Ultrasensitive photoelectrochemical immunosensor based on Dual-Photosensitive electrodes

In the study, a photoelectrochemical (PEC) immunosensor based on dual-photosensitive electrodes was developed for cardiac troponin I (cTnI) detection. The sensing photocathode with biometric functions was prepared by CuInS₂ and narrow band gap semiconductor In₂S₃ as the counter electrode. In this way, the separation of photoanode and biometric events was realized, and the ability of stability of the immunosensor could be effectively improved. Moreover, the attraction to the photogenerated electrons (e^-) from photoanode would be increased by the abundant holes (h⁺) of photocathode, under the radiation of light. This tremendously improves the photoelectric response, which further improves the sensitivity of the immunosensor. The controllable-synthesis uncomplicated photoelectric material not only accords with the principle of simplicity of electrode modification but also makes the immunosensor more conducive to the practical application. Additionally, even in the case of zero bias voltage, the constructed PEC immunosensor can operate with high efficiency, namely, self-powered. The immunosensor could provide the quantitative readout photocurrent to a concentration of cTnI in the range of 0.10 pg/mL to 1.00 μg/mL and the detection limit was 0.0113 pg/mL under the optimal experimental conditions. With favorable performance in terms of anti-interference, stability, specificity and reproducibility, this immunosensor will provide new prospects for general PEC bioanalysis development.

Effect of MnO2 Polymorphs' Structure on Low-Temperature Catalytic Oxidation: Crystalline Controlled Oxygen Vacancy Formation

MnO₂ polymorphs (α-, β-, and ε-MnO₂) were synthesized, and their chemical/physical properties for CO oxidation were systematically studied using multiple techniques. Density functional theory (DFT) calculations and temperature-programmed experiments reveal that β-MnO₂ shows low energies for oxygen vacancy generation and excellent redox properties, exhibiting significant CO oxidation activity (T₉₀ = 75 °C) and stability even under a humid atmosphere. For the first time, we report that the specific reaction rate for β-MnO₂ (0.135 molecule_CO·nm^-2·s^-1 at 90 °C) is roughly approximately 4 and 17 times higher than that of ε-MnO₂ and α-MnO₂, respectively. The specific reaction rate order (β-MnO₂ > ε-MnO₂ > α-MnO₂) is not only in good agreement with reduction rates (CO-TPSR measurements) but also agrees with the DFT calculation. In combination with in situ spectra and intrinsic kinetic studies, the mechanisms of CO oxidation over various crystal structures of MnO₂ were proposed as well. We believe the new insights from this study will largely inspire the design of such a kind of catalyst.

Manganese-Based Tunnel-Type Cathode Materials for Secondary Li-Ion and K-Ion Batteries

The rational design of novel cathode materials remains a key pursuit in the development of (post) Li-ion batteries. Considering the relative ionic and Stokes radii and open frameworks with large tunnels, Na-based compounds can act as versatile cathodes for monovalent Li-ion and post-Li-ion batteries. Here, tunnel-type sodium insertion material Na_0.44MnO₂ is demonstrated as an intercalation host for Li-ion and K-ion batteries. The rod-shaped Na_0.44MnO₂ was synthesized by a solution combustion method assuming an orthorhombic structure (space group Pbam), which led to Na_0.11K_0.27MnO₂ (NKMO) and Na_0.18Li_0.51MnO₂ (NLMO) cathodes for K-ion batteries and Li-ion batteries, respectively, via facile electrochemical ion exchange from Na_0.44MnO₂. These new compositions, NKMO and NLMO, exhibited capacities of ∼74 and 141 mAh g^-1, respectively (at a rate of C/20), with excellent cycling stability. The underlying mechanistic aspects (structural changes and charge storage mechanism) in these cathode compositions were probed by combining ex situ structural, spectroscopy, and electrochemical tools. Tunnel-type Na_0.44MnO₂ forms a versatile cathode material for non-aqueous alkali-ion batteries.

