Search Results (20)

Tunnel-structured Na_0.44MnO₂ (NMO) has been extensively studied as a potential cathode for sodium-ion batteries (SIBs) due to its favorable cycling endurance, cost-effectiveness, environmental benignity, and notable air-moisture stability. However, limitations, such as sluggish ion diffusion kinetics, an insufficient Na⁺ storage capacity, and an unsatisfactory Jahn–Teller effect, impede its widespread application. To address these problems, this study proposes a co-doping strategy that involves the simultaneous introduction of a cation and an anion. The optimized cathode Na_0.44Mn_0.99Ni_0.01O_1.985F_0.015 demonstrates remarkable rate capabilities with average discharge capacities of 136.2, 133.0, 129.6, 124.0, 115.9, and 95.8 mAh g⁻¹ under current rates ranging from 0.1 to 5 C. Furthermore, it also exhibits exceptional long-term cyclability, retaining 86.5% and 89.4% capacity retention at 1 and 5 C after 200 and 400 cycles, respectively, accompanied by nearly 100% Coulombic efficiency. A comprehensive structural characterization and experimental analysis reveal that the synergistic incorporation of Ni and F can effectively adjust the lattice parameters and alleviate the Jahn–Teller distortion of the NMO cathode, thereby resulting in enhanced structural integrity, rapid ion transfer dynamics, and excellent sodium storage performance. Consequently, this investigation establishes a significant approach for optimizing tunnel-phase Mn-based cathodes through the synergistic effect of cation and anion co-doping, which promotes the practical implementation of advanced SIBs. Full article

Materials engineering based on metal oxides for manipulating the solar spectrum and producing solar energy have been under intense investigation over the last years. In this work, we present NiO thin films double doped with niobium (Nb) and nitrogen (N) as cation and anion dopants (NiO:(Nb,N)) to be used as p-type layers in all oxide transparent solar cells. The films were grown by sputtering a composite Ni-Nb target on room-temperature substrates in plasma containing 50% Ar, 25% O₂, and 25% N₂gases. The existence of Nb and N dopants in the NiO structure was confirmed by the Energy Dispersive X-Ray and X-Ray Photoelectron Spectroscopy techniques. The nominally undoped NiO film, which was deposited by sputtering a Ni target and used as the reference film, was oxygen-rich, single-phase cubic NiO, having a visible transmittance of less than 20%. Upon double doping with Nb and N the visible transmittance of NiO:(Nb,N) film increased to 60%, which was further improved after thermal treatment to around 85%. The respective values of the direct band gap in the undoped and double-doped films were 3.28 eV and 3.73 eV just after deposition, and 3.67 eV and 3.76 eV after thermal treatment. The changes in the properties of the films such as structural disorder, direct and indirect energy band gaps, Urbach tail states, and resistivity were correlated with the incorporation of Nb and N in their structure. The thermally treated NiO:(Nb,N) film was used to form a diode with a spin-coated two-layer, mesoporous on top of a compact, TiO₂ film. The NiO:(Nb,N)/TiO₂heterojunction exhibited visible transparency of around 80%, showed rectifying characteristics and the diode’s parameters were deduced using the I-V method. The diode revealed photovoltaic behavior upon illumination with UV light exhibiting a short circuit current density of 0.2 mA/cm² and open-circuit voltage of 500 mV. Improvements of the output characteristics of the NiO:(Nb,N)/TiO₂ UV-photovoltaic by proper engineering of the individual layers and device processing procedures are addressed. Transparent NiO:(Nb,N) films can be potential candidates in all-oxide ultraviolet photovoltaics for tandem solar cells, smart windows, and other optoelectronic devices. Full article

In cation–anion co-doping, rare earth elements excel at regulating the electronic structure of perovskites, leading to their improved photocatalytic performance. In this regard, the impact of co-doping rare earth elements at the Ba and Ti sites in BaTiO₃ on its electronic and photocatalytic properties was thoroughly investigated based on 2 × 2 × 2 supercell structures of BaTiO₃ with different La concentrations of 12.5% and 25% using DFT calculations. The band structure, density of states, charge density difference, optical properties, and the redox band edge of the co-doped models mentioned above were analyzed. The results indicated that the BaTiO₃ structure co-doped with 25% La at the Ti site exhibited higher absorption in the visible range and displayed a remarkable photocatalytic water-splitting performance. The introduced La dopant at the Ti site effectively reduced the energy required for electronic transitions by introducing intermediate energy levels within the bandgap. Our calculations and findings of this study provide theoretical support and reliable predictions for the exploration of BaTiO₃ perovskites with superior photocatalytic performances. Full article

