, 167, 143505), we have proposed a reaction mechanism to explain such asymmetric behavior by invoking adsorption–desorption processes. In the proposed mechanism, reversible oxidation of 4–hydroxy–TEMPO leads to the adsorption of the oxidation product, which then undergoes slow rate–limiting desorption from the electrode surface. In the present contribution, supporting evidence is provided for this mechanism. In situ surface–enhanced Raman spectroscopy combined with density functional theory simulations are employed to confirm the presence of surface–adsorbed species at a Au electrode during electro–oxidation of 4–hydroxy–TEMPO. Furthermore, we employ chronopotentiometry to track the gradual re–equilibration of the electrode–electrolyte interface following the electro–oxidation of 4–hydroxy–TEMPO. Analysis of the chronopotentiometry data further suggests the presence of adsorbed species, which were previously proposed and are now confirmed by direct spectroscopic evidence.

The Performance of Polyaniline Electropolymerization at Various Acidic Electrolytes on Gold Electrodes for Electrochemical Biosensor Application

Polyaniline (PANI), a conductive polymer, has been played a significant role as an electrode material for electrochemical biosensor development. In this study, the electrochemical properties of PANI synthesized in two different acid dopants, i.e. 1.0 M HCl and 0.50 M H2SO4using chronopotentiometry, were investigated. The surface morphologies of the PANI modified gold electrodes were observed using SEM and EDS. The PANI electrodeposition times were also considered. The electrochemical characteristics in terms of the peak-to-peak potential separations (ΔEp), the current of the oxidation (Ipa), and reversible redox properties were investigated using cyclic voltammetry. The results showed that the modified electrode with PANI electropolymerization in H2SO4 as a dopant performed significantly better electrochemically than PANI in HCl at all electrodeposition times. In particular, the PANI prepared in H2SO4 with the electrodeposition time of 120 s demonstrated the best performance in terms of electron transfer and reversible redox reaction.

Electrocatalytic oxidation of catechol using IrOx-ITO electrode in aqueous medium

• IrOx film was fabricated on ITO glass with electro flocculation method. • Ir(III)/Ir(IV) redox couple catalyzes catechol oxidation reactions in the acidic medium. • Catechol may be used as fuel in a fuel cell. • IrOx-ITO film is extremely stable in attaining catechol oxidation. Catechol is extracted from the wastes of oil refineries which is source of o-benzoquinone, the starting material for many organic syntheses. Catechol can produce o-benzoquinone by releasing two electrons via a reversible reaction which could be exploited for fuel cell construction. Thus, for conversion of catechol into o-benzoquinone is crucial and requires a robust catalyst. In the present article, we propose IrO x immobilized ITO surface for efficient electrocatalytic oxidation of catechol. The catalysis and kinetics have been investigated using Cyclic Voltammetric (CV) technique in acidic medium. The Ir(III) species involves one electron transfer redox reaction on the ITO surface and the conversion of Ir(III) to Ir(IV) has been identified to catalyze catechol oxidation reaction. The concentration of the electro active Ir species on the ITO surface was calculated to be (3.32 ± 0.22) × 10 −9 mol cm −2 .

GREEN SYNTHESIS AND EVALUATION OF In-vitro ANTICANCER (MCF-7) AND MOLECULAR DOCKING STUDIES OF V2+ AND CO2+ COMPLEXES OF SCHIFF BASE

New V2+and Co2+complexes of Schiff base derived from the isonicotinicacidhydrazide (INH) and 4-isopropyl benzaldehyde by Eco-friendly synthetic method. Present synthesis complies with the principle of Green Chemistry. The synthesized compound was structurally characterized by elemental analysis, metal estimation, magnetic moment, molar conductance, UV-visible, IR & Far-IR, and fluorescence emission spectra. Elemental analysis of Schiff base and its complexes were carried out and the results indicate the percentage of elements (C, H, N, and O) and stoichiometry of the complexes. The molar conductance of complexes was carried out and the result indicates the non-electrolytic nature of the complexes. The electrochemical properties of the Co2+ complex were carried out and confirmed a quasi-reversible one-electron transfer redox reaction. The magnetic moment measurement indicates that the complexes are paramagnetic. The octahedral geometry of vanadium and cobalt complexes, as well as the functional groups present in them, was determined using UV-vis and IR spectroscopy. The fluorescence spectra of the ligand and complexes show the fluorescence nature of the ligand. The DPPH free radical scavenging method was used to evaluate the antioxidant activity of Schiff base and its V2+ complex in vitro. The MTT assay was used to measure cytotoxicity, and the vanadium complex's in vitro anticancer effect on MCF-7 (human breast cancer) cell lines was studied. In breast cancer therapy, the human epidermal growth factor receptor 2 (HER2) is considered a validated target. In addition, the Agar disc diffusion model was used to evaluate the antibacterial activity of Staphylococcusaureus, Escherichia coli, and Pseudomonas aeruginous in vitro.

