Correction: A proton conductor electrolyte based on molten CsH5(PO4)2 for intermediate-temperature fuel cells

Correction for ‘A proton conductor electrolyte based on molten CsH₅(PO₄)₂ for intermediate-temperature fuel cells’ by Xiaojing Chen et al., RSC Adv., 2018, 8, 5225–5232.

The authors regret that Paulo Ribeirinha’s name was spelled incorrectly in the original article. The correct spelling of all author names is presented above.The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.     

A graphene oxide polymer brush based cross-linked nanocomposite proton exchange membrane for direct methanol fuel cells

Functional polymer brush modified graphene oxide (FPGO) with functional linear polysiloxane brushes was synthesized via surface precipitation polymerization (sol–gel) and chemical modification. Then, FPGO was covalently cross-linked to the sulfonated polysulfone (SPSU) matrix to obtain novel SPSU/FPGO cross-linked nanocomposite membranes. Meanwhile, SPSU/GO composite membranes and a pristine SPSU membrane were fabricated as control groups. Reduced agglomeration of the inorganic filler and better interfacial interaction, which are benefit to increase diffusion resistance of methanol and to generate continuous channels for fast proton transportation at elevated temperature, were observed in SPSU/FPGO cross-linked membranes. Moreover, the enhanced membrane stability (thermal, oxidative and dimensional stability) and good mechanical performance also guaranteed their proton conducting durability. It is noteworthy that the SPSU/FPGO-1 cross-linked membrane possesses the best comprehensive properties among all the prepared membranes and Nafion®117, it acquires the highest proton conductivity of 0.462 S cm⁻¹ at 90 °C under hydrated conditions together with a low methanol permeability of 1.71 × 10⁻⁶ cm² s⁻¹ at 30 °C. The resulting high membrane selectivity displays the great potential of the SPSU/FPGO cross-linked membrane for DMFCs application.

A novel proton exchange nanocomposite which was cross-linked by functional graphene oxide polymer brushes shows interesting and comprehensive advantages for DMFCs.     

Ladder-type sulfonated poly(arylene perfluoroalkylene)s for high performance proton exchange membrane fuel cells

Sulfonated poly(arylene perfluoroalkylene)s containing a sulfone-bonded ladder structure (SPAF-P-Lad) were synthesized by treating the precursor SPAF-P polymers with oleum as a novel proton exchange membrane for fuel cells. SPAF-P-Lad membranes had excellent solubility in polar organic solvents and high molecular weight (M_n = 145.4–162.9 kDa, M_w = 356.9–399.1 kDa) to provide bendable membranes with ion exchange capacity (IEC) ranging from 1.76 to 2.01 meq. g⁻¹. SPAF-P-Lad membranes possessed higher proton conductivity than that of the precursor SPAF-P membranes because of the stronger water affinity. Compared with SPAF-P membranes (T_g: 72–90 °C, Young''s modulus: 0.08–0.42 GPa; yield stress: 5.7–15.1 MPa), SPAF-P-Lad membranes showed better mechanical stability to humidity and temperature and improved tensile properties (Young''s modulus: 0.51–0.59 GPa; yield stress: 23.9–29.6 MPa). The selected membrane, SPAF-mP-Lad, exhibited improved fuel cell performance, in particular, under low humidity with air; the current density at 0.5 V was 0.56 A cm⁻², while that for SPAF-pP was 0.46 A cm⁻². The SPAF-mP-Lad membrane endured an open circuit voltage hold test for 1000 h with average decay of as small as 70 μV h⁻¹. A series of post-analyses including current–voltage characteristics, molecular structure, molecular weight, and IEC suggested very minor degradation of the membrane under the accelerated testing conditions.

Sulfone-bonded ladder-type sulfonated poly(arylene perfluoroalkylene)s (SPAF-P-Lad) were synthesized by an easy method to achieve high thermo-mechanical stability, proton conductivity, fuel cell performance and remarkable in situ durability.     