Cation-anion co-doping has proven to be an effective method of improving the photocatalytic performances of CaTiO₃ perovskites. In this regard, (La/Ce-N/S) co-doped CaTiO₃ models were investigated for the first time using first-principles calculations based on a supercell of 2 × 2 × 2 with La/Ce concentrations of 0.125, 0.25, and 0.375. The energy band structure, density of states, charge differential density, electron-hole effective masses, optical properties, and the water redox potential were calculated for various models. According to our results, (La-S)-doped CaTiO₃ with a doping ratio of 0.25 (LCOS1-0.25) has superior photocatalytic hydrolysis properties due to the synergistic performances of its narrow band gap, fast carrier mobility, and superb ability to absorb visible light. Apart from the reduction of the band gap, the introduction of intermediate energy levels by La and Ce within the band gap also facilitates the transition of excited electrons from valence to the conduction band. Our calculations and findings provide theoretical insights and solid predictions for discovering CaTiO₃ perovskites with excellent photocatalysis performances. Full article

Molybdenum disulfide (MoS₂) is the second two-dimensional material after graphene that received a lot of attention from the research community. Strong S–Mo–S bonds make the sandwich-like layer mechanically and chemically stable, while the abundance of precursors and several developed synthesis methods allow obtaining various MoS₂ architectures, including those in combinations with a carbon component. Doping of MoS₂ with heteroatom substituents can occur by replacing Mo and S with other cations and anions. This creates active sites on the basal plane, which is important for the adsorption of reactive species. Adsorption is a key step in the gas detection and electrochemical energy storage processes discussed in this review. The literature data were analyzed in the light of the influence of a substitutional heteroatom on the interaction of MoS₂ with gas molecules and electrolyte ions. Theory predicts that the binding energy of molecules to a MoS₂ surface increases in the presence of heteroatoms, and experiments showed that such surfaces are more sensitive to certain gases. The best electrochemical performance of MoS₂-based nanomaterials is usually achieved by including foreign metals. Heteroatoms improve the electrical conductivity of MoS₂, which is a semiconductor in a thermodynamically stable hexagonal form, increase the distance between layers, and cause lattice deformation and electronic density redistribution. An analysis of literature data showed that co-doping with various elements is most attractive for improving the performance of MoS₂ in sensor and electrochemical applications. This is the first comprehensive review on the influence of foreign elements inserted into MoS₂ lattice on the performance of a nanomaterial in chemiresistive gas sensors, lithium-, sodium-, and potassium-ion batteries, and supercapacitors. The collected data can serve as a guide to determine which elements and combinations of elements can be used to obtain a MoS₂-based nanomaterial with the properties required for a particular application. Full article

Aqueous zinc-ion batteries (ZIBs) have been regarded as a promising alternative to traditional lithium-based batteries due to their intrinsic advantages of safety, low cost, and abundance. However, the strong electrostatic interaction between Zn²⁺ and the layer-structured cathodes is still a key issue that hinders the batteries from storing more Zn. Herein, we report partially nitrided and cation-doped vanadium oxide for improved Zn storage performance. Specifically, the defects and nitride species that are generated inside the material upon nitriding improve the conductivity of the material and introduce a new Zn storage mechanism. The intercalation of cations, in contrast, widens the interlayer spacing to store more Zn²⁺ ions and enhances the cycling stability of the material. These merits synergistically lead to significantly enhanced electrochemical Zn²⁺ ion storage performance, in terms of a high specific capacity of 418.5 mAh·g⁻¹ at a current density of 0.1 A·g⁻¹ and a capacity retention of 81.2% after 500 cycles at 2.0 A·g⁻¹. The new modification strategy for V₂O₅ suggested in this work could provide insight into the development of high-performance ZIBs. Full article

