Journal of Solid State Chemistry最新文献

The development of cheap, efficient and stable hydrogen-producing catalysts is the current research focus, especially the catalysts that can work stably in the whole pH range. In this work, a myrica rubra-like structure of P–Co_1-xS/C was synthesized by hydrothermal reaction, sulfurization and phosphorization using spherical flower-like cobalt glycerate (CoG) as precursor. The design of this multilevel structure of P–Co_1-xS/C effectively increases the specific surface area. The doping phosphorus and the protection of carbon layer greatly improve catalytic performance and enhance the stability of Co_1-xS in the hydrogen evolution reaction (HER) at full pH range. When the current density is 10 mA cm⁻², the HER overpotentials of P–Co_1-xS/C in acidic, alkaline and neutral solutions are 86, 93 and 167 mV, and respectively. The Tafel slopes of P–Co_1-xS/C in acidic, alkaline and neutral solutions are 82, 100 and 103 mV dec⁻¹, respectively. In addition, the electrocatalyst also displays excellent electrochemical long-term stability. After 2000 cycles or 20 h long-term testing, its catalytic activity remains stable without obvious decrease at full pH range.

Transition metal oxides have been identified as the best potential candidates to replace Pt-based HER catalysts. But they are still limited by the high HER overpotential, due to the undesirable adsorption/desorption of surface hydrogen. In this work, Zn with low concentrations were incorporated into the tetrahedral Co²⁺ sites of Co₃O₄ by hydrothermal and subsequent annealing treatment. They exhibit excellent HER performance. Particularly, when the Zn content in Co₃O₄ is 6.3 at%, an overpotential of 79.2 mV at the current density of 10 mA cm⁻² was obtained in alkaline medium, which significantly better than pure Co₃O₄ catalyst (196.3 mV). Moreover, the current density of the Zn-doped Co₃O₄ catalyst can maintained 93 % after 10 h and 80 % after 20 h. DFT calculations reveal that the ΔG_H* of Zn-doped Co₃O₄ (0.827 eV) is smaller and closer to zero than pure Co₃O₄ (1.023 eV). This work provides a deep insight into the rational design of low-level metal-doped cobalt oxide-based electrocatalysts.

In the quest for efficient and cost-effective catalysts to drive the hydrogen evolution reaction (HER) in electrochemical water splitting, copper foam (CuF) is a favorable candidate for electrode coating. Precious metal catalysts like Pt/C dominate the field but must be improved because of their high cost and scarcity. Therefore, we have synthesized and evaluated a sequence of nickel-originated electrocatalysts (Ni, NiMo, NiP, and NiMoP) with the electrodeposition of CuF to facilitate substantial improvements in HER performance. Herein, the Ni–Mo–P ternary system, owing to its desirable electronic structure and catalytic mechanism, contributes to enhancing the thermodynamics and kinetics of the HER. Performance analysis reveals that all studied catalysts follow the order of Ni/CuF > NiMo/CuF > NiP/CuF > NiMoP/CuF regarding both the Tafel slope and overpotential. Hence, the top performer, NiMoP/CuF, exhibits tremendous thermodynamics with an η₁₀ = 159 mV and Tafel slope kinetics of 126.66 mV·dec⁻¹ at 1.0 M KOH in water splitting. Overall, this report presents a well-capable way of optimizing the electrocatalytic function and stability of CuF-electro-coated catalysts for the HER. This research opens new avenues for cost-effective, stable, and efficient HER catalysts, showcasing the potential of NiMoP/CuF in advancing sustainable hydrogen production technologies.

The bright luminescence of the copper ion-exchange layer in glass has potential applications as a converter of electric spark and corona discharge radiation in devices for the rapid analysis of metals because of its selectivity. The selectivity of the luminescence of the copper ion-exchange layer was achieved by the presence of different luminescent centers within it. In this work, the copper monomers, Cu⁺-Cu⁺ monovalent dimers, and Cu_n molecular clusters were formed in an ion-exchange layer of sodium-potassium-magnesium silicate glass (SiO₂-Na₂O-CaO-MgO-Al₂O₃-K₂O-Fe₂O₃). The luminescence of the copper ion exchange layer was characterized by steady-state spectroscopy and time-resolved spectroscopy. Molecular copper clusters Cu_n exhibited luminescence in the nanosecond range, and Cu⁺ monomers and Cu⁺-Cu⁺ monovalent dimers in the microsecond range, respectively. At the same time the formation of divalent copper led to a limitation in the duration of ion exchange for the production of luminescent glasses. Heat treatment of the ion-exchange layers led to an increase in the concentration of molecular copper clusters, Cu⁺-Cu⁺ monovalent dimers, and Cu²⁺ divalent monomers.

