Engineering the electronic structure of Co3O4 by carbon-doping for efficient overall water splitting

Role of Plasma in Catalyst Preparation and Modification for Oxygen Evolution Reaction

Plasma as a promising solution to catalyst synthesis and modification has received great attention in the field of electrochemical water splitting. However, a comprehensive overview detailing how plasma treatments of catalysts enhance oxygen evolution reaction (OER) performance is currently lacking. Here, we review the advances and challenges in cold plasma for catalyst preparation and modification. We discuss the underlying mechanisms responsible for enhanced OER performance on plasma-treated catalysts, where the surface area, active sites, vacancy type/content, heteroatom doping, etching, and surface functionalization could be mediated. This review aims to provide valuable insights into the role of plasma treatments in advancing OER electrocatalysis for sustainable energy applications.

Fabrication of CuWO4@MIL-101 (Fe) nanocomposite for efficient OER and photodegradation of methylene blue

The development of an efficient catalyst to meet the world's increasing energy demand and eliminate organic pollutants in water, is a concern of current researchers. In this article, a highly effective composite has been synthesized using the solvothermal approach, by incorporating CuWO4 nanoparticles into Fe-based MOF, Fe (BDC). The synthesized samples were analyzed further by some characterization techniques such as X-ray diffraction, Fourier transform infrared spectroscope (FTIR) and scanning electron microscopy. The highest catalytic activity for the oxygen evolution reaction was observed in the CuWO4@MIL-101(Fe) composite, which exhibited low overpotential 188 mV to obtained the current density of 10 mA cm-2, and a smaller Tafel slope of 40 mV dec-1. The nanocomposite CuWO4@MIL-101(Fe) material showed enhanced visible light absorption and maximum degradation of methylene blue up to 96.92 %. It has been found that this research promotes the development of an efficient MOF-based catalyst for OER and photocatalytic technology.

Recent Advancements in Co3O4-Based Composites for Enhanced Electrocatalytic Water Splitting

The pursuit of efficient and economical catalysts for water splitting, a critical step in hydrogen production, has gained momentum with the increasing demand for sustainable energy. Among the various electrocatalysts developed to date, cobalt oxide (Co3O4) has emerged as a promising candidate owing to its availability, stability, and catalytic activity. However, intrinsic limitations, including low catalytic activity and poor electrical conductivity, often hinder its effectiveness in electrocatalytic water splitting. To overcome these challenges, substantial efforts have focused on enhancing the electrocatalytic performance of Co3O4 by synthesizing composites with conductive materials, transition metals, carbon-based nanomaterials, and metal-organic frameworks. This review explores the recent advancements in Co3O4-based composites for the oxygen evolution reaction and the hydrogen evolution reaction, emphasizing strategies such as nanostructuring, doping, hybridization, and surface modification to improve catalytic performance. Additionally, it examines the mechanisms driving the enhanced activity and stability of these composites while also discussing the future potential of Co3O4-based electrocatalysts for large-scale water-splitting applications.

Inducing Intermolecular Oxygen Coupling by Introducing S and FeOOH on Co(OH)2 Nanoneedle Arrays for Industrial Water Oxidation

The design of electrocatalysts for oxygen evolution reaction (OER) remains a limitation of industrial hydrogen production by electrolysis of water. Excellent and stable OER catalysts can be developed by activating lattice oxygen and changing the reaction path. Herein, S and FeOOH on the Co(OH)2 nanoneedle arrays are introduced to construct a heterostructure (S-FeOOH/Co(OH)2/NF) as a proof of concept. Theoretical calculations and experimental suggest that the Co-O-Fe motif formed at the heterogeneous interface with the introduction of FeOOH, inducing electron transfer from Co to Fe, enhancing Co─O covalency and reducing intramolecular charge transfer energy, thereby stimulating direct intramolecular lattice oxygen coupling. Doping of S in FeOOH further accelerates electron transfer, improves lattice oxygen activity, and prevents dissolution of FeOOH. Consequently, the overpotential of S-FeOOH/Co(OH)2/NF is only 199 mV at 10 mA cm-2, and coupled with the Pt/C electrode can be up to 1 A cm-2 under 1.79 V and remain stable for over 120 h in an anion exchange membrane water electrolyzer (AEMWE). This work proposes a strategy for the design of efficient and stable electrocatalysts for industrial water electrolysis and promotes the commercialization of AEMWE.

