Pyrolysis of Iron(III) porphyrin coated Pt/C toward oxygen reduction reaction in acidic medium

Design and synthesis of highly active and durable electrocatalysts toward oxygen reduction reaction (ORR) is of particular importance for proton exchange membrane fuel cells (PEMFCs), yet remains a grand challenge. Herein, we report the deposition of iron (III) porphyrin (FeP) on house-made Pt/C by rotary evaporation of the mixture of FeP and house-made Pt/C dispersed in chloroform, followed by pyrolysis at 650 °C in argon atmosphere. This approach led to the synthesis of new non-precious metal electrocatalyst (NPME)-Pt/C composites (Pt/C–FeP) with an average nanoparticle diameter of 3.1 ± 1.5 nm without aggregation. According to X-ray photoelectron spectroscopy (XPS), the binding energy of Pt 4f_7/2 became larger due to the presence of pyrolyzed FeP. In addition, the electrochemically active surface area (ECSA) of Pt/C–FeP-650 is 65 m²/g less than that of house-made Pt/C (80.2 m²/g). This implies that the pyrolyzed FeP may have partially covered the surface of Pt nanoparticles and thus lowering the ECSA. Interestingly, the mass activity (MA) of Pt/C–FeP turns out to be 349.0 mA/mg_Pt @0.9 V vs. RHE, which is 2.6 times and 1.5 times of house-made Pt/C and commercial Pt/C, respectively. It is speculated that the electronic interaction and possible synergy between Pt and pyrolyzed FeP as NPME might have contributed to the ORR activity improvement despite of partial loss of ECSA. During accelerated durability tests (ADTs), the MA of Pt/C–FeP-650 degrades 64.3% inferior to commercial Pt/C (52.2%). The main reason likely arises from the degradation of pyrolyzed FeP, which is a bottleneck problem confronting NPMEs.     

FeCo-based mesoporous carbon shells modified N-doped porous carbon spheres for oxygen reduction reaction

FeCo-based non-noble metal electrocatalysts (NNMEs) of FeCo/MCS-NPCS was fabricated by immobilization of hemin on mesoporous carbon shells modified N-doped porous carbon spheres (MCS-NPCS). The obtained FeCo/MCS-NPCS exhibits a half-wave potential (E_1/2) of 0.851 ​V versus the reversible hydrogen electrode (vs. RHE) and a limited-diffusion current density (J_L) of 5.45 ​mA ​cm⁻². In addition, FeCo/MCS-NPCS shows comparable oxygen reduction reaction (ORR) performances to 20 ​wt% Pt/C in terms of E_1/2 and J_L and better electrochemical properties, including the methanol tolerance and durability in alkaline solution. Such outstanding electrochemical activities of FeCo/MCS-NPCS can be ascribed to Fe and/or Co-based nitrides and carbides as well as N-doped carbon matrixes modified with mesoporous carbon shells. This research introduces a promising path to design and synthesize highly efficient FeCo–N–C electrocatalysts towards ORR.     

Large specific surface area S-doped Fe–N–C electrocatalysts derived from Metal–Organic frameworks for oxygen reduction reaction

It is highly desired but challenging to develop platinum group metal-free electrocatalysts for oxygen reduction reaction (ORR), which can promote the commercialization of fuel cell technology. To achieve this target, we report a one-step doping method to prepare S-doped Fe–N–C catalysts using zeolite imidazole framework (ZIF-8) and iron (III) thiocyanate (Fe(SCN)₃) as precursor. Different from conventional doping approach, i.e. physical mixing, Fe(SCN)₃ is in-situ added during ZIF-8 formation which would encapsulate Fe(SCN)₃ molecules inside ZIF-8 to avoid structure destruction and create potential replacement of Zn ions by Fe ions to form uniform Fe–N₄ complexes. As a result, the prepared S-doped Fe–N–C catalysts own large specific surface areas with a maximum value of 1326 ​m² ​g⁻¹ and a dual-scale porous structure that benefits mass transport. Significantly, the composition-optimized catalyst exhibits superior ORR activity in both 0.1 ​M HClO₄ electrolyte and 0.1 ​M KOH electrolyte, in which the half-wave potential reaches 0.81 ​V and 0.92 ​V (vs. RHE), respectively. Remarkable stability is also attained, which loses 2 ​mV only after 10000 potential cycles in O₂-saturated 0.1 ​M HClO₄ and remains almost constant in O₂-saturated 0.1 ​M KOH, surpassing commercial Pt/C catalyst in both acidic and alkaline medium.     