The widespread application of protonic ceramic fuel cells is limited by the lack of oxygen electrodes with excellent activity and stability. Herein, the strategy of halogen doping in a Ba_0.6Sr_0.4Co_0.7Fe_0.2Nb_0.1O_3-δ (BSCFN) cathode is discussed in detail for improving cathode activity. Ba_0.6Sr_0.4Co_0.7Fe_0.2Nb_0.1O_3-x-δF_x (x = 0, 0.05, 0.1) cathode materials are synthesised by a solid-phase method. The XRD results show that fluorine anion-doped BSCFN forms a single-phase perovskite structure. XPS and titration results reveal that fluorine ion doping increases active oxygen and surface adsorbed oxygen. It also confines chemical bonds between cations and anions, which enhances the cathode’s catalytic performance. Therefore, an anode-supported single cell with the configuration of Ni-BaZr_0.1Ce_0.7Y_0.1Yb_0.1O_3-δ (BZCYYb)|BZCYYb|Ba_0.6Sr_0.4Co_0.7Fe_0.2Nb_0.1O_3-0.1-δF_0.1 (BSCFN-F_0.1) achieved a high peak power density of 630 mW cm⁻² at 600 °C. Moreover, according to the symmetrical cell test, the BSCFN-F_0.1 electrode demonstrated a superb stability for nearly 400 h at 600 °C. This work focuses on the influence of fluorine anion incorporation upon the performance of cathode materials. It also analyses and discusses the effects of different fluorine ion incorporation amounts to occupy different oxygen positions. Full article

Rare-earth oxyhydride (ReO_xH_y) films are novel inorganic photochromic materials that have strong potential for applications in windows and optical sensors. Cations greatly influence many material properties and play an important role in the photochromic performance of ReO_xH_y. Here we propose a strategy for obtaining Gd_1−zY_zO_xH_y films (z = 1, 0.7, 0.5, 0.4, 0.35, 0.25, 0.15, 0) using one-step direct-current (DC) magnetron co-sputtering. Distinct from the mixed anion systems, such material would belong to the class of mixed anion and mixed cation materials. For Gd_1−zY_zO_xH_y films, different co-doping ratios can help tune the contrast ratio (that is, the difference between coloration and bleaching transmittance) and cycling degradation, which may be related to the lattice constant. X-ray diffraction (XRD) patterns show that the lattice constant increases from 5.38 Å for YO_xH_y to 5.51 Å, corresponding to Gd_0.75Y_0.25O_xH_y. The contrast ratio, in particular, can be enhanced to 37% from 6.3% by increasing the lattice constant, directly controlled by the co-sputtering power. When the lattice constant decreases, the surface morphology of the sample with the smallest lattice constant is essentially unchanged by testing in air with normal oxidation for 100 days, suggesting great improvement in environment durability. However, the crystal structure cannot be overly compressed, and co-sputtering with Cr gives black opaque films without photochromic properties. Moreover, because the atomic mass of different rare earth elements is different, the critical pressure p* (films deposited at p < p* remain metallic dihydrides) is different, and the preparation window is enlarged. Our work provides insights into innovative photochromic materials that can help to achieve commercial production and application. Full article

Congo red (CR) is a stable anionic diazo dye that causes allergic reactions with carcinogenic properties. The rapid removal of CR using cation-incorporated nanohydroxyapatite (pristine HAp: X (X = Fe, Ni, Zn, Co, and Ag)) was investigated. The pristine and cation ion-doped HAp adsorbents were coprecipitated and subjected to hydrothermal and ultrasound treatments and subsequent microwave drying. The dopant ions significantly engineered the crystallite size, crystallinity, particle size (decreased 38–77%), shape (a rod to sphere modification by the incorporation of Ag⁺, Ni²⁺, and Co²⁺ ions), and colloidal stability (CS) of the adsorbent. These modifications aided in the rapid removal of the CR dye (98%) within one minute, and the CR adsorption rate was found to be significantly higher (93–99%) compared to previously reported rates. Furthermore, the kinetic, Langmuir, Freundlich, and DKR isotherms and thermodynamic results confirmed that the CR adsorption on the HAp was due to the strong chemical adsorption process. The order of the maximum CR adsorption capacity was Fe-HAp > HAp > Ag-HAp > Co-HAp > Zn-HAp. Whereas the CR regeneration efficiency was Fe-HAp (92%) > Ag-HAp (42%) > Ni-HAp (30%), with the other adsorbents exhibiting a poor recycling efficiency (1–16%). These results reveal Fe-HAp as a potential adsorbent for removing CR without the formation of byproducts. Full article

