High Open Circuit Potential Research Articles

Oxygen vacancy-rich N-doped carbon encapsulated BiOCl-CNTs heterostructures as robust electrocatalyst synergistically promote oxygen reduction and Zn-air batteries

The development of non-precious metal catalysts for oxygen reduction reactions (ORR) is vital for promising clean energy technologies such as fuel cells, and zinc-air batteries. Herein, we present a stepwise synthesis of N-doped and carbon encapsulated BiOCl-CNTs heterostructures. Electrocatalytic ORR studies show that the optimized catalyst has a high half-wave potential (E1/2) of 0.85 V (vs. RHE), large limiting current density (-5.34 mA cm−2@0.6 V) in alkaline medium, and nearly perfect 4e− reduction characteristics, even surpassing commercial Pt/C. Meanwhile, the catalyst has exceptional durability (above 97.5 % after 40000 s) and strong resistance towards methanol poisoning. The good ORR activity also results in high-performance zinc-air batteries with a specific capacity (724 mAh g−1@10 mA cm−2), a high open-circuit potential of 1.51 V and a peak power density of 170.7 mW cm−2, as well as an ultra-long charge–discharge cycle stability (155 h), comparable with the Pt/C catalyst. The catalytic mechanism reveals that the excellent electrocatalytic performance originates from the synergistic effect of N doping, oxygen vacancies, and BiOCl sites.

Structure and tribological behavior of CrAlCN coating in artificial seawater

This study examined the tribological behavior of CrAlCN coatings on 316 l stainless steel and TC4 alloy sliding against Si3N4 ball in seawater. The coatings were systematically investigated by XRD, XPS, SEM, TEM and EDS. The mechanical and tribological properties were analyzed by nano indentation test and tribometer, respectively. The results showed that the coating contained CrN, CrC, AlN and amorphous (α–C) phases. The nanocrystalline was surrounded by α–C phases. The hardness of CrAlCN coatings on both substrates was about 21 GPa. The CrAlCN coating on TC4 had the highest Open Circuit Potential, lowest corrosive current density and wear rate, indicating that it had the best wear resistance and corrosion resistance in seawater.

Metal-Organic Framework-Derived Trimetallic Nanocomposites as Efficient Bifunctional Oxygen Catalysts for Zinc-Air Batteries.

Transition-metal-based multifunctional catalysts have attracted increasing attention owing to high possibilities of substituting the expensive noble-metal-based catalysts in various scenarios. Multivariate metal-organic frameworks (MTV-MOFs) are ideal precursors to prepare multimetallic nanocomposites with high catalytic activity since the uniform distribution and precise regulation of mixed metal centers, as well as the consequent strong synergistic effect, could be readily achieved. Herein, a Mn/Co/Ni trimetallic catalyst (MnCoNi-C-D) with a hollow rhombic dodecahedron shape was synthesized via pyrolysis of the corresponding trimetallic-based MTV-MOF. The catalyst shows outstanding electrochemical activity toward the oxygen reduction reaction including a half-wave potential of 0.82 V and superior tolerance against methanol as well as high stability in an alkaline medium, and its oxygen evolution reaction activity also surpasses a RuO2 catalyst. Moreover, primary and rechargeable zinc-air batteries based on MnCoNi-C-D delivered preferable performances compared with commercial Pt/C-RuO2, including higher peak power density (116.4 mW cm-2), higher specific capacity (841.3 mAh g-1), higher open-circuit potential (OCV) (1.46 V), and better stability for more than 180 h. A comprehensive comparison was also conducted to prove the necessity of employing the MTV-MOF as the precursor and investigate the intrinsic superiority of the catalyst.

