Promoted Overall Water Splitting Catalytic Activity and Durability of Ni3Fe Alloy by Designing N-Doped Carbon Encapsulation.

Combining an electrochemically stable material onto the surface of a catalyst can improve the durability of a transition metal catalyst, and enable the catalyst to operate stably at high current density. Herein, the contribution of the N-doped carbon shell (NCS) to the electrochemical properties is evaluated by comparing the characteristics of the Ni3Fe@NCS catalyst with the N-doped carbon shell, and the Ni3Fe catalyst. The synthesized Ni3Fe@NCS catalyst has a distinct overpotential difference from the Ni3Fe catalyst (ηOER = 468.8 mV, ηHER = 462.2 mV) at (200 and -200) mA cm-2 in 1 m KOH. In stability test at (10 and -10) mA cm-2, the Ni3Fe@NCS catalyst showed a stability of (95.47 and 99.6)%, while the Ni3Fe catalyst showed a stability of (72.4 and 95.9)%, respectively. In addition, the in situ X-ray Absorption Near Edge Spectroscopy (XANES) results show that redox reaction appeared in the Ni3Fe catalyst by applying voltages of (1.7 and -0.48) V. The decomposition of nickel and iron due to the redox reaction is detected as a high ppm concentration in the Ni3Fe catalyst through Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) analysis. This work presents the strategy and design of a next-generation electrochemical catalyst to improve the electrocatalytic properties and stability.

Self-Powered Water Splitting of Ni3FeN@Fe24N10 Bifunctional Catalyst Improved Catalytic Activity and Durability by Forming Fe24N10 on Catalyst Surface via the Kirkendall Effect.

Highly efficient water splitting electrocatalyst for producing hydrogen as a renewable energy source offers potential to achieve net-zero. However, it has significant challenges in using transition metal electrocatalysts as alternatives to noble metals due to their low efficiency and durability, furthermore, the reliance on electricity generation for electrocatalysts from fossil fuels leads to unavoidable carbon emissions. Here, a highly efficient self-powered water splitting system integrated is designed with triboelectric nanogenerator (TENG) and Ni3FeN@Fe24N10 catalyst with improved catalytic activity and durability. First, the durability of the Ni3FeN catalyst is improved by forming N, P carbon shell using melamine, polyetherimide, and phytic acid. The catalyst activity is improved by generating Fe24N10 in the carbon shell through the Kirkendall effect. The synthesized Ni3FeN@Fe24N10 catalyst exhibited excellent bifunctional catalytic activity (ηOER = 261.8 mV and ηHER = 151.8 mV) and remarkable stability (91.7% in OER and 90.5% in HER) in 1 m KOH. Furthermore, to achieve ecofriendly electricity generation, a rotation-mode TENG that sustainably generate high-performance is realized using butylated melamine formaldehyde. As a result, H2 is successfully generated using the integrated system composed of the designed TENG and catalyst. The finding provides a promising approach for energy generation to achieve net-zero.

Investigating the thermal stability of metallic and non-metallic nanoparticles using a novel graphene oxide-based transmission electron microscopy heating-membrane.

In recent years, graphene has been explored as a heating membrane for studying high-temperature dynamics inside the transmission electron microscope (TEM) due to several limitations with the existing silicon nitride-based membrane. However, the transfer of monolayer graphene films for TEM experiments is challenging and requires many complicated steps with a minimum success rate. This work developed a novelin situheating platform by combining the graphene oxide (GO) flakes in the pre-patterned chips. The isolated GO flake was self-suspended between the metal electrodes by a simple drop-casting process. The GO was reduced and characterized using Raman and electron energy-loss spectroscopy. Furthermore, a GO-based heater was used to investigate the thermal stability of gold and silica nanoparticles. The gold nanoparticles evaporated non-uniformly and left an empty carbon shell, while silica disappeared uniformly by etching carbon support. We successfully demonstrated a GO flake as a heating membrane to study high temperature thermal dynamic reactions: melting/evaporation, agglomeration, Rayleigh instability, and formation/or removal of carbon in the nanoparticles.

Polyaniline Derived N-Doped Carbon-Coated Cobalt Phosphide Nanoparticles Deposited on N-Doped Graphene as an Efficient Electrocatalyst for Hydrogen Evolution Reaction.