A Better Zn-Ion Storage Device: Recent Progress for Zn-Ion Hybrid Supercapacitors

As a new generation of Zn-ion storage systems, Zn-ion hybrid supercapacitors (ZHSCs) garner tremendous interests recently from researchers due to the perfect integration of batteries and supercapacitors. ZHSCs have excellent integration of high energy density and power density, which seamlessly bridges the gap between batteries and supercapacitors, becoming one of the most viable future options for large-scale equipment and portable electronic devices. However, the currently reported two configurations of ZHSCs and corresponding energy storage mechanisms still lack systematic analyses. Herein, this review will be prudently organized from the perspectives of design strategies, electrode configurations, energy storage mechanisms, recent advances in electrode materials, electrolyte behaviors and further applications (micro or flexible devices) of ZHSCs. The synthesis processes and electrochemical properties of well-designed Zn anodes, capacitor-type electrodes and novel Zn-ion battery-type cathodes are comprehensively discussed. Finally, a brief summary and outlook for the further development of ZHSCs are presented as well. This review will provide timely access for researchers to the recent works regarding ZHSCs.

A highly compressible hydrogel electrolyte for flexible Zn-MnO2 battery

Compressibility of zinc-manganese oxide (Zn-MnO₂) batteries is an essential element of modern flexible electronics. Hydrogel electrolytes with superior elasticity and compressibility are highly demand to guarantee a stable energy output of the flexible Zn-MnO₂ battery. Herein, a highly compressible hydrogel electrolyte was developed by introducing soybean protein isolate nanoparticles (SPI) into covalently cross-linked polyacrylamide (PAAM) polymer networks. The SPI/PAAM hydrogel electrolyte for Zn-MnO₂ battery possessed outstanding reversible compressibility due to the aggregation of SPI nanoparticles on the PAAM chains through the weak electrostatic interaction, which could dissipate energy effectively. Consequently, the Zn-MnO₂ battery based on the compressible hydrogel electrolyte displayed a decent specific capacity (299.3 mA h g^-1) and desirable capacity retention rate (78.2%) after 500 charge/discharge cycles. Notably, the device could maintain stable power output under 96% compress strain and light the bulb even under severe mechanical stimulation like being-bent and hammered. It's believed that the compressible Zn-MnO₂ batteries hold enormous potential as the energy storage devices in the field of flexible wearable electronics.

Improved ORR/OER bifunctional catalytic performance of amorphous manganese oxides prepared by photochemical metal-organic deposition

Transition metal oxide nanomaterials or nanocomposites containing transition metal oxides have the potential to replace traditional catalysts for electrochemical applications, photocatalysis, and energy storage. Amorphous manganese oxide catalysts were prepared via photochemical metal-organic deposition (PMOD). Through XRD, SEM-EDS, Raman spectroscopy, FTIR spectroscopy, HRTEM-EDS, and XPS, we confirmed that amorphous manganese oxide catalysts were successfully prepared. Amorphous catalysts prepared with different photolysis times were compared in terms of their performance for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), and catalyst MnO x -PMOD48 showed the best performance because of its high Mn3+ proportion and electrochemically active surface area. MnO x -PMOD48 showed better ORR/OER performance than the crystalline MnO x and MnO x /Ti4O7 catalysts from our previous work. Following our previous work on crystalline manganese oxide catalysts, we added Ti4O7 during the PMOD process with 48 h of treatment and obtained the amorphous catalyst MnO x /Ti4O7-PMOD. MnO x /Ti4O7-PMOD was supported by Ti4O7 particles, which led to improved stability. The ORR/OER catalytic activity of MnO x /Ti4O7-PMOD was better than that of crystalline catalyst MnO x /Ti4O7-300, which was the best crystalline catalyst in our previous work. We also compared lithium-oxygen batteries assembled with MnO x /Ti4O7-PMOD and MnO x /Ti4O7-300. The battery performance tests confirmed that the amorphous manganese catalyst had better ORR/OER bifunctional catalytic performance than the crystalline manganese catalyst because of its high defect state with more abundant edge active sites and more surface-exposed catalytic active sites.

Construction of a ternary MoO2/Ni/C hybrid towards lithium-ion batteries as a high-performance electrode

The high lithium storage performance of 3D flower-like MoO2/Ni/C through a temperature annealing strategy is benefitted from the high capacitive contribution, high electrical conductivity, and good structural stability.