Physical and chemical properties have been studied in lithium niobate (LiNbO₃, LN) crystals grown by Czochralski from a boron doped melt. Optical uniformity and optical damage resistance of LiNbO₃:B crystals have been compared with control crystals of nominally pure congruent (CLN) and near-stoichiometric (NSLN K₂O) composition. LiNbO₃:B crystals structure has been studied. Studied LiNbO₃:B crystals have been grown from differently synthesized charges. The charges have been synthesized from a mixture Nb₂O₅:B-Li₂CO₃ using homogeneously doped Nb₂O₅:B precursor (sample 1, (B) = 0.0034 wt% in the charge) and by a direct solid phase synthesis from Nb₂O₅-Li₂CO₃-H₃BO₃ mixture (sample 2, (B) = 0.0079 wt% in the charge). Only traces of boron (10⁻⁵–10⁻⁴ wt%) have been detected in the samples. We have established that concentration of anti-site defects Nb_Li is lower in both LiNbO₃:B than in CLN crystals. XRD analysis has confirmed that B³⁺ cations localize in faces of tetrahedral voids O₄ of LN structure. The voids act as buffers at the anion sublattice distortion. Sample 1 has been shown to have a structure closer to NSLN K₂O crystal than sample 2. We have also shown that the chemical purity of LN crystal increases compared to the melt purity because boron creates strong compounds with impurities in the melt system Li₂O-Nb₂O₅-B₂O₃. Metals impurities thus stay in the melt and do not transfer to the crystal. Full article

Argyrodite solid electrolytes such as lithium phosphorus sulfur chloride (Li₆PS₅Cl) have recently attracted great attention due to their excellent lithium-ion transport properties, which are applicable to all-solid-state lithium batteries. In this study, we report the improved ionic conductivity of an argyrodite solid electrolyte, Li₆PS₅Cl, in all-solid-state lithium batteries via the co-doping of chlorine (Cl) and aluminum (Al) elements. Electrochemical analysis was conducted on the doped argyrodite structure of Li₆PS₅Cl, which revealed that the substitution of cations and anions greatly improved the ionic conductivity of solid electrolytes. The ionic conductivity of the Cl- and Al-doped Li₆PS₅Cl (Li_5.4Al_0.1PS_4.7Cl_1.3) electrolyte was 7.29 × 10⁻³ S cm⁻¹ at room temperature, which is 4.7 times higher than that of Li₆PS₅Cl. The Arrhenius plot of the Li_5.4Al_0.1PS_4.7Cl_1.3 electrolyte further elucidated its low activation energy at 0.09 eV. Full article

This work is a mini-review highlighting the relevance of the θ metallabis(dicarbollide) [3,3′-Co(1,2-C₂B₉H₁₁)₂]⁻ with its peculiar and differentiating characteristics, among them the capacity to generate hydrogen and dihydrogen bonds, to generate micelles and vesicles, to be able to be dissolved in water or benzene, to have a wide range of redox reversible couples and many more, and to use these properties, in this case, for producing potentiometric membrane sensors to monitor amine-containing drugs or other nitrogen-containing molecules. Sensors have been produced with this monoanionic cluster [3,3′-Co(1,2-C₂B₉H₁₁)₂]⁻. Other monoanionic boron clusters are also discussed, but they are much fewer. It is noteworthy that most of the electrochemical sensor species incorporate an ammonium cation and that this cation is the species to be detected. Alternatively, the detection of the borate anion itself has also been studied, but with significantly fewer examples. The functions of the borate anion in the membrane are different, even as a doping agent for polypyrrole which was the conductive ground on which the PVC membrane was deposited. Apart from these cases related to closo borates, the bulk of the work has been devoted to sensors in which the θ metallabis (dicarbollide) [3,3′-Co(1,2-C₂B₉H₁₁)₂]⁻ is the key element. The metallabis (dicarbollide) anion, [3,3′-Co(1,2-C₂B₉H₁₁)₂]⁻, has many applications; one of these is as new material used to prepare an ion-pair complex with bioactive protonable nitrogen containing compounds, [YH]_x[3,3′-Co(1,2-C₂B₉H₁₁)₂]_y as an active part of PVC membrane potentiometric sensors. The developed electrodes have Nernstian responses for target analytes, i.e., antibiotics, amino acids, neurotransmitters, analgesics, for some decades of concentrations, with a short response time, around 5 s, a good stability of membrane over 45 days, and an optimal selectivity, even for optical isomers, to be used also for real sample analysis and environmental, clinical, pharmaceutical and food analysis. Full article