Ion‐Induced Formation of Hierarchical Porous Nitrogen‐Doped Carbon Materials with Enhanced Oxygen Reduction

AbstractNanostructured nitrogen‐doped carbon materials are considered as an appealing material to replace precious‐metal Pt‐based catalysts in fuel cells due to a high oxygen reduction reaction (ORR) activity and outstanding stability. In the present work, we developed an ion‐induced method for the fabrication of hierarchical porous nitrogen‐doped carbon materials (HPNC) using Cd‐organic complexes as sacrificial templates and precursors. During pyrolysis, a hierarchical porous structure with a high specific surface area was formed through the combination of a metal‐free ion as structure‐directing agent and the evaporation property of Cd. Benefiting from this unique structure, the resulting HPNC exhibited comparable ORR performance with commercial Pt/C, including positive onset potential of 0.96 V vs. RHE (reversible hydrogen electrode), positive half‐wave potential of 0.86 V vs. RHE, good methanol tolerance and stability. On this basis, the assembled Zn‐air battery showed high open circuit potential, power density and excellent stability.

Hollow Co3O4-x nanoparticles decorated N-doped porous carbon prepared by one-step pyrolysis as an efficient ORR electrocatalyst for rechargeable Zn-air batteries

Composites of cobalt oxides and nitrogen-doped porous carbon, as electrocatalysts for oxygen reduction reaction (ORR), offer considerable potential in new-style energy conversion and storage devices. Herein, a straightforward method for production of N-doped porous carbon (Co3O4-‍x@N–C) decorated by hollow Co3O4-x nanoparticles with oxygen vacancies has been studied by one-step pyrolysis of Co-doped quinone-amine polymer in gas mixture of NH3 and Ar. The nanosized CoO/Co3O4 heterostructure can boost the electron transport, while the hollow structure can ensure the structural and chemical stability of the catalyst, and the oxygen vacancy can change the surface electron structure and lower the activation energy barrier for oxygen reduction. Consequently, the as-prepared catalyst Co3O4-x@N–C exhibits excellent ORR catalytic performance (E1/2 = 0.845 V vs. RHE), exceeding that of Pt/C and most recently reported ORR catalysts. The Zn-air batteries assembled with Co3O4-x@N–C present a high open circuit potential (1.524 V), a large peak power density (105.2 mW cm−‍2) and great discharge-charge cycling performance, superior to the Zn-air batteries assembled with Pt/C. The excellent electrocatalytic performances of Co3O4-x@N–C make it an ideal alternative for precious metal catalyst (Pt/C) in rechargeable Zn-air batteries.

Microstructure and corrosion resistance of stainless steel manufactured by laser melting deposition

Abstract Additive manufacturing can not only fabricate complicate shaped parts, but also produce new non-equilibrium structures during the rapid heating and cooling process, involving new solid-solution phases and inhomogeous elemental distribution. The 316 L stainless steel (SS) plates were manufactured by laser melting deposition, and the effects of non-equilibrium structures on the corrosion resistance are investigated. The microstructures of the manufactured specimens are analyzed by X-ray diffraction, scanning electron microscopy, electron backscatter diffraction, and transmission electron microscopy. The corrosion performances are evaluated by electrochemical tests and salt spray tests in NaCl solution. The microstructures of the manufactured 316 L SS specimen are composed of cellular structures, where the boundaries of the cellular structures are enriched with Cr, Mn, Mo, and Nb elements. These cellular structures can significantly enhance the corrosion resistance, representing by higher open circuit potential and small pitting pores compared with the commercial 316 L SS. The reasons of the improved corrosion resistance can be attributed to the high densification and fine cellular structures with the enrichment of Cr and Mo elements at the interfaces.

