Redox Potential Research Articles

Stretching vibration driven adiabatic transfer kinetics for photoexcited hole transfer from semiconductor to adsorbate

Interfacial hole transfer from a photoexcited semiconductor to surface adsorbates is pivotal for initiating solar-to-chemical energy conversion, yet the atomic-level transfer kinetics remains elusive. Using the methoxy/TiO2(110) system as an archetype, here we elucidate the hole transfer mechanism from hole-trapping lattice oxygen to the methoxy adsorbate at gas/solid and liquid/solid interfaces through molecular dynamics simulations and static minimum energy path calculations. Instead of direct nonadiabatic hopping, we uncover an adiabatic migration pathway adapted to local substrate relaxation, driven by a bond-stretching mechanism supported by stronger Ti-O stretching vibrations. Notably, this mechanism persists at the aqueous methoxy/TiO2(110) interface, albeit hindered by interfacial water and coadsorbates. Surprisingly, the hole transfer barriers across various photoexcited adsorbate/TiO2 interfaces correlate more closely with the vertical excitation energies of the adsorbates rather than their redox potentials, indicating an early-type transition-state nature. These insights deepen our understanding of elementary hole transfer kinetics in surface photochemistry.

Polar Covalent Triazine Frameworks as High-Performance Potassium Metal Battery Cathodes.

The exploration of potassium metal batteries (PMBs) has been intensified, leveraging potassium's abundant availability, low redox potential, and small Stokes radius. Covalent triazine frameworks (CTFs) stand out for their accessible nitrogen sites and customizable structures, making them attractive electrode materials. Nonetheless, there is a lack of established design principles to guide the development of high-performance PMBs using CTFs. In this work, CTFs consisting of different monomers are used as PMB cathodes to investigate the structure-performance correlation. The electronic structure analysis reveals the polar characteristic of a CTF derived from the tetracyanoquinodimethane monomer, setting it apart with superior capacity (161 mAhg-1 at 0.1A g-1), rate performance (85 mAhg-1 at 5 Ag-1), and stability (capacity retention of 81% after 1000 cycles) over three non-polar counterparts in PMBs. Calculations based on density functional theory support the exceptional performance with increased K+ adsorption energy. Ultimately, among multifaceted factors, the polarity of CTF is the leading element that determines the K+ storage capability. These findings pave the way for the development of prudent CTF electrodes for high-performance PMBs.

Photoredox Oxidation of Alkanes by Monometallic Copper-Oxygen Complexes Using Visible Light Including One Sun Illumination.

Oxygenation of hydrocarbons offers versatile catalytic routes to more valuable compounds, such as alcohols, aldehydes, and ketones. Despite the importance of monometallic copper-oxygen species as hydroxylating agents in biology, few synthetic model compounds are known to react with hydrocarbons, owing to high C-H bond dissociation energies. To overcome this challenge, the photoredox chemistry of monometallic copper (pyrazolyl)borate complexes coordinated by chlorate has been explored in the presence of C1-C6 alkanes with BDEs ≥ 93 kcal/mol. Ethane is photooxidized at room temperature under N2 with yields of 15-30%, which increases to 77% for the most oxidizing tris(3,5-trifluoromethyl-pyrazolyl)borate complex (Cu-3). This complex also promotes the photooxidation of methane to methanol in significant yield (38%) when the photoredox reaction is run under aerobic conditions. Ligand modification alters the reaction selectivity by tuning the redox potential. The ability to activate 1° C-H bonds of C1-C6 alkanes using visible light is consistent with the photogeneration of a powerfully oxidizing copper-oxyl, which is supported by photocrystallographic studies of the tris(3,4,5-tribromopyrazolyl)borate chlorate complex. Mechanistic studies are consistent with the hydrogen atom abstraction of the C-H bond by the copper-oxyl intermediate. We demonstrate for Cu-3 with hexane as an exemplar, that the photoredox chemistry may be achieved under solar conditions of one-sun illumination.

Band alignment of CoO(100)-water and CoO(111)-water interfaces accelerated by machine learning potentials.