Graphitic C₃N₄-based materials are promising for photocatalytic H₂ evolution applications, but they still suffer from low photocatalytic activity due to the insufficient light absorption, unfavorable structure and fast recombination of photogenerated charge. Herein, a novel anion–cation co-doped g-C₃N₄ porous nanotube is successfully synthesized using a self-assembly impregnation-assisted polymerization method. Ni ions on the surface of the self-assembly nanorod precursor can not only cooperate with H₃P gas from the thermal cracking of NaH₂PO₂ as an anion–cation co-doping source, but, more importantly, suppress the shape-collapsing effect of the etching of H₃P gas due to the strong coordinate bonding of Ni-P, which leads to a Ni and P co-doped g-C₃N₄ porous nanotube (PNCNT). Ni and P co-doping can build a new intermediate state near the conduction band in the bandgap of the PNCNT, and the porous nanotube structure gives it a higher BET surface area and light reflection path, showing a synergistic ability to broaden the visible-light absorption, facilitate photogenerated charge separation and the light-electron excitation rate of g-C₃N₄ and provide more reaction sites for photocatalytic H₂ evolution reaction. Therefore, as expected, the PNCNT exhibits an excellent photocatalytic H₂ evolution rate of 240.91 μmol·g⁻¹·h⁻¹, which is 30.5, 3.8 and 27.8 times as that of the pure g-C₃N₄ nanotube (CNT), single Ni-doped g-C₃N₄ nanotube (NCNT) and single P-doped g-C₃N₄ nanotube (PCNT), respectively. Moreover, the PNCNT shows good stability and long-term photocatalytic H₂ production activity, which makes it a promising candidate for practical applications. Full article

Co-doped Fe-MOF bimetallic organic framework materials at different ratios were synthesized based on the solvothermal method, and we evaluated their morphological characteristics by modern analytical methods such as SEM, XRD, FT-IR, and isotherm of nitrogen adsorption-desorption (BET). The specific surface area of the 0.3 CoFe-MOF sample (280.9 m²/g) is much larger than the Fe-MOF and samples at other ratios. The post-synthesized materials were evaluated for their ability to absorb various dyes, including Methylene Blue (MB), Methyl orange (MO), Congo red (CR), and Rhodamine (RhB), and evaluated for the effects of pH, the initial concentration of the dye solution, time, and dose of adsorbent. The results show that the 0.3 CoFe-MOF material has a high adsorption capacity that is superior to both the original Fe-MOF and the CoFe-MOFs at other ratios. The highest adsorption capacity of MB dye by 0.3 CoFe-MOF reaches up to 562.1 mg/g at pH 10, the initial concentration of MB of 200 mg/L, after 90 min. The charged properties of the dyes and the charged nature of the bimetallic organic frameworks are best demonstrated through the adsorption of dye mixtures. The adsorption efficiency on the mixed system of cationic (MB) and anionic (MO) dyes yielded the highest removal efficiency of 70% and 81%, respectively, after 30 min. Therefore, the research has opened up the potential application of M/Fe-MOF modified materials and CoFe-MOF in organic dyes adsorption in wastewater treatment for environmental protection. Full article

Elemental doping for substituting lithium or oxygen sites has become a simple and effective technique to improve the electrochemical performance of layered cathode materials. Compared with single-element doping, this work presents an unprecedented contribution to the study of the effect of Na⁺/F⁻ co-doping on the structure and electrochemical performance of LiNi_1/3Mn_1/3Co_1/3O₂. The co-doped Li_1-zNa_zNi_1/3Mn_1/3Co_1/3O_2-zF_z (z = 0.025) and pristine LiNi_1/3Co_1/3Mn_1/3O₂ materials were synthesized via the sol–gel method using EDTA as a chelating agent. Structural analyses, carried out by X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy, revealed that the Na⁺ and F⁻ dopants were successfully incorporated into the Li and O sites, respectively. The co-doping resulted in larger Li-slab spacing, a lower degree of cation mixing, and the stabilization of the surface structure, which substantially enhanced the cycling stability and rate capability of the cathode material. The Na/F co-doped LiNi_1/3Mn_1/3Co_1/3O₂ electrode delivered an initial specific capacity of 142 mAh g⁻¹ at a 1C rate (178 mAh g⁻¹ at 0.1C), and it maintained 50% of its initial capacity after 1000 charge–discharge cycles at a 1C rate. Full article