β-MnO2 nanoparticles as heterogenous catalysts for aerobic oxidative transformation of alcohols to carbonyl compounds, nitriles, and amides

β-MnO2 nanoparticles exhibit high catalytic performance for the aerobic oxidation of various aromatic, allylic, and heteroaromatic alcohols and one-pot tandem oxidation of alcohols to nitriles and amides in the presence of NH3.

Challenges and Strategies of Low-Cost Aluminum Anodes for High-Performance Al-Based Batteries

The ever-growing market of electric vehicles and the upcoming grid-scale storage systems have stimulated the fast growth of renewable energy storage technologies. Aluminum-based batteries are considered one of the most promising alternatives to complement or possibly replace the current lithium-ion batteries owing to their high specific capacity, good safety, low cost, light weight, and abundant reserves of Al. However, the anode problems in primary and secondary Al batteries, such as, self-corrosion, passive film, and volume expansion, severely limit the batteries' practical performance, thus hindering their commercialization. Herein, an overview of the currently emerged Al-based batteries is provided, that primarily focus on the recent research progress for Al anodes in both primary and rechargeable systems. The anode reaction mechanisms and problems in various Al-based batteries are discussed, and various strategies to overcome the challenges of Al anodes, including surface oxidation, self-corrosion, volume expansion, and dendrite growth, are systematically summarized. Finally, future research perspectives toward advanced Al batteries with higher performance and better safety are presented.

A rechargeable aqueous manganese-ion battery based on intercalation chemistry

Aqueous rechargeable metal batteries are intrinsically safe due to the utilization of low-cost and non-flammable water-based electrolyte solutions. However, the discharge voltages of these electrochemical energy storage systems are often limited, thus, resulting in unsatisfactory energy density. Therefore, it is of paramount importance to investigate alternative aqueous metal battery systems to improve the discharge voltage. Herein, we report reversible manganese-ion intercalation chemistry in an aqueous electrolyte solution, where inorganic and organic compounds act as positive electrode active materials for Mn2+ storage when coupled with a Mn/carbon composite negative electrode. In one case, the layered Mn0.18V2O5·nH2O inorganic cathode demonstrates fast and reversible Mn2+ insertion/extraction due to the large lattice spacing, thus, enabling adequate power performances and stable cycling behavior. In the other case, the tetrachloro-1,4-benzoquinone organic cathode molecules undergo enolization during charge/discharge processes, thus, contributing to achieving a stable cell discharge plateau at about 1.37 V. Interestingly, the low redox potential of the Mn/Mn2+ redox couple vs. standard hydrogen electrode (i.e., -1.19 V) enables the production of aqueous manganese metal cells with operational voltages higher than their zinc metal counterparts.

Interfacial Strategies for Suppression of Mn Dissolution in Rechargeable Battery Cathode Materials

It is urgent to develop high-performance cathode materials for rechargeable batteries to address the globally growing concerns of energy shortage and environmental pollution. Among many candidate materials, Mn-based materials are promising and already used in some commercial batteries. Yet, their applicable future in reversible energy storage is severely plagued by the notorious Mn dissolution behaviors associated with structural instability during long-term cycling. As such, interfacial strategies aiming to protect Mn-based electrodes against Mn dissolution are being widely developed in recent years. A variety of interface-driven designs have been reported to function efficiently in suppressing Mn dissolution, necessitating a timely summary of recent advancements in the field. In this review, various interfaces, including the prebuilt interface and the electrochemically induced interface, to suppress Mn dissolution for Mn-based cathodes are discussed in terms of their fabrication details and functional outcomes. Perspectives for the future of interfacial strategies aiming at Mn dissolution suppression are also shared.

Reaction mechanisms for electrolytic manganese dioxide in rechargeable aqueous zinc-ion batteries