Cobalt monoxide (CoO) nanomaterials have drawn attention for their remarkable photocatalytic water splitting without an externally applied potential or co-catalyst. The success of overall water splitting is due to the appropriate band edge positions of the catalyst, which span the redox potentials of water splitting. Typically, CoO nanomaterials possess complex morphologies, which consist of multiple active surfaces. As a result, the precise roles of the surfaces in the overall water-splitting process remain to be elucidated. In this work, we have undertaken a thorough investigation into the band alignments at the CoO(100)-water and CoO(111)-water interfaces using abinitio molecular dynamics and machine learning accelerated molecular dynamics simulations. The results of band alignment reveal that CoO(100) supports both the Hydrogen Evolution Reaction (HER) and the oxygen evolution reaction, whereas CoO(111) only facilitates the HER. Moreover, the variance in band positions between CoO(100) and CoO(111) results in an intrinsic potential difference, facilitating the migration of electrons toward CoO(100), while holes accumulate on CoO(111). The separation of photoexcited carriers effectively promotes water splitting in CoO.

A Molten Alkali Approach to Tailor Hydroxyl Groups of Hexaazatrinaphthalene Toward High-Capacity and Low-Potential Anode of Aqueous Proton Batteries.

Hexaazatrinaphthalene (HATN) has attracted a lot of attention in aqueous proton batteries (APBs). However, its redox potential as an anode is insufficiently negative. The introduction of electron-donating substituent groups, such as hydroxyl groups, is considered as a good approach to reduce the redox potential of HATN. Nevertheless, manufacturing hydroxyl-substituted HATN (HATN-OH) requires either expensive precursors or multi-step process, limiting their research. Herein, a straightforward strategy is proposed to synthesize HATN-OH based on the nucleophilic substitution reaction of halogenated HATN in a molten alkali. The redox potential of 1,2,7,8,13,14-hexahydroxy-5,6,11,12,17,18-hexaazatrinaphthalene (34-HATN-6OH) electrode may be lowered by 0.15V in comparison to HATN, and exhibits a high specific capacity, low redox potential, remarkable rate capability, and outstanding long-term cycling performance. The electrochemical redox kinetics is significantly enhanced owing to the formation of rapid proton transport channels created by intermolecular hydrogen bond network. The assembled MnO2||34-HATN-6OH full battery delivers a high discharge voltage (1.16V) and cycling stability (74% capacity retention after 5000 cycles). This study provides a general cost-effective molten alkali approach for the synthesis of hydroxyl-substituted conjugated small molecules from their halogenated counterparts and further enriches the regulation means of electro-chemical performances of organic electrodes for enabling high-capacity and high-voltage APBs.

Degradation Mechanism and Enhanced Stability of Organolithium for Chemical Lithiation

AbstractOrganolithium solutions, especially Li‐arene solutions (LASs) with high reactivity and controllable redox potentials, have gained significant attention because of their wide applications in chemical lithiation, liquid anodes, and battery recycling. However, the sudden loss of reactivity when stored or applied at room temperature is still puzzling and inhibits the application of LASs. In this work, the degradation mechanism of LASs is fully investigated and revealed by combining various experimental characterization and computational simulations. A hierarchical reaction mechanism for lithium biphenyl/2‐methyl tetrahydrofuran (Li‐Bp‐2MT), a lithiation solution used for most anodes, explains degradation and side product formation. Specifically, the dimerization of the active component Li1Bp[2MT]1 forms an inactive dimer that is irreversibly reduced in the presence of locally accumulated highly reductive Li0. This reaction mechanism reveals the atomic origins of lithiation solution deactivation and accounts for all solid and gaseous byproducts. LiH is identified as the dominating solid byproduct, indicating irreversible destruction of the active components and facilitating side reactions producing H2 and CH4. Based on reaction mechanism insights, modifying molecular interactions and reaction kinetics are experimentally shown to inhibit Li0 aggregation kinetics, enhancing long‐term prelithiation performance. This research provides comprehensive guidelines for practical applications of LASs.

