Studies on metal oxides suitable for enhancement of the O2-releasing step in water splitting by the MnFe2O4–Na2CO3 system

Reactivities of three metal oxides (Fe₂O₃, TiO₂ and MnO₂) with Na₂CO₃, and of their reaction products with CO₂, have been studied to enhance the O₂-releasing step in the two-step water splitting by the MnFe₂O₄–Na₂CO₃ system. X-ray diffraction analysis and thermogravimetric measurements showed that the reaction of α-Fe₂O₃ with Na₂CO₃ (mole ratio=1:1) completed within 10 min at 1073 K to produce NaFeO₂ (Fe₂O₃+Na₂CO₃→NaFeO₂+CO₂). Also, the regeneration of Fe₂O₃ and Na₂CO₃ proceeded readily by passing CO₂ gas through NaFeO₂ (71% yield). TiO₂ reacted with Na₂CO₃ (mole ratio=1:1) at 1073 K for 1 h to form Na₈Ti₅O₁₄ and Na₂TiO₃ (93% yield). However, in the reaction of the products with CO₂, the starting material (TiO₂) was not reproduced at the temperature range from 673 K to 1073 K, but Na₄Ti₅O₁₂ (having a lower Na content than the form Na₈Ti₅O₁₄) was formed. In the case of MnO₂ with Na₂CO₃ (mole ratio=2:1), Na_0.7MnO_2–2.05 and NaMnO₂ were produced at 1073 K for 1 h (80% yield), but the reaction between these products and CO₂ hardly proceeded.     

Ni3(PO4)2-coated Li[Ni0.8Co0.15Al0.05]O2 lithium battery electrode with improved cycling performance at 55 °C

To improve the cycling performance of LiNi_0.8Co_0.15Al_0.05O₂ at 55 °C, a thin Ni₃(PO₄) layer was homogeneously coated onto the cathode particle via simple ball milling. The morphology of the Ni₃(PO₄)₂-coated LiNi_0.8Co_0.15Al_0.05O₂ particle was characterized using SEM and TEM analysis, and the coating thickness was found to be approximately 10-20 nm. The Ni₃(PO₄)₂-coated LiNi_0.8Co_0.15Al_0.05O₂ cell showed improved lithium intercalation stability and rate capability especially at high C rates. This improved cycling performance was ascribed to the presence of Ni₃(PO₄)₂ on the LiNi_0.8Co_0.15Al_0.05O₂ particle, which protected the cathode from chemical attack by HF and thus suppressed an increase in charge transfer resistance. Transmission electron microscopy of extensively cycled particles confirmed that the particle surface of the Ni₃(PO₄)₂-coated LiNi_0.8Co_0.15Al_0.05O₂ remained almost undamaged, whereas pristine particles were severely serrated. The stabilization of the host structure by Ni₃(PO₄)₂ coating was also verified using X-ray diffraction.     

Promotion of CO2 methanation activity and CH4 selectivity at low temperatures over Ru/CeO2/Al2O3 catalysts

The effect of CeO₂ loading amount of Ru/CeO₂/Al₂O₃ on CO₂ methanation activity and CH₄ selectivity was studied. The CO₂ reaction rate was increased by adding CeO₂ to Ru/Al₂O₃, and the order of CO₂ reaction rate at 250 °C is Ru/30%CeO₂/Al₂O₃ > Ru/60%CeO₂/Al₂O₃ > Ru/CeO₂ > Ru/Al₂O₃. With a decrease in CeO₂ loading of Ru/CeO₂/Al₂O₃ from 98% to 30%, partial reduction of CeO₂ surface was promoted and the specific surface area was enlarged. Furthermore, it was observed using FTIR technique that intermediates of CO₂ methanation, such as formate and carbonate species, reacted with H₂ faster over Ru/30%CeO₂/Al₂O₃ and Ru/CeO₂ than over Ru/Al₂O₃. These could result in the high CO₂ reaction rate over CeO₂-containing catalysts. As for the selectivity to CH₄, Ru/30%CeO₂/Al₂O₃ exhibited high CH₄ selectivity compared with Ru/CeO₂, due to prompt CO conversion into CH₄ over Ru/30%CeO₂/Al₂O₃.     