This study reports the phase transformation behaviour associated with electrolytic manganese dioxide (EMD) utilized as the positive electrode active material for aqueous zinc-ion batteries. Electrochemical techniques, including galvanostatic charge–discharge and rotating ring-disk electrode measurements, and microstructural techniques, using X-ray powder diffraction, scanning electron microscopy, and transmission/scanning transmission electron microscopy, were utilized to characterize the positive electrode at different stages of discharge and charge of zinc-ion cells. The results indicate that, during discharge, a fraction of EMD undergoes a transformation to ZnMn₂O₄ (spinel-type) and Zn²⁺ is intercalated into the tunnels of the γ- and ε-MnO₂ phases, forming Zn_xMnO₂ (tunnel-type). When a critical concentration of Mn³⁺ in the intercalated Zn_xMnO₂ species is reached, a disproportionation/dissolution reaction is triggered leading to the formation of soluble Mn²⁺ and hydroxide (OH^–) ions; the latter precipitates as zinc hydroxide sulfate (ZHS, Zn₄(OH)₆(SO₄)·5H₂O) by combination with the ZnSO₄/H₂O electrolyte. During charge, Zn²⁺ is reversibly deintercalated from the intergrown tunneled phases (γ-/ε-Zn_xMnO₂), Mn²⁺ is redeposited as layered chalcophanite (ZnMn₃O₇·3H₂O), and ZHS is decomposed by protons (H⁺) formed during the electrochemical deposition of chalcophanite.

Optimization of Monomer Molecular Structure for Polymer Electrodes Fabricated through in-situ Electro-Polymerization Strategy

In-situ electro-polymerization of redox-active monomers has been proved to be a novel and facile strategy to prepare polymer electrodes with superior electrochemical performance. The monomer molecular structure would have a profound impact on electro-polymerization behavior and thus electrochemical performance. However, this impact is poorly understood and has barely been investigated yet. Herein, three carbazole-based monomers, 9-phenylcarbazole (CB), 1,4-bis(carbazol-9-yl)benzene (DCB), and 2,6-bis(carbazol-9-yl)naphthalene (DCN), were applied to study the above issue systematically and achieve excellent long cycle performance. The monomers were rationally designed with different polymerizable sites and solubilities. It was found that a monomer with increased polymerizable sites and decreased solubility brought about enhanced electrochemical performance. This is because poor solubility could enhance utilization of the monomer for polymerization and more polymerizable sites could lead to a stable crosslinked polymer network after electro-polymerization. DCN with four polymerizable sites and the poorest solubility displayed the best electrochemical performance, which showed stable cycling up to 5000 cycles with high capacity retention of 76.2 % (among the best cycle in the literature). Our work for the first time reveals the relationship between monomer structure and in-situ electro-polymerization behavior. This work could shed light on the structure design/optimization of monomers for high-performance polymer electrodes prepared through in-situ electro-polymerization.

Two-Phase Transition Induced Amorphous Metal Phosphides Enabling Rapid, Reversible Alkali-Metal Ion Storage

Metal phosphides as anode materials for alkali-metal ion batteries have captured considerable interest due to their high theoretical capacities and electronic conductivity. However, they suffer from huge volume expansion and element segregation during repetitive insertion/extraction of guest ions, leading to structure deterioration and rapid capacity decay. Herein, an amorphous Sn_0.5Ge_0.5P₃ was constructed through a two-phase intermediate strategy based on the elemental composition modulation from two crystalline counterparts and applied in alkali-metal ion batteries. Differing from crystalline P-based compounds, the amorphous structure of Sn_0.5Ge_0.5P₃ effectively reduces the volume variation from above 300% to 225% during cycling. The ordered distribution of cations and anions in the short-range ensures the uniform distribution of each element during cycles and thus contributes to durable cycling stability. Moreover, the long-range disordered structure of amorphous material shortens the ion transport distance, which facilitates diffusion kinetics. Benefiting from the aforementioned effects, the amorphous Sn_0.5Ge_0.5P₃ delivers a high Na storage capacity of 1132 mAh g^-1 at 0.1 A g^-1 over 100 cycles. Even at high current densities of 2 and 10 A g^-1, its capacities still reach 666 and 321 mAh g^-1, respectively. As an anode for Li storage, the Sn_0.5Ge_0.5P₃ similarly also exhibits better cycling stability and rate performance compared to its crystalline counterparts. Significantly, the two-phase transition strategy is generally applicable to achieving other amorphous metal phosphides such as GeP₂. This work would be helpful for constructing high-performance amorphous anode materials for alkali-metal ion batteries.