Electrochemical studies of a high voltage Na4Co3(PO4)2P2O7–MWCNT composite through a selected stable electrolyte

Cathode materials that operate at high voltages are required to realize the commercialization of high-energy-density sodium-ion batteries. In this study, we prepared different composites of sodium cobalt mixed-phosphate with multiwalled carbon nanotubes (Na₄Co₃(PO₄)₂P₂O₇–MWCNTs) by the sol–gel synthesis technique. The crystal structure and microstructure were characterized by using PXRD, TGA, Raman spectroscopy, SEM and TEM. The electrochemical properties of the Na₄Co₃(PO₄)₂P₂O₇–20 wt% MWCNT composite were explored using two different electrolytes. The composite electrode exhibited excellent cyclability and rate capabilities with the electrolyte composed of 1 M sodium hexafluorophosphate in ethylene carbonate:dimethyl carbonate (EC:DMC). The composite electrode delivered stable discharge capacities of 80 mA h g⁻¹ and 78 mA h g⁻¹ at room and elevated (55 °C) temperatures, respectively. The average discharge voltage was around 4.45 V versus Na⁺/Na, which corresponded to the Co^2+/3+ redox couple. The feasibility of the Na₄Co₃(PO₄)₂P₂O₇ cathode for sodium-ion batteries has been confirmed in real time using a full cell configuration vs. NaTi₂(PO₄)₃–20 wt% MWCNT, and it delivers an initial discharge capacity of 78 mA h g⁻¹ at 0.2C rate.

Na₄Co₃(PO₄)₂P₂O₇–MWCNT composites in 1 M NaPF₆ in EC:DMC electrolytes deliver stable discharge capacities of 80 mA h g⁻¹ and 78 mA h g⁻¹ at normal and elevated temperatures, respectively. In a full cell configuration vs. NaTi₂(PO₄)₃–MWCNT, they deliver an initial discharge capacity of 78 mA h g⁻¹ at 0.2C rate.     

Novel cross-linked poly(vinyl alcohol)-based electrolyte membranes for fuel cell applications

Herein, a new series of polymer electrolyte membranes was prepared by chemically cross-linked poly(vinyl alcohol) (PVA) and sulfonated poly(ether sulfone) (SPES). A typical polymerization reaction was conducted using three different monomers i.e. bisphenol A, phenolphthalein, and 4,4′-dichlorodiphenyl sulfone. The SPES polymer was obtained by the post-sulfonation technique using chlorosulfonic acid as a sulfonating agent. The resultant SPES polymer at different concentrations was blended with cross-linked poly(vinyl alcohol). Structural analysis of the samples was conducted by FTIR, SEM, and XRD. Among the prepared PEM materials, PVA–SPES-20 blend membranes exhibited higher ion-exchange capacity and % water uptake values than those of the other membranes. In addition, the PVA–SPES-20 membrane exhibits the proton conductivity of 0.0367 S cm⁻¹ at 30 °C, whereas pristine PVA shows the proton conductivity of 0.0259 S cm⁻¹. The overall experimental results revealed that the PVA–SPES blend membranes are promising candidates for fuel cell applications.

A series of cross-linked poly(vinyl alcohol)-sulfonated poly(ether sulfone) blend membranes were prepared. The studies of physico-chemical properties revealed that the reported membranes are promising candidate for PEMFC applications.     

Genomic DNA-mediated formation of a porous Cu2(OH)PO4/Co3(PO4)2·8H2O rolling pin shape bifunctional electrocatalyst for water splitting reactions

Among the accessible techniques, the production of hydrogen by electrocatalytic water oxidation is the most established process, which comprises oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Here, we synthesized a genomic DNA-guided porous Cu₂(OH)PO₄/Co₃(PO₄)₂·8H₂O rolling pin shape composite structure in one pot. The nucleation and development of the porous rolling pin shape Cu₂(OH)PO₄/Co₃(PO₄)₂·8H₂O composite was controlled and stabilized by the DNA biomolecules. This porous rolling pin shape composite was explored towards electrocatalytic water oxidation for both OER and HER as a bi-functional catalyst. The as-prepared catalyst exhibited a very high OER and HER activity compared to its various counterparts in the absence of an external binder (such as Nafion). The synergistic effects between Cu and Co metals together with the porous structure of the composite greatly helped in enhancing the catalytic activity. These outcomes undoubtedly demonstrated the beneficial utilization of the genomic DNA-stabilised porous electrocatalyst for OER and HER, which has never been observed.

Among the accessible techniques, the production of hydrogen by electrocatalytic water oxidation is the most established process, which comprises oxygen evolution reaction (OER) and hydrogen evolution reaction (HER).     