Site-Directed Mutagenesis of Two-Domain Laccase ScaSL for Obtaining a Biocatalyst with Improved Characteristics

Analysis of the structure of two-domain laccase ScaSL from Streptomyces carpinensis VKM Ac-1300 (with a middle-redox potential) revealed determinants that could affect the increased potential of ScaSL. Site-directed mutagenesis of the ScaSL laccase was carried out, and mutants H286A, H286T, H286W, and F232Y/F233Y were obtained. Replacement of His 286 with Ala led to a decrease in redox potential (0.45 V) and an increase in stability at pH 9 and 11; replacement with Thr led to an increase in redox potential (0.51 V) but to a decrease in the thermal stability of the protein; replacement with Trp did not affect the enzyme properties. Replacement of Phe residues 232 and 233 with Tyr led to a shift in enzyme activity to the acidic pH range without changing the redox potential and a decrease in the thermostability and pH stability of the enzyme. All mutants more efficiently oxidized phenolic substrate 2,6-DMP and were able to participate in direct electron transfer (DET) with MWCNT-modified electrodes. The F232Y/F233/Y mutant was unable to degrade triphenylmethane dyes without a mediator but showed a greater degree of decolorization of azo dyes in the presence of the mediator. The crystal structure of laccase with the highest potential was determined with high resolution.

High‐performance vanadium oxide‐based aqueous zinc batteries: Organic molecule modification, challenges, and future prospects

AbstractAqueous Zn‐vanadium batteries have been attracting significant interest due to the high theoretical capacity, diverse crystalline structures, and cost‐effectiveness of vanadium oxide cathodes. Despite these advantages, challenges such as low redox potential, sluggish reaction kinetics, and vanadium dissolution lead to inferior energy density and unsatisfactory lifespan of vanadium oxide cathodes. Addressing these issues, given the abundant redox groups and flexible structures in organic compounds, this study comprehensively reviews the latest developments of organic‐modified vanadium‐based oxide strategies, especially organic interfacial modification, and pre‐intercalation. The review presents detailed analyses of the energy storage mechanism and multiple electron transfer reactions that contribute to enhanced battery performance, including boosted redox kinetics, higher energy density, and broadened lifespan. Furthermore, the review emphasizes the necessity of in situ characterization and theoretical calculation techniques for the further investigation of appropriate organic “guest” materials and matched redox couples in the organic‐vanadium oxide hybrids with muti‐energy storage mechanisms. The review also highlights strategies for Zn anode protection and electrolyte solvation regulation, which are critical for developing advanced Zn‐vanadium battery systems suitable for large‐scale energy storage applications.

Revealing Asymmetric Phase Transformation of the BiVO4 Anodes for Potassium-Ion Batteries by In Situ Transmission Electron Microscopy.

Potassium-ion batteries (PIBs) have emerged as a promising alternative to lithium-ion batteries (LIBs), thanks to the cost-effectiveness of potassium resources and a favorable redox potential of approximately -2.936 V. The monoclinic BiVO4, known for its layered structure, shows noteworthy electrochemical properties when utilized as an anode material for both LIBs and sodium-ion batteries. However, the fundamental electrochemical reaction mechanisms of the BiVO4 anode during the potassium insertion/extraction processes remain unclear. Here, we constructed a BiVO4 anode PIB inside the transmission electron microscope (TEM) to explore the real-time potassiation/depotassiation behaviors of BiVO4 during electrochemical cycling. Utilizing the state-of-art in situ TEM technique, the BiVO4 nanorods are found to undergo an asymmetric phase transformation for the first time, where the pristine BiVO4 material is transformed into an amorphous KxBiVO4 phase after the first cycle. More interestingly, the anode materials near and far from the potassium source exhibit opposite volume-changing trends under the same voltage potential. Also, this phenomenon should be attributed to the mass flow of the unstable K-Bi alloy under the electric field. Our findings provide significant insights into the electrochemical mechanism of BiVO4 nanorods during the potassiation/depotassiation process, with the hope of assistance in designing anodes for high-performance PIBs.

Recent Achievements in Heterogeneous Bimetallic Atomically Dispersed Catalysts for Zn-Air Batteries: A Minireview.

Rechargeable Zn-air batteries (ZABs) hold promise as the next-generation energy-storage devices owing to their affordability, environmental friendliness, and safety. However, cathodic catalysts are easily inactivated in prolonged redox potential environments, resulting in inadequate energy efficiency and poor cycle stability. To address these challenges, anodic active sites require multiple-atom combinations, that is, ensembles of metals. Heterogeneous bimetallic atomically dispersed catalysts (HBADCs), consisting of heterogeneous isolated single atoms and atomic pairs, are expected to synergistically boost the cyclic oxygen reduction and evolution reactions of ZABs owing to their tuneable microenvironments. This minireview revisits recent achievements in HBADCs for ZABs. Coordination environment engineering and catalytic substrate structure optimization strategies are summarized to predict the innovation direction for HBADCs in ZAB performance enhancement. These HBADCs are divided into ferrous and nonferrous dual sites with unique microenvironments, including synergistic effects, ion modulation, electronic coupling, and catalytic activity. Finally, conclusions and perspectives relating to future challenges and potential opportunities are provided to optimise the performance of ZABs.