Chemical Heterointerface Engineering on Hybrid Electrode Materials for Electrochemical Energy Storage

The chemical heterointerfaces in hybrid electrode materials play an important role in overcoming the intrinsic drawbacks of individual materials and thus expedite the in-depth development of electrochemical energy storage. Benefiting from the three enhancement effects of accelerating charge transport, increasing the number of storage sites, and reinforcing structural stability, the chemical heterointerfaces have attracted extensive interest and the electrochemical performances of hybrid electrode materials have been significantly optimized. In this review, recent advances regarding chemical heterointerface engineering in hybrid electrode materials are systematically summarized. Especially, the intrinsic behaviors of chemical heterointerfaces on hybrid electrode materials are refined based on built-in electric field, van der Waals interaction, lattice mismatch and connection, electron cloud bias and chemical bond, and their combination. The strategies for introducing chemical heterointerfaces are classified into in situ local transformation, in situ growth, cosynthesis, and other strategy. The recent progress about the chemical heterointerfaces engineering specially focusing on metal-ion batteries, supercapacitors, and Li-S batteries are introduced in detail. Furthermore, the classification and characterization of chemical heterointerfaces are briefly described. Finally, the emerging challenges and perspectives about future directions of chemical heterointerface engineering are proposed.

Local and Bulk Probe of Vanadium-Substituted α-Manganese Oxide (α-KxVyMn8-yO16) Lithium Electrochemistry

A series of V-substituted α-MnO₂ (K_xMn_8-yV_yO₁₆·nH₂O, y = 0, 0.2, 0.34, 0.75) samples were successfully synthesized without crystalline or amorphous impurities, as evidenced by X-ray diffraction (XRD) and Raman spectroscopy. Transmission electron microscopy (TEM) revealed a morphological evolution from nanorods to nanoplatelets as V-substitution increased, while electron-energy loss spectroscopy (EELS) confirmed uniform distribution of vanadium within the materials. Rietveld refinement of synchrotron XRD showed an increase in bond lengths and a larger range of bond angles with increasing V-substitution. X-ray absorption spectroscopy (XAS) of the as-prepared materials revealed the V valence to be >4+ and the Mn valence to decrease with increasing V content. Upon electrochemical lithiation, increasing amounts of V were found to preserve the Mn-Mn_edge relationship at higher depths of discharge, indicating enhanced structural stability. Electrochemical testing showed the y = 0.75 V-substituted sample to deliver the highest capacity and capacity retention after 50 cycles. The experimental findings were consistent with the predictions of density functional theory (DFT), where the V centers impart structural stability to the manganese oxide framework upon lithiation. The enhanced electrochemistry of the y = 0.75 V-substituted sample is also attributed to its smaller crystallite size in the form of a nanoplatelet morphology, which promotes facile ion access via reduced Li-ion diffusion path lengths.

Synthesis of MnO/C/Co3O4 nanocomposites by a Mn2+-oxidizing bacterium as a biotemplate for lithium-ion batteries

The biotemplate and bioconversion strategy represents a sustainable and environmentally friendly approach to material manufacturing. In the current study, biogenic manganese oxide aggregates of the Mn²⁺-oxidizing bacterium Pseudomonas sp. T34 were used as a precursor to synthesize a biocomposite that incorporated Co (CMC-Co) under mild shake-flask conditions based on the biomineralization process of biogenic Mn oxides and the characteristics of metal ion subsidies. X-ray photoelectron spectroscopy, phase composition and fine structure analyses demonstrated that hollow MnO/C/Co₃O₄ multiphase composites were fabricated after high-temperature annealing of the biocomposites at 800°C. The cycling and rate performance of the prepared anode materials for lithium-ion batteries were compared. Due to the unique hollow structure and multiphasic state, the reversible discharge capacity of CMC-Co remained at 650 mAh g^-1 after 50 cycles at a current density of 0.1 Ag^-1, and the coulombic efficiency remained above 99% after the second cycle, indicating a good application potential as an anode material for lithium-ion batteries.

