Fe Substitution Research Articles

Effect of goethite doping using elements with different preferential oxidation states for improved reversible phosphate adsorption

Phosphorus (P) removal from freshwater bodies to ultra-low concentrations is fundamental to prevent eutrophication, while its recovery is necessary to close the P usage cycle. Iron oxide-based adsorbents seem promising candidates, being abundant, cheap, and easy to synthesize compounds, with good affinity for P. Affinity is the key parameter when targeting ultra-low concentrations. Also, adsorbent regeneration and re-use is fundamental for the economic viability, hence the adsorbent stability is important. Goethite, (α-FeOOH), is one of the most stable iron (Fe3+) (hydr)oxide species, with higher affinity, but lower adsorption capacity (per kg) compared to other species. Doping could change goethite surface properties, to boost the adsorption capacity, while preserving the high stability and affinity for P. In this work, pure goethite was compared to goethite doped (5%at.) with different elements of different preferential oxidation states: Zn2+, Mn3+, and Zr4+. Doping was successfully achieved for all elements, albeit Zr showed a lower Fe substitution than targeted. Zn doping increased the goethite point of zero charge and adsorption capacity (per mass and per surface area), preserving the high affinity, while Mn- and Zr- doping displayed a decrease in all the parameters. These could be explained with surface protonation as a charge compensation mechanism in Zn2+-for-Fe3+ substitution. The regeneration test showed improved P recovery for Zr- and Zn-doped goethite. All samples remained stable throughout the whole process. This work provides promising insights on doping as a strategy to manipulate iron oxides surface properties and for developing a highly performing and long-lasting goethite-based adsorbent.

Effect of Fe substitution over ZSM-48 on performance of n-dodecane hydroisomerization and distribution of isomers

A series of Fe substituted ZSM-48 nanocrystal aggregates were synthesized by the dynamic hydrothermal method. Through incorporation of Fe into ZSM-48 framework, the acidity of ZSM-48 zeolites has been modified. The hydroisomerization performances of n-dodecane were investigated on Pt supported ZSM-48 and Fe incorporated ZSM-48 zeolites. Fe incorporated ZSM-48 catalysts show higher n-C12 hydroisomerization selectivity compared with parent sample due to weaker acid strength of Si–OH–Fe than Si–OH–Al. High temperature favor the generation of the multi-branched isomers (mainly dimethyl isomers) following the “Key-Lock” mode. Meanwhile, 5-methylundecane is the main product in the monomethyl isomers (MOB) and 2,6-dimethyldecane is the main product in the multi-branched isomers (MUB), which suggests the excellent shape selectivity of ZSM-48 and the “Key-Lock” mode is preferred on ZSM-48 catalysts regardless Fe substituted or not. The relationship between the mono-methyl isomers and the butene-TPD results has been correlated and investigated. Four desorption peaks corresponding to butene weakly adsorbed over Si–OH, Fe–OH or Lewis acid sites, the “Key-Lock” mode adsorbed butene, the “Pore-Mouth” mode adsorbed butene and the strongly adsorbed butene respectively, can be distinguished. ZLC results indicate that Fe modified ZSM-48 can effectively increase n-hexane diffusion rate and reduce the activation energy of diffusion of n-hexane, which is benefit for the hydroisomerization performance. SMOB/SMUB can be altered by Fe modification, however, the distribution of the mono-methyl isomers can hardly be affected.

Tailoring hydrogenation and anti-oxidation properties of titanium - iron - chromium alloys by regulating zirconium content at room temperature

The effects of Fe substitution by Zr on the microstructure, hydrogen storage properties and oxidation resistance of the TiFe0.85-xCr0.15Zrx (x = 0, 0.05, 0.10, 0.15) alloys are studied in this work. It is shown that all the alloys are consisted of TiFe phase, MgZn2-type phase and minor Ti phase. The introduction of Zr causes no change for the TiFe main phase. All the alloys absorb hydrogen directly under mild conditions without any activation process. As Zr content increases, the maximum hydrogen storage capacity of the first hydrogenation increases while the reversible hydrogen storage capacity decreases. The marked change of the first hydrogenation properties may be due to the formation of the bright phase (MgZn2-type phase). The decrease of the reversible hydrogen storage capacity is due to the formation of the stable hydrides Cr2ZrH3 and TiH2, which start to decompose at around 700 °C. During the air exposure test, the alloys with higher Zr content show good oxidation resistance. For the PCT measurement, the alloys with higher Zr show lower hydrogen absorption and desorption platform pressure, which means more stable hydrides are formed during the first hydrogenation. Moreover, the rate limiting step model of the first and fifth hydrogenation processes of all the alloys has also been investigated in detail.