Structural and optical properties of langbeinite-related red-emitting K2Sc2(MoO4)(PO4)2:Eu phosphors

The concentration series of langbeinite-related solid solutions K₂Sc₂(MoO₄)(PO₄)₂:xEu (x = 0.1, 0.2, 0.6, 0.8, and 1.0 mol%) has been prepared via a solid state route and the effects of europium content on the phase composition, morphology, crystal structure and luminescence properties have been studied by scanning electron microscopy, X-ray powder diffraction, UV-vis, IR and luminescence spectroscopy. The band gap values have been estimated from UV-vis spectra and are in the range of 3.7–3.8 eV for all concentrations studied. The electronic band structure calculations have shown that Sc d, Mo d and O^phos p states dominate in the band edge region and determine the optical transitions in the K₂Sc₂(MoO₄)(PO₄)₂ host. The photoluminescence (PL) spectra, intensity and decay time dependences on the Eu³⁺ concentration revealed complex behavior of europium-containing emitting centers. The PL characteristics indicated the presence of at least two types of luminescence centers. One of them (Eu_K) is shown to be formed by the Eu³⁺ ion located within K sites, while the other one is formed by the Eu³⁺ ions that reside in Sc sites (Eu_Sc). The luminescence color coordinates calculated for K₂Sc₂(MoO₄)(PO₄)₂:xEu indicated that these ceramics can be potential candidates for UV-based lighting applications as efficient red phosphors.

The luminescence properties of K₂Sc₂(MoO₄)(PO₄)₂:Eu indicate that these ceramics can be potential candidates for UV-based lighting applications as red phosphors.     

Superior performance of Na7V4(P2O7)4PO4 in sodium ion batteries

A novel synthetic method has been investigated to fabricate a 1D nanostructure Na₇V₄(P₂O₇)₄PO₄. Mixed polyanion materials with a well-defined 3D framework channel can improve the electrochemical performance of sodium reversible insertion/extraction reactions, and can be especially beneficial for high rate performance and cycling capability. It approaches an initial reversible electrochemical capacity of 92.0 mA h g⁻¹ with a high discharge potential over 3.85 V (vs. Na/Na⁺) and good cycling properties with a capacity retention of 81.4% after 300 cycles at a 0.5C rate in sodium systems. Taking into consideration the superior electrochemical characteristics, the phase-pure composite is considered to have a promising high rate capability as well as being a high capacity electrode material for advanced energy storage applications.

A novel synthetic method has been investigated to fabricate a 1D nanostructure Na₇V₄(P₂O₇)₄PO₄.     

Crystal growth,layered structure and luminescence properties of K2Eu(PO4)(WO4)

K₂Eu(PO₄)(WO₄) has been prepared via the high-temperature solution growth (HTSG) method using K₂WO₄–KPO₃ molten salts as a self-flux and characterized by single-crystal X-ray diffraction analysis, IR and luminescence spectroscopy. The structure of this new compound features a 2D framework containing [EuPO₆]⁴⁻ layers, which are composed of zigzag chains of [EuO₈]_n interlinked by slightly distorted PO₄ tetrahedra. Isolated WO₄ tetrahedra are attached above and below these layers, leaving space for the K⁺ counter-cations. The photoluminescence (PL) characteristics (spectra, line intensity distribution and decay kinetics) confirm structural data concerning one distinct position for europium ions. The luminescence color coordinates suggest K₂Eu(PO₄)(WO₄) as an efficient red phosphor for lighting applications.

K₂Eu(PO₄)(WO₄) has been prepared via the high-temperature solution growth (HTSG) method using K₂WO₄–KPO₃ molten salts as a self-flux and characterized by single-crystal X-ray diffraction analysis, IR and luminescence spectroscopy.     

Suppressing H2 evolution by using a hydrogel for reversible Na storage in Na3V2(PO4)3

We report a low-cost hydrogel electrolyte by adding 3 wt% poly(acrylate sodium) (PAAS) into 1 M Na₂SO₄ aqueous electrolyte, which achieves a widened electrochemical stability window (ESW) of 2.45 V on stainless steel current collector from 2.12 V in 1 M Na₂SO₄ aqueous electrolytes (AE). Moreover, the H₂ evolution potential reaches −1.75 V vs. Ag/AgCl on titanium current collector. The results reveal that the polymer network structure of PAAS has the ability to interact with water molecules and thus the hydrogen evolution reaction can be limited effectively, which broadens the ESW of aqueous electrolyte and allows the reversible Na-ion intercalation/deintercalation of Na₃V₂(PO₄)₃ as an anode material in aqueous electrolyte reported for the first time.

Hydrogen evolution suppression of hydrogel electrolyte with 3 wt% poly(acrylate sodium) (PAAS) ensures reversible Na-ion storage of Na₃V₂(PO₄)₃ as negative electrode.     

