Facile synthesis of amorphous/crystalline Ni-Fe thiophenedicarboxylate coordination polymer nanobelts for efficient water oxidation

The oxygen evolution reaction (OER) is a complex four-electron transfer process that poses a significant challenge to the efficient production of hydrogen through water splitting. However, developing non-noble metal electrocatalyst with excellent OER performance is still a big challenge. Herein, we propose a new strategy for the in-situ growth of two-dimensional amorphous/crystalline thiophene-based Ni-Fe metal-organic frameworks (MOFs) using Ni-Fe foam (NFF) as metal source and current collector, and thiophene-2,5-dicarboxylic acid (TDC) as corrosion agent and ligand. TDC was ionized at high temperature to produce H+ ions that etch NFF to release Ni2+ and Fe2+ ions, which were coordinated with TDC to in situ synthesize two-dimensional Ni-Fe thiophenedicarboxylate coordination polymer (NiFe-TDC) nanobelts on NFF. The unique structure and synergistic effect of Ni and Fe ions of NiFe-TDC0.05 result in the excellent OER performance with an overpotential of 224 and 256 mV at current densities of 10 and 100 mA cm-2, respectively, and it can run stably for 100 h at a current density of 100 mA cm-2, indicating the outstanding stability. Furthermore, NiFe-TDC0.05 remains the excellent OER performance with an extremely low potential of 196 and 271 mV at current densities of 10 and 100 mA cm-2 in seawater with 1 mol L-1 (M) KOH, respectively. The assembled NiFe-TDC0.05 || Pt/C water electrolysis cell achieves a current density of 100 mA cm-2 at a low voltage of 1.78 V. The work provides a new method to prepare two dimensional MOFs for efficient water oxidation.

Bifunctional Ni Foam Supported TiO2 @Ni3 S2 core@shell Nanorod Arrays for Boosting Electrocatalytic Biomass Upgrading and H2 Production Reactions

Replacing traditional oxygen evoltion reaction (OER) with biomass oxidation reaction (BOR) is an advantageous alternative choice to obtain green hydrogen energy from electrocatalytic water splitting. Herein, a novel of extremely homogeneous Ni3 S2 nanosheets covered TiO2 nanorod arrays are in situ growth on conductive Ni foam (Ni/TiO2 @Ni3 S2 ). The Ni/TiO2 @Ni3 S2 electrode exhibits excellent electrocatalytic activity and long-term stability for both BOR and hydrogen evolution reaction (HER). Especially, taking glucose as a typical biomass, the average hydrogen production rate of the HER-glucose oxidation reaction (GOR) two-electrode system reached 984.74 µmol h-1 , about 2.7 times higher than that of in a common HER//OER two-electrode water splitting system (365.50 µmol h-1 ). The calculated power energy saving efficiency of the GOR//HER system is about 13% less than that of the OER//HER system. Meanwhile, the corresponding selectivity of the value-added formic acid produced by GOR reaches about 80%. Moreover, the Ni/TiO2 @Ni3 S2 electrode also exhibits excellent electrocatalytic activity on a diverse range of typical biomass intermediates, such as urea, sucrose, fructose, furfuryl alcohol (FFA), 5-hydroxymethylfurfural (HMF), and alcohol (EtOH). These results show that Ni/TiO2 @Ni3 S2 has great potential in electrocatalysis, especially in replacing OER reaction with BOR reaction and promoting the sustainable development of hydrogen production.

Spectrophotometric Determination of Trace Amount of Total FeII/FeIII and Live Cell Imaging of a Carboxylato Zn(II) Coordination Polymer