A Novel Approach for Designing a Sub-Bandgap in CuGa(S,Te)2 Thin Films Assisted with Numerical Simulation of Solar Cell Devices for Photovoltaic Application.

As a well-explored chalcopyrite material, copper gallium sulfide CGS has been considered a potential material for solar cell absorber layers. However, its photovoltaic attributes still require to be improved. In this research, a novel chalcopyrite material, copper gallium sulfide telluride CGST, has been deposited and verified as a thin film absorber layer to fabricate high-efficiency solar cells by experimental testing and numerical simulations. The results display the intermediate band formation in CGST with incorporation of Fe ions. Electrical studies showed enhancement in mobility from 1.181 to 1.473 cm2 V-1 s-1 and conductivity from 2.182 to 5.952 S cm-1 for pure and 0.08 Fe-substituted thin films. The I-V curves display the photoresponse and ohmic nature of the deposited thin films, and the maximum photoresponsivity (0.109 A W-1) was observed for 0.08 Fe-substituted films. Theoretical simulation of the prepared solar cells was carried out using SCAPS-1D software, and the obtained efficiency displayed an increasing trend from 6.14 to 11.07% as the Fe concentration increased from 0.0 to 0.08. This variation in efficiency is attributed to the decrease in bandgap (2.51-1.94 eV) and the formation of an intermediate band in CGST with Fe substitution, which is evidenced in UV-vis spectroscopy. The above revealed results open the way to 0.08 Fe-substituted CGST as a promising candidate as a thin film absorber layer in solar photovoltaic technology.

Microstructure and mechanical properties of L12-strengthened Co–Ni–Fe-based superalloys

The effect of partial Fe substitution for Ni on microstructure, lattice misfit, oxidation, creep, and yield strength are investigated for six W-free cobalt-based superalloys with compositions Co-(30-x)Ni-xFe-yCr-5Al–3V–2Ti-1.5Nb-1.5Ta-0.08B (at.%), with three levels of Fe (x = 12, 14, or 18, replacing Ni) and two levels of Cr (y = 4 or 8, replacing Co). Alloys with 12 and 14% Fe exhibit mostly γ/γʹ microstructures after aging up to 1000 h at 850 °C, while those with 18% Fe display additional intermetallic phases. All alloys show positive lattice misfit from 0.56 to 0.34%, with Fe substitutions reducing lattice misfit by ∼0.02% per 1 at.% Fe. Increasing Fe from 12 to 18% reduces oxidation rates for both levels of Cr. Substitution of Ni by Fe also increases solvus temperature but reduces creep resistance at 850 °C as well as yield strength below 800 °C. By contrast, increasing Cr from 4 to 8 at.% improves both oxidation and creep resistance at 850 °C.

Origin of Fe-rich clay minerals in Early Devonian volcanic rocks of the Northern Minusa basin, Eastern Siberia