Promoting the Performance of Li-CO2 Batteries via Constructing Three-Dimensional Interconnected K+ Doped MnO2 Nanowires Networks

Nowadays, Li–CO₂ batteries have attracted enormous interests due to their high energy density for integrated energy storage and conversion devices, superiorities of capturing and converting CO₂. Nevertheless, the actual application of Li–CO₂ batteries is hindered attributed to excessive overpotential and poor lifespan. In the past decades, catalysts have been employed in the Li–CO₂ batteries and been demonstrated to reduce the decomposition potential of the as-formed Li₂CO₃ during charge process with high efficiency. However, as a representative of promising catalysts, the high costs of noble metals limit the further development, which gives rise to the exploration of catalysts with high efficiency and low cost. In this work, we prepared a K⁺ doped MnO₂ nanowires networks with three-dimensional interconnections (3D KMO NWs) catalyst through a simple hydrothermal method. The interconnected 3D nanowires network catalysts could accelerate the Li ions diffusion, CO₂ transfer and the decomposition of discharge products Li₂CO₃. It is found that high content of K⁺ doping can promote the diffusion of ions, electrons and CO₂ in the MnO₂ air cathode, and promote the octahedral effect of MnO₆, stabilize the structure of MnO₂ hosts, and improve the catalytic activity of CO₂. Therefore, it shows a high total discharge capacity of 9,043 mAh g⁻¹, a low overpotential of 1.25 V, and a longer cycle performance.

Facile synthesis of 2Dα-MnO2nanosheets for the removal of heavy metal ions

Removal of heavy metal ions (HMIs) has attracted great attentions due to the fact that they have serious effect on environment and human beings. Manganese oxide (MnO₂) was widely used as absorbent for the HMIs removal on account of its low-cost, eco-friendly and biocompatibility. The modification of morphological and structure is recognized as the effective route to improve the adsorption capacity. In this work, 2Dα-MnO₂nanosheets were synthesized by hydrothermal method with Al³⁺additive. With the merits of high specific surface area, high dispersity in aqueous solution and abundant surface defects, 2Dα-MnO₂nanosheets exhibited excellent HMIs adsorption performance. The maximum adsorption capacity of 2Dα-MnO₂nanosheets reached 1.604 mmol g^-1(Pb²⁺) and 0.813 mmol g^-1(Cd²⁺), respectively and can maintain stable after five cycles. Besides, the established adsorption kinetics fitted well with pseudo-second-order adsorption kinetics model. Based on the above results, 2Dα-MnO₂is efficient for the removal of HMIs and possesses remarkable practical application potential.

MnO2 -Based Materials for Environmental Applications

Manganese dioxide (MnO₂ ) is a promising photo-thermo-electric-responsive semiconductor material for environmental applications, owing to its various favorable properties. However, the unsatisfactory environmental purification efficiency of this material has limited its further applications. Fortunately, in the last few years, significant efforts have been undertaken for improving the environmental purification efficiency of this material and understanding its underlying mechanism. Here, the aim is to summarize the recent experimental and computational research progress in the modification of MnO₂ single species by morphology control, structure construction, facet engineering, and element doping. Moreover, the design and fabrication of MnO₂ -based composites via the construction of homojunctions and MnO₂ /semiconductor/conductor binary/ternary heterojunctions is discussed. Their applications in environmental purification systems, either as an adsorbent material for removing heavy metals, dyes, and microwave (MW) pollution, or as a thermal catalyst, photocatalyst, and electrocatalyst for the degradation of pollutants (water and gas, organic and inorganic) are also highlighted. Finally, the research gaps are summarized and a perspective on the challenges and the direction of future research in nanostructured MnO₂ -based materials in the field of environmental applications is presented. Therefore, basic guidance for rational design and fabrication of high-efficiency MnO₂ -based materials for comprehensive environmental applications is provided.

Recent Progress on Layered Cathode Materials for Nonaqueous Rechargeable Magnesium Batteries

Rechargeable magnesium batteries (RMBs) are promising candidates for next-generation energy storage systems owing to their high safety and the low cost of magnesium resources. One of the main challenges for RMBs is to develop suitable high-performance cathode materials. Layered materials are one of the most promising cathode materials for RMBs due to their relatively high specific capacity and facile synthesis process. This review focuses on recent progress on layered cathode materials for RMBs, including layered oxides, sulfides, selenides, and other layered materials. In addition, effective strategies to improve the electrochemical performance of layered cathode materials are summarized. Moreover, future perspectives about the application of layered materials in RMBs are also discussed. This review provides some significant guidance for the further development of layered materials for RMBs.