The development of highly efficient and durable non-noble metal electrocatalysts for the hydrogen evolution reaction (HER) is significant for clean and renewable energy research. This work reports the synthesis of N-doped graphene nanosheets supported N-doped carbon coated cobalt phosphide (CoP) nanoparticles via a pyrolysis and a subsequent phosphating process by using polyaniline. The obtained electrocatalyst exhibits excellent electrochemical activity for HER with a small overpotential of -135 mV at 10 mA cm-2 and a low Tafel slope of 59.3 mV dec-1 in 0.5 m H2 SO4 . Additionally, the encapsulation of N-doped carbon shell prevents CoP nanoparticles from corrosion, exhibiting good stability after 14 h operation. Moreover, the as-prepared electrocatalyst also shows outstanding activity and stability in basic and neutral electrolytes.

Vertical-Aligned Li2 S-Graphene Encapsulated within a Carbon Shell as a Free-Standing Cathode for Lithium-Sulfur Batteries.

Construction of a novel matrix with both high conductivity and an excellent confinement effect for polysulfides is of great importance for developing high-performance lithium-sulfur (Li-S) batteries. In this work, we have developed a double-modification strategy to integrate lithium sulfide (Li2 S) into a conductive composite network consisting of vertical graphene (VG) arrays and an amorphous carbon shell, forming an integrated cathode (VG/Li2 S-C). Facile liquid-solution/evaporation methods in combination with chemical vapor deposition were successfully adopted for preparation of the above cathode. Due to the enhanced electrical conductivity and noticeable blocking effect for the shuttle of polysulfides, the binder-free flexible VG/Li2 S-C cathode exhibits high rate performance and reinforced cycles (656.2 mAh g-1 after 100 cycles). The pronounced electrochemical performance is ascribed to the unique architecture with a coherent conductive network of VG and the carbon shell, which not only provides a conductive network for fast reaction kinetics, but also forms a durable protective shield to suppress the shuttle of polysulfides. Our research further demonstrates the synergistic effectiveness by means of inner and outer carbon matrixes for electrochemical enhancement of Li-S batteries.

Synthesis of carbon-coated magnetic nanocomposite (Fe3O4@C) and its application for sulfonamide antibiotics removal from water.

The occurrence of antibiotics in the environment has recently raised serious concerns regarding their potential threat to human health and aquatic ecosystem. A new magnetic nanocomposite, Fe3O4@C (Fe3O4 coated with carbon), was synthesized, characterized, and then applied to remove five commonly-used sulfonamides (SAs) from water. Due to its combinational merits of the outer functionalized carbon shell and the inner magnetite core, Fe3O4@C exhibited a high adsorption affinity for selected SAs and a fast magnetic separability. The adsorption kinetics of SAs on Fe3O4@C could be expressed by the pseudo second-order model. The adsorption isotherms were fitted well with the Dual-mode model, revealing that the adsorption process consisted of an initial partitioning stage and a subsequent hole-filling stage. Solution pH exerted a strong impact on the adsorption process with the maximum removal efficiencies (74% to 96%) obtained at pH 4.8 for all selected SAs. Electrostatic force and hydrogen bonding were two major driving forces for adsorption, and electron-donor-acceptor interactions may also make a certain contribution. Because the synthesized Fe3O4@C showed comprehensive advantages of high adsorptivity, fast magnetic separability, and prominent reusability, it has potential applications in water treatment.

Graphene Chainmail Shelled Dilute Ni─Cu Alloy for Selective and Robust Aqueous Phase Catalytic Hydrogenation.

Cost-effective non-noble metal-based catalysts for selective hydrogenation with excellent activity, selectivity, and durability are still the holy grail. Herein, an oxygen-doped carbon (OC) chainmail encapsulated dilute Cu-Ni alloy is developed by simple pyrolysis of Cu/Ni-metal-organic framework. The CuNi0.05@OC catalyst displays superior performance for atmospheric pressure transfer hydrogenation of p-chloronitrobenzene and p-nitrophenol, and for hydrogenation of furfural, all in water and with exceptional durability. Comprehensive characterizations confirm the close interactions between the diluted Ni sites, the base Cu, and optimized three-layered graphene chainmail. Theoretical calculations demonstrate that the properly tuned lattice strain and Schottky junction can adjust electron density to facilitate specific adsorption on the active centers, thus enhancing the catalytic activity and selectivity, while the OC shell also offers robust protection. This work provides a simple and environmentally friendly strategy for developing practical heterogeneous catalysts that bring the synergistic effect into play between dilute alloy and functional carbon wrapping.