Cobalt nickel boride nanocomposite as high-performance anode catalyst for direct borohydride fuel cell

Similar to MXene, MAB is a group of 2D ceramic/metallic boride materials which exhibits unique properties for various applications. However, these 2D sheets tend to stack and therefore lose their active surface area and functions. Herein, an amorphous cobalt nickel boride (Co–Ni–B) nanocomposite is prepared with a combination of 2D sheets and nanoparticles in the center to avoid agglomeration. This unique structure holds the 2D nano-sheets with massive surface area which contains numerous catalytic active sites. This nanocomposite is prepared as an electrocatalyst for borohydride electrooxidation reaction (BOR). It shows outstanding catalytic activity through improving the kinetic parameters of BH4− oxidation, owing to abundant ultrathin 2D structure on the surface, which provide free interspace and electroactive sites for charge/mass transport. The anode catalyst led to a 209 mW/cm2 maximum power density with high open circuit potential of 1.06 V at room temperature in a miniature direct borohydride fuel cell (DBFC). It also showed a great longevity of up to 45 h at an output power density of 64 mW/cm2, which is higher than the Co–B, Ni–B and PtRu/C. The cost reduction and prospective scale-up production of the Co–Ni–B catalyst are also addressed.

Flexible Nanogenerator from Electrospun PVDF-Polycarbazole Nanofiber Membranes for Human Motion Energy-Harvesting Device Applications.

Poly(vinylidene difluoride) (PVDF) has become the polymer matrix of choice for fabrication of wearable electronics and physiological monitoring devices. Despite possessing a high piezoelectric constant, additives are required to increase the charge transfer from PVDF matrix to connected signal readout units. Many of these additives also stabilize the β-phase of PVDF, which is associated with highest piezoelectric coefficients. However, most of the additives used are often brittle ceramic-phase materials resulting in decreased flexibility of the devices and offsetting the gain in β-phase content. Intrinsically conducting polymers (ICP), on the other hand, are ideal candidates to improve the device-related properties of PVDF, due to their higher flexibility than ceramic fillers as well as ability to form conducting network in PVDF membranes. This work reports the performance and device feasibility of PVDF-polycarbazole (PCZ) electrospun nanofiber membranes. A higher β-phase was observed by FTIR spectroscopy in PVDF/PCZ compared to other PVDF phases. Moreover, a higher open-circuit potential was recorded over PVDF/polyaniline composites, which were studied for comparison. The addition of PCZ reduced the flexibility of pure PVDF nanofibers by 20% only. Besides, the work investigated the bacterial biofouling and cell compatibility of the matrix, as essential properties to examine any putative medical device application. PVDF/PCZ membranes were then used to develop a nanogenerator, which was capable of instantly lighting an entire LED array employing the rectified output power, and charged up a 2.2 μF capacitors using a bridge rectifier through a vertical compressive force applied periodically. Finally, the nanogenerator demonstrated electrical energy harvesting from movements of various parts of the human body, such as toe and heel movement and wrist bending. In conclusion, PCZ can be considered as an attractive, biocompatible, and anti-biofouling conducting polymer for electrical actuation and flexible electronic device applications.

Efficient Water Splitting System Enabled by Multifunctional Platinum‐Free Electrocatalysts

AbstractTremendous research efforts have been focused on the development of a water splitting system (WSS) to harvest hydrogen fuels, but currently available WSSs are complicated and cost‐ineffective mainly due to the applications of noble platinum or different electrocatalysts. Herein, a novel WSS comprising electricity generation from solar panels, electricity storage in rechargeable zinc–air batteries (ZABs), and water splitting in electrolyzers, enabled by hybrid cobalt nanoparticles/N‐doped carbon embellished on carbon cloth (Co–NC@CC) as multifunctional platinum‐free electrocatalysts is reported. Consequently, the Co–NC@CC electrode presents excellent trifunctional electrocatalytic activity with an onset potential of 0.94 V for oxygen reduction reaction, and an overpotential of 240 and 73 mV to achieve a current density of 10 mA cm−2 for oxygen and hydrogen evolution reactions, respectively. For a proof‐of‐concept application, a rechargeable ZAB assembled from the high‐performance Co–NC@CC air cathode exhibits a high open circuit potential of 1.63 V and a superior energy density of 1051 Wh kg−1Zn. Furthermore, an overall water splitting electrolyzer constructed by the symmetrical Co–NC@CC electrodes delivers a current density of 10 mA cm−2 at a low cell voltage of 1.57 V. Such a solar‐powered WSS can harvest hydrogen day and night, demonstrating a potential for application in sustainable renewable energy.