Pd–Ni–P metallic glass nanoparticles for nonenzymatic glucose sensing

Metallic glass nanoparticles hold great promise as nonenzymatic glucose sensors due to their rich low-coordinated active sites and high biocompatibility. However,their non-periodic atomic structure and unclear structure-property relationship pose significant challenges for realizing and optimizing their sensing performance. In this work, Pd–Ni–P metallic glass nanoparticles with variable compositions were successfully prepared as nonenzymatic glucose sensors via a laser-evaporated inertgas conde...     

Synthesis of amorphous SeP2/C composite by plasma assisted ball milling for high-performance anode materials of lithium and sodium-ion batteries

To promote substantially the performances of red phosphorous(P) anode for lithium and sodium-ion batteries, a simple plasma assisted milling(P-milling) method was used to in-situ synthesize SeP₂/C composite. The results showed that the amorphous SeP₂/C composite exhibits the excellent lithium and sodium storage performances duo to the small nano-granules size and complete combination of selenium(Se) and phosphorous(P) to generate Se–P alloy phase. It was observed that insid...     

Corrosion resistance and thermal stability of sputtered Fe44Al34Ti7N15 and Al61Ti11N28 thin films for prospective application in oil and gas industry

Fe-and Al-based thin-film metallic glass coatings (Fe₄₄Al₃₄Ti₇N₁₅ and Al₆₁Ti₁₁N₂₈) were fabricated using magnetron co-sputtering technique, and their corrosion performances compared against wrought 316L stainless steel. The results of GI-XRD and XPS analyses demonstrated amorphous structure and oxide layer formation on the surface of the fabricated thin films, respectively. The potentiodynamic (PD) polarization test in chloride-thiosulfate (NH₄Cl ​+ ​Na₂S₂O₃) solution revealed lower corrosion current (I_corr) (0.42 ​± ​0.02 ​μA/cm² and 0.086 ​± ​0.001 ​μA/cm² Vs. 0.76 ​± ​0.05 ​μA/cm²), lower passivation current (I_pass) (1.45 ​± ​0.03 ​μA/cm² and 1.83 ​± ​0.07 ​μA/cm² Vs. 1.98 ​± ​0.04 ​μA/cm²), and approximately six-fold higher breakdown potential (E_bd) for Fe- and Al-based coatings than those of wrought 316L stainless steel. Electrochemical Impedance Spectroscopy (EIS) of both films showed 4- and 2-fold higher charge transfer resistance (R_ct), 7- and 2.5-times higher film resistance (R_f), lower film capacitance values (Q_f) (10 ​± ​2.4 ​μS-s^acm^-2, and 5.41 ​± ​0.8 ​μS-s^acm^-2 Vs. 18 ​± ​2.21 ​μS-s^acm^-2), and lower double-layer capacitance values (Q_dl) (31.33 ​± ​4.74 ​μS-s^acm^-2, and 15.3 ​± ​0.48 ​μS-s^acm^-2 Vs. 43 ​± ​4.23 ​μS-s^acm^-2), indicating higher corrosion resistance of the thin films. Cyclic Voltammetry (CV) scan exhibited that the passive films formed on the Fe- and Al-based coatings were more stable and less prone to pitting corrosion than the wrought 316L stainless steel. The surface morphology of both films via SEM endorsed the CV scan results, showing better resistance to pitting corrosion. Furthermore, the thermal analysis via TGA and DSC revealed the excellent thermal stability of the thin films over a wide temperature range typically observed in oil-gas industries.     