The coordination polymer, (Zn(II)-CP, 1), {[Zn(2,6-NDC)(4-Cltpy)](H₂O)₄} (1) (2,6-H₂NDC = 2,6-naphthalene dicarboxylic acid and 4-Cltpy = 4'-chloro-[2,2';6',2″]terpyridine) is structurally characterized by single crystal X-ray diffraction measurement and other physicochemical studies (PXRD, FTIR, thermal analysis, microanalytical data). 4-Cltpy acts as end-capping ligand, and NDC^2- is a carboxylato bridging motif to constitute ZnN₃O₂ distorted trigonal bipyramid core that propagates to construct 1D chain. The coordination polymer, 1, detects total iron (Fe³⁺ and Fe²⁺) in aqueous solution by visual color change, colorless to pink. Absorption spectrophotometric technique in aqueous medium measures the limit of detection (LOD) 0.11 μM (Fe²⁺) and 0.15 μM (Fe³⁺), and binding constants (K_d) are 6.7 × 10⁴ M^-1 (Fe³⁺) and 3.33 × 10⁴ M^-1 (Fe²⁺). Biocompatibility of 1 is examined in live cells, and intracellular Fe²⁺ and Fe³⁺ are detected in MDA-MB 231 cells. Zn(II) substitution is assumed upon addition of Fe^III/Fe^II solution to the suspension of the coordination polymer, 1, in water-acetonitrile (41:1) (LZn^II + Fe^III/II → LFe^III + Zn^II, where L is defined as coordinated ligands), which is accompanied by changing from colorless to pink at room temperature. The color of the mixture may be assumed to the charge transfer transition from carboxylate-O to Cltpy via Fe(II/III) bridging center (carboxylate-O-Fe-CltPy). The product isolated from the reaction is finally characterized as Fe(III)@1-CP. It is presumed that product Fe(II)@1-CP may undergo fast aerial oxidation to transform Fe(III)@1-CP. The Fe^III exchanged framework (Fe(III)@1-CP) has been characterized by PXRD, IR, TGA and energy dispersive X-ray analysis (EDX)-SEM. The MTT assay calculates the cell viability (%), and the tolerance limit is 100 μM to total Fe²⁺ and Fe³⁺.

Carbon Nanotube-Coupled Seaweed-like Cobalt Sulfide as a Dual-Functional Catalyst for Overall Water Splitting

Preparation of high-efficiency dual-functional catalysts remains the bottleneck for electrochemical water splitting. To prepare a non-precious metal catalyst with high activity and stability, here, we present a seaweed-like structure consisting of transition-metal sulfide nanoplates self-assembled on carbon nanotube sponge networks (SW-CoS@CNT). By adjusting the key parameters during synthesis (e.g., the loading amount and ratio of Co and S precursors), the microstructure can be tailored in a wide range, and sulfur defects can be introduced into the nanoplates by thermal annealing. The resulting SW-CoS@CNT serves as a freestanding dual-functional catalytic electrode, showing low overpotentials of 105 and 218 mV for the hydrogen evolution reaction and the oxygen evolution reaction, respectively, which are superior to most reported transition-metal-sulfide-based catalysts in alkaline solution. Rational design of this hierarchical biomimetic structure may be useful in developing high-performance electrochemical catalysts in renewable energy and environmental fields.

Gas sensing based on metal-organic frameworks: Concepts, functions, and developments

Effective detection of pollutant gases is vital for protection of natural environment and human health. There is an increasing demand for sensing devices that are equipped with high sensitivity, fast response/recovery speed, and remarkable selectivity. Particularly, attention is given to the designability of sensing materials with porous structures. Among diverse kinds of porous materials, metal-organic frameworks (MOFs) exhibit high porosity, high degree of crystallinity and exceptional chemical activity. Their strong host-guest interactions with guest molecules facilitate the application of MOFs in adsorption, catalysis and sensing systems. In particular, the tailorable framework/composition and potential for post-synthetic modification of MOFs endow them with widely promising application in gas sensing devices. In this review, we outlined the fundamental aspects and applications of MOFs for gas sensors, and discussed various techniques of monitoring gases based on MOFs as functional materials. Insights and perspectives for further challenges faced by MOFs are discussed in the end.

Manipulation of Mott-Schottky Ni/CeO2 Heterojunctions into N-Doped Carbon Nanofibers for High-Efficiency Electrochemical Water Splitting

Designing affordable and efficient bifunctional electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) has remained a long-lasting target for the progressing hydrogen economy. Utilization of metal/semiconductor interface effect has been lately established as a viable implementation to realize the favorable electrocatalytic performance due to the built-in electric field. Herein, a typical Mott-Schottky electrocatalyst by immobilizing Ni/CeO₂ hetero-nanoparticles onto N-doped carbon nanofibers (abbreviated as Ni/CeO₂ @N-CNFs hereafter) has been developed via a feasible electrospinning-carbonization tactic. Experimental findings and theoretic calculations substantiate that the elaborated constructed Ni/CeO₂ heterojunction effectively triggers the self-driven charge transfer on heterointerfaces, leading to the promoted charge transfer rate, the optimized chemisorption energies for reaction intermediates and ultimately the expedited reaction kinetics. Therefore, the well-designed Ni/CeO₂ @N-CNFs deliver superior HER and OER catalytic activities with overpotentials of 100 and 230 mV at 10 mA cm^-2 , respectively, in alkaline solution. Furthermore, the Ni/CeO₂ @N-CNFs-equipped electrolyzer also exhibits a low cell voltage of 1.56 V to attain 10 mA cm^-2 and impressive long-term durability over 55 h. The innovative manipulation of electronic modulation via Mott-Schottky establishment may inspire the future development of economical electrocatalysts for diverse sustainable energy systems.