Two-dimensional triazine-based porous framework as a novel metal-free bifunctional electrocatalyst for zinc-air batty

A metal-free carbon catalyst, melem-cyanuric acid complex (MCAC), was prepared by hydrogen bonding assembly and further explored as a novel bifunctional electrocatalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). The proposed MCAC network presented nanosheet-like structure, nitrogen-rich, and large specific surface area, which are close to the natures of graphitic carbon nitride (g-C3N4) and N-doped reduced graphene oxide (N-rGO), but giving much more defect active sites and regular framework structure. Compared with the g-C3N4, N-rGO and other reported carbon-nitride electrocatalysts, the MCAC nanosheets exhibited a lower overpotential of 1.45 V at a current density of 10 mA cm−2 for OER, along with a higher half-potential of 0.8 V and larger limit current density of −6.0 mA cm−2 for ORR. Density functional theory calculation revealed that the melem N atoms bonded with cyanurate greatly enhanced the OER activity by increasing the interaction between catalysts and intermediates. Furthermore, as a metal-free electrocatalyst, MCAC displayed superior reversible oxygen electrocatalytic activity, giving a small overpotential difference (0.76 V). The rechargeable zinc-air battery with MCAC as the air electrode in a two-electrode configuration showed a high open-circuit potential of 1.383 V and a specific capacity of 613.5 mA h gZn−1 at 10 mA cm−2. This work opens up a new avenue to develop advanced porous solids as metal-free electrocatalysts for the energy storage and conversion applications.

Interfacing spinel NiCo2O4 and NiCo alloy derived N-doped carbon nanotubes for enhanced oxygen electrocatalysis

The active sites on oxygen electrocatalyst and the number of inherent active species are important factors affecting the performance of Zn-air battery. Constructing multiphase interfaces is an effective strategy to increase the number of active species for oxygen electrocatalysts. In this work, the number of intrinsic active species of spinel oxygen electrocatalyst was increased and its catalytic activity was enhanced by the synergistic action of bimetallic center three interfaces and heteroatom-doped carbon nanostructures. The resulting NiCo2O4/NCNTs/NiCo as catalyst exhibits superior activity toward ORR (E1/2 = 0.83 V, JL = −5.38 mA cm−2) and OER (Ej10 = 1.58 V). Further, the obtained catalyst work as a cathode assembles as Zn-air battery with a high open-circuit potential of 1.51 V and excellent cycle stability (586 h). Theoretical results indicate that the desorption of *OH species is the rate-determining step for ORR, the multiphase interfaces in the NiCo2O4/NCNTs/NiCo will provide additional electrons due to the upward shift of antibonding orbitals relative to the Fermi level. Consequently, it boosts the oxygen adsorption and charge transfer and accelerate the reaction kinetics. This work emphasizes the synergistic effect between multiphase interfaces in transition metal composite catalysts and opens up a promising way for the preparation of efficient and stable transition metal electrocatalysts.

Microstructure and tribocorrosion properties of NiTi/AlNi2Ti ternary intermetallic alloy

NiTi/AlNi2Ti intermetallic alloy consisting of AlNi2Ti primary dendrites and NiTi interdendritic phase was fabricated by arc melting process. Tribocorrosion behaviors of the alloy in 0.5 mol/L H2SO4 solutions were characterized using tribocorrosion tests and X-ray photoelectron spectroscopy (XPS). Corrosion-wear synergistic effect and tribocorrosion mechanism were also discussed. The tribocorrosion test results showed that the open circuit potential (OCP) of NiTi/AlNi2Ti alloy decreases and the corrosion current density increases as the sliding starts, and the decrease in the OCP value is proportional to the increase in the frictional force, indicating a strong corrosion-wear synergistic effect. The NiTi/AlNi2Ti alloy has better tribocorrosion resistance than the 0Cr18Ni9 material in 0.5 mol/L H2SO4 solution with a high OCP, low corrosion current and low wear volume. The wear volume of NiTi/AlNi2Ti alloy is about 10 times lower than that of reference material 0Cr18Ni9. The calculation results of materials loss (ΔV) during tribocorrosion test indicated that corrosion accelerated wear (Vcw) was the main corrosion-wear synergistic mechanism.