Hybrid composite of Nafion with surface-modified electrospun polybenzoxazine (PBz) fibers via ozonation as fillers for proton conducting membranes of fuel cells

Nafion was investigated for its compatibility in the preparation of hybrid composites with electrospun Polybenzoxazine (PBz) surface-modified fibers by evaluating the effects on the surface and structure of the composite. A PBz fiber mat was first crosslinked by thermal treatment after electrospinning to enhance the mechanical integrity of the fibers prior to modification. Further surface modification via free radical ozonation was carried out by potentiating oxygen-based functional groups of hydroxyl radicals (–OH) onto fibers'' exposed surfaces. The sequential modifications by crosslinking and ozone treatment were evaluated by analyzing surface properties using XPS, ATR-FTIR and water contact angle which determined the enhanced properties of the fibers that were beneficial to the target functionality. Electron spectroscopy confirmed that fibers'' surfaces were changed with the new surface chemistry without altering the chemical structure of PBz. The presence of higher oxygen-based functional groups on fibers'' surfaces based on the resulting atomic compositions was correlated with the change in surface wettability by becoming hydrophilic with contact angle ranging from 21.27° to 59.83° compared to hydrophobic pristine PBz fibers. This is due to electrophilic aromatic substitution with hydroxyl groups present on the surfaces of the fibers endowed by ozonation. The resulting surface-modified fiber mat was used for the preparation of composites by varying two process parameters, the amount of Nafion dispersion and its homogenization and curing time, which was evaluated for compatibility and interaction as fillers to form hybrid composites. The analyses of SEM images revealed the effects of shorter homogenization and curing time on composites with rougher and wrinkled surfaces shown on the final hybrid composite''s structure while decreasing the amount of Nafion at the same homogenization time but longer curing time showed its influence on improvement of compatibility and surface morphology.

Nafion compatibility in the preparation of hybrid composites with electrospun Polybenzoxazine (PBz) surface-modified fibers via ozonation by evaluating the effects on the surface and structure of the composite.     

Efficient promiscuous Knoevenagel condensation catalyzed by papain confined in Cu3(PO4)2 nanoflowers

To develop an efficient and green immobilized biocatalyst for promiscuous catalysis which has a broad scope of applications, hybrid nanoflower (hNF) confined papain as a biocatalyst has been proposed and characterized in this study. hNFs were firstly prepared through mixing CuSO₄ aqueous solution with papain in phosphate saline (PBS) at room temperature. The resulting hNFs were characterized by SEM and verified through a hydrolysis reaction with N-benzoyl-dl-arginine amide as substrate. Under optimal conditions, this nano-biocatalyst demonstrated a 15-fold hydrolytic activity compared with papain of free form, along with better thermal stability. A series of reaction factors (reaction temperature, time, and solvent) have been investigated for Knoevenagel condensation reactions with hNFs as catalyst. At optimal conditions, product yield of the hNFs catalyzed reaction was 1.3 fold higher than that of the free enzyme with benzaldehyde and acetylacetone as substrates. A few aldehydes and methylene compounds have also been used to test the generality and scope of this new enzymatic promiscuity. To sum up, the obtained hNFs demonstrate better catalytic properties than free papain and the inorganic metal-salt crystal can function as both support and promotor in biocatalysis.

Knoevenagel condensation was catalyzed and enhanced by Cu²⁺ and papain on hybrid nanoflowers (hNFs) in the promiscuous catalysis.     

An in situ DRIFTS study on nitrogen electrochemical reduction over an Fe/BaZr0.8Y0.2O3−δ-Ru catalyst at 220 °C in an electrolysis cell using a CsH2PO4/SiP2O7 electrolyte

In situ DRIFTS measurements of an Fe/BZY-Ru cathode catalyst in an electrolysis cell using a CsH₂PO₄/SiP₂O₇ electrolyte were carried out in a mixed N₂–H₂ gas flow under polarization. The formation of N₂H_x species was confirmed under polarization, and an associative mechanism in the electrochemical NRR process was verified.

In situ DRIFTS measurements of an Fe/BZY-Ru cathode catalyst in an electrolysis cell using a CsH₂PO₄/SiP₂O₇ electrolyte were carried out in a mixed N₂–H₂ gas flow under polarization.