Superprotonic Conductivity of UiO-66 with Missing-Linker Defects in Aqua-Ammonia Vapor

The design and preparation of proton-conducting metal-organic frameworks (MOFs) with superconductivity are of significance for the proton-exchange membrane fuel cell (PEMFC). Introducing functional structural defects to enhance proton conductivity is a good approach. Here, we synthesized a series of UiO-66 (first synthesized in the University of Oslo) with missing-linker defects and investigated the effect of defect numbers on the proton conductivity of the samples. Among them, 60-UiO-66-1.8 (60 represents the synthesis temperature and 1.8 the number of defects) prepared with 3-mercaptopropionic acid as a modulator has the best proton conductivity, which is 3 × 10^-2 S cm^-1 at 100 °C and under 98% relative humidity (RH). The acidic sites induced by missing-linker defects further promote the chemisorption of ammonia molecules, resulting in the formation of a richer hydrogen-bond network and hence boosting the proton conductivity to 1.04 × 10^-1 S cm^-1 at 80 °C, which is one of the highest values among the reported MOF-based proton conductor. Therefore, this work provides a new strategy for enhancing proton conduction in MOF-based materials.

Free-standing Co/Zn sulfide supported on Cu-foam for efficient overall water splitting

High-performance bifunctional electrocatalyst for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is arousing great interest aiming at efficient electrochemical splitting of water. Herein, we report a...

Double-wall carbon nanotube assisted phase engineering in CoOxSy complex for efficient oxygen evolution reaction

Sluggish electron kinetics in oxygen evolution reaction (OER) is one of the main factors restricting the development of hydrogen production technology from electrical water splitting, while the key to break...

Vanadium -mediated ultrafine Co/Co9S8 nanoparticles anchored on Co-N-doped porous carbon enable efficient hydrogen evolution and oxygen reduction reactions

Developing cost-effective, highly-active and robust electrocatalysts is of vital importance to supersede noble-metal ones for both hydrogen evolution reactions (HERs) and oxygen reduction reactions (ORRs). Herein, a unique vanadium-mediated space confined strategy is reported to construct a composite structure involving Co/Co₉S₈ nanoparticles anchored on Co-N-doped porous carbon (VCS@NC) as bifunctional electrocatalysts toward HER and ORR. Benefitting from the ultrafine nanostructure, abundant Co-N_x active sites, large specific surface area and defect-rich carbon framework, the resultant VCS@NC exhibits unexceptionable HER catalytic activity, needing extremely low HER overpotentials in pH-universal media (alkaline: 117 mV, acid: 178 mV, neutral: 210 mV) at a current density of 10 mA cm^-2, paralleling at least 100 h catalytic durability. Notably, the VCS@NC catalyst delivers high-efficiency ORR performance in alkaline solution, accompanied with a quite high half wave potential of 0.901 V, far overmatching the commercial Pt/C catalyst. Our research opens up novel insight into engineering highly-efficient multifunctional non-precious metal electrocatalysts by a metal-mediated space-confined strategy in energy storage and conversion system.

Uniformly Dispersed Ru Nanoparticles Constructed by In Situ Confined Polymerization of Ionic Liquids for the Electrocatalytic Hydrogen Evolution Reaction

Design and development of cost-effective electrocatalysts with high efficiency and stability for scalable and sustainable hydrogen production through water splitting is still challenging. Herein, with the aid of divinyl functionalized ionic liquids, uniformly distributed Ru nanoparticles (NPs) on nitrogen-doped carbon frameworks are obtained via an in situ confined polymerization strategy. Attributed to the unique lamellar structure and confinement effect of carbon supports, the optimized homo-PIL-Ru/C-600 (with Ru 10 wt%) catalyst exhibits superior catalytic efficiency for the hydrogen evolution reaction with the overpotential of only 16 mV at a current density of 10 mA cm^-2 and the corresponding Tafel slope of only 42 mV dec^-1 . Moreover, the performance can be well reserved even after 10 000 cycles, demonstrating excellent stability and promising potentials for industrial application. This work not only provides a facile approach for the preparation of highly efficient Ru-based catalysts, but also guides the synthesis of other highly dispersed metallic NPs for special applications.