Effect of Heat Treatment on Structure of Carbon Shell-Encapsulated Pt Nanoparticles for Fuel Cells.

Polymer electrolyte membrane fuel cells (PEMFCs) have attracted much attention as highly efficient, eco-friendly energy conversion devices. However, carbon-supported Pt (Pt/C) catalysts for PEMFCs still have several problems, such as low long-term stability, to be widely commercialized in fuel cell applications. To address the stability issues of Pt/C such as the dissolution, detachment, and agglomeration of Pt nanoparticles under harsh operating conditions, we design an interesting fabrication process to produce a highly active and durable Pt catalyst by introducing a robust carbon shell on the Pt surface. Furthermore, this approach provides insights into how to regulate the carbon shell layer for fuel cell applications. Through the application of an appropriate amount of H2 gas during heat treatment, the carbon shell pores, which are integral to the structure, can be systematically modulated to facilitate oxygen adsorption for the oxygen reduction reaction. Simultaneously, the carbon shell functions as a protective barrier, preventing catalyst degradation. In this regard, we investigate an in-depth analysis of the effects of critical parameters including H2 content and the flow rate of H2/N2 mixed gas during heat treatment to prepare better catalysts.

Construction of poly (ionic liquid)-derived gold/silver alloy@nitrogen-doped carbon shell and its application for ratiometric electrochemical detection of nitric oxide.

A nitrogen-doped carbon shell loaded with a gold and silver alloy (Au/Ag@NCS) was constructed for highly sensitive electrochemical detection of NO. The Au/Ag@NCS material was prepared by use of SiO2 particles as a template to polymerize imidazolium-based ionic liquids loaded with gold and silver salts, and subsequent carbonization treatment and template removal. The hollow structure of the carbon material acted as a carrier for electrochemical sensing, offering high specific surface area, large pore capacity, robust electron conductivity, and excellent mechanical stability. The inclusion of gold in the composite enhanced its catalytic and sensing capabilities, while silver oxidation was employed as a reference signal for accurate detection. By utilization of the Au/Ag@NCS-modified electrode, a wide detection range from 0.5 nM to 1.05 µM with a low detection limit of 0.32 nM was achieved for NO detection. The electrochemical sensor also exhibited high selectivity and excellent stability. The fabricated sensor was further utilized to explore the release of NO from breast cancer cells, revealing that the electrochemical platform could be regarded as an important method to study the daily tests of NO in clinical application.

Origin and Formation Mechanism of Carbon Shell-Encapsulated Metal Nanoparticles for Powerful Fuel Cell Durability.

Proton exchange membrane fuel cells (PEMFCs) face technical issues of performance degradation due to catalyst dissolution and agglomeration in real-world operations. To address these challenges, intensive research has been recently conducted to introduce additional structural units on the catalyst surface. Among various concepts for surface modification, carbon shell encapsulation is known to be a promising strategy since the carbon shell can act as a protective layer for metal nanoparticles. As an interesting approach to form carbon shells on catalyst surfaces, the precursor ligand-induced formation is preferred due to its facile synthesis and tunable control over the carbon shell porosity. However, the origin of the carbon source and the carbon shell formation mechanism have not been studied in depth yet. Herein, this study aims to investigate carbon sources through the use of different precursors and the introduction of new methodologies related to the ligand exchange phenomenon. Subsequently, we provide new insights into the carbon shell formation mechanism using X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Finally, the thermal stability and electrochemical durability of carbon shells are thoroughly investigated through in situ transmission electron microscopy (in situ TEM) and accelerated durability tests.

Expired milk powder emulsion-derived carbonaceous framework/Si composite as efficient anode for lithium-ion batteries.