NH₃ production contributes about 2% of the world''s energy consumption annually, and most of the consumption is from the strongly endothermic steam reforming of methane (SRM) at 800–1000 °C in the Haber–Bosch process. Other major energy consuming processes include CO₂ removal, reactant gas purification, reactant gas compression for NH₃ synthesis, and NH₃ separation.¹ Due to its high energy density, NH₃ was expected to be a promising energy carrier in recent years.² NH₃ produced by renewable energy sources can be used as a carbon-free energy carrier. One of the promising methods to utilize renewable energy sources for NH₃ production is electrochemical N₂ reduction. Various electrolysis cells with solid and liquid electrolytes have been reported for electrochemical N₂ reduction over a wide temperature range. For the electrochemical N₂ reduction reaction (NRR) at low temperatures (T < 100 °C), the main limitation is the difficulty of N₂ activation and the low solubility of N₂ in aqueous media. High temperatures (T > 500 °C) can lead to decomposition of the produced NH₃. Hence, an electrochemical NRR at intermediate temperatures is desirable. Phosphates such as CsH₂PO₄ and CsH₅(PO₄)₂ are typically used as electrolytes at intermediate temperatures. These inorganic oxyacid salts have high proton conductivity and stability. CsH₂PO₄ mixed with SiP₂O₇ as a matrix exhibits a proton conductivity of ca. 1 × 10⁻² S cm⁻¹ at 220 °C.³ In our previous work on electrochemical NH₃ synthesis using an Fe/BZY-RuO₂ catalyst and CsH₂PO₄/SiP₂O₇ electrolyte at 220 °C and ambient pressure, the highest current efficiency of 7.1% and the highest NH₃ yield rate of 4.5 × 10⁻¹⁰ mol (s⁻¹ cm²) were achieved at −0.4 V (vs. open circuit voltage (OCV)) and −1.5 V, respectively. In addition, N₂H₄ was successfully detected at −0.2 V (vs. OCV), which indicated an associative mechanism,⁴ which is one of the two main reaction mechanisms in NH₃ synthesis, namely, associative and dissociative mechanisms. In the associative mechanism the N N bond in a N₂ molecule adsorbed on the catalyst surface is cleaved after an H atom attaches to the N atom of the adsorbed N₂ molecule, whereas in the dissociative mechanism the N N bond is broken on the catalyst surface before an H atom attaches to the N₂ molecule.Typical electrochemical characterizations such as impedance spectroscopy,^5,6 current–voltage curve (IV curve) testing,^7,8 cyclic voltammetry,⁹ and potentiostatic pulse experiment¹⁰ can only provide indirect information on surface reactions at the electrode. It is indispensable to analyse directly adsorbed species on the electrode catalysts for the understanding of the reaction mechanism. In situ spectroscopy is making rapid progress and has already been applied to electrochemical devices, providing valuable information of the chemical species during the reactions.¹¹In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) for electrolysis cells attracts much attention recently.^12,13In situ DRIFTS has recently become a powerful tool for investigating the reaction pathway in electrochemical N₂ reduction reaction.^14–16 In DRIFTS, infrared (IR) beam irradiates the sample disk, and then can be reflected at or transmitted through the sample disk. The scattered IR beam is collected by the spherical focusing mirrors and finally converted by a detector.In this work, a commercial DRIFTS setup was modified and applied to electrochemical N₂ reduction as shown in Fig. 1. To enable an operation temperature higher than 200 °C that is requisite for proton conduction in the electrolyte, an electrical heating wire was placed in the base near the micro-cup. The temperature was measured by a thermocouple located next to the heating wire. An electrolysis cell was set on the micro-cup of the metal base. For protection of the ZnSe window from oxidation at the high operating temperature, a water-cooling system was attached to the metal base near the dome to keep the temperature of the window below 200 °C. The specific size of the apparatus is shown in the Fig. 2. An O-ring fits to the dome can ensure gas tightness of the small space in the dome. There are three pathways which connect the inside space of the dome and atmosphere. Two of them are used for the inlet and outlet gas flows, and the one connecting directly with the micro-cup was used for Pt lead wires. To avoid a short-circuit between the two Pt lead wires, a thin polyimide film (12.5 μm thick, Kapton, Dupont, Delaware, United States) which is stable from −269 to +400 °C was used to cover the Pt wires.Open in a separate windowFig. 