Tuning of Oxygen Vacancies in Co3O4 Electrocatalyst for Effectiveness in Urea Oxidation and Water Splitting

The development of an excellent multifunctional electrocatalyst that is based on non-precious metal is critical for improving the electrochemical processes of the hydrogen evolution reaction (HER), the oxygen evolution reaction (OER), and the urea oxidation reaction (UOR) in alkaline media. This study demonstrates that incorporating Mo into Co3O4 facilitated the formation of rich oxygen vacancies (Vo), which promotes effective nitrate adsorption and activation in urea electrolysis. Subsequently, in situ/operando X-ray absorption spectroscopy is used to explore the active sites in Mo-Co3O4-3 under OER, indicating the oxygen vacancies are first filled with OH• in Mo-Co3O4; facilitated the pre-oxidation of low-valence Co, and promoted the reconstruction/deprotonation of intermediate Co-OOH•. Mo-Co3O4-3 electrocatalysts show impressive HER, OER, and UOR with low overpotentials of 141 mV, 220 mV, and 1.32 V, respectively, at 10 mA cm-2 in an alkaline medium. Furthermore, in situ/Operando Raman spectroscopy results reveal the importance of CoOOH active sites for enhanced electrochemical performance in Mo-Co3O4-3 compared to the pure Co3O4. The urea electrolyzer with Mo-Co3O4 electrocatalysts acts as an anode and the cathode delivers 1.42 V at 10 mA cm-2. A viable approach to creating effective UOR electrocatalysts involves synergistic engineering exploiting doping and oxygen vacancies.

Ligand-engineered Ru-doped cobalt oxides derived from metal-organic frameworks for large-current-density water splitting

The influence of the preorganized structure and chemical composition of metal-organic frameworks (MOFs) on the morphology, surface properties, and catalytic activity of the MOFs-derived metal oxides is yet to be revealed. In this work, two types of Co-MOFs with different coordination configurations are synthesized for the preparation of the structure-engineered ruthenium (Ru)-doped cobalt oxides. The effect of the preorganized coordination structure of the MOFs on the morphology and surface properties is investigated. Interestingly, the oxalate-based MOFs derived Ru-doped cobalt oxide (OX-Co3O4-Ru) exhibits much better surface wettability and more oxygen vacancies than the zeolitic imidazolate framework-67 derived Ru-doped cobalt oxide. As expected, the OX-Co3O4-Ru owns excellent catalytic properties towards both hydrogen evolution reaction and oxygen evolution reaction with an overpotential of 49 and 286 mV, respectively at a current density of 100 mA cm-2 in 1.0 M KOH. Importantly, the bifunctional OX-Co3O4-Ru catalyst offers an extremely high current density of 500 mA cm-2 at a cell voltage of 1.71 V for overall water splitting and as well demonstrates robust working stability.

Oxygen Vacancy and Interface Effect Adjusted Hollow Dodecahedrons for Efficient Oxygen Evolution Reaction

Metal-organic frameworks (MOFs) with special morphologies provide the geometric morphology and composition basis for the construction of platforms with excellent catalytic activity. In this work, cobalt-cerium composite oxide hollow dodecahedrons (Co/Cex-COHDs) with controllable morphology and tunable composition are successfully prepared via a high-temperature pyrolysis strategy using Co/Ce-MOFs as self-sacrificial templates. The construction of the hollow structure can expose a larger surface area to provide abundant active sites and pores to facilitate the diffusion of substances. The formation and optimization of phase interface between Co3O4 and CeO2 regulate the electronic structure of the catalytic site and form a fast channel favorable to electron transport, thereby enhancing the electrocatalytic oxygen evolution activity. Based on the above advantages, the optimized Co/Ce0.2-COHDs obtained an enhanced oxygen evolution reaction (OER) performance.

Plasma-Induced Oxygen Vacancies in N-Doped Hollow NiCoPBA Nanocages Derived from Prussian Blue Analogue for Efficient OER in Alkaline Media

Although water splitting is a promising method to produce clean hydrogen energy, it requires efficient and low-cost catalysts for the oxygen evolution reaction (OER). This study focused on plasma treatment's significance of surface oxygen vacancies in improving OER electrocatalytic activity. For this, we directly grew hollow NiCoPBA nanocages using a Prussian blue analogue (PBA) on nickel foam (NF). The material was treated with N plasma, followed by a thermal reduction process for inducing oxygen vacancies and N doping on the structure of NiCoPBA. These oxygen defects were found to play an essential role as a catalyst center for the OER in enhancing the charge transfer efficiency of NiCoPBA. The N-doped hollow NiCoPBA/NF showed excellent OER performance in an alkaline medium, with a low overpotential of 289 mV at 10 mA cm^-2 and a high stability for 24 h. The catalyst also outperformed a commercial RuO₂ (350 mV). We believe that using plasma-induced oxygen vacancies with simultaneous N doping will provide a novel insight into the design of low-priced NiCoPBA electrocatalysts.