Publisher Correction: Machine learning-aided first-principles calculations of redox potentials

Publisher Correction: Machine learning-aided first-principles calculations of redox potentials

Determination of saturated dissolved oxygen concentration in iron sulfate solutions containing iron oxidizing microorganisms

Iron sulfate solutions and the extremophile lifeforms that can live within them are industrially and environmentally important in many applications and require proper assessments of solution properties. Determination of saturated dissolved oxygen concentration is an important parameter for monitoring iron biooxidation processes. However, its determination is not so straight forward using commercially available dissolved oxygen meters. Such meters utilize internal calculation models based on the saline properties of seawater which can be easily overlooked. A method for determination of the saturated dissolved oxygen concentration in acidic iron sulfate solutions with the inclusion of other inorganic salts is proposed in this work using the biooxidation of ferrous iron as an indicator measured with redox potential and converted to oxygen concentration through bioreaction stoichiometry. The technique was tested on a BioGenerator system over the course of four days and proved satisfactory in establishing a value for the saturated dissolved oxygen concentration of the bioreactor broth. Study of the lifespan properties of the microorganisms in absence of ferrous iron substrate was briefly examined to determine the effective handling period of solutions for assessment.

Cation/Anion Doping Strategy for Na4MnV(PO4)3 with High Energy Density and Long Cycling Life through Construction by Aspergillus niger.

Na4MnV(PO4)3 (NMVP) has gained attention for its high redox potential, good cycling stability, and competitive price but suffers from poor intrinsic electronic conductivity and Jahn-Teller effect from Mn3+. In this work, cation/anion doping strategy was used for Aspergillus niger-bioderived carbon-coated NMVP (NMVP/AN) to improve the structural stability and electrochemical performance, where Al3+ doping inhibited the dissolution of Mn and enhanced the Mn3+/Mn2+ redox pair activity; besides, F- doping not only weakens the Na2-O bond but also endows the hierarchical and porous structure of NMVP/AN, which led to a more rapid and fluid transfer of Na+. The elaborately designed Na3.9Mn0.9Al0.1V(PO4)3/AN (NMAVP/AN) exhibits 105.9 mA h g-1 at 0.5 C, and the as-prepared Na3.1MnV(PO3.7F0.3)3/AN (NMVPF/AN) delivers 104.1 mA h g-1 at 5 C. Further demonstration of the hard carbon//NMAVP/AN full cell manifests the good potential of Al3+-doped NMVP/AN for practical applications (100.6 mA h g-1 at 1 C). These findings open up the possibility of unlocking the high-performance Na superionic conductor (NASICON).

Synergizing Proton‐Dominated Storage and Electron Transfer for High‐Loading, Fast‐Rate Organic Anode in Metal‐Free Aqueous Zinc‐Ion Batteries

AbstractDeveloping suitable anode materials to fabricate metal‐free Zinc ion battery is a promising strategy to solve the issues of Zn metal anode, such as dendrite growth and side reactions. However, the reported anode materials face shortcomings such as unsatisfactory rate performance, low mass loading, etc. Herein, featuring synergetic proton‐dominated storage and electron transfer, a conjugated polyimide nanocomposite trapped by multi‐walled carbon nanotubes (PPN‐MWCNT) is developed for high‐loading, fast‐rate organic anode materials in metal‐free Zinc ion battery. Specifically, abundant hydrophilic active sites and nonplaner conjunctional structure in PPN achieve proton‐dominated storage with two steps four electrons mechanism, leading to fast ion diffusion, and the intimate contact between the polymer and MWCNT via in situ polymerization ensures the excellent charge transfer and robust structure. Thus, the PPN‐MWCNT electrode delivers low redox potential, ultrahigh rate performance (50 A g−1), superior loading capability (≈40 mg cm−2) and exceptional long‐term cyclability (over 12 000 cycles). More importantly, the full batteries assembled with PPN‐MWCNT anode and different cathodes deliver a high energy density of 106.4 Wh kg−1 (PPN‐MWCNT//MnO2) and 83.7 Wh kg−1 (PPN‐MWCNT//active carbon‐I2), exceeding the most reported metal‐free Zinc ion batteries.