Direct conversion from amorphous calcium carbonate (ACC) to aragonite has been extremely difficult compared to the other two polymorphs, calcite and vaterite. In the present study, aragonite formation with a high polymorph fraction (>97 %) was achieved from ACC immersed in n-butylamine under 90 % RH (relative humidity) at 30 °C for 2 h. It is noteworthy that aragonite with a high polymorphic fraction was obtained without the addition of Mg²⁺ ion, which is well known to promote aragonite formation.

To understand the effects of hydrophobic and basic properties of n-butylamine, hexane, NH₃ aq., and hexane + NH₃ aq. were mixed with ACC and left for two weeks. Aragonite was formed only from the mixture of hexane and NH₃ aq. Although the detailed mechanism requires further investigations, the obtained results suggest that both hydrophobic and basic properties are required for the crystallization of ACC to aragonite.

The cathode's oxygen reduction reaction (ORR) plays a crucial role in a variety of fuel cells. Developing affordable and efficient non-precious electrocatalysts for the ORR poses a major hurdle in the realm of electrochemical energy technologies. This work presents a transition metal-based catalyst, Fe-ONC, in which Fe is loaded in an oxygen-enriched nitrogen-doped carbon (NC) material. Oxygen enrichment of the catalyst was achieved by a pre-oxidation strategy. The XPS analysis reveals that Fe-ONC exhibits a higher abundance of oxidized species. The Fe of Fe-ONC exists in the form of Fe₃O₄ particles and Fe-N_x, respectively, which are uniformly distributed in the NC. The even spread of iron sites and the plentiful presence of oxygen-rich species are key factors in the superior ORR efficiency of Fe-ONC. Fe-ONC's half-wave potential (E_1/2) in an alkaline environment (0.1 M KOH) stands at 0.891 V, markedly surpassing the standard commercial Pt/C value (0.840 V). Additionally, Fe-ONC demonstrated enhanced longevity and resistance to ethanol in comparison to commercially available Pt/C. Fe-ONC's outstanding efficacy highlights its potential as an alternative to precious metal catalysts. The document outlines a plan for creating ORR catalytic materials that are sustainable, economical, and efficient.

Tetracycline antibiotics as one of the most widely used antibiotics at present, are difficult to degrade in the environment, which poses a serious threat to the ecosystem and human health. In this work, NiTiO₃/g-C₃N₄ composites were successfully constructed by calcination method using nickel acetate tetrahydrate as nickel source and tetrabutyl titanate as titanium source. The photocatalytic degradation efficiency of the 5 wt% NiTiO₃/g-C₃N₄ composite of TC can reach 88.2 % within 150 min, which was 1.4 and 2.2 times higher than that of pure g-C₃N₄ (63 %) and NiTiO₃ (40 %), respectively. The 5 wt% NiTiO₃/g-C₃N₄ composite can still maintain good stability after four cycles. The experimental results showed that the construction of Z-scheme heterojunction can effectively improve the photocatalytic activity of the catalysts and maintain good redox properties at the same time. Furthermore, a possible mechanism of photocatalytic degradation of NiTiO₃/g-C₃N₄ heterojunction has been suggested.

Two series of open metal site MOFs, HKUST-1 and MIL-100(Fe), have been successfully prepared using different methods of synthesis. Their features depend on the synthetic route as well as their role play in different environmental applications. The stability and performance of these BTC-based MOFs have been tested bearing in mind Congo Red (CR) removal, humidity adsorption and iodine capture and release. HKUST-1 and MIL-100(Fe) samples could offer a remarkable role in the adsorption of CR from aqueous solutions. However, the lability of HKUST-1 in water is revealed as a drawback for its reutilization in both static and agitation conditions. The former contrasts to the stability under ambient moisture. MIL-100(Fe) shows promising properties in both CR adsorption in aqueous solutions and humidity adsorption. Nonetheless, the performance largely depends on the synthesis conditions. Although CR removal is based on surface interaction, there is a relation between the adsorpted quantity and the specific surface area. The size and nature of iodine allows the diffusion in the pores of both HKUST-1 and MIL-100(Fe) MOFs. This way, the uptake of iodine is driving by the porosity and surface area of samples rather than their inherent nature. As a rule, the results of this work indicate that not only is it important the specific nature of the MOF chosen for a given application but also the way in which it has been synthesized and the conditions in which they are used. MIL-100(Fe)-R is revealed as the best suitable candidate to be used as a sorbent for CR in aqueous solutions, moisture and I₂ gas.