The formation of clay minerals in volcanic successions follows various evolutionary trends, the understanding of which is crucial for estimating the age of volcanism and the prospecting clay deposits. Early Devonian volcanics within the Byskar Series of the Minusa Depression (Khakassia) are variably altered to a range of phyllosilicate mineral assemblages. This study highlights the origin and formational conditions of the clay minerals, including illite, glauconite, smectite (saponite) and chlorite. Detailed mineralogical and chemical investigation identifies the predominant phyllosilicates, including 1 M illite, illite-smectite (R = 3), 1 M glauconite, smectite, chlorite and kaolinite within trachyandesite, trachyte, and rhyodacite. The phyllosilicates formed by the diagenetic transformation of volcanics after eruptive phases. Evolution trends of phyllosilicates depend largely on the composition of the volcanic substrate. The smectite to illite trend developed due to the dissolution of felsic volcanics and the alteration of smectites into illites with the K+, Al3+ and Mg2+ dominating the mineral formation system. The illites evolved by the substitution of Fe2+ and Mg2+ for Al3+ in the octahedral sheets of smectites. The K+, which was released due to devitrification of felsic substances, was introduced into the interlayer sites for compensating the layer charge originated by the isomorphic substitution in tetrahedral and octahedral sheets. The smectite to glauconite transition trend corresponds to the devitrification and dissolution of alkaline intermediate-felsic volcanics. Early formed dioctahedral smectites evolved into glauconite probably with the predominance of K+ and Fe2+/3+ ions in the formation environment. The substitution of Fe2+/3+ to Al3+ and Mg2+ in the octahedral sheets of smectite contributed to the formation of a layer charge and the entry of exchangeable K+ into the interlayers of glauconite. The third trend involved the formation of smectites (saponites) or chlorites within the intermediate volcanics possibly with Mg-rich but K-poor mineral system.

Cobalt mineralogy at the Iron Creek deposit, Idaho cobalt belt, USA: Implications for domestic critical mineral production

Abstract Current U.S. policies aim to establish domestic supply chains of critical minerals for the energy transition. The Iron Creek deposit in the Idaho cobalt belt (ICB) is one of the most promising cobalt (Co) targets. Our case study illustrates the importance of mineralogy in strategic evaluations of critical mineral potential. Most of the Co at Iron Creek occurs as Fe substitution in pyrite, with lattice-bound and inclusion-hosted Ag, As, Bi, Ni, Pb, Se, Te ± trace Au and Sb. Cobalt also occurs in minor cattierite-vaesite. The Co minerals are intergrown with Co-poor chalcopyrite hosting Cu ± minor In and Zn. Worldwide, most Co is recovered from deposits mineralogically distinct from the ICB, and the United States currently lacks infrastructure to recover this Co and its associated metals. ICB ore minerals could be processed by autoclave, roaster, smelter, bioleach, or heap leach. Recovery of the Ag, As, Au, Bi, In, Pb, Se, Te, and Zn would be costly by autoclave, and construction of a custom smelter for ICB ores is likely uneconomic, so these elements would become waste irrespective of criticality. The Co-Fe and Co-As sulfide minerals are most suitable for Co and Ni recovery by a hydrometallurgical autoclave process, with potential pretreatment of cobaltiferous pyrite/arsenopyrite in an inert-atmosphere roaster, in new domestic or anticipated international facilities. The ICB is the second largest known Co resource in the United States. Consideration of ore mineralogy in the ICB is essential in strategies for domestic production.

Physical properties of the full Heusler-type Ru2-Fe NbAl (x = 0.00–0.50) alloys

We report the physical properties of a series of full Heusler-type Ru2-xFexNbAl (x = 0.00–0.50) alloys using magnetization, electrical resistivity (ρ), Seebeck coefficient (S), and thermal conductivity (κ) measurements. Structure and phase analysis via x-ray diffraction and scanning electron microscopy indicate that Fe replaces the Ru in Ru2NbAl, and the antisite disorders reduce. The dc magnetization shows predominantly paramagnetic behavior for all Fe-doped samples, as in the pristine Ru2NbAl sample. Interestingly, the electrical resistivity measurements reveal that the conduction behavior of Ru2NbAl alloy changes from semiconducting-like to metal-like with Fe substitution. In addition, a minimum in resistivity at low temperatures is observed in the Fe-doped samples. It is noted that the minimum shifts to low temperatures with Fe content, presumably due to the weak localization effect. The Seebeck coefficient measurements show that charge carriers of these alloys remain hole type with a maximum S value of ∼27 µV/K at 300 K for x = 0.13, a result of the modification of the electronic band structure. The Fe substitution is found to reduce thermal conductivity significantly. An analysis of the lattice thermal conductivity indicates that the reduction in κ is primarily due to more grain boundaries, Umklapp phonons, and electron scatterings. These observations lead to an increase in the thermoelectric performance, i.e., the figure of merit and power factor, to about 0.007 and 1.7 μW/cm K2 at 300 K for the optimized composition of Fe with x = 0.13.