Mechanisms of manganese-tolerant Bacillus brevis MM2 mediated oxytetracycline biodegradation process

Addressing the environmental threat of oxytetracycline (OTC) contamination, this study harnesses the bioremediation capabilities of Bacillus brevis MM2, a manganese-oxidizing bacterium from acid mine drainage. We demonstrate the strain's exceptional efficiency in degrading OTC under high manganese conditions, with complete removal achieved within 24 h. The degradation is facilitated by the production of Bio-MnOx, utilizing their high redox potential and large specific surface area, which significantly enhance the adsorption and oxidation of OTC. Advanced characterization techniques, including X-ray diffraction, scanning electron microscopy, High Resolution-Transmission Electronic Microscope and X-ray photoelectron spectroscopy, provide a detailed analysis of the structural and functional properties of Bio-MnOx. The study also reveals the crucial role of Mn(III) intermediates and reactive oxygen species in the OTC degradation process, with quenching experiments validating their substantial impact on efficiency. Laccase activity, a key manganese-oxidizing enzyme, is assessed spectrophotometrically, further highlighting the enzymatic contribution to Mn(II) oxidation and OTC breakdown. This research contributes valuable insights and approaches for the targeted bioremediation of OTC-contaminated aquatic environments, offering a promising strategy for combating pollution from antibiotics and analogous compounds.

Efficient biodecolorization of direct black 22 Azo Dye by Aspergillus tamarii Kita UCP1279 isolated from caatinga soil

The textile industry is a major consumer of water, generating large volumes of wastewater contaminated with harmful substances, particularly azo dyes, which contain aromatic rings, amines, and sulfonic groups that contribute to their environmental toxicity. The use of microbial agents for wastewater treatment offers a cost-effective and sustainable solution, minimizing sludge production. Fungi from the Caatinga biome have demonstrated potential for bioremediation, especially under extreme environmental conditions. This study explores the ability of Aspergillus tamarii Kita to decolorize the azo dye Direct Black 22 (DB22) under varying conditions, including the use of both active and inactive fungal biomass, in static and agitated systems (120 rpm), at a controlled temperature of 30°C. Dye concentrations of 50, 125, and 250 mg/L were evaluated over time intervals of 75, 180, and 180 minutes, respectively. The influence of dissolved oxygen concentration and redox potential on the decolorization process was also investigated to identify optimal treatment conditions. Decolorization efficiency was quantified via spectrophotometric analysis. Results revealed decolorization rates of 100%, 97%, and 63% for the respective dye concentrations, with active biomass in agitated conditions achieving the highest removal rates. The study further demonstrated that dissolved oxygen levels and redox potential are critical factors in enhancing dye decolorization. These findings underscore the bioremediation potential of Aspergillus tamarii Kita in treating textile dye effluents, offering a promising approach to sustainable industrial wastewater management.

Physicochemical Stimulus-Responsive Systems Targeted with Antibody Derivatives.

The application of monoclonal antibodies and antibody fragments with the advent of recombinant antibody technology has made notable progress in clinical trials to provide a regulated drug release and extra targeting to the special conditions in the function site. Modification of antibodies has facilitated using mAbs and antibody fragments in numerous models of therapeutic and detection utilizations, such as stimuli-responsive systems. Antibodies and antibody derivatives conjugated with diverse stimuli-responsive materials have been constructed for drug delivery in response to a wide range of endogenous (electric, magnetic, light, radiation, ultrasound) and exogenous (temperature, pH, redox potential, enzymes) stimuli. In this report, we highlighted the recent progress on antibody-conjugated stimuli-responsive and dual/multi-responsive systems that affect modern medicine by improving a multitude of diagnostic and treatment strategies.