1A schematic of modified DRIFTS setup applied to electrochemical N₂ reduction. The temperature of the electrolysis cell is measured at the same place where it is heated.Open in a separate windowFig. 2(a) The bottom-up view of the dome. (b) The vertical view of the metal base.In our previous study of the electrochemical NH₃ synthesis process at 220 °C, a ø 10 mm carbon paper was used on the cathode side to increase the current collection area.⁴ However, in the in situ DRIFTS tests, the cathode catalysts must be exposed to the IR beam, hence a carbon ring with an inside diameter of 7 mm was used instead as shown in Fig. 3. On the anode side, a ø 10 mm Pt/C loaded on carbon paper was used for current collection. The electrolysis cell consists of 0.1 g SiP₂O₇/CsH₂PO₄ electrolyte (mix ratio of SiP₂O₇ : CsH₂PO₄ was 1 : 1) compressed with 0.035 g Fe/BZY-Ru (mix ratio of Fe/BZY : RuO₂ was 1 : 1) catalyst on the top layer. In our previous work of the electrochemical NH₃ synthesis using Fe/BZY-RuO₂, we have successfully detected N₂H₄ as well as NH₃, which indicated the triple bond of N₂ was broken simultaneously with the addition of H. Fe/BZY was prepared in the same way as in the previous work.⁴ The as-prepared Fe/BZY powder was mixed with RuO₂ powder, and then the mixture was reduced in H₂ flow at 220 °C for 1 h. To fix the electrolysis cell, the current collection materials and the Pt lead wires, PTFE sheets (Gore Hyper-Sheet Gasket, W. L. Gore & Associate, Inc., Delaware, USA) formed into rings were used as the support. The experimental conditions in the dome are similar to those in a single-chamber reactor. The inlet gas is a mixture of N₂ and H₂, which is different from the two-chamber reactor in electrolysis tests in the previous work. A background spectrum was measured under H₂ gas flow of 8 mL min⁻¹ at 160 °C with 100 scans at OCV. All DRIFTS spectra are displayed as log(I₀/I) where I₀/I is the relative reflectance (I₀ is the background reflectance). Then the measurements were carried out under N₂ gas flow of 8 mL min⁻¹ at 300 °C at OCV and under mixed N₂ and H₂ gas flow (both are 8 mL min⁻¹) at 250 °C at OCV and various applied biases.Open in a separate windowFig. 3A schematic of electrolysis cell on the micro-cup.According to the results in Fig. 4, three kinds of sharp peaks at 1050, 1300 and 1540 cm⁻¹, and a broad peak at 3300 cm⁻¹ were observed. Peak at 1050 cm⁻¹ is attributed to N–N stretching (reported at 1106 cm⁻¹),¹⁷ which appeared in all experimental conditions even when only N₂ gas was supplied. This implies that the N₂ adsorption sites on the catalyst surface are highly active. Peaks at 1300, 1540 and 3300 cm⁻¹ are assigned to H–N–H wagging, H–N–H bending and N–H stretching (reported at 1270, 1461 and 3235 cm⁻¹).¹⁷ These three kinds of peaks appeared only when both N₂ and H₂ were supplied, and seem to become stronger with applied bias. It is obvious that N₂H_x species, which can be intermediate species in the associative mechanism, were formed on the surface of Fe/BZY-Ru. The peak at 900 cm⁻¹ is probably attributed to NH₃ gas.¹⁸ It is likely that the peaks at 1400 cm⁻¹ and 2800 cm⁻¹ are assigned to NH₄⁺.¹⁹ The strong signal at 2360 cm⁻¹ is associative with gas-phase CO₂ that exists in IR beam path outside the dome.Open in a separate windowFig. 4Electrochemical in situ-FTIR spectra of the NRR on the Fe/BZY-Ru electrode at various electrochemical potentials. Then the measurements were carried out under N₂ at 300 °C at OCV and under mixed N₂ and H₂ at 250 °C at OCV, −0.2, −0.4, −1.5, −3.2 and −4.0 V.Only quite low current densities were able to be loaded as shown in Fig. 5. Reactant gases were introduced to the system without humidification, which might have led to low proton conductivity and electrolyte decomposition. In addition, current collection area of the carbon paper ring on the cathode side is small.Open in a separate windowFig. 5Currents for applied voltages of −0.2 V, −0.4 V, −1.5 V, −3.2 V, and −4.0 V. In situ DRIFTS measurements were carried out in a N₂–H₂ gas mixture under polarization, which corresponds to a situation in a single-chamber reactor. The background was measured in H₂ flow, and the sample measurements were carried out in a mixed N₂–H₂ gas flow. In the obtained spectra, a peak at 1100 cm⁻¹ was assigned to N–N stretching, and those at 1301, 1600, and 3300 cm⁻¹ were assigned to –NH₂ wagging, H–N–H bending, and N–H stretching. The intensity of the H–N–H wagging peak was enhanced by increasing the applied voltage. Appearance of these peaks confirmed the formation of N₂H_x (1 ≤ x ≤ 4) species in the NRR process and consequently demonstrated that NRR proceeded via an associative mechanism over Fe/BZY-Ru cathode catalyst on a SiP₂O₇/CsH₂PO₄ electrolyte.     