Microstructure and hydrogen storage properties of Ti–V–Cr based BCC-type high entropy alloys

In this work, the crystal structure and hydrogen storage properties of V₃₅Ti₃₀Cr₂₅Fe₁₀, V₃₅Ti₃₀Cr₂₅Mn₁₀, V₃₀Ti₃₀Cr₂₅Fe₁₀Nb₅ and V₃₅Ti₃₀Cr₂₅Fe₅Mn₅ BCC-type high entropy alloys have been investigated. It was found that high entropy promotes the formation of BCC phase while large atomic difference (δ) has the opposite effect. Among the four alloys, the V₃₅Ti₃₀Cr₂₅Mn₁₀ alloy shows the highest hydrogen absorption capacity while the V₃₅Ti₃₀Cr₂₆Fe₅Mn₅ alloy exhibits the highest reversible capacity. The cause of the loss of desorption capacity is mainly due to the high stability of the hydrides. The higher room-temperature desorption capacity of the V₃₅Ti₃₀Cr₂₅Fe₅Mn₅ alloy is due to higher hydrogen desorption pressure. After pumping at 400 °C, the hydrides can return to the original BCC structure with only a small expansion in the cell volume.     

Synthesis and experimental study of novel double perovskite Ba2NixCo2−xO6 as promising oxygen carrier materials for CO2 capture application

Novel oxygen-deficient double-perovskite type oxide Ba₂Ni_xCo_2−xO₆ was applied to produce O₂/CO₂ mixed stream gas for oxyfuel combustion application. A series of different Co concentration substituted Ba₂Ni_xCo_2−xO₆ was synthesized by an EDTA-citrate sol-gel combustion method. The oxygen carriers, Ba₂Ni_0.25Co_1.75O_6, Ba₂Ni_0.45Co_1.55O₆, Ba₂Ni_0.65Co_1.35O₆ and Ba₂Ni_0.85Co_1.15O₆ were c\characterized by scanning electron microscopy and cyclic oxygen adsorption/desorption experiments. The results showed that the capacity of provided O₂ was improved by the partial substitution of Ni by Co. In addition, the synthesized perovskites exhibit good regeneration ability. The optimal degree of Co substitution was x = 0.25 for Ba₂Ni_xCo_2−xO₆ with consideration of oxygen desorption ability. Therefore, Ba₂Ni_0.25Co_1.75O₆ was selected to examine the influence of the operating parameters on the oxygen release performance. It was found that the desorption temperature and CO₂ partial pressure are the two main operating parameters for the oxygen desorption performance. Further, the proposed novel double perovskite Ba₂Ni_0.25Co_1.75O₆ provided excellent performance, the O₂ production of Ba₂Ni_0.25Co_1.75O₆ can still reach 120 mg/g after 10 cycles.     

Microstructure and electrochemical behavior of Cr-added V2.1TiNi0.4Zr0.06Cr0.152 hydrogen storage electrode alloy

The microstructure and electrochemical behavior of V_2.1TiNi_0.4Zr_0.06Cr_0.152 hydrogen storage electrode alloy have been investigated in comparison with V_2.1TiNi_0.4Zr_0.06 alloy. The results show that V_2.1TiNi_0.4Zr_0.06Cr_0.152 alloy consists of a V-based solid solution main phase and a C14-type Laves secondary phase in the form of three-dimensional network, being similar to V_2.1TiNi_0.4Zr_0.06 alloy, the secondary phase precipitates along the grain boundaries of the main phase. As compared with V_2.1TiNi_0.4Zr_0.06 alloy, the unit cell volume of each phase in the V_2.1TiNi_0.4Zr_0.06Cr_0.152 alloy contracts. It is found that adding Cr restricts the dissolution of vanadium and titanium into the KOH electrolyte, and improves the corrosion resistance of the alloy, thus the cycling stability after 30 cycles increases from 22.34% (V_2.1TiNi_0.4Zr_0.06) to 77.96% (V_2.1TiNi_0.4Zr_0.06Cr_0.152). Furthermore, V_2.1TiNi_0.4Zr_0.06Cr_0.152 alloy has a better high-rate dischargeability and higher exchange current density compared with V_2.1TiNi_0.4Zr_0.06 alloy, but its maximum discharge capacity decreases.     