Electrochemical assessment of high active area of cobalt deposited in deep eutectic solvent

• Green electrodeposition of nanostructured Co films using deep eutectic solvent (DES). • Influence of substrate and potential conditions on the morphology and composition of Co films. • Use of outer sphere electron transfer redox pairs to assess the increase of the active area of Co films. • The validity of 1,4-benzoquinone and hexaammineruthenium(III) redox pairs probes is tested. • Lead underpotential deposition on Co films covered by gold to quantify the surface active area. Preparation of nanostructured materials with highly efficient active area is crucial for advancement in fields of electrocatalytic conversion of energy, energy storage, or biomedicine. In this regard, there are two main challenges in the electrochemical preparation of high-extended surface area of the nanostructures: 1) establishing the optimal potential conditions to enhance the active area while reducing the size of the prepared material and, 2) simultaneously, finding a practice and simple in situ methodology to qualitatively test the increase in the active surface area. Herein, we investigate the cobalt electrodeposition in choline chloride plus urea deep eutectic solvent (DES) and the effect of the DES in the increase of the active surface area of deposited Co films. In situ classical electrochemical techniques, in combination with ex situ characterization techniques, were employed to establish the best potential conditions to obtain metallic Co films with high active surface area. Then, the increase in active area was tested by using different voltammetric methodologies. The increase in intensity of the outer sphere electron transfer was tested as a tool to analyze the superficial change after cobalt deposition. Voltammetric response in organic medium using benzoquinone on Co films and in an aqueous medium using Ru(NH 3 ) 6 , after covering the Co films with gold via galvanic displacement, was assessed. Later, as alternative method, the active area of the freshly deposited Co films, after superficial modification with Au, was tested by lead underpotential deposition. Lead underpotential deposition on gold is a surface-structure process that indirectly allows the estimation of the increment in active area of prepared Co films.

Controlling One-Electron vs Two-Electron Pathways in the Multi-Electron Redox Cycle of Nickel Diethyldithiocarbamate.

The unique redox cycle of NiII(dtc)2, where dtc- is N,N-diethyldithiocarbamate, in acetonitrile displays 2e- redox chemistry upon oxidation from NiII(dtc)2 → [NiIV(dtc)3]+ but 1e- redox chemistry upon reduction from [NiIV(dtc)3]+ → NiIII(dtc)3 → NiII(dtc)2. The underlying reasons for this cycle lie in the structural changes that occur between four-coordinate NiII(dtc)2 and six-coordinate [NiIV(dtc)3]+. Cyclic voltammetry (CV) experiments show that these 1e- and 2e- pathways can be controlled by the addition of pyridine-based ligands (L) to the electrolyte solution. Specifically, the addition of these ligands resulted in a 1e- ligand-coupled electron transfer (LCET) redox wave, which produced a mixture of pyridine-bound Ni(III) complexes, [NiIII(dtc)2(L)]+, and [NiIII(dtc)2(L)2]+. Although the complexes could not be isolated, electron paramagnetic resonance (EPR) measurements using a chemical oxidant in the presence of 4-methoxypyridine confirmed the formation of trans-[NiIII(dtc)2(L)2]+. Density functional theory calculations were also used to support the formation of pyridine coordinated Ni(III) complexes through structural optimization and calculation of EPR parameters. The reversibility of the LCET process was found to be dependent on both the basicity of the pyridine ligand and the scan rate of the CV experiment. For strongly basic pyridines (e.g., 4-methoxypyridine) and/or fast scan rates, high reversibility was achieved, allowing [NiIII(dtc)2(L)x]+ to be reduced directly back to NiII(dtc)2 + xL. For weakly basic pyridines (e.g., 3-bromopyridine) and/or slow scan rates, [NiIII(dtc)2(L)x]+ decayed irreversibly to form [NiIV(dtc)3]+. Detailed kinetics studies using CV reveal that [NiIII(dtc)2(L)]+ and [NiIII(dtc)2(L)2]+ decay by parallel pathways due to a small equilibrium between the two species. The rate constants for ligand dissociation ([NiIII(dtc)2(L)2]+ → [NiIII(dtc)2(L)]+ + L) along with decomposition of [NiIII(dtc)2(L)]+ and [NiIII(dtc)2(L)2]+ species were found to increase with the electron-withdrawing character of the pyridine ligand, indicating pyridine dissociation is likely the rate-limiting step for decomposition of these complexes. These studies establish a general trend for kinetically trapping 1e- intermediates along a 2e- oxidation path.

Hierarchically structured Ti3C2T MXene paper for Li-S batteries with high volumetric capacity

Due to the low density of sulfur and the large portion of carbon-based materials used as conducting network and lithium polysulfide (LiPS) host, the practical volumetric energy density of lithium–sulfur (Li–S) batteries barely rivals the Li-ion batteries. Here, MXene (Ti 3 C 2 T x )-based membrane with unique 3D hierarchical structure, high electronic conductivity, abundent active binding sites, fast ion transport, and high affinity for lithium polysulfides has been developed as a new host material to improve the electrochemical performance of Li-S batteries. With a density of 2.2 g cm −3 , a MXene-based cathode containing 4.0 mg cm −2 sulfur delivers a high volumetric capacity of 2.7 Ah cm −3 after 200 cycles. Based on operando XRD and ex-situ XPS results, we find that the Ti-OH bonds present on the surface of MXene membrane can effectively trigger the LiPS transformation. Furthermore, α -S 8 , as the stable charge product, is first reported in MXene-based host along with its possible important role in curtailing active mass loss and enhancing cycling capability. Our results reveal that 2D MXene with rationally-designed architecture enable high volumetric capacity Li-S batteries for practical applications. An excellent lithium-sulfur battery with high volumetric capacity is enabled by a 3D hierarchical MXene (Ti 3 C 2 T x ) electrode, which can effectively regulate the polysulfides shuttling via a dual-play immobilization mechanism of thiosulphate/polythionate redox conversion and Lewis acid-base interactions. α -S 8 is first reported as the stable charge product and its important role is studied in detail. • An efficient encapsulation strategy was developed to construct a robust hierarchically structured MXene cathode of Li-S batteries. • Combined in-situ and ex-situ measurements suggest that the thiosulphate/polythionate complex serves as key redox transfer mediator to facilitate the surface-redox reaction. • α-S 8 is firstly reported as the stable charge-stage product and its fast nucleation and stability effectively curtail active mass loss and enhances cycling capability.