Nanostructured NiCo2S4@NiCo2O4-reduced graphene oxide as an efficient hydrogen evolution electrocatalyst in alkaline electrolyte

Metal-organic frameworks (MOFs), serving as precursors or templated to construct nanomaterials, which have gained great attentions in the field of electrocatalysis. However, their applications still remain some challenges due to poor conductivity and easy agglomeration. In this work, the MOFs-derived NiCo₂S₄@NiCo₂O₄ deposited on reduced Graphene Oxide (rGO) surface is designed by using a facile hydrothermal procedure. Attribute to the enlarged active surface area of the nanostructure and the strong synergistic effect between NiCo₂S₄ and NiCo₂O₄, as well as the excellent conductivity of rGO. The NiCo₂S₄@NiCo₂O₄-rGO catalyst displays ultrahigh hydrogen evolution reaction (HER) property and excellent stability, only need an overpotential of η₁₀ = 95 mV to attain 10 mA cm^-2 and deliver a small Tafel slope of b = 52 mV dec^-1 in 1 M KOH. This work can provide a window to construct and develop new noble metal-free HER catalysts base on Ni-MOFs served as precursors.

Co9 S8 @CN Composites Obtained from Thiacalix[4]arene-Based Coordination Polymers for Supercapacitor Applications

Metal sulfides have been recognized as promising electrodes for electrochemical energy storage owing to their remarkable electrochemical properties. Here, we demonstrate the preparation of Co₉ S₈ nanoparticles anchored on a carbon matrix (denoted as Co₉ S₈ -X@CN (X=1, 2)) from precursor sources, two 1D infinite coordination polymers 1 and 2. The two polymers were assembled by linking Co₄ -TC4A secondary building blocks (SBUs) with ligands L₁ and L₂ , respectively (H₄ TC4A=p-tert-butylthiacalix[4]arene, L₁ =1,4-bis(2H-tetrazol-5-yl)benzene, L₂ =1,3-bis(2H-tetrazol-5-yl)benzene). The composites obtained from 1D polymers showed different morphologies, that is, the Co₉ S₈ nanoparticles of Co₉ S₈ -1@CN are octahedral with a size of ca. 140 nm, while the lamellar Co₉ S₈ nanoparticles in Co₉ S₈ -2@CN possess different sizes (50-150 nm). The Co₉ S₈ -2@CN immobilized on nickel foam (Co₉ S₈ -2@CN/NF) show better supercapacitive performance than that of Co₉ S₈ -1@CN. Co₉ S₈ -2@CN showed exceptionally high activities, combining higher specific capacitances (445.2 F g^-1 at 2 A g^-1 and 393.9 F g^-1 and 5 A g^-1 ), rate capacity (94.5% retention at 2 A g^-1 ), and long-term stability (79.2% retention at 5 A g^-1 over 1000 cycles). The smaller size and larger BET surface area of Co₉ S₈ -2@CN nanoparticles can improve the electrical conductivity and provide facile pathways for charge transport, thus leading to conspicuous electrochemical performance of Co₉ S₈ -2@CN compared with its Co₉ S₈ -1@CN counterpart.

Designing MOF Nanoarchitectures for Electrochemical Water Splitting

Electrochemical water splitting has attracted significant attention as a key pathway for the development of renewable energy systems. Fabricating efficient electrocatalysts for these processes is intensely desired to reduce their overpotentials and facilitate practical applications. Recently, metal-organic framework (MOF) nanoarchitectures featuring ultrahigh surface areas, tunable nanostructures, and excellent porosities have emerged as promising materials for the development of highly active catalysts for electrochemical water splitting. Herein, the most pivotal advances in recent research on engineering MOF nanoarchitectures for efficient electrochemical water splitting are presented. First, the design of catalytic centers for MOF-based/derived electrocatalysts is summarized and compared from the aspects of chemical composition optimization and structural functionalization at the atomic and molecular levels. Subsequently, the fast-growing breakthroughs in catalytic activities, identification of highly active sites, and fundamental mechanisms are thoroughly discussed. Finally, a comprehensive commentary on the current primary challenges and future perspectives in water splitting and its commercialization for hydrogen production is provided. Hereby, new insights into the synthetic principles and electrocatalysis for designing MOF nanoarchitectures for the practical utilization of water splitting are offered, thus further promoting their future prosperity for a wide range of applications.