Iterative cluster expansion approach for predicting the structure evolution of mixed Ruddelsden-Popper oxides La2−xSrxNi1−yFeyO4±δ

Layered perovskites viz. Ruddlesden-Popper (RP) compounds have attracted a significant research interest lately due to their superior electrocatalytic activities, on top of their rich physics. Although the versatility of their compositional space is the key to tune their stability and applicability, its complexity also makes the understanding and design of new functional RP-based materials difficult. Herein by parameterizing a cluster expansion model Hamiltonian with density-functional inputs, we have successfully scanned over the complex configurational space of an RP phase, taking ${\mathrm{La}}_{2\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{Ni}}_{1\ensuremath{-}y}{\mathrm{Fe}}_{y}{\mathrm{O}}_{4\ifmmode\pm\else\textpm\fi{}\ensuremath{\delta}}$ as an example. This surrogate model is then used to predict the energies of unknown compositions and performing Metropolis Monte Carlo sampling for finding the ground-state structures. By analyzing these stable configurations at different $x, y$'s, and $\ensuremath{\delta}$=0, 0.125, we found that apical vacancies in the rock-salt layer are more favorable due to lesser steric forces but changes in $A$-site oxidation state due to Sr substitution can facilitate equatorial O-vacancy formation even in the perovskite layers. Our results uncover the structural evolution of RP oxides with increasing $A$-site (Sr) and $B$-site (Fe) substitutions. We find that a critical Sr concentration is required to stabilize Fe in these systems. With increasing Sr concentration, the $A$-site charge state changes gradually from ${\mathrm{La}}^{+3}$ to ${\mathrm{Sr}}^{+2}$, which facilitates both O-vacancy formation and stabilization of the $B$-site dopants. The findings further highlight the effects of configurational changes for the same composition on electronic structure. Thus, our work clearly demonstrates the importance of exploring configurational space of these complex oxides when using electronic-structure features as descriptors of their catalytic and other functional properties.

Effect of replacing M (M=Cu, Zn) with Fe on the properties of high entropy (MgCoNiZnCu)O

Fe substitution of Cu or Zn in the high-entropy powder (MgCoNiCuZn)O was realized with a hydrothermal method. The effects of different substitution amounts on the crystal structure, product morphology and electrochemical properties of high entropy (MgCoNiCuZn)O were determined with X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEMEDS) and electrochemical methods. The results showed that when Zn was replaced by 0.05 mol of Fe at 160 ℃ for 12 h or 900 ℃ for 3 h, all of the Fe entered the high entropy rock salt structure and cooperated with Cu2+ to provide more channels for the removal/insertion of Li+, thus improving the electrochemical performance. The discharge capacity was 631.5 F/g at 0.1 A/g, and the capacity retention rate was 89% after 500 cycles.

Synthesis, structure, morphology, magnetism, and magnetocaloric-effect studies of La0.7Sr0.3Mn1−xFexO3 perovskite nanoparticles

Single-phase La0.7Sr0.3Mn1−xFexO3 (x = 0.0, 0.04, 0.08, 0.12, 0.16, 0.20, 0.24, and 0.30) perovskites were synthesized by the sol-gel method followed by sintering at 800 °C for 5 h. The XRD showed the rhombohedral structure with the R-3c space group and there was a slight change in the lattice parameters as well as the unit cell volume of the compounds with Fe doping. The average particle size of the samples was in the range of 43–70 nm. All samples show a ferromagnetic to paramagnetic second-order magnetic phase transition at TC and TC decreases linearly from 370 K for x = 0 to 98 K for x = 0.3. From the XPS measurement, it was found that the oxidation state of Fe and La are + 3 and the Mn has a mixed valence state of Mn4+/Mn3+. The saturation magnetization and the blocking temperature were suppressed by the Fe substitution while (-ΔSM)max was found to decrease as Fe content increased. The sample with x = 0.08 has a Curie temperature of 297 K, the highest relative cooling power (RCP) of 153 J/kg, and (-ΔSM)max value of 1.46 J/kg.K at µoΔH = 2.8 T. The La0.7Sr0.3Mn1−xFexO3 iron-substituted manganites may be regarded as a prospective candidate for room-temperature magnetic refrigeration applications.