Defects enriched hollow porous Co-N-doped carbons embedded with ultrafine CoFe/Co nanoparticles as bifunctional oxygen electrocatalyst for rechargeable flexible solid zinc-air batteries

The construction and design of highly efficient and inexpensive bifunctional oxygen electrocatalysts substitute for noble-metal-based catalysts is highly desirable for the development of rechargeable Zn-air battery (ZAB). In this work, a bifunctional oxygen electrocatalysts of based on ultrafine CoFe alloy (4-5 nm) dispersed in defects enriched hollow porous Co-N-doped carbons, made by annealing SiO2 coated zeolitic imidazolate framework-67 (ZIF-67) encapsulated Fe ions. The hollow porous structure not only exposed the active sites inside ZIF-67, but also provided efficient charge and mass transfer. The strong synergetic coupling among high-density CoFe alloys and Co-Nx sites in Co, N-doped carbon species ensures high oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activity. First-principles simulations reveal that the synergistic promotion effect between CoFe alloy and Co-N site effectively reduced the formation energy of from O* to OH*. The optimized CoFe-Co@PNC exhibits outstanding electrocatalytic stability and activity with the overpotential of only 320 mV for OER at 10 mA·cm−2 and the half-wave potential of 0.887 V for ORR, outperforming that of most recent reported bifunctional electrocatalysts. A rechargeable ZAB constructed with CoFe-Co@PNC as the air cathode displays long-term cyclability for over 200 h and high power density (152.8 mW·cm−2). Flexible solid-state ZAB with our CoFe-Co@PNC as the air cathode possesses a high open circuit potential (OCP) up to 1.46 V as well as good bending flexibility. This universal structure design provides an attractive and instructive model for the application of nanomaterials derived from MOF in the field of sustainable flexible energy applications device.

1D/2D hierarchical Co1-xFexO@N-doped carbon nanostructures for flexible zinc–air batteries

Flexible zinc–air batteries (ZABs) are capable of powering the wearable electronic devices due to its high energy density and low cost. However, the sluggish oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) of the cathode materials greatly impede the practical application of ZABs. Here, we propose a synthetic strategy to prepare a unique 1D/2D hierarchical Co1-xFexO@NC nanostructures grown on flexible carbon cloth (Co1-xFexO@NC/CC), featuring enhanced OER and ORR reaction kinetics. The unique architecture is obtained from 1D Co1-xFex carbonate hydroxide hydrate nanowires grafted with 2D Co1-xFex-ZIF (ZIF = zeolitic imidazolate framework) nanosheets. For OER, the overpotential of Co0.68Fe0.32O@NC/CC is 260 mV. The half-wave potential of Co0.68Fe0.32O@NC/CC is 0.81 V for ORR. Moreover, the voltage gap is only 0.68 V. The assembled Co0.68Fe0.32O@NC/CC-based flexible ZABs exhibits a high open-circuit potential of 1.300 V, a high specific capacity of 673 mAh gZn−1, excellent cycling stability and outstanding flexibility, overwhelming the state-of-the-art Pt/C-based ZABs. The work will open up a new avenue for the development of the practical application of ZABs in wearable electronic devices.

MOF-Derived 2D/3D Hierarchical N-Doped Graphene as Support for Advanced Pt Utilization in Ethanol Fuel Cell.