Microstructure and electrical conductivity of 10% Yb-doped SrCeO3 ceramics

As a candidate material for hydrogen separation, Yb-doped SrCeO₃ has attracted increasing attention in recent decades. In the present study, Yb-doped SrCe_0.9Yb_0.1O_3-α ceramics were prepared by the dry pressing and sintering approach, with the microstructure evolution and the micro morphology investigated. It was indicated that the ceramics sintered in air were of a pure perovskite structure, and that the sintering temperature had a significant effect on the growth of ceramic grains. The average grain size increased from 1 ​μm to 10 ​μm with an increase in sintering temperature from 1300 to 1500 ​°C. Further investigation of the thermodynamics and kinetics of grain growth revealed that the grain boundary diffusion was the main driving force of grain growth during solid phase sintering, with a grain growth index of 4 and an activation energy of approximately 61.23 ​kJ ​mol⁻¹. These results illustrate an obvious tendency of grain size growth. By electrochemical workstation with different atmospheres the effects of sintering temperature on the conductivity were characterized in the temperature range of 700–900 ​°C. The electrical conductivities σ of SrCe_0.9Yb_0.1O_3-α ceramics in different atmospheres were as follows: σ(wet hydrogen) ​> ​σ(dry hydrogen) ​> ​σ(dry air) ​> ​σ(wet air). In the test atmosphere containing water and hydrogen the conductivity of protons increased with increasing temperature because of the protons jump between lattices in the form of interstitial hydrogen ions or bare protons.     

Creep behavior and dislocation mechanism of Ni3Al based single crystal alloy IC6SX at 760℃

The creep behavior and dislocation mechanism of Ni₃Al-based single crystal alloys IC6 SX with crystal orientation[001] which was prepared by seed crystal method under the testing conditions of 760℃/500 MPa,760℃/540 MPa and 760℃/580 MPa were investigated. The experimental results showed that the creep properties,dislocation morphology and mechanism of this alloy were different under different stress conditions. With the stress increasing from 500 MPa to 580 MPa, the creep life decrease...     

Towards understanding the influence of Mg content on phase transformations in the La3-xMgxNi9 alloys by in-situ neutron powder diffraction study

The present work is focused on the studies of the phase-structural transformations in the La_3-xMg_xNi₉ (x = 1.0, 1.1 and 1.2) alloys as active materials of negative electrodes in the Nickel-Metal Hydride(Ni/MH) batteries. The phase equilibria and phase-structural transformations in the alloys were probed by in situ neutron powder diffraction(NPD) at the temperatures ranging from 300 K to 1273 K using the measurements of the equilibrated alloys at 8 setpoint temper...     

Current Research Progress in Magnesium Borohydride for Hydrogen Storage (A review)

Hydrogen storage in solid-state materials is believed to be a most promising hydrogen-storage technology for high efficiency, low risk and low cost. Mg(BH₄)₂ is regarded as one of most potential materials in hydrogen storage areas in view of its high hydrogen capacities(14.9 wt% and 145–147 kg cm^-3). However, the drawbacks of Mg(BH₄)₂ including high desorption temperatures(about 250°C–580°C), sluggish kinetics, and poor reversibility make it...     

Effect of carbon addition on microstructure and mechanical properties of a typical hard-to-deform Ni-base superalloy

In this paper, the as-cast microstructure, microsegregation, and mechanical properties of GH4151 superalloys with a carbon addition were studied by scanner electron microscopy(SEM), transmission electron microscope(TEM), electron probe microanalysis(EPMA), differential thermal analyzer(DSC), and electron backscattered diffraction(EBSD). The results show that the solid solution effect of carbon in alloys is limited, the addition of C from 0.01 to 0.08 wt% significantly refines the secondary dendr...     