Orderly aligned manganese-based nanotube arrays with controllable secondary structures

By combining a hard template with a dynamic negative template, orderly aligned micrometer-length manganese nanotubes (Mn-NTs) decorated with nanopores on their walls as the secondary structure are successfully grown by electrodeposition in aqueous solution. These nanopores were characterized and analyzed statistically. It is found that these nanopores evolve along the growth direction of the Mn-NTs and their morphology is well controlled by the deposition potential. In addition, the morphology evolution of the nanopores exhibits distinguished size distribution compared with that found in conventional nanoporous foam grown solely by the dynamic template approach, which is attributed to the nanoconfinement of the hard template.

Stabilization of Organic Cathodes by a Temperature-Induced Effect Enabling Higher Energy and Excellent Cyclability

To face the challenge of all-climate application, organic rechargeable batteries must hold the capability of efficiently operating both at high temperatures (>50 °C) and low temperatures (-20 °C). However, the low electronic conductivity and high solubility of organic molecules significantly impede the development in electrochemical energy storage. This issue can be effectively diminished using functionalized porphyrin complex-based organic cathodes by the in-situ electropolymerization of electrodes at elevating temperatures during electrochemical cycling. [5,15-bis(ethynyl)-10,20-diphenylporphinato]copper(II) (CuDEPP)- and 5,15-bis(ethynyl)-10,20-diphenylporphinato (DEPP)-based cathodes are proposed as models, and it is proved that a largely improved electrochemical performance is observed in both cathodes at a high operating temperature. Reversible capacities of 249 and 105 mA h g^-1 are obtained for the CuDEPP and DEPP cathodes after 1000 cycles at 50 °C, respectively. The result indicates that the temperature-induced in situ electropolymerization strategy responds to the enhanced electrochemical performance. This study would open new opportunities for developing highly stable organic cathodes for electrochemical energy storage even at high temperatures.

Synthesis of MnO/C/NiO-Doped Porous Multiphasic Composites for Lithium-Ion Batteries by Biomineralized Mn Oxides from Engineered Pseudomonas putida Cells

A biotemplated cation-incoporating method based on bacterial cell-surface display technology and biogenic Mn oxide mineralization process was developed to fabricate Mn-based multiphasic composites as anodes for Li-ion batteries. The engineered Pseudomonas putida MB285 cells with surface-immobilized multicopper oxidase serve as nucleation centers in the Mn oxide biomineralization process, and the Mn oxides act as a settler for incorporating Ni ions to form aggregates in this process. The assays using X-ray photoelectron spectroscopy, phase compositions, and fine structures verified that the resulting material MnO/C/NiO (CMB-Ni) was porous multiphasic composites with spherical and porous nanostructures. The electrochemical properties of materials were improved in the presence of NiO. The reversible discharge capacity of CMB-Ni remained at 352.92 mAh g^-1 after 200 cycles at 0.1 A g^-1 current density. In particular, the coulombic efficiency was approximately 100% after the second cycle for CMB-Ni.

Effect of the valence state of Mn in MnOx/Ti4O7 composites on the catalytic performance for oxygen reduction reaction and oxygen evolution reaction

Manganese oxide composites with mixed valence states were prepared through the hydrothermal method by compositing with Ti₄O₇ and calcining at different temperatures, and their ORR and OER catalytic performance were investigated. The prepared catalysts were characterized by XRD, SEM-EDS, HRTEM-EDS, and XPS methods to analyse their phase constitution, morphology feature, and surface composition. The major phase of manganese oxides was Mn₃O₄, which is a one-dimensional structure, and its growth was induced by Ti₄O₇. The ORR and OER catalytic activity can be enhanced due to the preferred orientation of manganese oxides. Electrochemical measurements, namely CV, LSV and EIS, were utilized for determining the ORR and OER catalytic activity, whereas CA and ADT were used for studying the durability and stability. A Li–O₂ battery was assembled to test the electrochemical behavior and properties in practical application. MnO_x/Ti₄O₇ calcined at 300 °C exhibited the best catalytic activity of 0.72 V vs. RHE half-wave potential for ORR and 0.67 V vs. RHE overpotential for OER. The proportion of Mn³⁺ was also highest in all the MnO_x/Ti₄O₇ composites. The assembled Li–O₂ battery shows high performance with a voltage gap of only 0.85 V. Therefore, it can be affirmed that the inducement of Ti₄O₇ could strengthen the preferred orientation in manganese oxide growth and Mn³⁺ in MnO_x/Ti₄O₇ plays a vital role in catalyzing ORR and OER, with both improving the ORR and OER bifunctional catalytic performance of manganese oxides.