Development of bifunctional catalysts with low platinum (Pt) content for the ethanol oxidation reaction (EOR) and the oxygen reduction reaction (ORR) is highly desirable, yet challenging. Herein, we present structural engineering of a series of two-dimensional/three-dimensional (2D/3D) hierarchical N-doped graphene-supported nanosized Pt3Co alloys and Co clusters (PtCo@N-GNSs) via a hydrolysis-pyrolysis route. For the ORR, the optimal PtCo@N-GNS exhibits a high mass activity of 3.01 A mgPt-1, which is comparable to the best Pt-based catalyst obtained through sophisticated synthesis. It also possesses excellent stability with minor decay after 50 000 cyclic voltammograms (CV) cycles in acidic medium. For the EOR, PtCo@N-GNS achieves the highest mass-specific and area-specific activities of 1.96 A mgPt-1 and 5.75 mA cm-2, respectively, among all of the reported EOR catalysts to date. The unique 2D/3D hierarchy, high Pt utilization, and valid encapsulation of nanosized Pt3Co/Co synergistically contribute to the robust ORR and EOR activities of the present PtCo@N-GNS. A direct ethanol fuel cell based on PtCo@N-GNS delivers a high open-circuit potential of 0.9 V, a stable power density of 10.5 mW cm-2, and an excellent rate performance, implying the feasibility of the bifunctional PtCo@N-GNS. This work offers a new strategy for designing an ultralow Pt loading yet highly active and durable catalyst for ethanol fuel cell application.

Atomically-dispersed Fe-Nx and C–S–C ordered mesoporous carbons as efficient catalysts for the oxygen reduction reaction in a microbial fuel cell

An efficient catalyst (Fe/S–N/C) possessing abundant ordered mesoporous was synthesized via a facile strategy, in which the active Fe-Nx and C–S–C species exhibited atomic dispersion. Attributing to its well-developed porosity, the total pore volume and specific surface area of Fe/S–N/C catalyst reach 0.556 cm3 g−1 and 980.9 m2 g−1 respectively. Electron microscopy results reveal the uniform dispersion of atomic Fe-Nx and C–S–C in this catalyst, which has inherited a polyhedral morphology derived from ZIF-8. X-ray spectroscopy measurements further validate that the Fe/S–N/C composite can provide abundant and highly efficient active sites for ORR. The atomic ratio of nitrogen is 4.28%, with high relative concentrations of the active pyridinic N and Fe-Nx. Furthermore, the Fe/S–N/C catalysts demonstrate significant ORR activity in the practical application of MFC devices. Based on a high open circuit potential (0.674 V) and maximum power density (1436.42 mW m−2) of the MFC device which uses the Fe/S–N/C as air-cathode catalyst, the Fe/S–N/C displays better catalytic activity than commercial 20% Pt/C catalyst. This investigation provides a new strategy to design an effective, low-cost ORR catalyst for MFC devices.

Effects of graphene polymer nano composite coating on corrosion resistance of Astm A106 carbon steel pipe

Wide application prospects of graphene in the corrosion protection coatings field are owing to its excellent mechanical properties, outstanding chemical stability, corrosion resistance, and high corrosion resistance. Anti-corrosion composite was prepared using multilayer graphene powder as a filler and epoxy resin in this work to investigate the effect of graphene compositions in the zinc-rich epoxy (ZRE) as the modified anti-corrosion coating for carbon steel pipe. Using SEM for morphology along with the electrochemical performance was associated with changed content composite coating of graphene and pure epoxy resin coating. The measurement for open-circuit potential (OCP), the potentiostat polarization curve (Tafel Plot), and the electrochemical impedance spectroscopy (EIS) of the coating were conducted in order to investigate the influence of additional of graphene on the basic properties and corrosion resistance. From the experimental results, the increasing content of graphene led by the increasing value of OCP as the test system was stable, also the coating of high content graphene sustained a moderately high OCP ability with the increase of immersion time. From the results in the industrial environment, 0.1wt% Graphene + 99.9wt% ZRE in a 240μm coating layer would be sufficient as the corrosion rate is 0.0087204mmpy and three times lower compare to 100wt% ZRE. In a nutshell, the addition of graphene improves the impenetrability of the composite coating.