A novel bimetallic RuFe nanocluster to enable highly efficient oxygen reduction in zinc-air batteries

Zinc-air batteries (ZABs) have the advantages of high energy density and safety but their large-scale application is hindered by sluggish kinetics of four-electron aqueous O₂ redox reactions. Widely used Ruthenium (Ru)-based catalysts possess intrinsic oxygen evolution catalytic activity but suffer from insufficient oxygen reduction reaction (ORR) performance. Herein, to optimize the ORR activity of Ru-based catalyst, an iron (Fe)-coordinated, bimetallic RuFe cluster is constructed and homogeneously dispersed within nitrogen (N)-doped carbon layers (denoted as RuFe@NC). Benefitting from the optimized ORR activity and more active site exposure, the RuFe@NC exhibits superior ORR activity with a half wave potential (E_1/2) of 0.88 ?V higher than that of Pt/C (0.82 ?V). Accordingly, the RuFe@NC-based ZAB outperforms the Pt/C ?+ ?IrO₂-based device, presenting a reduced polarization of 0.7 ?V and an enhanced cycling lifetime of 50 ?h at 10 ?mA ?cm^?2. Moreover, the optimized structural design ultralow Ru loading (0.013 mg_Ru cm^?2) overcomes the cost barriers and demonstrates its high practicality. This bimetallic RuFe nanocluster opens a new way for future design of more efficient and stable catalytic systems.     

Li3N film modified separator with homogenization effect of lithium ions for stable lithium metal battery

Lithium metal anode with high theoretical capacity is considered to be one of the most potential anode materials of the next generation. However, the growth of lithium dendrite seriously affects the application of lithium metal anode and the development of lithium metal batteries(LMBs). Herein, an ultrathin Li₃N film modified separator to homogenize the lithium ions and protect the lithium metal anode was reported. Due to the intrinsic properties of Li₃N, the functional sep...     

Ameliorating mechanical properties and reducing anisotropy of as-extruded Mg-1.0Sn-0.5Ca alloy via Al addition

Effects of Al addition to a Mg–Sn–Ca ternary alloy on its microstructure and tensile properties after extrusion were studied via extrusion of Mg-1.0 Sn-0.5 Ca-x Al(x = 0, 0.8, 2.4 wt%) sheets and analysis of the extruded materials.The results showed that Al addition not only refined the grain size(from 9.8 ± 0.7 μm to 8.3 ± 0.4 μm and7.6 ± 0.5 μm) but also accelerated the generation of more second phase(from 0.98 to 1.72 and 4.32%). Except for the CaMgSn and Mg₂Ca in Mg-1.0Sn-0.5 Ca a...     

Enhanced hydrogen storage properties of NaBH4–Mg(BH4)2 composites by NdF3 addition

As two important members of complex hydrides,Mg(BH₄)₂ and Na BH₄ have a high gravimetric capacity (14.9 and10.8 wt%,respectively).In this study,the Mg(BH₄)₂ was synthesized by the ion exchange method.Afterwards,the Mg(BH₄)₂ and Na BH₄ composites with different amounts (30,40 and 50 wt%) of NdF₃ were prepared by mechanical milling.Effects of the Nd F₃ on the microstructural evolution and ...     

Flexible free-standing polyaniline/poly(vinyl alcohol) composite electrode with good capacitance performance and shape memory behavior

The increasing demand for portable and flexible energy storage devices drives the development of flexible electrodes and electrolytes. The aim of this work is to fabricate the flexible free-standing polyaniline/poly(vinyl alcohol)(PANI/PVA) composite electrode with good capacitance performance and shape memory behavior. The electrodes were fabricated by chemical oxidation polymerization of aniline in porous PVA(P-PVA) films. The morphology, electrochemical and mechanical properties of PANI/P-PVA...     