Design and Characterization of Novel A2B2 Porphyrins: Solar Cell Applications, Antimicrobial Properties, and Molecular Docking Insights

We synthesized novel A2B2 porphyrin derivatives (5a-e, 7a,b) with yields of 60-73%. Porphyrin 2 was prepared by reacting dipyrromethane 1 with p-bromobenzaldehyde. Porphyrin 2 was then treated with n-BuLi in DMF at -15°C to produce porphyrin 3. The final compounds, 5a-e and 7a,b, were synthesized by reacting porphyrin 3 with activated nitriles (4a-e) and thiazolone derivatives (6a,b). The structures of the novel compounds were confirmed using infrared (IR) spectroscopy, proton nuclear magnetic resonance (1H-NMR), carbon-13 nuclear magnetic resonance (13C-NMR), mass spectrometry (MS), and elemental analysis. DFT calculations were used to explore the electronic structures and energy levels of the synthesized compounds. Compounds 7a and 7b showed improved electron transfer efficiency compared to 5a-e, with HOMO and LUMO levels aligned for optimal DSSC performance. The HOMO levels are below the electrolyte's redox potential (-5.2 eV), and the LUMO levels are above TiO2's conduction band (-4.2 eV), facilitating efficient electron injection and dye regeneration. Key parameters such as open-circuit voltage (VOC), free energy of injection (ΔGinj), and regeneration (ΔGreg) were calculated, highlighting these compounds' potential for DSSC applications. The newly synthesized compounds were tested for antibacterial activity against C. albicans, B. subtilis, and E. coli. Compounds 5e (MIC50 3.125 µg/mL, with inhibition zone 45 mm against B. subtilis) and (MIC50 12.5 µg/mL, with inhibition zone 31 mm against E. coli) and 7a (MIC50 3.125 µg/mL, with inhibition zone 44 mm against B. subtilis) and (MIC50 12.5 µg/mL, with inhibition zone 30 mm against E. coli) showed the highest antimicrobial activity. Compound 5e's carboxylic acid group likely enhances activity through strong hydrogen bonding and improved solubility, aiding interaction with microbial enzymes or cell walls. Compound 7a's dimalononitrile groups, being highly electron-withdrawing, increase reactivity, while phenylthiazolidine rings offer additional binding sites through hydrogen bonding and pi-stacking interactions. Docking studies of the most potent antibacterial porphyrin analogues, 5e and 7a, against the target protein PDB: 1ECl showed promising results. Compound 5e achieved a docking score of ‐7.9559 kcal/mol with an RMSD of 1.9743 Å, while compound 7a had an even better score of ‐8.9174 kcal/mol. Compound 7a formed interactions with two H-acceptors from its cyano groups, binding to Arg136 and Lys488, and a Pi-H interaction between the thiazolone ring and Asn158, with distances of 3.19, 3.63, and 3.71 Å, respectively.

Enabling Data-Driven Process Dynamic Modelling for Extractive Leaching and Chemical Precipitation

To address the limitations of static models and gain insight into the processes of extractive leaching and chemical precipitation, a data-driven dynamic modelling strategy is proposed using a Lithium-ion battery recycling case study. The data correlations among pH, temperature, redox potential, conductivity and system state are investigated. Predictive models are then developed to describe the system state online and are employed as surrogate models for time-intensive offline chemical analyses. This enables further process optimization, such as time-saving measures and improved process efficiency through dynamic parameter studies. The proposed strategy serves as a guideline for dynamic modelling and integrates big data methodologies into chemical engineering.

Cofactor F420 tail length distribution in different environmental samples

Cofactor F420 is an electron carrier playing a crucial role in a variety of microorganisms during redox reactions of the primary and secondary metabolism due to its low redox potential and thus arouses increasing interest. In this study, cofactor F420 glutamyl tail length spectra in various habitats like manure, compost, soil, and digester sludge samples and their respective microbial communities were investigated using high performance liquid chromatography and an amplicon sequencing approach A previous in-silico study was used to identify F420 producing microorganisms. The highest concentration of cofactor F420 could be achieved in the horse manure, digester sludge, and mixed manure samples, which was approximately 100-fold higher than in all the other samples. The high content of the cofactor in the samples with high O2 availability pointed to the important role of the cofactor not only in redox reactions of anaerobic but also for aerobic microorganisms and indicated its ubiquitous character. The most abundant derivate was F420-3 comprising the largest part of the cofactor derivates in seven out of ten samples. The high abundance of F420-3 in samples with distinct properties (e.g. O2 and H2O availability) showed its important role in redox reactions of the primary and secondary metabolism among prokaryotes.