Interactions between receptors for interleukin 2 and interleukin 4 on lines of helper T cells (HT-2) and B lymphoma cells (BCL1)

IL-2 and IL-4 induce a synergistic proliferative response in HT-2 cells, suggesting that IL-2Rs and IL-4Rs may interact. The purpose of this study was to examine the effect of IL-4 on the expression and function of IL-2Rs. Preincubation of HT-2 and BCL1-3B3 cells with IL-4 for 60 min at 4 degrees C or 37 degrees C resulted in a partial decrease in the number, but not the affinity of high affinity IL-2Rs as evidenced by Scatchard analysis of binding data. The decrease in the number of high affinity receptors correlated with decreased internalization of IL-2. After preincubation with IL-4, crosslinking of 125I-IL-2 to high affinity IL-2Rs also demonstrated a approximately 50% reduction in the number of high affinity IL-2Rs. Another lymphokine, IL-1, which acts on HT-2 cells, had no measurable effect on the affinity or number of IL-2Rs. Taken together, these results indicate that IL-4 downregulates the expression of high affinity IL-2Rs on some cells. It is not known whether this occurs by a direct ligand-mediated receptor interaction, by the sharing of a common receptor subunit, or by interaction of the two receptors with another membrane molecule or cytoskeletal component.     

Fabrication and performance evaluation of new nanocomposite membranes based on sulfonated poly(phthalazinone ether ketone) for PEM fuel cells

The purpose of this work is to enhance the proton conductivity and fuel cell performance of sulfonated poly(phthalazinone ether ketone) (SPPEK) as a proton exchange membrane through the application of SrTiO₃ perovskite nanoparticles. Nanocomposite membranes based on SPPEK and SrTiO₃ perovskite nanoparticles were prepared via a casting method. The highest proton conductivity of nanocomposite membranes obtained was 120 mS cm⁻¹ at 90 °C and 95% RH. These enhancements could be related to the hygroscopic structure of SrTiO₃ perovskite nanoparticles and the formation of hydrogen bonds between nanoparticles and water molecules. The satisfactory power density, 0.41 W cm⁻² at 0.5 V and 85 °C, of the nanocomposite membrane (5 wt% content of nanoparticles) confirms their potential for application in the PEM fuel cells.

The purpose of this work is to enhance the proton conductivity and fuel cell performance of sulfonated poly(phthalazinone ether ketone) (SPPEK) as a proton exchange membrane through the application of SrTiO₃ perovskite nanoparticles.     

Reducing interfacial resistance of a Li1.5Al0.5Ge1.5(PO4)3 solid electrolyte/electrode interface by polymer interlayer protection

High interfacial resistance of an electrode/electrolyte interface is the most challenging barrier for the expanding application of all-solid-state lithium batteries (ASSLBs). To address this challenge, poly(propylene carbonate)-based solid polymer electrolytes (PPC-SPEs) were introduced as interlayers combined with a Li_1.5Al_0.5Ge_1.5(PO₄)₃ (LAGP) solid state electrolyte (SSE), which successfully decreased the interfacial resistance of the SSE/electrolyte interface by suppressing the reduction reaction of Ge⁴⁺ against the Li metal, as well as producing intimate contact between the cathode and electrolyte. This work provides a systematic analysis of the interfacial resistance of the cathode/SSE, Li/SSE and the polymer/LAGP interfaces. As a consequence, the interfacial resistance of the Li/SSE interface decreased about 35%, and the interfacial resistance of the cathode/SSE interface decreased from 3.2 × 10⁴ to 543 Ω cm². With a PPC–LAGP–PPC sandwich structure composite electrolyte (PLSSCE), the all-solid-state LiFePO₄/Li cell showed a high capacity of 148.1 mA h g⁻¹ at 0.1C and a great cycle performance over 90 cycles.