Nanostructured Ni:BiVO4 photoanode in photoelectrochemical water splitting for hydrogen generation

Photoelectrochemical water splitting using bismuth vanadate (BiVO4) is drawing attention but on account of presence of high charge recombination and poor water oxidation kinetics its performance is restricted. Present study attempts to understand the role of dopant Ni on BiVO4 in a) reducing the charge recombination and b) to improve water oxidation kinetics. Ni doped BiVO4 thin films are prepared via electrodeposition method and photoelectrochemical properties are investigated in 0.1 M phosphate buffer solution with and without sodium sulfite hole scavenger. Photocurrent density of 1.36 mA/cm2 at 1.23 V vs. RHE has been obtained using 1.5% Ni doped BiVO4. This sample also offered lower flat band potential, high open circuit potential and applied bias photon-to-current conversion efficiency. Addition of hole scavenger significantly increases the photoelectrochemical performance. Ni as a dopant therefore can play an important role in not only suppressing the electron-hole pair recombination but also in offering significantly enhanced photoelectrochemical response.

Yttrium fluoride doped nitrogen-contained carbon as an efficient cathode catalyst in zinc-air battery

Recently, advanced nitrogen-containing carbon materials create a huge opportunity for developing efficient catalysts, and show great potential in zinc-air batteries (ZABs). In this study, YF3 doped nitrogen-containing carbon (YF3@NC) electrocatalyst is prepared using m-phenylenediamine as nitrogen and carbon sources. Yttrium chloride, ammonium fluoride and l-arginine are used as Y source, F source and assistant, respectively. Spherical YF3 precursor is obtained through a facile arginine-assisted hydrothermal method, which is then coated with nitrogen-containing carbon and pyrolyzed at high temperature to fabricate YF3@NC. It exhibits a positive onset potential (0.943 V), half-wave potential (0.836 V), high current density and good cycling stability (10 h degradation: 13%). When YF3@NC is applied as air cathode electrode in ZABs, the obtained battery has a high open circuit potential (1.478 V) and peak power density (75 mW cm−2). This approach makes YF3@NC to be a promising candidate as cathode catalyst in ZABs in the future.

Tribocorrosion behaviors of TiSiCN nanocomposite coatings deposited by high power impulse magnetron sputtering

High-performance coatings originated in ingenious coating designs and advanced preparation techniques are expected to fulfill imperious demands in propulsion, bearings and mechanical seals, etc in marine systems for seawater lubrication. In this work, TiSiCN nanocomposite coatings were deposited by high power impulse magnetron sputtering at a power of 4–8 kW. As power is increased, TiSiCN coatings possess nanocrystalline (TiN, TiC, TiCN)/amorphous (Si3N4, SiC, sp2-C) nanocomposite structure without distinctly preferred orientation. The highest hardness (H) of 43 GPa and effective Young’s modulus (E*) of 360 GPa were achieved at 8 kW, while the highest H/E* of 0.123 and H3/E*2 of 0.61 appear at 7 kW due to refined nano-grains, uniform distribution, high surface/interface integrity and fully dense microstructure. Rockwell C adhesion level increased from HF2 at 4 kW to HF1 at 8 kW. TiSiCN coatings with high H, H/E*, H3/E*2 and adhesion exhibit high open circuit potential of −0.07 V, low friction coefficient of 0.25 and specific wear rate of 4.78 × 10−5 mm3 N−1 m−1, resulting from mild abrasive wear without the occurrence of pitting corrosion in 3.5 wt.% NaCl aqueous solution. Moreover, cycling tribocorrosion tests revealed that passive films possess strong abilities of regeneration and self-repairation on sliding contact surface.