Anodes based on silicon/carbon composites promise their commercial prospects for next-generation lithium ion batteries owing to their merits of high specific capacity, enhanced ionic and electronic conductivity, and excellent compatibility. Herein, a series of carbonaceous framework/Si composites are designed and prepared by rational waste utilization. N, P codoped foam-like porous carbon/Si composites (FPC@Si) and N, P codoped carbon coated Si composites (NPC@Si) are fabricated by utilizing expired milk powder as a carbon source with facile treatment methods. The results indicate that the porous carbon skeleton and carbon shell can improve the conductivity of Si and stabilize the solid electrolyte interfaces to avoid direct contact between active material and electrolyte. Moreover, the influence of drastic volume expansion of Si on the anode can be efficiently alleviated during charge/discharge processes. Therefore, the Si/C composite electrodes present excellent long-term cycling stability and rate capability. The electrochemical performance shows that the reversible capacity of FPC@Si and NPC@Si can be respectively maintained at 587.3 and 731.2 mAh g-1 after 1000 charge/discharge cycles under 400 mA g-1. Most significantly, the optimized Si/C composite electrodes exhibit outstanding performance in the full cell tests, promising them great potential for practical applications. This study not only provides a valuable guidance for recycling of waste resources, but also supports a rational design strategy of advanced composite materials for high-performance energy storage devices.

Solvent Influence on the Magnetization and Phase of Fe-Ni Alloy Nanoparticles Generated by Laser Ablation in Liquids.

The synthesis of bimetallic iron-nickel nanoparticles with control over the synthesized phases, particle size, surface chemistry, and oxidation level remains a challenge that limits the application of these nanoparticles. Pulsed laser ablation in liquid allows the properties tuning of the generated nanoparticles by changing the ablation solvent. Organic solvents such as acetone can minimize nanoparticle oxidation. Yet, economical laboratory and technical grade solvents that allow cost-effective production of FeNi nanoparticles contain water impurities, which are a potential source of oxidation. Here, we investigated the influence of water impurities in acetone on the properties of FeNi nanoparticles generated by pulsed laser ablation in liquids. To remove water impurities and produce "dried acetone", cost-effective and reusable molecular sieves (3 Å) are employed. The results show that the Fe50Ni50 nanoparticles' properties are influenced by the water content of the solvent. The metastable HCP FeNi phase is found in NPs prepared in acetone, while only the FCC phase is observed in NPs formed in water. Mössbauer spectroscopy revealed that the FeNi nanoparticles oxidation in dried acetone is reduced by 8% compared to acetone. The high-field magnetization of Fe50Ni50 nanoparticles in water is the highest, 68 Am2/kg, followed by the nanoparticles obtained after ablation in acetone without water impurities, 59 Am2/kg, and acetone, 52 Am2/kg. The core-shell structures formed in these three liquids are also distinctive, demonstrating that a core-shell structure with an outer oxide layer is formed in water, while carbon external layers are obtained in acetone without water impurity. The results confirm that the size, structure, phase, and oxidation of FeNi nanoparticles produced by pulsed laser ablation in liquids can be modified by changing the solvent or just reducing the water impurities in the organic solvent.

Nickel Phosphide Coated with Ultrathin Nitrogen-Doped Carbon Shell as a Highly Durable and Active Catalyst towards Hydrogen Evolution Reaction.

Developing non-precious metal catalysts towards hydrogen evolution reaction (HER) is of both high scientific and technical importance for the widespread application of water electrolysis. Herein, Ni2 P nanoparticles coated with a ultrathin N-doped carbon shell were prepared as a highly efficient HER catalyst. Ni2 P@CN exhibits both enhanced catalytic activity and durability in comparison with the carbon-supported Ni2 P counterpart, and represents 100% faradaic yield for HER in an acidic medium. The improved charge transfer of N-doped graphitic carbon shells contributes to the increase in activity. Meanwhile, the carbon shells suppress the aggregation and exfoliation of Ni2 P nanoparticles. As a result, the synergistic role of the N-doped carbon layer confers the Ni2 P cores with boosted activity and stability.

Preparation of CoFe@N-doped C/rGO composites derived from CoFe Prussian blue analogues for efficient microwave absorption.

