Metal Ion Doping Research Articles

Prompting CO2 Electroreduction to Ethanol by Iron Group Metal Ion Dopants Induced Multi-sites at the Interface of SnSe/SnSe2 p-n Heterojunction.

The development of non-copper-based materials for CO2 electroreduction to ethanol with high selectivity at large current density is highly desirable, but still a great challenge. Herein, we report iron group metal ions of M2+ (M=Fe, Co, or Ni)-doped amorphous/crystalline SnSe/SnSe2 nanorod/nanosheet hierarchical structures (a/c-SnSe/SnSe2) for selective CO2 electroreduction to ethanol. Iron group metal ions doping induces multiple active sites at the interface of M2+-doped SnSe/SnSe2 p-n heterojunction, which strengthens *CO intermediate binding for further C-C coupling to eventual ethanol generation. As a representative, Fe9.0%-a/c-SnSe/SnSe2 exhibits an ethanol Faradaic efficiency of 62.7 % and a partial current density of 239.0 mA cm-2 at -0.6 V in a flow cell. Moreover, it can output an ethanol Faradaic efficiency of 63.5 % and a partial current density of 201.2 mA cm-2 with a full-cell energy efficiency of 24.1 % at 3.0 V in a membrane electrode assembly (MEA) electrolyzer. This work provides insight into non-Cu based catalyst design for stabilizing the key intermediates for selective ethanol production from CO2 electroreduction.

Prompting CO2 Electroreduction to Ethanol by Iron Group Metal Ion Dopants Induced Multi‐sites at the Interface of SnSe/SnSe2 p–n Heterojunction

AbstractThe development of non‐copper‐based materials for CO2 electroreduction to ethanol with high selectivity at large current density is highly desirable, but still a great challenge. Herein, we report iron group metal ions of M2+ (M=Fe, Co, or Ni)‐doped amorphous/crystalline SnSe/SnSe2 nanorod/nanosheet hierarchical structures (a/c‐SnSe/SnSe2) for selective CO2 electroreduction to ethanol. Iron group metal ions doping induces multiple active sites at the interface of M2+‐doped SnSe/SnSe2 p‐n heterojunction, which strengthens *CO intermediate binding for further C−C coupling to eventual ethanol generation. As a representative, Fe9.0%‐a/c‐SnSe/SnSe2 exhibits an ethanol Faradaic efficiency of 62.7 % and a partial current density of 239.0 mA cm−2 at −0.6 V in a flow cell. Moreover, it can output an ethanol Faradaic efficiency of 63.5 % and a partial current density of 201.2 mA cm−2 with a full‐cell energy efficiency of 24.1 % at 3.0 V in a membrane electrode assembly (MEA) electrolyzer. This work provides insight into non‐Cu based catalyst design for stabilizing the key intermediates for selective ethanol production from CO2 electroreduction.

Advances in Lithium Iron Phosphate Cathode Materials for Lithium-Ion Batteries

LiFePO4 has become very prospective cathode materials for lithium-ion batteries because of its stable charge/discharge performance, high specific capacity and high safety. At present, the main challenges facing lithium iron phosphate cathode materials is the poor conductivity and low energy density, which urgently need to be optimized. This paper summarizes the mainstream modification strategies for lithium iron phosphate cathode materials by exploring the relevant literature in recent years. In detail, the crystal structure and the reaction mechanism of LiFePO4 cathode materials during the charging and discharging process were investigated and reviewed. Based on the disadvantages of LiFePO4 cathode, the three targeted modification methods including carbon coating, metal ion doping and nanosizing are also analyzed. By strengthening the research on the above improvement strategies, the ideal LiFePO4 with excellent performance is expected.

Acceleration Photochromic Performance in Tungsten Oxide

Tungsten oxide (WO3) photochromic films require external force to accelerate the return to their original state after being photoinduced to color under ultraviolet light; otherwise, the fading process is exceedingly slow. The research explores the effects of various metal ion dopants on WO3 photochromic performance, with a focus on Fe doping. Fe-WO3 composite films demonstrate rapid coloration (3 minutes) and bleaching (30 minutes) processes, significantly improving upon undoped WO3. The mechanism of Fe ion catalysis in electron transfer is elucidated through HRTEM, SEM, EDS, and XPS analyses. The practical application of Fe-WO3 composite films in smart windows is evaluated using Energy-plus software, showing substantial energy savings across diverse climate zones. Our findings render great opportunities for innovative photochromic designs that can help achieve energy-saving performance in windows.

Non-metallic cation and anion co-doped perovskite oxide ceramic membranes for high-efficiency oxygen permeation at low temperatures

Insufficient structural stability and limited lattice oxygen mobility at low temperatures seriously limit the application of perovskite-type oxides in mixed ionic-electronic conducting oxygen-permeable membranes. Engineering the crystal structure and oxygen vacancies by ion doping is an effective strategy to enhance both structural stability and lattice oxygen mobility. Different from conventional metal ion doping, we report that the co-doping of the classical SrCoO3-δ by the non-metallic cation P5+ and the anion Cl- stabilizes the cubic perovskite structure and allows low temperature oxygen permeation due to improved lattice oxygen mobility. In detail, P doped at the Co site transforms the crystal structure from the hexagonal phase to the cubic phase, and Cl doped at the oxygen site weakens the metal-oxygen bond, which significantly enhances the lattice oxygen mobility. Optimal doping concentrations were found to be SrCo0.95P0.05O3-δCl0.05 (SCP5Cl5). Furthermore, by constructing an asymmetric membrane with a sandwich structure, the oxygen permeation flux of the SCP5Cl5 ceramic membrane was up to 1.10 mL min-1 cm-2 at 873 K, which provides an effective strategy for developing oxygen-permeable membranes with high permeation flux at low temperatures.