Spectroscopic properties of Er3+/Ho3+/Tm3+ doped α-SiAlON ceramics under 793 ​nm excitation

This paper reports the first demonstration of super broadband infrared downshifting emission extending from 1640 ​nm to 2200 ​nm with the full width at half maximum of ∼ 417 ​nm in lanthanides (Er³⁺, Ho³⁺, and Tm³⁺)-doped α-SiAlON ceramics upon 793 ​nm excitation. Using α-Si₃N₄ ceramic as a precursor the lanthanides-doped α-SiAlON ceramics were synthesized by the hot-press method. The lanthanides induced no significant secondary phases in the sintered α-SiAlON ceramics. Strong two-photon upconversion emission bands centered at 547, 671 and 694 ​nm have also been observed upon 793 ​nm excitation. The time-resolved measurements of the upconversion emissions confirm that the efficient energy transfer among the Er³⁺, Ho³⁺ and Tm³⁺ ions as well as the ground state absorption in Er³⁺ and Tm³⁺ are responsible for the observed spectroscopic properties.     

Improvement in hydrogen storage performance of Mg by mechanical grinding with molten salt etching Ti3C2Clx

Mg-based materials are currently a hot research topic as hydrogen storage materials due to their considerable theoretical hydrogen storage capacity. However, the kinetic performance of hydrogen absorption and desorption of Mg is too slow and requires high temperature, which seriously hinders the application of this material. MXene is a new type of two-dimensional material with significant role in improving thermodynamics and kinetics. In this experiment, a two-dimensional layered MXene containing Cl functional group was prepared by molten salt etching using the Ti-containing MAX phase as the raw material. Then different ratios of Ti₃C₂Cl_x were uniformly dispersed onto the surface of Mg by high energy ball milling. The samples were characterized by hydrogen absorption and desorption kinetics, SEM, XRD, XPS, and DSC to investigate the effect of Ti₃C₂Cl_x on the hydrogen absorption and desorption performance of Mg. The onset hydrogen absorption temperature can be reduced to room temperature and the hydrogen release temperature is reduced by 200 ​°C by doping Ti₃C₂Cl_x. And there is also 5.4 ​wt% hydrogen storage in the isothermal hydrogen absorption test at 400 ​°C. The results of DSC demonstrate that the E_a of Mg+15 ​wt% Ti₃C₂Cl_x was reduced by 12.6% compared to pristine Mg. The ΔH is almost invariable. The results of XPS show that the presence of multivalent Ti promotes electron transfer and thus improves the conversion between Mg²⁺/Mg and H⁻/H. This study provides a guideline for further improving the hydrogen absorption and desorption performance of Mg-based hydrogen storage materials.     

Rational design of MnS nanoparticles anchored on N,S-codoped carbon matrix as anode for lithium-ion batteries

The manganese sulfide (MnS) has attracted more attention as anode material on energy storage and conversion field, owing to its high theoretical capacity (616 ​mA ​h ​g⁻¹) and good electrochemical activity. However, low electronic conductivity and large volume expansion during charge-discharge processes have limited its further application. In order to address above mentioned problems, the composites, MnS nanoparticles embedded in N,S-codoped porous carbon skeleton (named as MnS/N,S–C composites), herein have been prepared successfully using metal organic framework (Mn-NTA) as template. The porous carbon skeleton not only can enhance electrode conductivity, but also relieve volume expansion during charge-discharge processes. Thus, the rational design towards electrode architectures has endowed MnS/N,S–C nanocomposites with superior electrochemical performance, which delivers the specific capacities of 676.7 ​mA ​h ​g⁻¹ at the current density of 100 ​mA ​g⁻¹.     

Effects of heat treatment on microstructure and mechanical properties of SLMed Sc-modified AlSi10Mg alloy

The influence of heat treatments on the microstructures and mechanical properties of the selective laser melting manufactured AlSi10Mg alloy modified with Sc was systematically investigated. The results showed that the addition of Sc element introduced primary Al₃ Sc, which increased the heterogeneous nucleation during the solidification of AlSi10Mg alloy, and then the ultrafine network eutectic structure was obtained, and hence the tensile strength was improved significantly(nearly 2...