In Situ Filling of the Oxygen Vacancies with Dual Heteroatoms in Co3O4 for Efficient Overall Water Splitting

Electrocatalytic water splitting is a crucial area in sustainable energy development, and the development of highly efficient bifunctional catalysts that exhibit activity toward both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is of paramount importance. Co₃O₄ is a promising candidate catalyst, owing to the variable valence of Co, which can be exploited to enhance the bifunctional catalytic activity of HER and OER through rational adjustments of the electronic structure of Co atoms. In this study, we employed a plasma-etching strategy in combination with an in situ filling of heteroatoms to etch the surface of Co₃O₄, creating abundant oxygen vacancies, while simultaneously filling them with nitrogen and sulfur heteroatoms. The resulting N/S-V_O-Co₃O₄ exhibited favorable bifunctional activity for alkaline electrocatalytic water splitting, with significantly enhanced HER and OER catalytic activity compared to pristine Co₃O₄. In an alkaline overall water-splitting simulated electrolytic cell, N/S-V_O-Co₃O₄ || N/S-V_O-Co₃O₄ showed excellent overall water splitting catalytic activity, comparable to noble metal benchmark catalysts Pt/C || IrO₂, and demonstrated superior long-term catalytic stability. Additionally, the combination of in situ Raman spectroscopy with other ex situ characterizations provided further insight into the reasons behind the enhanced catalyst performance achieved through the in situ incorporation of N and S heteroatoms. This study presents a facile strategy for fabricating highly efficient cobalt-based spinel electrocatalysts incorporated with double heteroatoms for alkaline electrocatalytic monolithic water splitting.

Oxygen-vacancy-rich Co3O4@Fe-B-O heterostructure for efficient oxygen evolution reaction in alkaline and neutral media

Developing highly efficient OER catalysts is essential for producing hydrogen from water electrolysis to compensate for conventional fossil fuel shortages. Here, the oxygen-vacancy-rich heterostructure grown on the Ni foam (NF) (Co₃O₄@Fe-B-O/NF) is fabricated. The synergistic effect between Co₃O₄ and Fe-B-O has been proven effectively modulate the electronic structure and produce highly active interface sites, ultimately leading to enhanced electrocatalytic activity. Co₃O₄@Fe-B-O/NFrequiresan overpotential of 237 mV to drive 20 mA cm^-2 in 1 M KOH, and 384 mV to drive 10 mA cm^-2 in 0.1 M PBS, superior to most catalysts currently used. Moreover, Co₃O₄@Fe-B-O/NF as an oxygen evolution reaction (OER) electrode shows great potential in overall water splitting and CO₂ reduction reaction (CO₂RR). This work may provide effective ideas for designing efficient oxide catalysts.

Understanding the Role of (W, Mo, Sb) Dopants in the Catalyst Evolution and Activity Enhancement of Co3 O4 during Water Electrolysis via In Situ Spectroelectrochemical Techniques

Unlocking the potential of the hydrogen economy is dependent on achieving green hydrogen (H₂ ) production at competitive costs. Engineering highly active and durable catalysts for both oxygen and hydrogen evolution reactions (OER and HER) from earth-abundant elements is key to decreasing costs of electrolysis, a carbon-free route for H₂ production. Here, a scalable strategy to prepare doped cobalt oxide (Co₃ O₄ ) electrocatalysts with ultralow loading, disclosing the role of tungsten (W), molybdenum (Mo), and antimony (Sb) dopants in enhancing OER/HER activity in alkaline conditions, is reported. In situ Raman and X-ray absorption spectroscopies, and electrochemical measurements demonstrate that the dopants do not alter the reaction mechanisms but increase the bulk conductivity and density of redox active sites. As a result, the W-doped Co₃ O₄ electrode requires ≈390 and ≈560 mV overpotentials to reach ±10 and ±100 mA cm^-2 for OER and HER, respectively, over long-term electrolysis. Furthermore, optimal Mo-doping leads to the highest OER and HER activities of 8524 and 634 A g^-1 at overpotentials of 0.67 and 0.45 V, respectively. These novel insights provide directions for the effective engineering of Co₃ O₄ as a low-cost material for green hydrogen electrocatalysis at large scales.