Multiferroic and half-metallic character of hexagonal BaTi0.5Fe0.5O3: DFT based calculation

ABSTRACT In this paper, we report a density functional theory (DFT) calculation study based on the full potential linear augmented plane wave (FP-LAPW) to investigate the effect of Fe incorporation in hexagonal BaTiO3 with a high Fe content : BaTi0.5Fe0.5O3.We discuss the structural, mechanical, electronic and magnetic properties as well as the spontaneous electrical polarisation P. The partial Fe substitution in BaTiO3 conserves and doubles its initial polarisation value from 0.12 to 0.25 C/m2. In contrast to nonmagnetic BaTiO3, we observe a net magnetic moment of 6.0 μB/formula unit. But, when the strong correlations among d electrons of Fe atoms are taken into account, the total magnetic is increasing and is equal to 10 μB/formula unit, due to a net increasing of magnetic moment of Fe atoms. Therefore, the coexistence of spontaneous electrical polarisation P along with a magnetic moment leads to a new and interesting multiferroic behaviour. We also observe a half-metallic behaviour in which spin down bands structure shows metallic character whereas spin up bands structure shows semi-conductor character with an energy gap of 1.48 eV. This reveals that the multiferroic BaTi0.5Fe0.5O3 could be potential candidate for spintronics devices.

Dual metal (Fe and Mg) substituted layered titanium-based P2 and O3-type negative electrodes for rechargeable sodium batteries

A first attempt was made to enhance the electrochemical performances, using the binary metal (Fe and Mg) substitution on the layered Titanium-based P2-type Na0.5Ni0.2Ti0.6O2 (P2-NNTFMO) and O3-type NaNi0.2Ti0.6O2 (O3-NNTFMO) anode materials, via traditional solid state reaction for sodium ion batteries (SIBs). The XPS analysis of the O3-NNTFMO negative material exhibit the presence of Ti, Ni, Fe and Mg ions happens in +4, +2, +3 and +1 valance states respectively. The discharge and charge curves reveal the P2-NNTFMO and O3-NNTFMO anode materials have the charge capacities of 117.60 and 128.48 mAh/g respectively. The limited amount of co-substitution (Fe and Mg) in transition metal oxide layers would enlarge the sodium ion diffusion layers during cycling for O3 and P2-type anodes, due to the shrinkage of TMO6 octahedrons and decrease of TM-O bond lengths.

Fast and Durable Lithium Storage Enabled by Tuning Entropy in Wadsley-Roth Phase Titanium Niobium Oxides.

Wadsley-Roth phase titanium niobium oxides have received considerable interest as anodes for lithium ion batteries. However, the volume expansion and sluggish ion/electron transport kinetics retard its application in grid scale. Here, fast and durable lithium storage in entropy-stabilized Fe0.4 Ti1.6 Nb10 O28.8 (FTNO) is enabled by tuning entropy via Fe substitution. By increasing the entropy, a reduction of the calcination temperature to form a phase pure material is achieved, leading to a reduced grain size and, therefore, a shortening of Li+ pathway along the diffusion channels. Furthermore, in situ X-ray diffraction reveals that the increased entropy leads to the decreased expansion along a-axis, which stabilizes the lithium intercalation channel. Density functional theory modeling indicates the origin to be the more stable FeO bond as compared to TiO bond. As a result, the rate performance is significantly enhanced exhibiting a reversible capacity of 73.7 mAh g-1 at 50 C for FTNO as compared to 37.9 mAh g-1 for its TNO counterpart. Besides, durable cycling is achieved by FTNO, which delivers a discharge capacity of 130.0 mAh g-1 after 6000 cycles at 10 C. Finally, the potential impact for practical application of FTNO anodes has been demonstrated by successfully constructing fast charging and stable LiFePO4 ‖FTNO full cells.