Designing rational heterojunctions to achieve efficient separation and transmission of photoinduced charge carriers is one of the effective strategies to improve the activity of semiconductor photocatalysts. In this study, the novel In₂S₃/BiOIO₃ binary heterojunctions were facilely synthesized at room temperature using a simple in-situ growth method. The physicochemical properties of the fabricated In₂S₃/BiOIO₃ heterojunction catalyst were investigated using various techniques including XRD, FT-IR, BET, XPS, TEM, UV–vis DRS, PL, EIS, and PC analysis. The In₂S₃/BiOIO₃ composite catalyst possesses suitable band position and bandgap energy and therefore is capable of degrading organic contaminants under visible light irradiation. The optimized composite catalyst with In₂S₃/BiOIO₃ molar ratio of 0.5 (In₂S₃/BiOIO₃-5) exhibited superior photocatalytic activity, achieving 98.6 % degradation rate for Rhodamine B (RhB), far surpassing the performance of the individual components. In addition, In₂S₃/BiOIO₃-5 showed broad-spectrum photocatalytic activity in the decomposition of various organic pollutants including methyl orange (MO), methylene blue (MB), tetracycline (TC) and bisphenol A (BPA). The improved photocatalytic activity of the prepared composite catalysts can be ascribed to the formation of type-II heterojunction, which facilitates the separation and migration of e^–/h⁺ pairs. The excellent photocatalytic properties and favorable structural stability make In₂S₃/BiOIO₃-5 a viable material for degrading various persistent organic pollutants.

A series of five novel lanthanide-based fluorinated metal-organic frameworks (Ln-F-MOFs) have been synthesized under solvothermal conditions by the reaction of 3,3′-bis(trifluoromethyl)-[1,1′-biphenyl]-4,4′-dicarboxylic acid (H₂L) and lanthanide Ln(III) ions (Ln(III)La, Ce, Pr, Nd and Eu). Powder X-ray diffraction (PXRD) analysis revealed that all prepared complexes are isostructural. A single-crystal X-ray crystallographic study of one representative of the isostructural group, namely {[La₂(L)₃(DMF)₂(H₂O)₂]}_n showed, that compound crystallizes in a triclinic system with space group P-1. The lattice parameter values are a = 8.563(2) Å, b = 13.199(3) Å, c = 16.008(4) Å, α = 104.588(7) °, β = 92.904(7) ° and γ = 92.717(7) °, with two formula units in the unit cell. The overall structure is formed by 2D polymeric layers, which are arranged into a semi-3D supramolecular structure through hydrogen bonds and other intramolecular interactions. The study of the hydrophobic properties of the complexes showed that the complexes exhibit surface hydrophobicity with a “rose petal effect” and a contact angle of approximately 107°. However, the structures are not hydrolytically stable in the long term and the structure starts to delaminate after two days in water. This is a manifestation of the fact that the complexes do not form a 3D polymer network, it is made up of 2D layers connected only by weak non-bonding interactions. The photoluminescence properties of the Ln(III) complexes are determined by the characteristic 5d-4f or 4f-4f electron transitions for the individual lanthanide ions. The magnetic properties of Nd(III), Pr(III) and Eu(III) variants were studied. The magnetic properties of {[Pr₂(L)₃(DMF)₂(H₂O)₂]}_n are characterized by the presence of a low-lying quasi-doublet with 15.6 cm⁻¹ energy splitting, whereas Eu(III) variant is nonmagnetic at low temperatures, but the magnetic ⁷F₁ state is accessible by thermal excitation. For Nd(III) complex, the X-band EPR measurements were performed. Since 1D channels with dimensions of 4.90 × 7.23 Å² are present within the structure, the adsorption of N₂, CO₂ and H₂ gases was also studied.