Facile synthesis of multiphase cobalt-iron spinel with enriched oxygen vacancies as a bifunctional oxygen electrocatalyst

The multiphase cobalt-iron spinel was firstly synthesized via a facile cold plasma method and applied as a bifunctional electrocatalyst for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Compared with the single-phase obtained by the traditional calcination method, the CoFe₂O₄ and Co₃O₄ phase were obtained by the plasma method. The multivalence states of cobalt and iron facilitated electron transport in electrochemical reactions. The plasma sample had a small particle size (5 nm) due to the low operation temperature. Notably, electron impact produced more oxygen vacancies and a larger surface area on Co_xFe_yO₄, which increased the active sites and electronic conductivity. Electrochemical investigations indicated that the multiphase spinel obtained with a quasi-four-electron transfer process showed an onset potential of 0.76 V versus the RHE for the oxygen reduction reaction. In the oxygen evolution reaction, the potential of current density at 10 mA cm^-2 was 1.53 V versus RHE. As for the overall electrocatalytic activity, the multiphase spinel had a ΔE (the difference between E₁₀(OER) and E_1/2(ORR)) of 0.89 V, exhibiting greater bifunctional activity than the other prepared catalysts.

Red Blood Cells-Derived Iron Self–Doped 3D Porous Carbon Networks for Efficient Oxygen Reduction

In addition to C, H and O, some biomass is also rich in mineral elements. The recovery and utilization of special mineral elements is of great significance to prepare functional materials and alleviate the current energy shortage. Herein, we describe a facile strategy for making full use of the chemical composition (C, Fe) and special structure of red blood cells (RBCs) from waste pig blood to fabricate a dual metal (Fe, Co)-nitrogen (N)-doped porous carbon catalyst by pyrolysis of a mixture of RBCs biomass, cobaltous acetate, and melamine. The porous catalyst displays a comparable activity for oxygen reduction reaction (ORR) to that of commercial Pt/C catalyst, with a half-wave potential of 0.821 VvsRHE in alkaline media and 0.672 VvsRHE in acid electrolyte. Especially, the as-prepared catalyst shows excellent methanol tolerance and stability in both acidic and alkaline electrolytes, which is superior to commercial Pt/C catalysts. The excellent ORR activity of FeCo-N/C(RBC) can be ascribed to the porous morphology and the cooperation between metal and nitrogen species. This work provides a novel idea of exploiting the composition of renewable biomass to modulate the activity and stability of carbon-based ORR catalysts.

Oxygen-Deficient Cobalt-Based Oxides for Electrocatalytic Water Splitting

An apparent increased interest has been recently devoted towards the previously untrodden path for anionic point defect engineering of electrocatalytic surfaces. The role of vacancy engineering in improving photo- and electrocatalytic activities of transition metal oxides (TMOs) has been widely reported. In particular, oxygen vacancy modulation on electrocatalysts of cobalt-based TMOs has seen a fresh spike of research work due to the substantial improvements they have shown towards oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Oxygen vacancy engineering is an effective scheme to quintessentially tune the electronic structure and charge transport, generate secondary active surface phases, and modify the surface adsorption/desorption behavior of reaction intermediates during water splitting. Based on contemporary efforts for inducing oxygen vacancies in a variety of cobalt oxide types, this work addresses facile and environmentally benign synthesis strategies, characterization techniques, and detailed insight into the intrinsic mechanistic modulation of electrocatalysts. It is our foresight that appropriate utilization of the principles discussed herein will aid researchers in rationally designing novel materials that can outperform noble metal-based electrocatalysts. Ultimately, future electrocatalysis implementation for selective seawater splitting is believed to depend on regulating the surface chemistry of active and stable TMOs.