At present, in order to solve the problem of microwave radiation and interference, it is urgent to study high performance microwave absorption (MA) materials with strong absorption ability, light weight, thin thickness and broad bandwidth. In this work, CoFe@nitrogen-doped carbon/rGO (CoFe@NC/rGO) composites derived from CoFe Prussian blue analogues were successfully prepared by in situ growth and annealing. And the effects of GO content on the MA performances of the composites were studied systematically. Results reveal that MA properties of CoFe@NC/rGO composites are enhanced by introduction of GO, this is mainly because the addition of GO can provide large specific surface area for microwave reflection, enhance interfacial polarization and compensate the insufficient dielectric loss. Moreover, impedance matching, conduction loss and attenuation ability are also improved obviously. CoFe@NC/rGO composites show outstanding MA capability, and the minimum reflection loss is up to -53.0 dB at a thickness of 2.4 mm, the largest effective absorption bandwidth can achieve 4.48 GHz at a thin thickness of 1.7 mm. In consideration of the superior MA performances, the CoFe@NC/rGO composites will be ideal candidates for high-efficient MA applications.

Porous ZnO Nanosphere Inherently Encapsulated in Carbon Framework as a High-Performance Anode For Ni-Zn Secondary Batteries.

Nickel-zinc (Ni-Zn) secondary battery that is environmentally friendly and inexpensive has been regarded as a promising rechargeable battery system. However, the generation of deformation and dendrites of the traditional zinc anode during the cycling can cause capacity degradation and impede its practical application. Herein, we design a hierarchical ZnO nanosphere coated with an inherently derived ZIF-8 porous carbon shell (ZnO@CZIF-8) using a simple controllable method. The conductive carbon shell and porous ZnO core can provide more active sites, allow the fast transfer of electrons, and buffer the volume expansion of the electrode effectively. Benefiting from the synergistic effect amid the inherently ZIF-8-derived carbon shell and ZnO core, ZnO@CZIF-8 nanospheres exhibit a satisfying capacity of 316 mAh g-1 at a current density of 1 A g-1 after 50 cycles and an outstanding rate capacity when acting as the anode for a Ni-Zn secondary battery with merchant agglomerative Ni(OH)2 as the cathode. These results imply that the ZnO@CZIF-8 nanosphere is a hopeful anode for a high-energy Ni-Zn secondary battery.

Heterogeneous interface in hollow ferroferric oxide/ iron phosphide@carbon spheres towards enhanced Li storage.

Heterogeneous interface and structural engineering play important roles for electrochemical performance of lithium-ion batteries. Herein, heterostructures of hollow Fe3O4/FeP spheres coated with carbon shell (H-Fe3O4/FeP@C) are designed to enhance lithium storage performance. As bifunctional anode materials, the H-Fe3O4/FeP@C spheres show the good rate performance with 458.4 mAh g-1 at 5 A g-1 and long-cyclic performance (630.2 mAh g-1 at 2.0 A g-1 after 1000 cycles). Density functional theory calculations demonstrate that the heterogeneous interfaces from (311) plane of Fe3O4 and (002) plane of FeP possess high charge density and distinct metallic character, which can improve the conductivity, increase the adsorption energy, provide more active sites and reduce the transfer barrier of ions and electrons. Besides, hollow structure of H-Fe3O4/FeP@C not only alleviates the volume expansion during lithiation/delithiation process but also shortens the diffusion distance of Li ions. In addition, the ex-situ X-ray diffraction and X-ray photoelectron spectroscopy are used to reveal the electrochemical Li storage mechanisms of H-Fe3O4/FeP@C. This work provides a novel route for design and preparation of Fe-based heterostructures for various energy storage systems in the future.

Encapsulated ruthenium nanoparticles activated few-layer carbon frameworks as high robust oxygen evolution electrocatalysts in acidic media.

Noble metals have been extensively employed as high active catalysts for oxygen evolution reaction (OER), are usually subjected to serious surface transformation and poor structural stability, especially in acid media, which need imperatively remedied. Herein, the interfacial engineering of Ru via few-layer carbon (Ru@FLC) was carried out, in which FLC can significantly suppress the corrosion of Ru in acid media, ensuring the efficient interfacial charge transport between Ru and FLC. As a result, a low overpotentials@10 mA cm-2 of 258 mV and small Tafel slopes of 53.1 mV dec-1 for oxygen evolution OER were achieved in acid media. DFT calculations disclose that outer FLC could induce charge redistribution and effectively optimize intermediates free energy adsorption, resulting in greatly reduce the energy barrier for OER. Our work may offer a new avenue to produce progressive OER electrocatalysts for energy-related applications in acid solution.