Using PPC interlayers to protect the LAGP electrolyte and reduce the interfacial impedance between electrode and electrolyte.     

Application of a conversion electrode based on decomposition derivatives of Ag4[Fe(CN)6] for aqueous electrolyte batteries

The lack of stable electrode materials for water-based electrolytes due to the intercalation and conversion reaction mechanisms encourage scientists to design new or renovate existing materials with better cyclability, capacity, and cost-effectiveness. Ag₄[Fe(CN)₆] is a material belonging to the Prussian blue family that can be used, as its other family members, as an electrode material with the intercalation/deintercalation reaction or conversion-type mechanism through Ag oxidation/reduction. However, due to the instability of this material in its dry state, it decomposes to AgCN and a Prussian blue residual complex. A possible reason for Ag₄[Fe(CN)₆] decomposition is discussed. Nevertheless, it is shown that the decomposition products of Ag₄[Fe(CN)₆] have electrochemical activity due to the reversible oxidation/reduction of Ag atoms in water-based electrolytes.

The lack of stable electrode materials for water-based electrolytes based on intercalation and conversion reaction mechanisms encourage scientists to design new or renovate existing materials with better cyclability, capacity, and cost-effectiveness.     

Realizing outstanding electrochemical performance with Na3V2(PO4)2F3 modified with an ionic liquid for sodium-ion batteries

Na₃V₂(PO₄)₂F₃ is a typical NASICON structure with a high voltage plateau and capacity. Nevertheless, its applications are limited due to its low conductivity and poor rate performance. In this study, nitrogen–boron co-doped carbon-coated Na₃V₂(PO₄)₂F₃ (NVPF-CNB) was prepared by a simple sol–gel method using an ionic liquid (1-vinyl-3-methyl imidazole tetrafluoroborate) as a source of nitrogen and boron for the first time. The morphology and electrochemical properties of NVPF-CNB composites were investigated. The results show that a nitrogen–boron co-doped carbon layer could increase the electron and ion diffusion rate, reduce internal resistance, and help alleviate particle agglomeration. NVPF-CNB-30 exhibited better rate performance under 5C and 10C charge/discharge with initial reversible capacities of 99 and 90 mA h g⁻¹, respectively. Furthermore, NVPF-CNB-30 illustrates excellent cyclic performance with the capacity retention rate reaching 91.9% after 500 cycles at 5C, as well as a capacity retention rate of about 95.5% after 730 cycles at 10C. The evolution of the material''s structure during charge/discharge processes studied by in situ X-ray diffraction confirms the stable structure of nitrogen–boron co-doped carbon-coated Na₃V₂(PO₄)₂F₃. Co-doping of nitrogen and boron also provides more active sites on the surface of Na₃V₂(PO₄)₂F₃, revealing a new strategy for the modification of sodium-ion batteries.

An ionic liquid is used as a new nitrogen and boron source to synthesize nitrogen–boron co-doped carbon-coated Na₃V₂(PO₄)₂F₃ (NVPF-CNB).     

Combined wet milling and heat treatment in water vapor for producing amorphous to crystalline ultrafine Li1.3Al0.3Ti1.7(PO4)3 solid electrolyte particles

Bulk-type all-solid-state batteries (ASSBs) consisting of composite electrodes of homogeneously mixed fine particles of both active materials and solid electrolytes (SEs) exhibit a high safety, high energy density, and long cycle life. SE nanoparticles are required for the construction of ion-conducting pathways as a response to the particle size reduction of active materials; however, simple and low-cost milling processes for producing nanoparticles cause a collapse in the crystal structure and eventually amorphization, decreasing the conductivity. This study develops a heat treatment process in water vapor for the low-temperature crystallization of ultrafine SE amorphous particles and the size control of crystalline nanoparticles. An ultrafine (approximately 5 nm) amorphous powder of Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP), as a typical oxide-type SE, is produced via wet planetary ball milling in ethanol. The water vapor induces a rearrangement of the crystal framework in LATP and accelerates crystallization at a lower temperature than that in air. Further, since particle growth is also promoted by water vapor, depending on the heating temperature and time, this heat treatment process can be also applied to the size control of crystalline LATP nanoparticles. A combination of the wet planetary ball milling and heat treatment in water vapor will accelerate the practical application of bulk-type ASSBs.

The preparation of ultrafine particles through combined wet planetary ball milling and heat treatment in water vapor contributes to the fabrication of extensive composite electrodes with solid electrolytes for bulk-type all-solid-state batteries.