Graphene oxide induced assembly and crumpling of Co3O4 nanoplates

Cobalt (II, III) oxide (Co₃O₄) has been widely studied and applied in various fields, however, it suffers from slow mass and electron transfer during applications. Herein, crumpled Co₃O₄ and Co₃O₄/reduced graphene oxide (rGO) with tunable 2D-in-3D structures were prepared by combining spray pyrolysis with a graphene oxide (GO) template. The 2D Co₃O₄ nanoplates were interconnected with each other to form a 3D ball with many wrinkles, resulting in defect enrichment on the abundant boundaries of the nanosheets, which provided more active sites for catalytic reactions. In addition, the unique 2D-in-3D structure allowed fast mass transfer and structural stability. Furthermore, the assembled structure could be understood as being composed of uniformly distributed oxygen-containing functional groups pinning metal cations on the GO surface through electrostatic interaction, and the 2D structure of the GO enabled the in situ converted Co₃O₄ to grow along the GO surface with excellent dispersion. Taking advantage of the above, the Co₃O₄/rGO balls demonstrated an excellent oxygen evolution reaction performance, an overpotential of 298 mV at a current density of 10.0 mA cm^-2 and a current density of 115.9 mA cm^-2 at the overpotential of η = 500 mV.

Vacancy Occupation-Driven Polymorphic Transformation in Cobalt Ditelluride for Boosted Oxygen Evolution Reaction

Transition-metal dichalcogenides (TMDs) hold great potential as an advanced electrocatalyst for oxygen evolution reaction (OER), but to date the activity of transition metal telluride catalysts are demonstrated to be poor for this reaction. In this study, we report the activation of CoTe₂ for OER by doping secondary anions into Te vacancies to trigger a structural transition from the hexagonal to the orthorhombic phase. The achieved orthorhombic CoTe₂ with partial vacancies occupied by P-doping exhibits an exceptional OER catalytic activity with an overpotential of only 241 mV at 10 mA cm^-2 and a robust stability more than 24 h. The combined experimental and theoretical studies suggest that the defective phase transformation is controllable and allows the synergism of vacancy, doping as well as the reconstructed crystallographic structure, ensuring more exposure of catalytic active sites, rapid charge transfer, and energetically favorable intermediates. This vacancy occupation-driven strategy of structural transformation can also be manipulated by S- and Se-doping, which may offer useful guidance for developing tellurides-based electrocatalyst for OER.

Turning Waste into Treasure: Regulating the Oxygen Corrosion on Fe Foam for Efficient Electrocatalysis

Iron corrosion causes a great damage to the economy due to the function attenuation of iron-based devices. However, the corrosion products can be used as active materials for some electrocatalytic reactions, such as oxygen evolution reaction (OER). Herein, the oxygen corrosion on Fe foams (FF) to synthesize effective self-supporting electrocatalysts for OER, leading to "turning waste into treasure," is regulated. A dual chloride aqueous system of "NaCl-NiCl₂ " is employed to tailor the structures and OER properties of corrosion layers. The corrosion behaviors identify that Cl^- anions serve as accelerators for oxygen corrosion, while Ni²⁺ cations guarantee the uniform growth of corrosion layers owing to the appeared chemical plating. The synergistic effect of "NaCl-NiCl₂ " generates one of the highest OER activities that only an overpotential of 212 mV is required to achieve 100 mA cm^-2 in 1.0 m KOH solution. The as-prepared catalyst also exhibits excellent durability over 168 h (one week) at 100 mA cm^-2 and promising application for overall water splitting. Specially, a large self-supporting electrode (9 × 10 cm² ) is successfully synthesized via this cost-effective and easily scale-up approach. By combining with corrosion science, this work provides a significant stepping stone in exploring high-performance OER electrocatalysts.

Electrospun Carbon Nanofibers with Embedded Co-Ceria Nanoparticles for Efficient Hydrogen Evolution and Overall Water Splitting

In this study, simple electrospinning combined with pyrolysis were used to fabricate transition-metal-based-nanoparticle-incorporated carbon nanofiber (CNF) electrocatalysts for a high-efficiency hydrogen evolution reaction (HER) and overall water splitting. Co-CeO₂ nanoparticle-incorporated carbon nanofibers (Co-CeO₂@CNF) exhibit an outstanding electrocatalytic HER performance with an overpotential and Tafel slope of 92 mV and 54 mV/dec, respectively. For the counterpart, electrolysis, we incorporate the widely used Ni₂Fe catalyst with a high oxygen evolution reaction (OER) activity into the carbon nanofiber (Ni₂Fe@CNF). To evaluate their electrochemical properties for the overall water splitting, Co-CeO₂@CNF and Ni₂Fe@CNF were used as the HER and OER electrocatalysts in an alkaline electrolyzer. With the paired Co-CeO₂@CNF and Ni₂Fe@CNF electrodes, an overall water splitting current density of 10 mA/cm² was achieved by applying 1.587 V across the electrodes with a remarkably lower overpotential of 257 mV compared to that of an electrolyzer comprised of Pt/C and IrO₂ electrodes (400 mV). Owing to the conformal incorporation of nanoparticles into the CNF, the electrocatalysts exhibit significant long-term durability over 70 h of overall water splitting. This study provides rational designs of catalysts with high electrochemical catalytic activity and durability to achieve overall water splitting.