A Co-MOF-derived Co9S8@NS-C electrocatalyst for efficient hydrogen evolution reaction

The exploitation of efficient hydrogen evolution reaction (HER) electrocatalysts has become increasingly urgent and imperative; however, it is also challenging for high-performance sustainable clean energy applications. Herein, novel Co9S8 nanoparticles embedded in a porous N,S-dual doped carbon composite (abbr. Co9S8@NS-C-900) were fabricated by the pyrolysis of a single crystal Co-MOF assisted with thiourea. Due to the synergistic benefit of combining Co9S8 nanoparticles with N,S-dual doped carbon, the composite showed efficient HER electrocatalytic activities and long-term durability in an alkaline solution. It shows a small overpotential of -86.4 mV at a current density of 10.0 mA cm-2, a small Tafel slope of 81.1 mV dec-1, and a large exchange current density (J 0) of 0.40 mA cm-2, which are comparable to those of Pt/C. More importantly, due to the protection of Co9S8 nanoparticles by the N,S-dual doped carbon shell, the Co9S8@NS-C-900 catalyst displays excellent long-term durability. There is almost no decay in HER activities after 1000 potential cycles or it retains 99.5% of the initial current after 48 h.

Hydrogen and Potassium Acetate Co-Production from Electrochemical Reforming of Ethanol at Ultrathin Cobalt Sulfide Nanosheets on Nickel Foam

The sluggish reaction kinetics of the anodic oxygen evolution reaction increases the energy consumption of the overall water electrolysis for high-purity hydrogen generation. In this work, ultrathin cobalt sulfide nanosheets (Co₃S₄-NSs) on nickel foam (Ni-F) nanohybrids (termed as Co₃S₄-NSs/Ni-F) are synthesized using cyanogel hydrolysis and a sulfurization two-step approach. Physical characterizations reveal that Co₃S₄-NSs with a 1.7 nm thickness have abundant holes, implying the big surface area, abundant active edge atoms, and sufficient active sites. Electrochemical measurements show that as-synthesized Co₃S₄-NSs/Ni-F have excellent electrocatalytic activity and selectivity for ethanol oxidation reaction and hydrogen evolution reaction. Due to their bifunctional property of Co₃S₄-NSs/Ni-F nanohybrids, a symmetric Co₃S₄-NSs/Ni-F∥Co₃S₄-NSs/Ni-F ethanol electrolyzer can be effectively constructed, which only requires a 1.48 V electrolysis voltage to reach a current density of 10 mA cm^-2 for high-purity hydrogen generation at the cathode as well as value-added potassium acetate generation at the anode, much lower than the electrolysis voltage of traditional electrochemical water splitting (1.64 V).

Nanocomposite synthesis strategies based on the transformation of well-tailored metal-organic frameworks

Increasing the complexity of nanomaterials in terms of their structure and chemical composition has attracted significant attention, because it can yield unique scientific outcomes and considerable improvements for practical applications. Various approaches are being developed for the synthesis of nanostructured composites. Coordination polymers (CPs) emerged as new precursors in solid-state reactions for nanomaterials nearly two decades ago; the repetitively arranged inorganic and organic units can facilitate the production of nanoscale particles and porous carbon upon thermal decomposition. Metal-organic frameworks (MOFs), a subgroup of CPs featuring crystalline and porous structures, have subsequently become primary objects of interest in this field, as can be seen by the rapidly increasing number of reports on this topic. However, unique composite materials with increasingly complex nanostructures, which cannot be achieved via conventional methods, have been rarely realised, even though conventional MOF research has enabled the delicate control of structures at the molecular level and extensive applications as templates. In this regard, a comprehensive review of the fabrication strategies of MOF-based precursors and the thermal transformation into functional nanomaterials is provided herein, with a particular emphasis on the recent developments in nanocomposite research. We briefly introduce the roles and capabilities of MOFs in the synthesis of nanomaterials and subsequently discuss diverse synthetic routes for obtaining morphologically or compositionally advanced composite nanomaterials, based on our understanding of the MOF conversion mechanism.