Doping the transition metal atom Fe,Co, Ni into C48B12 fullerene for enhancing H2 capture: A theoretical study

The feasibility of transition metal coated fullerene cages M₁₂C₄₈B₁₂(M = Fe, Co, and Ni) for hydrogen storage is investigated by the pseudopotential density functional theory. Fe₁₂C₄₈B₁₂(Co₁₂C₄₈B₁₂ and Ni₁₂C₄₈B₁₂) adsorbs 60(48 and 48) H₂ with moderate average adsorption energy of 0.50(0.45 and 0.32) eV/H₂. The gravimetric hydrogen density of Fe₁₂C₄₈B₁₂(Co₁₂C₄₈B₁₂ and Ni₁₂C₄₈B₁₂) can reach 8.7(6.8 and 6.8) wt%. The Dewar–Kubas interaction dominates the adsorption of H₂ on the outer surface of Fe₁₂C₄₈B₁₂(Co₁₂C₄₈B₁₂ and Ni₁₂C₄₈B₁₂). Therefore, the stable M₁₂C₄₈B₁₂(M = Fe, Co, and Ni) cages can be applied as candidates for hydrogen storage under near-ambient conditions.     

Effect of oxygen vacancies on electrical properties of Ce0.8Sm0.1Nd0.1O2−δ electrolyte: An in situ Raman spectroscopic study

Ce_0.8Sm_0.2O_2−δ, Ce_0.8Nd_0.2O_2−δ and Ce_0.8Sm_0.1Nd_0.1O_2−δ samples were prepared by a citrate sol-gel method. Effects of microstructures and oxygen vacancies of the samples on their electrical properties were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), in situ Raman spectroscopy and AC impedance spectroscopy. SEM results indicated that larger grains were formed on the Ce_0.8Nd_0.2O_2−δ and Ce_0.8Sm_0.1Nd_0.1O_2−δ electrolytes compared to that on the Ce_0.8Sm_0.2O_2−δ. In situ Raman spectra suggested that the concentration of oxygen vacancies of the Ce_0.8Sm_0.1Nd_0.1O_2−δ sample was the highest while that of Ce_0.8Sm_0.2O_2−δ was the lowest. It was found that the difference in the electrical conductivity for these electrolytes was closely related to the microstructure and oxygen vacancies of the samples. The highest electrical conductivity obtained on the Ce_0.8Sm_0.1Nd_0.1O_2−δ sample was ascribed to its larger grain size and higher concentration of oxygen vacancies.     

Facile fabrication of mesoporous In2O3/LaNaTaO3 nanocomposites for photocatalytic H2 evolution

The incorporation of In₂O₃ nanoparticles on mesoporous La_0.02Na_0.98TaO₃ photocatalysts is very interesting for promoting the H₂ production under UV illumination in the presence of [10%] glycerol as a hole scavenger. It is demonstrated that an outstanding mesoporous In₂O₃/La_0.02Na_0.98TaO₃ photocatalyst can be constructed by incorporating In₂O₃ nanoparticles (0-2 wt%) and mesoporous La_0.02Na_0.98TaO₃ nanocomposites for highly promoting photocatalytic H₂ evolution. The maximum yield of H₂ ~ 2350 μmol g⁻¹ was obtained over mesoporous 1%In₂O₃/La_0.02Na_0.98TaO₃ nanocomposite. The mesoporous 1%In₂O₃/La_0.02Na_0.98TaO₃ nanocomposite exhibited further enhancement H₂ production, in which the rate of H₂ evolution can be as high as 235 μmol g⁻¹ h⁻¹, 435 times higher than those of mesoporous La_0.02Na_0.98TaO₃. The results showed that the 1%In₂O₃/La_0.02Na_0.98TaO₃ photocatalyst possesses high stability and durability for H₂ evolution by implying almost no photoactivity reduce after five cycles for 45 h continuous illumination. The measurement of photoluminescence spectroscopy, transient photocurrent spectra and UV- diffuse reflectance spectra for all synthesized samples exhibited that the promoted H₂ production is mainly explained by its effective electron-hole separation and broaden photoresponse region due to its compositions and structures of the obtained heterostructures.     