Reducing Oxygen Evolution Reaction Overpotential in Cobalt-Based Electrocatalysts via Optimizing the "Microparticles-in-Spider Web" Electrode Configurations

Sluggish kinetics of the multielectron transfer process is still a bottleneck for efficient oxygen evolution reaction (OER) activity, and the reduction of reaction overpotential is crucial to boost reaction kinetics. Herein, a correlation between the OER overpotential and the cobalt-based electrode composition in a "Microparticles-in-Spider Web" (MSW) superstructure electrode is revealed. The overpotential is dramatically decreased first and then slightly increased with the continuous increase ratio of Co/Co₃ O₄ in the cobalt-based composite electrode, corresponding to the dynamic change of electrochemically active surface area and charge-transfer resistance with the electrode composition. As a proof-of-concept, the optimized electrode displays a low overpotential of 260 mV at 10.0 mA cm^-2 in alkaline conditions with a long-time stability. This electrochemical performance is comparable and even superior to the most currently reported Co-based OER electrocatalysts. The remarkable electrocatalytic activity is attributed to the optimization of the electrochemically active sites and electron transfer in the MSW superstructure. Theoretical calculations identify that the metallic Co and Co₃ O₄ surface catalytic sites play a vital role in improving electron transport and reaction Gibbs free energies for reducing overpotential, respectively. A general way of boosting OER kinetics via optimizing the electrode configurations to mitigate reaction overpotential is offered in this study.

The synergistic effect of Co/Ni in ultrathin metal–organic framework nanosheets for the prominent optimization of non-enzymatic electrochemical glucose detection

Co–Ni ultrathin metal organic framework nanosheets exhibited extremely high sensitivity, wide linear range, low detection limit and excellent selectivity as a glucose sensing electrode material.

Adjustable anchoring of Ni/Co cations by oxygen-containing functional groups on functionalized graphite paper and accelerated mass/electron transfer for overall water splitting

NCS–NCO/FGP_0.44 with a cellular network of porous nanosheets and close-contact heterointerface reveals accelerated interfacial mass/electron transportation for overall water splitting.

Multipathway Antibacterial Mechanism of a Nanoparticle-Supported Artemisinin Promoted by Nitrogen Plasma Treatment

Artemisinin has excellent antimalarial, antiparasitic, and antibacterial activities; however, the poor water solubility of artemisinin crystal limits their application in antibiosis. Herein, artemisinin crystal was first composited with silica nanoparticles (SNPs) to form an artemisinin@silica nanoparticle (A@SNP). After treating with nitrogen plasma, the aqueous solubility of plasma-treated A@SNP (A@SNP-p) approaches 42.26%, which is possibly attributed to the exposure of hydrophilic groups such as -OH groups on the SNPs during the plasma process. Compared with the pristine A@SNP, the antibacterial activity of A@SNP-p against both Gram-positive and Gram-negative strains is further enhanced, and its bactericidal rate against both strains exceeded 6 log CFU/mL (>99.9999%), which is contributed by the increased water solubility of the A@SNP-p. A possible multipathway antibacterial mechanism of A@SNP was proposed and preliminarily proved by the changes of intracellular materials of bacteria and the inhibition of bacterial metabolism processes, including the HMP pathway in Gram-negative strain and EMP pathway in Gram-positive strain, after treating with A@SNP-p. These findings from the present work will provide a new view for fabricating artemisinin-based materials as antibiotics.

