A Monocrystalline Coordination Polymer with Multiple Redox Centers as a High-Performance Cathode for Lithium-Ion Batteries.

Coordination polymers can take advantage of both transition metal redox and organic ligand redox, thus serving as promising cathodes with multiple redox centers toward higher-performance lithium-ion batteries (LIBs). Here, we selected the high-capacity carbonyl compound of chloranilic acid (CA) as organic ligand to coordinate with the high-voltage Cu2+ as transition metal node and successfully synthesized copper(II) chloranilate (CuCA) with π-d conjugation, layered structure and monocrystalline nature. The resulting CuCA presents inorganic and organic redox centers, high electronic conductivity and fast Li+ diffusion kinetics, leading to high discharge capacity (297.0 mAh g-1 at 50 mA g-1 ), excellent rate capability (160.6 mAh g-1 at 1000 mA g-1 ) and good cycling stability (165.5 mAh g-1 at 500 mA g-1 after 50 cycles) with quasi-solid-state electrolyte. This work will provide insightful understanding of the materials design strategies to develop more efficient coordination polymer cathodes for LIBs.

Spatially Separating Redox Centers on Z-Scheme ZnIn2 S4 /BiVO4 Hierarchical Heterostructure for Highly Efficient Photocatalytic Hydrogen Evolution.

Photocatalysis technology using solar energy for hydrogen (H2 ) production still faces great challenges to design and synthesize highly efficient photocatalysts, which should realize the precise regulation of reactive sites, rapid migration of photoinduced carriers and strong visible light harvest. Here, a facile hierarchical Z-scheme system with ZnIn2 S4 /BiVO4 heterojunction is proposed, which can precisely regulate redox centers at the ZnIn2 S4 /BiVO4 hetero-interface by accelerating the separation and migration of photoinduced charges, and then enhance the oxidation and reduction ability of holes and electrons, respectively. Therefore, the ZnIn2 S4 /BiVO4 heterojunction exhibits excellent photocatalytic performance with a much higher H2 -evolution rate of 5.944 mmol g-1 h-1 , which is about five times higher than that of pure ZnIn2 S4 . Moreover, this heterojunction shows good stability and recycle ability, providing a promising photocatalyst for efficient H2 production and a new strategy for the manufacture of remarkable photocatalytic materials.

Biomimetic Membranes for Multi-Redox Center Proteins.

His-tag technology was applied for biosensing purposes involving multi-redox center proteins (MRPs). An overview is presented on various surfaces ranging from flat to spherical and modified with linker molecules with nitrile-tri-acetic acid (NTA) terminal groups to bind his-tagged proteins in a strict orientation. The bound proteins are submitted to in situ dialysis in the presence of lipid micelles to form a so-called protein-tethered bilayer lipid membrane (ptBLM). MRPs, such as the cytochrome c oxidase (CcO) from R. sphaeroides and P. denitrificans, as well as photosynthetic reactions centers (RCs) from R. sphaeroides, were thus investigated. Electrochemical and surface-sensitive optical techniques, such as surface plasmon resonance, surface plasmon-enhanced fluorescence, surface-enhanced infrared absorption spectroscopy (SEIRAS) and surface-enhanced resonance Raman spectroscopy (SERRS), were employed in the case of the ptBLM structure on flat surfaces. Spherical particles ranging from µm size agarose gel beads to nm size nanoparticles modified in a similar fashion were called proteo-lipobeads (PLBs). The particles were investigated by laser-scanning confocal fluorescence microscopy (LSM) and UV/Vis spectroscopy. Electron and proton transfer through the proteins were demonstrated to take place, which was strongly affected by the membrane potential. MRPs can thus be used for biosensing purposes under quasi-physiological conditions.

Versatile Nitrogen-Centered Organic Redox-Active Materials for Alkali Metal-Ion Batteries.