Cobalt-Based Metal-Organic Frameworks and Their Derivatives for Hydrogen Evolution Reaction

Hydrogen has been considered as a promising alternative energy to replace fossil fuels. Electrochemical water splitting, as a green and renewable method for hydrogen production, has been drawing more and more attention. In order to improve hydrogen production efficiency and lower energy consumption, efficient catalysts are required to drive the hydrogen evolution reaction (HER). Cobalt (Co)-based metal-organic frameworks (MOFs) are porous materials with tunable structure, adjustable pores and large specific surface areas, which has attracted great attention in the field of electrocatalysis. In this review, we focus on the recent progress of Co-based metal-organic frameworks and their derivatives, including their compositions, morphologies, architectures and electrochemical performances. The challenges and development prospects related to Co-based metal-organic frameworks as HER electrocatalysts are also discussed, which might provide some insight in electrochemical water splitting for future development.

Exploiting a High-Performance "Double-Carbon" Structure Co9S8/GN Bifunctional Catalysts for Rechargeable Zn-Air Batteries

Rational synthesis of bifunctional electrocatalysts with high performance and strong durability is highly demanded rechargeable metal-air battery. In this work, ZIF-derived Co₉S₈/C coated with conductive graphene nanosheet (Co₉S₈/GN) was synthesized by a simple solvothermal method and formed a stable double-carbon structure. As expected, the prepared Co₉S₈/GN catalyst exhibits a high catalytic activity (ΔE: 0.88 V) and long-term durability toward both oxygen reduction reaction and oxygen evolution reaction (ORR and OER), which is even superior to the Pt/C + Ir/C mixture (0.91 V). In addition, the Zn-air battery with the Co₉S₈/GN catalyst showed higher power density (186 mW cm^-2) and more stable charge-discharge cycling performances (2000 cycles) than the Pt/C + Ir/C (118 mW cm^-2). Based on these analysis results, the favorable catalytic performance of ORR/OER should be illustrated by the following reasons: (i) large specific surface area and unique mesoporous structure, providing abundant active sites; (ii) good conductivity, accelerating the electrons transfer; and (iii) the unique stable "double-carbon" structures (metal-S-C-C), preventing the agglomeration of metal sulfide, building new quick transfer pathway, and forming the strong electron coupling ability and synergistic effect.

Mesoporous anion-cation-codoped Co9S8 nanorings for enhanced electrocatalytic oxygen evolution reactions

Recently, the design and synthesis of Co₉S₈ micro/nanostructures have attracted attention as electrochemical energy storage and conversion devices due to their low cost and environmental friendliness. Herein, Co₉S₈ nanorings were synthesized via a one-step solvothermal method with the incorporation of Fe ions, subsequently, properly selenized to boost their electrocatalytic performance. The morphology and structure of the series of cation and anion regulated Co₉S₈ nanorings were characterized, the electrochemical oxygen evolution reaction (OER) properties were assessed. It is worth noting that the as-prepared catalysts, especially the innovative Fe and Se ions double doped Co₉S₈ nanorings, denoted as Se/Fe-Co₉S₈-0.14, exhibited good electrocatalytic OER performance with low overpotential (298 mV) and high durability under alkaline conditions. This work provides a new perspective to develop non-noble metal Co₉S₈-based OER electrocatalysts with a superior electrocatalytic performance.

MOF-Derived Sulfide-Based Electrocatalyst and Scaffold for Boosted Hydrogen Production

Metal-organic frameworks (MOFs) can act as precursors or templates to a myriad of nanostructured materials that are difficult to prepare. In this study, Co-MOF nanorods (NRs) were prepared at room temperature followed by a calcination and hydrothermal sulfurization strategy to transform the MOF into CoS NRs on carbon cloth (CoS/CC). Intriguingly, the resultant 3D sulfide NRs can serve as scaffolds to electrodeposit layered double hydroxides (LDHs) on the surfaces. Through combining the advantages of structure and composition, the as-fabricated CoS@CoNi-LDH/CC exhibits remarkable electrocatalytic activity for the hydrogen evolution reaction (HER). An overpotential of 124 mV is needed to reach a current density of 10 mA cm^-2 with a Tafel slope of only 89 mV dec^-1, which is superior to that of pure CoS/CC (141 mV along with 103 mV dec^-1) and other reported cobalt-based catalysts. Notably, after the chronopotentiometry test for 50 h, the overpotential of CoS@CoNi-LDH/CC increased by 17 mV only.