An infinite chain, {[Ni(tn)2]3[Fe(CN)4(μ-CN)2]2}n,a new catalyst for electrochemical-driven water splitting and photochemical-driven hydrogen evolution from water under blue light

A new catalyst for both water reduction and oxidation, based on an infinite chain, {[Ni(tn)₂]₃ [Fe(CN)₄ (μ-CN)₂]₂}_n, is formed by the reaction of NiCl₂, 1,3-propanediamine (tn) and K₃ [Fe(CN)₆]. {[Ni(tn)₂]₃ [Fe(CN)₄ (μ-CN)₂]₂}_n can electro-catalyze hydrogen evolution from a neutral aqueous buffer (pH 7.0) with a turnover frequency (TOF) of 1561 mol of hydrogen per mole of catalyst per hour (H₂/mol catalyst/h) at an overpotential (OP) of 837 mV {[Ni(tn)₂]₃ [Fe(CN)₄ (μ-CN)₂]₂}_n also can electro-catalyze O₂ production from water with a TOF of ～45 mol O₂ (mol cat)^?1s^?1 at an OP of 591 mV. Under blue light (λ = 469 nm), together with CdS nanorods (CdS NRs) as a photosensitizer, and ascorbic acid (H₂A) as a sacrificial electron donor, {[Ni(tn)₂]₃ [Fe(CN)₄ (μ-CN)₂]₂}_n can photo-catalyze hydrogen generation from an aqueous buffer (pH 4.0) with a turnover number (TON) of 11,450 mol H₂ per mole of catalyst (mol of H₂ (mol of cat)^?1) during 10 h irradiation. The average of apparent quantum yield (AQY) is as high as 40.96% during 10 h irradiation. Studies indicate that {[Ni(tn)₂]₃ [Fe(CN)₄ (μ-CN)₂]₂}_n exists in two forms: a cyano-bridged chain ({[Ni(tn)₂]₃ [Fe(CN)₄ (μ-CN)₂]₂}_n) in solid, and a salt ([Ni(tn)₂]₃ [Fe(CN)₆]₂) in aqueous media; Catalytic reaction occurs on the nickel center of [Ni(tn)₂]²⁺, and the introduction of [Fe(CN)₆]^3- can improve the catalytic efficiency of [Ni(tn)₂]²⁺ for H₂ or O₂ generation. We hope these findings can afford a new method for the design of catalysts for both water reduction and oxidation.     

Promotional Effect of ZrO2 on supported FeCoK Catalysts for Ethylene Synthesis from catalytic CO2 hydrogenation

This study is to convert renewable H₂ and increasingly concerned CO₂ to ethylene or C₂H₄ over Fe_3.33Co_1.67K₅/ZrO₂ and Fe_3.33Co_1.67K₅/Al₂O₃ catalysts. The ZrO₂ support provides amounts of surface oxygen vacancies (OVs) as well as stable and rich surface hydroxyl groups (-OH), which promotes the Fe_3.33Co_1.67K₅/ZrO₂ catalysts with 5% Fe and Co loadings to achieve C₂H₄ space time yield (STY) of 0.064 mmol_C2H4∙m⁻²_cat∙h⁻¹ at 290 °C and 2.0 MPa, while the Fe_3.33Co_1.67K₅/Al₂O₃ catalysts only reach C₂H₄ STY of 0.009 mmol_C2H4∙m⁻²_cat∙h⁻¹ at 330 °C and 2 MPa Fe_3.33Co_1.67K₅/ZrO₂ catalysts are very promising for converting the captured CO₂ and renewable H₂ to highly demanded C₂H₄. This work not only provides a guideline for developing efficient catalysts but also advances the mechanistic understanding of catalytic CO₂ hydrogenation.     

Characterization of LiCoO2 coated Li1.05Ni0.35Co0.25Mn0.4O2 cathode material for lithium secondary cells

In this study, nano-crystalline LiCoO₂ was coated onto the surface of Li_1.05Ni_0.35Co_0.25Mn_0.4O₂ powders via sol–gel method. The influence of the coating on the electrochemical behavior of Li_1.05Ni_0.35Co_0.25Mn_0.4O₂ is discussed. The surface morphology was characterized by transmission electron microscopy (TEM). Nano-crystallized LiCoO₂ was clearly observed on the surfaces of Li_1.05Ni_0.35Co_0.25Mn_0.4O₂. The phase and structural changes of the cathode materials before and after coating were revealed by X-ray diffraction spectroscopy (XRD). It was found that LiCoO₂ coated Li_1.05Ni_0.35Co_0.25Mn_0.4O₂ cathode material exhibited distinct surface morphology and lattice constants. Cyclic voltammetry (2.8–4.6 V versus Li/Li⁺) shows that the characteristic voltage transitions on cycling exhibited by the uncoated material are suppressed by the 7 wt.% LiCoO₂ coating. This behavior implies that LiCoO₂ inhibits structural change of Li_1.05Ni_0.35Co_0.25Mn_0.4O₂ or reaction with the electrolyte on cycling. In addition, the LiCoO₂ coating on Li_1.05Ni_0.35Co_0.25Mn_0.4O₂ significantly improves the rate capability over the range 0.1–4.0C. Comparative data for the coated and uncoated materials are presented and discussed.     