Structural incorporation of iron influences biomethylation potential of mercury sulfide

Mercury and ferrous iron commonly co-exist in anaerobic environments, the hotspots of microbial mercury methylation that leads to formation of neurotoxic methylmercury. However, the influence of ferrous iron on mercury bioavailability and methylation remains unclear. Here, we discover that microbial methylmercury production is inhibited by iron addition in a non-monotonical manner, reaching the minimal level at the initial molar ratio of dissolved Fe/Hg as 1/3, when highly aggregated Hg–S–Fe nanoparticles occur and prevent the nanoparticle–bacteria interactions. The dominant mercury species formed upon Hg–S–Fe co-precipitation is iron-incorporated nano-metacinnabar with short-range structural disorder. The methylation potential of this mercury species is inversely correlated with the aggregation state of nanoparticles. The non-monotonical trends of the aggregation state and subsequent methylation of nano-metacinnabar are due to the opposite effects of ferrous iron on the nucleation and particle attachment that determine the formation of nanoparticle aggregates. Increased Fe/Hg ratio hinders particle nucleation and thus decreases the density of particle monomers for aggregation. However, Fe substitution of sub-surface Hg weakens the inner-sphere coordination of surface Hg with natural thiol ligands and consequently enhances nano-metacinnabar aggregation. This new mechanistic insight is important for assessing and minimizing the risks of mercury methylation, and informs how intertwined iron and sulfur cycling may influence metal bioavailability in the changing environment.

Synthesis and characterization of PrBa0.5Sr0·5Co2-xFexO5+δ (x=0.5, 1.0, 1.5, 2.0) as oxygen electrode for proton-conducting solid oxide cells

As clean energy conversion devices with the functions of power generation and hydrogen evolution, solid oxide cells (SOCs) are facing the obstacle of insufficient catalytic activity of traditional electrode materials under the trend of lower operation temperature. Here a double-perovskite material PrBa0.5Sr0·5Co2-xFexO5+δ (PBSCF, x = 0.5, 1.0, 1.5, 2.0) is reported and its application as oxygen electrode of symmetrical cells on the proton conductor BaZr0·1Ce0·7Y0.1Yb0.1O3-δ (BZCYYb1711) is investigated. The tests are carried out under atmospheres with different water content (0, 20% and 40%), showing the influence of Fe/Co molar ratio on the crystal structure, conductivity, electrochemical properties and micro morphology of PBSCF series materials. With the increasing of Fe substitution content, the polarization resistance of PBSCF series symmetrical cells decreases. PrBa0.5Sr0.5Co1.5Fe0.5O5+δ (PBSCF05) symmetrical cell always shows the optimal performance and exhibits area-specific polarization resistance (ASR) of 0.08 Ω cm2 at 700 °C under 20%H2O+80%air. Further experimental results and the distribution of relaxation times (DRT) analysis show that the presence of an appropriate amount of steam in atmosphere would optimize the conductive mechanism and promote proton migration, while the presence of excessive steam would hinder the diffusion of oxygen molecule. For the electrochemical reaction on the PBSCF electrode, the adsorption, dissociation and precipitation of oxygen are always the crucial rate-limiting steps, which is a direction worthy of further optimization.

Optical bandgap variation and photo-Fenton property evolution in Fe-doped Bi2YO4Cl

The current study addresses the existing research gap on the effects of transition metal doping in layered Bi2YO4Cl and searches for a new visible light photocatalyst in the bismuth-based oxychloride system. The extent of Fe substitution in place of Y in Bi2YO4Cl and its consequences on the structure, optical, and catalytic properties have been examined by synthesizing the samples using a solution combustion method. Nearly 20 mol% of Fe could be introduced in a monophasic layer structural arrangement. The Fe-containing samples have also been characterized by electron microscopic and vibrational spectroscopic techniques. The optical absorbance shifted to the visible region with the Fe inclusion, and the bandgap decreased from 2.40 eV (pristine) to 1.77 eV (20 mol % Fe-substituted). XPS analysis of the Fe-containing sample indicated that Fe existed majorly in the III oxidation state with traces of the II oxidation state. The photo-Fenton function of Bi2Y1-xFexO4Cl (x = 0.10 and 0.20) for the oxidative degradation of RhB and MB dye molecules under LED illumination has been demonstrated. From scavenger experiments, OH• radicals and holes have been identified as the reactive oxidation species (ROS) involved in these reactions. The catalyst showed recyclability and structural integrity.