Manganese oxide composites with mixed valence states were prepared by compositing with Ti₄O₇ and calcination temperature could influence their ORR and OER catalytic performance observably.

A Brief Review on High-Performance Capacitive Deionization Enabled by Intercalation Electrodes

Owing to the advantages of cost-effectiveness, environmental-friendliness and high desalination capacity, capacitive deionization (CDI) has emerged as an advanced desalination technique. Recently, the ions intercalation materials inspired by sodium ion batteries have been widely implemented in CDI due to their exceptional salt removal capacity. They are able to extract sodium ions from the brine through intercalation or redox reactions, instead of electrostatic forces associated with the carbonaceous electrode. As a result, the ions intercalation materials have caught the attention of the CDI research community. In this article, the recent progress in various sodium ion intercalation materials as highly-efficient CDI electrodes is summarized and reviewed. Further, an outlook on the future development of ion intercalation electrodes is proposed.

Preintercalation Strategy in Manganese Oxides for Electrochemical Energy Storage: Review and Prospects

Manganese oxides (MnO₂ ) are promising cathode materials for various kinds of battery applications, including Li-ion, Na-ion, Mg-ion, and Zn-ion batteries, etc., due to their low-cost and high-capacity. However, the practical application of MnO₂ cathodes has been restricted by some critical issues including low electronic conductivity, low utilization of discharge depth, sluggish diffusion kinetics, and structural instability upon cycling. Preintercalation of ions/molecules into the crystal structure with/without structural reconstruction provides essential optimizations to alleviate these issues. Here, the intrinsic advantages and mechanisms of the preintercalation strategy in enhancing electronic conductivity, activating more active sites, promoting diffusion kinetics, and stabilizing the structural integrity of MnO₂ cathode materials are summarized. The current challenges related to the preintercalation strategy, along with prospects for the future research and development regarding its implementation in the design of high-performance MnO₂ cathodes for the next-generation batteries are also discussed.

Faradaic Electrodes Open a New Era for Capacitive Deionization

Capacitive deionization (CDI) is an emerging desalination technology for effective removal of ionic species from aqueous solutions. Compared to conventional CDI, which is based on carbon electrodes and struggles with high salinity streams due to a limited salt removal capacity by ion electrosorption and excessive co-ion expulsion, the emerging Faradaic electrodes provide unique opportunities to upgrade the CDI performance, i.e., achieving much higher salt removal capacities and energy-efficient desalination for high salinity streams, due to the Faradaic reaction for ion capture. This article presents a comprehensive overview on the current developments of Faradaic electrode materials for CDI. Here, the fundamentals of Faradaic electrode-based CDI are first introduced in detail, including novel CDI cell architectures, key CDI performance metrics, ion capture mechanisms, and the design principles of Faradaic electrode materials. Three main categories of Faradaic electrode materials are summarized and discussed regarding their crystal structure, physicochemical characteristics, and desalination performance. In particular, the ion capture mechanisms in Faradaic electrode materials are highlighted to obtain a better understanding of the CDI process. Moreover, novel tailored applications, including selective ion removal and contaminant removal, are specifically introduced. Finally, the remaining challenges and research directions are also outlined to provide guidelines for future research.

Covalent Organic Frameworks as Electrode Materials for Metal Ion Batteries: A Current Review

As the world moves toward electromobility, our daily lives are flooded with variety of lithium ion batteries (LIBs), and the concerns of cost, safety and environmental friendliness of LIBs spring up in the minds of scientists. Although organic electrodes have been considered as promising alternatives to their inorganic counterparts, some intrinsic weaknesses still plague scientists, such as high solubility, low conductivity and sluggish ion diffusion. The emergence of covalent organic frameworks (COFs) attracts our attention because of their robust networks and open pores that could facilitate the infiltration of electrolyte ions when used as electrodes for metal-ion batteries (MIBs). In this review, we summarized the recent progress of COFs as electrode materials, and the strategies toward enhancing electrochemical performance of COF-based electrode in MIBs are discussed. Hopefully, this review will provide a fundamental guidance for future development of COF-based electrodes.