DFT study of coinage metal-hydrogen associations as hydrogen storage materials stabilized by weakly coordinating anions

Density Functional Theory (DFT) calculations were employed to study a series of coinage metal-hydrogen associations formulated as [M(Η₂)_n][A] (M = Cu^I, Ag^I or Au^I, n = 1–5). The [M(Η₂)_n][A] salts utilize both their anions and cations for H₂ storage. The [M(Η₂)_n]⁺ cations could be stabilized in the solid state by voluminous counter-anions, i.e. the [(H₃B) (BH₂NH₂)₅(NH₂)]^-, [B(CNBH₃)₃]^- and [B₁₂H₁₂]^- anions. The estimated bond dissociation energies (BDEs) of the M···(η²-H₂) bonds are 5–17, 4–11 and 1–26 kcal/mol for the [Cu(Η₂)₄]⁺, [Ag (Η₂)₄]⁺ and [Au (Η₂)₄]⁺ cationic species respectively, while the fifth H₂ molecule is estimated to be very loosely associated to the metal center. Four H₂ molecules could be exploited from the [Cu(Η₂)_n][A] and [Ag (Η₂)_n][A] molecules in addition to the amount of H₂ stored in the anion [A]^-. Among the [M(Η₂)_n][A] salts optimal gravimetric, kinetic and thermodynamic properties and relatively low cost, are predicted for [Cu(Η₂)_n][(H₃B) (BH₂NH₂)₅(NH₂)].     

Firs-principles investigation of ZrCo and its hydrides

The electronic structures of Zr₈Co₈ and its hydrides have been systematically investigated using the first-principles calculation based on density functional theory. Additionally, the influence of the Ti and Hf doping on the atomic bonding properties of Zr₈Co₈ and its hydrides (Zr₇HfCo₈, Zr₇HfCo₈H, Zr₁₆Co₁₅HfH₄₈, Zr₇TiCo₈, Zr₇TiCo₈H, and Zr₁₆Co₁₅TiH₄₈ compounds) were also studied to provide new insights into the hydrogenation of Zr₈Co₈. The Ti and Hf atoms were occupied the Zr position in the ZrCo alloy, while they were occupied the Co position in the Zr₁₆Co₁₆H₄₈ system. Ti and Hf doping could achieve the purpose of anti-disproportionation. Ti and Hf could weak the Zr–Co bond for the improvement of the hydrogenation performance of Zr₈Co₈, and the covalence of the Co–H bond was higher than that of the Zr–H bond. The existence of a Co–H covalent bond in the crystal is conducive to the hydrogen absorption of Zr₈Co₈ to form Zr₁₆Co₁₆H₄₈. Inhibition of Co–H interaction during Zr₈Co₈ hydrogenation can accelerate the formation of Zr₈Co₈H for the improvement of its hydrogenation performance.     

Enhanced low temperature hydrogen desorption properties and mechanism of Mg(BH4)2 composited with 2D MXene

Mg(BH₄)₂ occupies a large hydrogen storage capacity of 14.7 wt%, and has been widely recognized to be one of the potential candidates for hydrogen storage. In this work, 2D MXene Ti₃C₂ was introduced into Mg(BH₄)₂ by a facile ball-milling method in order to improve its dehydrogenation properties. After milling with Ti₃C₂, Mg(BH₄)₂–Ti₃C₂ composites exhibit a novel “layered cake” structure. Mg(BH₄)₂ with greatly reduced particle sizes are found to disperse uniformly on Ti₃C₂ layered structure. The initial dehydrogenation temperature of Mg(BH₄)₂ has been decreased to 124.6 °C with Ti₃C₂ additive and the hydrogen liberation process can be fully accomplished below 400 °C. Besides, more than 10.8 wt% H₂ is able to be liberated from Mg(BH₄)₂–40Ti₃C₂ composite at 330 °C within 15 min, while pristine Mg(BH₄)₂ merely releases 5.3 wt% hydrogen. Moreover, the improved dehydrogenation kinetics can be retained during the subsequent second and third cycles. Detailed investigations reveal that not only Ti₃C₂ keeps Mg(BH₄)₂ particles from aggregation during de/rehydrogenation, but also the metallic Ti formed in-situ serves as the active sites to catalyze the decomposition of Mg(BH₄)₂ by destabilizing the B–H covalent bonds. This synergistic effect of size reduction and catalysis actually contributes to the greatly advanced hydrogen storage characteristics of Mg(BH₄)₂.     