Thin NiFeCr-LDHs nanosheets promoted by g-C3N4: a highly active electrocatalyst for oxygen evolution reaction

NiFeCr layered double hydroxides (NiFeCr-LDHs) supported on graphitic carbon nitride (g-C₃N₄) hybrids (NiFeCr-LDHs/g-C₃N₄) are synthesized and used as an electrocatalyst for oxygen evolution reaction (OER) in alkaline media. Effect of g-C₃N₄ on the structure and OER performance of NiFeCr-LDHs are investigated in detail. g-C₃N₄ can promote the formation of thin NiFeCr-LDHs nanosheets, thereby enhancing both the number of active sites and OER activity. X-ray photoelectron spectra measurements confirm the electronic interaction between g-C₃N₄ and NiFeCr-LDHs nanosheets. The OER performance of NiFeCr-LDHs/g-C₃N₄ hybrids highly relates to the weight ratio of g-C₃N₄ to NiFeCr-LDHs. When the weight ratio of g-C₃N₄ to NiFeCr-LDHs is 5%, the corresponding electrocatalyst shows the best OER activity. The component optimized NiFeCr-LDHs/g-C₃N₄ hybrids display the overpotential of ∼223 mV at 10 mA cm^-2 and Tafel slope of 89 mV dec^-1 for OER in 1 M KOH solution, which is better than that of pristine NiFeCr-LDHs, bare g-C₃N₄, and commercial RuO₂.

Stimulating antibacterial activities of graphitic carbon nitride nanosheets with plasma treatment

As a widely studied photoactive antibacterial nanomaterial, the intrinsic antibacterial traits of graphitic carbon nitride (g-C3N4) as a two-dimensional nanomaterial have not been reported so far. Herein, nitrogen-plasma-treated g-C3N4 (N-g-C3N4) nanosheets and their influence on bactericidal characteristics are investigated. Bactericidal rates of more than 99% have been successfully achieved for 8 kinds of foodborne pathogenic bacteria by N-g-C3N4 with 8 h incubation in the dark. The achieved rates are percentage wise 10 times higher than those for pristine g-C3N4. Cell rupture caused by direct mechanical contact between g-C3N4 nanosheets and cell membranes is observed. X-ray photoelectron spectroscopy revealed a substantial loss of surface defects and nitrogen vacancies in N-g-C3N4. Molecular dynamics simulations further indicated that the largely sealed defects of N-g-C3N4 enhanced the electrostatic attraction between inherent pores and lipid heads; thus, further insertion of N-g-C3N4 was promoted, resulting in enhanced antibacterial activity. This study establishes novel fabrication and application strategies for carbon based antibacterial nanomaterials.

Micropore-Boosted Layered Double Hydroxide Catalysts: EIS Analysis in Structure and Activity for Effective Oxygen Evolution Reactions

Since the oxygen evolution catalysis process is vital yet arduous in energy conversion and storage devices, it is highly desirous but extremely challenging to engineer earth-abundant, noble-metal-free nanomaterials with superior electrocatalytic activity toward effective oxygen evolution reactions (OERs). Herein, we construct a prismlike cobalt-iron layered double hydroxide (Co-Fe LDH) with a Co/Fe ratio of 3:1 utilizing a facile self-templated strategy. Instead of carbon-species-coupled treatment, we focus on ameliorating the intrinsic properties of LDHs as OER electrocatalysts accompanied by the hierarchical nanoflake shell, well-defined interior cavity, and numerous microporous defects. In contrary to conventional LDHs synthesized via a one-pot method, Co-Fe LDHs fabricated in this work possess a huge specific surface area up to 294.1 m² g^-1, which not only provides abundant active sites but also expedites the kinetics of the OER process. The as-prepared Co-Fe LDH electrocatalysts exhibit advanced electrocatalytic performance and a dramatic stability of the OER in an alkaline environment. In particular, the contribution of micropore defects is clearly discussed according to the electrochemical impedance spectroscopy analysis, in which the time constant of the OER at the micropore defect is several orders of magnitude smaller than that at the exterior of Co-Fe LDHs, forcefully verifying the intrinsic catalytic activity enhancement derived from the micropore defects. This work provides a promising model to improve OER electrocatalyst activity via produce defects and research the contribution of micropore defects.

The Co2+/Ni2+ ion-mediated formation of a topochemically converted copper coordination polymer: structure-dependent electrocatalytic activity

The presence of Co²⁺/Ni²⁺ ions strongly influenced the formation of copper coordination polymers that showed a structure-dependent hydrogen evolution reaction catalytic activity.

A mesoporous C,N-co doped Co-based phosphate ultrathin nanosheet derived from a phosphonate-based-MOF as an efficient electrocatalyst for water oxidation

A mesoporous C,N-co doped Co-based phosphate ultrathin nanosheet derived from 2D phosphate MOFs has been explored and exhibits highly efficient OER performance.