The emergence of considerable room temperature magnetocaloric performances in the transition metal high-entropy alloys

We herein investigated the structural, magnetic, and magnetocaloric properties of Mn20Al20Co14Fe20+xCr26-xhigh entropy (HE) alloys by experimental determination and first principle calculations. The results indicated that these alloys were crystallized in a disordered body-centered cubic structure.The Fe substitution of Cr enhanced the energy and net magnetic moment of these alloys, resulting in the improvement of magnetic properties. All the Mn20Al20Co14Fe20+xCr26-x HE alloys underwent a second-order magnetic transition with theCurie temperature ranges of 268.2–310.6 K. The magnetocaloric performances of Mn20Al20Co14Fe20+xCr26-x HE alloys were examined by using the magnetic entropy change, relative cooling power, refrigerant capacity, temperature average entropy change, and mechanical properties, which are superior to the reported transition metal-based magnetocaloric materials with second order magnetic phase transition. By considering the realized considerablemagnetocaloricperformances and the benefits of transition metal HE alloys, the present Mn20Al20Co14Fe20+xCr26-x HE alloys are also of potential for room temperature MR application. The present work would provide a large family of transition metal HE alloys with significant magnetocaloric performances.

Vertically aligned nickel-iron-phosphide nanosheets on three-dimensional porous nickel foam for overall water splitting

A low-cost, earth-abundant and efficient bifunctional electrocatalysts for overall electrochemical water splitting is an important development in the field of electrochemistry. In this work, nickel-iron phosphide (NiFeP) nanosheets on three-dimensional (3D) porous interconnected nickel foam with rich active sites are processed by two-step synthesis. Conversion of nickel foam to nickel iron layered double hydroxide (NiFeLDH) by low-temperature hydrothermal reaction followed by thermal phosphidation using red phosphorus as the source. The thermal phosphidation process is optimized with respect to temperature and duration. The electrochemical performances of the electrocatalyst are strongly depends on the phosphidation temperature and duration. The NiFeP (NFP) electrocatalyst synthesized at 500 °C for 30 mins (NFP500–30) shows the overall water splitting voltage of 1.69 V at 50 mA/cm2 in 1.0 M KOH. The improvement in electrocatalyst performance is attributed to the Fe substitution, vertically aligned nanostructure surface with abundant active sites and 3D porous interconnect network structure. The electrocatalyst exhibits robust durability with high conductivity and excellent corrosion resistance.

Internal and External Co‐Engineering of Stable Cathode Interface Improves Cycle Performance of Polymer Sodium Batteries

AbstractThe development of polymer sodium batteries requires cathode materials with stable interfaces to avoid poor interfacial contact and interfacial side reactions during cycling. Here, a co‐engineering strategy is deployed to tailor the cathode internal structure and improve the cathode interface stability through bonding interactions. Internally, the effect of low‐cost Fe substitution in the obtained Na0.67Mn2/3Fe1/3O2 cathode material renders favorable effects in several aspects. First, the increased lattice constant facilitates Na+ intercalation and thereby lowers the diffusion barrier of Na+ ions. Second, it increases the electronic conductivity, thereby improving the reaction reversibility. Third, the MnO bond length is shortened, which alleviates the Jahn‐Taylor effect and improves structural stability. In addition to these internal effects, the FeOB bond interactions due to Fe substitution promote the decomposition of the tris(trimethylsilane)borate additive and the formation of a dense and uniform cathode electrolyte interface film, leading to improved cycling stability. Owing to the co‐engineering of both internal structure and surface modification, the polymer solid‐state sodium battery with a stable interface exhibits a specific capacity of 85.2 mAh g‐1 after 800 cycles at 1 C.