The synthesis and characterization of the Sm0.5Sr0.5Co1−xCuxO3−δ cathode by the glycine-nitrate process

In this study, a new oxygen-deficient cathode material, Sm_0.5Sr_0.5Co_1−xCu_xO_3−δ (SSCCu) was developed. It is expected to enhance the efficiency of intermediate-temperature solid oxide fuel cells (IT-SOFCs). The structure, conductivity and electrochemical performance of SSCCu were examined as a function of copper content. The structure of Sm_0.5Sr_0.5Co_0.9Cu_0.1O_3−δ and Sm_0.5Sr_0.5Co_0.8Cu_0.2O_3−δ samples was a single orthorhombic perovskite phase. Second phase SrCoO_2.8, however, formed in the Sm_0.5Sr_0.5Co_0.7Cu_0.3O_3−δ and Sm_0.5Sr_0.5Co_0.6Cu_0.4O_3−δ samples. The conductivity of the Sm_0.5Sr_0.5Co_0.7Cu_0.3O_3−δ cathode was higher than that of other samples. However, the Sm_0.5Sr_0.5Co_0.8Cu_0.2O_3−δ electrode exhibited the lowest overpotential of 25 mV at 400 mA cm⁻² and the lowest area special resistance of 0.2 Ω cm² at 700 °C.     

Decoration of g-C3N4 by inorganic cluster of polyoxometalate through organic linker strategy for enhancing photoelectrocatalytic performance under visible light

The efficient visible light-driven photoelectrocatalyst (denoted as g-C₃N₄-CO-TETA-Pr-SiW₁₁) was designed through the organic linker strategy by combination of polyoxometalate (POM) (cluster of [SiW₁₁O₃₉]^?8 (SiW₁₁)) with graphitic carbon nitride (g-C₃N₄). For this purpose, a reactive tetradentate NH₂ linker was introduced by oxidation and subsequently amidation reactions on the surface of g-C₃N₄ frameworks then SiW₁₁ was bonded to the organic linker to generate g-C₃N₄-CO-TETA-Pr-SiW₁₁. In this study, for the first time, this organic linker strategy was applied for covalent combination of POM and g-C₃N₄ to design a stable photocatalyst with high-performance. Photoelectrocatalytic performance of prepared catalysts was investigated under visible light irradiation. The photocurrent density of 0.17 mA cm^?2 for g-C₃N₄-CO-TETA-Pr-SiW₁₁ compared with 0.077 mA cm^?2 for g-C₃N₄ was achieved. Investigation of the transient open circuit potential decay and photoluminescence showed the efficient electron-hole separation for g-C₃N₄-CO-TETA-Pr-SiW₁₁. The arc diameter in Nyquist plots indicated the improved charge transfer and charge carrier's lifetimes after decorating of g-C₃N₄ with POM. Mott?Schottky plots demonstrated a greater electron transfer at the photo electrode/electrolyte interface for g-C₃N₄-CO-TETA-Pr-SiW₁₁2.8 in compared to g-C₃N₄. Also, the photoconversion efficiency exhibited more than 2.4 time enhancement for g-C₃N₄-CO-TETA-Pr-SiW₁₁ photoanode compared to g-C₃N₄.     