FeP Coated in Nitrogen/Phosphorus Co-doped Carbon Shell Nanorods Arrays as High-Rate Capable Flexible Anode for K-ion Half/Full Batteries.

Building a proper flexible electrode with high cycling stability, rate capacity and initial coulombic efficiency (ICE) for flexible potassium-ion batteries (PIBs) remains a challenge. Herein, nitrogen/phosphorus co-doped carbon coated FeP nanorods arrays on carbon cloth (FeP@N, PC NRs/CC) as high-rate capable flexible self-supporting anode was successfully fabricated. The composite electrode combines the advantages of FeP nanorods arrays (FeP NRs), carbon cloth (CC) and N, P co-doped carbon shell (N, P-C), which comprehensively improves the electrochemical stability of the flexible electrode, while the open space between FeP nanorods can facilitate electrolyte impregnation and enhance K+ transfer, thus effectively elevating the corresponding rate capability. For the FeP@N, PC NRs/CC electrode, it delivers a reversible capacity of 388.8 mA h g-1 at 0.5 A g-1 up to 400 cycles. Even at 1.5 A g-1, it can still achieve a remarkable rate capacity of 346.9 mA h g-1. Moreover, the assembled soft-packed cell can always light the LED lights when it is bent at different angles, which exhibits excellent mechanical flexibility.

Carbon-encapsulated V2O3 nanorods for high-performance aqueous Zn-ion batteries.

Searching for stable cathodes is of paramount importance to the commercial development of low-cost and safe aqueous Zn-ion batteries (AZIBs). V2O3 is a good candidate for AZIB cathodes but has unsatisfied cycling stability. Herein, we solve the stability issue of a V2O3 cathode by coating a robust carbon shell. Strong evidence was provided that V2O3 was oxidized to favorable V2O5·nH2O during charging and the carbon shell could promote the oxidation of V2O3 to V2O5·nH2O. The discharge capacity was increased from ∼45 mA h g-1 to 336 mA h g-1 after V2O3 was oxidized to V2O5·nH2O, indicating a higher Zn2+-storage capability of V2O5·nH2O than V2O3. In addition, the rate-capability and long-term cycling performance are greatly enhanced after coating carbon shells on the surface of V2O3 nanorods. Therefore, the presented strategy of introducing carbon shells and fundamental insights into the favorable role of carbon shells in this study contribute to the advancement of highly stable AZIBs.

Laser synthesis of iron nanoparticles as effective catalysts for the growth of vertically aligned MWCNTs with amorphous shell.

Vertically aligned multi-walled carbon nanotubes (MWCNTs) are attractive for use in nanoelectronics, nanosensors, electrodes for energy storage and harvesting devices, composites, weaving yarns and many other devices. However, in order to reach practical relevance in these applications, the vertically aligned MWCNTs must be dense and sufficient height. Fulfilling those requirements is often challenging. Herein, we report production of high density vertically aligned MWCNTs with amorphous shell on iron nanoparticles by the modified CVD method in the tube flow reactor via catalytic pyrolysis of acetylene. The iron thin films of thickness from 0.5 to 68 nm were obtained by the pulsed laser deposition in droplet-free mode on single crystal silicon substrates (100). The obtained films of the thickness from 0.5 to 20 nm were arrays of nanoparticles with a size from 5 to 17 nm as a result of thermal annealing. These nanoparticles were used as catalysts for the growth of MWCNTs. SEM investigations have shown that height of the obtained vertically aligned MWCNTs depends on the thickness of the initial iron film. The height of the MWCNTs array of 42 µm was achieved on the iron nanoparticles obtained after annealing the metal film of 5 nm thickness. The growth temperature of the obtained MWCNTs array was 700 °C at the volume flow ratio of the C2H2 and H2(5%)/Ar gas mixture was 1:4. TEM investigations have shown that the diameter of the obtained MWCNTs reached 15-20 nm with amorphous shell thickness of 5-10 nm. Four distinguished Raman peaks at 1360, 1603, 2711, and 2932 cm- 1 correspond to the D-band, G-band, 2D-band, and (D + G)-band, respectively and confirm the formation MWCNTs with good graphitization.