Recent Studies on Multifunctional Electrocatalysts for Fuel Cell by Various Nanomaterials

Based on nanotechnology, nanocomposites are synthesized using nanoparticles (NP), which have some advantages in terms of multifunctional, economic, and environmental factors. In this review, we discuss the inorganic applications as well as catalytic applications of NPs. Recently, structural defects, heteroatomic doping, and heterostructures of such efficient ideal catalysts and their application as multifunctional catalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in water splitting. It has been verified that the catalysts used in oxygen reduction reaction and OER can be used effectively in metal/air batteries. Moreover, it has been reported that high-efficiency catalysts are required to implement urea oxidation reaction (UOR), which involves a six-electron reaction, as an electrochemical reaction. We expect that this review can be applied to sustainable and diverse electrochemistry fields.

Ultrathin rGO-wrapped free-standing bimetallic CoNi2S4-carbon nanofibers: an efficient and robust bifunctional electrocatalyst for water splitting

Electrochemical water splitting represents an ideal strategy for producing clean hydrogen as an energy carrier that serves as an alternative to fossil fuels. As an effective method for hydrogen production, an efficient inexpensive multifunctional electrocatalyst with high durability is designed. Herein, we describe the heterostructural design of a three-dimensional catalytic network with self-embedded CoNi₂S₄ nanograins grown on electrospun carbon nanofibers (CoNi₂S₄-CNFs) with anchored thin-layer reduced graphene oxide. This is achieved via facile electrospinning followed by carbonization, low-temperature sulfidation, and surface functionalization. As a bifunctional catalyst, CoNi₂S₄-CNFs exhibited robust high activity toward the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in an alkaline medium. The anchored ultrathin graphene oxide layer promoted the stability and durability of the catalytic network with an efficient path for the transportation of electrons. The rGO-anchored CoNi₂S₄-CNFs yielded overpotential values of 228 mV and 205 mV for the HER and OER, respectively, that drives a current density of 20 mA cm^-2 in an alkaline medium. Notably, the excellent electrochemical properties are attributed to the functional effect of the CoNi₂S₄ on the CNF network. The ultrathin feature of rGO improved the durability of the catalytic network. Moreover, using the rGO-anchored CoNi₂S₄-CNFs as a cathode and anode in a two-electrode water splitting system required a cell voltage of only 1.55 V to reach a current density of 10 mA cm^-2. These CNFs exhibited outstanding durability for 48 h. The present work offers new insight for the design of a catalytic network with a non-noble metal catalyst that exhibits excellent electrocatalytic activity and durability on the metal sulfides in overall water splitting.

Features of electron beam deposition of polymer coatings with the prolonged release of the drug component

The first part of the paper provides a comprehensive analysis of the features of electron beam formation of polymer coatings with the prolonged release of the drug compound using ciprofloxacin and clotrimazole as an example. The influence features of the low-energy electron beam on the molecular structure of medicinal chemical preparations have been established. The impossibility of producing the coatings based on medicinal compounds with a complex molecular structure (vancomycin, micafungin, etc.) by a low-energy electron beam has been justified. The second part of the paper introduces a fundamentally new vacuum method for the formation of the composite coatings based on antibiotics and antifungal drugs, accompanied by the prolonged release of the drug component. This method allows the formation of composite coatings based on medicinal compounds with a complex molecular structure. It is effective for modifying implants to prevent the risk of implant-associated infectious complications which are the result of the occurrence of mixed biofilms. The method can be used to form composite layers based on topical antitumor drugs for cancer control.

Interfacial effect of Co4S3–Co9S8 nanoparticles hosted on rGO sheets derived from molecular precursor pyrolysis on enhancing electrochemical behaviour

Co₄S₃–Co₉S₈ nanoparticles with abundant interfaces hosted on reduced graphene oxide were synthesized via a monomolecular pyrolysis strategy to boost catalytic activity.

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.

Co/Co9S8 nanoparticles coupled with N,S-doped graphene-based mixed-dimensional heterostructures as bifunctional electrocatalysts for the overall oxygen electrode

A Co/Co₉S₈/rGO/MWCNT composite catalyst was designed and fabricated via a combined hydrothermal reaction with a calcination method for the ORR/OER.