Effect of Sm on the cyclic stability of La–Y–Ni-based alloys and their comparison with RE–Mg–Ni-based hydrogen storage alloy

The LaY₂Ni_9.7Mn_0.5Al_0.3 and LaSm_0.3Y_1.7Ni_9.7Mn_0.5Al_0.3 alloys have been synthesized to investigate the effect of Sm partial substitution for Y on the cyclic stability of A₂B₇-type La–Y–Ni-based alloys. Their cyclic properties were also compared with the A₂B₇-type (RE_0.85Mg_0.15)₂(NiAl)₇ (RE = Rare Earth) alloys. The gas-solid and electrochemical cycle lives were tested. The structural stability, pulverization, and oxidation/corrosion performances were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical methods. The partial substitution of Sm for Y improves anti-corrosion and anti-pulverization performances, thereby increasing the cycle life of A₂B₇-type La–Y–Ni-based hydrogen storage alloys. The A₂B₇-type RE–Y–Ni-based alloys exhibit better crystal structure stability, but the gas-solid and electrochemical cyclic stability is worse than A₂B₇-type (RE_0.85Mg_0.15)₂(NiAl)₇ alloys due to easier pulverization of particles and the oxidation of Y elements.     

Effect of pyrophosphates as supporting matrices on proton conductivity for NH4PO3 composites at intermediate temperatures

Composite electrolytes of NH₄PO₃/pyrophosphate (NH₄PO₃/ZrP₂O₇, NH₄PO₃/Sr₂P₂O₇, and NH₄PO₃/TiP₂O₇) with various molar ratios were fabricated, and their thermal and electrochemical properties were compared at intermediate temperatures. The XRD pattern of NH₄PO₃/Sr₂P₂O₇ composite was consistent with a mixed phase of crystalline NH₄PO₃ and Sr₂P₂O₇ regardless of the composition ratio, whereas those of the other composites were identical to pyrophosphates. A significant difference in conductivity was observed depending on the supporting matrices of pyrophosphates although each composite contained almost the same molar concentration of NH₄PO₃. Among the composites, NH₄PO₃/ZrP₂O₇ (molar ratio; 1:1) exhibited the highest proton conductivity, which was more than twice that of NH₄PO₃/TiP₂O₇ (1:1). The conductivity of NH₄PO₃/Sr₂P₂O₇ (2:1) composite was 2–3 orders of magnitude lower than that of NH₄PO₃/ZrP₂O₇ (1:1). These results suggest that the surface property of pyrophosphates strongly affects the electrochemical properties of composites. Furthermore, a fuel cell that used NH₄PO₃/ZrP₂O₇ composite as an electrolyte was successfully demonstrated at 300 °C.     

New trends to grow the n-CdZn (S1−xSex)2/p-CuIn(S1−xSex)2 heterojunction thin films for solar cell applications

The n-CdZn(S_1−xSe_x) and p-CuIn(S_1−xSe_x)₂ thin films have been grown by the solution growth technique (SGT) on glass substrates. Also the heterojunction (p–n) based on n-CdZn (S_1−xSe_x)₂ and p-CuIn (S_1−xSe_x)₂ thin films fabricated by same technique. The n-CdZn(S_1−xSe_x)₂ thin film has been used as a window material which reduced the lattice mismatch problem at the junction with CuIn (S_1−xSe_x)₂ thin film as an absorber layer for stable solar cell preparation. Elemental analysis of the n-CdZn (S_1−xSe_x)₂ and p-CuIn(S_1−xSe_x)₂ thin films was confirmed by energy-dispersive analysis of X-ray (EDAX). The structural and optical properties were changed with respect to composition ‘x’ values. The best results of these parameters were obtained at x=0.5 composition. The uniform morphology of each film as well as the continuous smooth thickness deposition onto the glass substrates was confirmed by SEM study. The optical band gaps were determined from transmittance spectra in the range of 350–1000 nm. These values are 1.22 and 2.39 eV for CuIn(S_0.5Se_0.5)₂ and CdZn(S_0.5Se_0.5)₂ thin films, respectively. J–V characteristic was measured for the n-CdZn(S_1−xSe_x)₂/p-CuIn(S_1−xSe_x)₂ heterojunction thin films under light illumination. The device parameters V_oc=474.4 mV, J_sc=13.21 mA/cm², FF=47.8% and η=3.5% under an illumination of 85 mW/cm² on a cell active area of 1 cm² have been calculated for solar cell fabrication. The J–V characteristic of the device under dark condition was also studied and the ideality factor was calculated which is equal to 1.9 for n-CdZn(S_0.5Se_0.5)₂/p-CuIn(S_0.5Se_0.5)₂ heterojunction thin films.