Versatile nitrogen-centered organic redox-active molecules have gained significant attention in alkali metal-ion batteries (AMIBs) due to their low cost, low toxicity, and ease of preparation. Specially, their multiple reaction categories (anion/cation insertion types of reaction) and higher operating voltage, when compared to traditional conjugated carbonyl materials, underscore their promising prospects. However, the high solubility of nitrogen-centered redox active materials in organic electrolyte and their low electronic conductivity contribute to inferior cycling performance, sluggish reaction kinetics, and limited rate capability. This review provides a detailed overview of nitrogen-centered redox-active materials, encompassing their redox chemistry, solutions to overcome shortcomings, characterization of charge storage mechanisms, and recent progress. Additionally, prospects and directions are proposed for future investigations. It is anticipated that this review will stimulate further exploration of underlying mechanisms and interface chemistry through in situ characterization techniques, thereby promoting the practical application of nitrogen-centered redox-active materials in AMIBs.

Adsorption-Assisted Redox Center in Porous Organic Frameworks for Boosting Lithium Storage.

Due to the designable structure and capacity, organic materials are promising candidates for lithium-ion batteries. Herein, we report a novel type of porous organic frameworks (POFs) based on the coupling reaction of diazonium salt as the anodes for lithium ion storage. The active center containing an azo group and the adjacent lithium-philic adsorption site is constructed to investigate the electrochemical behaviors and reaction mechanism. As synthesized POF material (named as POF-AN) exhibits high reversible lithium storage capacities of 523 mAh g-1 at 0.5 A g-1 and 445 mAh g-1 at 2.0 A g-1 after 1500 cycles, showing excellent cycle stability and rate performance. The detailed characterizations reveal that the azo group can act as an electrochemical active site that reversibly bonds with Li-ions, and the adjacent oxygen atoms can electrostatically adsorb with Li-ions to promote the lithium storage reaction. This adsorption-assisted three-atom redox center is beneficial to synergistically enhance the adsorption and intercalation of lithium ions, which can further improve the capacity and cycle stability. By replacing the precursor, it is also facile to synthesize more similar structure types. The reversible redox chemistry of the adsorption-assisted three-atom active center provides new opportunities for the development of long lifespan and high-rate organic anodes.

Regulating the redox centers of Fe through the enrichment of Mo moiety for persulfate activation: A new strategy to achieve maximum persulfate utilization efficiency.

Persulfate Fe-based catalytic oxidation is considered as one of the most attractive strategy for the growing concerns of water pollution. However, the undesirable FeIII/FeII redox cycle restrict them from attending the sustainable activity during practical applications. This study was intended to develop a new strategy to regulate the redox cycles of FeIII/FeII by introducing the second redox center of MoS42- in the interlayers of Fe-based layered double hydroxide (FeMgAl-MoS4 LDH). Based on the first-order kinetic model, the fabricated FeMgAl-MoS4 catalyst was 10-100 fold more reactive than the bench marked peroxymonosulfate (PMS) activators including FeMgAl LDHs and other widely reported nano-catalysts such as Co3O4, Fe3O4, α-MnO2, CuO-Fe3O4 and Fe3O4. The enhanced catalytic activity of FeMgAl-MoS4 LDH was related to the continuous regeneration of active sites (FeII/MoIV), excellent PMS utilization efficiency and generation of abundant free radicals. Moreover, the FeMgAl-MoS4/PMS system shows an effective pH range from 3.0 to 7.0 and the degradation kinetics of parahydroxy benzoic acid (PHB) were not effected in the presence of huge amount of background electrolytes and natural organic matters. Based on the in-situ electron paramagnetic resonance spectroscopy (EPR), chemical scavengers, XPS analysis and gas chromatography couple with mass spectrometer (GC-MS), a degradation pathway based on dominant free radicals (•SO4- and •OH), passing through the redox cycles of FeIII/FeII and MoVI/MoIV was proposed for PMS activation. We believe that this strategy of regulating the redox center through MoS42- not only provides a base to prepare new materials with stable catalytic activity but also broaden the scope of Fe-based material for real application of contaminated water.

Resolving the Mystery of the Elusive Peak: Negative Differential Resistance in Redox Proteins.

Vertical molecular transistors are used to explain the nonconformal electron transfer results obtained for redox proteins. The transport characteristics of a negative differential resistance peak as appears in the transport data of azurin and its nonredox derivative are explored. A correlation between the peak and its redox center is demonstrated.