Synergistic effect of Fe/Zr dual doping endows hydrophilic spinel-structured H4Ti5O12 ion sieves for efficient lithium extraction from liquid resources

The practical application of spinel-structured H4Ti5O12(HTO) lithium-ion sieves (LISs) is hampered by their poor adsorption properties and recyclability. Within this research, the surface properties and internal structure of lithium-ion sieve (LIS) materials were modulated by co-doping Fe and Zr metal ions to enhance their adsorption properties. The results show that Fe and Zr have been successfully introduced to the LIS lattice, increasing Li-O bond length of position 8a and O2− content. The synthesized H4Ti4.77Fe0.2Zr0.03O12 (HTFZO-II) LIS was made up of evenly distributed nanosheets layered on top of one another to create an open laminar structure, which possesses a hydrophilic surface (contact angle: 17.8°), a high surface area (95.89 m2/g), and hierarchical porous structure. Compared with the undoped HTO, the HTFZO-II LISs enjoy a high capacity for Li+ adsorption (28.72 mg/g), a strong cycling stability (Ti4+ dissolving loss: 0.12 %), and a fast reaching of the equilibrium in adsorption (adsorption equilibrium: 4 h). Theoretical calculation of DFT shows that Li(H2O)4+ on HTFZO-II and HTO dehydration were partially dehydrated into Li(H2O)+. The energy required for the dehydration of Li(H2O)4+ on HTFZO-II is lower than that on undoped HTO, indicating that metal ion doping modification was beneficial for the dehydration of hydrated lithium ions on the adsorbent surface, thereby accelerating the exchange reaction between H+ and dehydrated Li+ ions. This study reveals the key role of the synergistic effect of multi-element co-doping in enhancing the adsorption performance and structural stability of LISs.

Boosting Photoluminescence of Rare-Earth-Based Double Perovskites by Isoelectronic Doping of ns2 Metal Ions.

Doping of ns2 metal ions as an energy transfer (ET) bridge can significantly elevate the photoluminescence properties. Nonetheless, the fundamental influence of ns2 metal ions on the local lattice structures remains unclear, hindering the advancement of functional materials. Herein, Sb3+ doped rare earth double perovskites is employed as a typical case to demonstrate this issue. It is found that the isoelectronic doping of Sb3+ ions not only enhances the ET efficiency but also changes their localized electronic and lattice structures. Both density functional theory (DFT) and Judd-Ofelt (J-O) theory calculations provide unambiguous evidence that the isoelectronic doping of Sb3+ ions enables a more localized charge density in the [LnCl6]3- (Ln: Lanthanide) octahedron and reduces the symmetry of the environment around the Ln3+, facilitating the radiative transition rates of Ln3+ while enhancing their ET efficiency. Compared with Cs2NaScCl6:Ln3+, the ET efficiency of Cs2NaScCl6:Sb3+/Ln3+ is enhanced by 1.5-fold, reaching up to 98.3%. To the best of available knowledge, this work is the first to unravel the intrinsic mechanism of enhanced ET process enabled by isoelectronic doping via DFT and J-O theory. This research sheds light on understanding the mechanism of photophysics and rational design of the functional perovskite materials.

Navigating Challenges and Promises for Next‐Generation CsPbIBr2 Perovskite Solar Cells: A Review

AbstractGiven the increasing demand for electricity due to modernization and population growth, there is an urgent need to develop renewable energy conversion technologies such as photovoltaics. Among these technologies, CsPbIBr2, an all‐inorganic lead halide‐based perovskite, has shown promise due to its thermal stability, phase stability, and ease of fabrication. However, challenges remain, particularly in addressing device hysteresis and stability. Novel materials and optimized device designs could help overcome these challenges. This comprehensive review discusses strategies such as interface engineering, film quality improvement, compositional engineering, defect passivation, band alignments, and metal ion doping to enhance the performance of CsPbIBr2‐based perovskite films and, in turn, their potential for photovoltaic applications.

Achieving efficient self-trapped excitons emission by suppressing defect level in Sb3+ doped metal halide

The field of metal halide engineering has made considerable progress, yet additional studies are needed to completely grasp the intriguing principles that govern their luminescence. In this work, we report a novel zero-dimensional (0D) organic-inorganic metal halide hybrid (OIMH) (C3H12N2)2InCl7 (C3H12N2 = 1,3-propane diamine cation) and reveal its interesting luminescent properties through experimental research and theoretical calculations. The photoluminescence (PL) of (C3H12N2)2InCl7 is a synergistic combination of intrinsic self-trapped exciton (STE) emission and defect-bound exciton (DBE) emission. Doping with Sb3+ induces several changes in (C3H12N2)2InCl7, including defect passivation, a reduction in the band gap, and structural shrinkage. These modifications result in a transition of PL centers to external STE emission, with the photoluminescence quantum yield (PLQY) increasing from 4.44 % to 68.70 %. Our work proposes, for the first time, the synergistic emission of STE and DBE and reveals the effect of metal ion doping, providing new insights into the mechanisms of materials exhibiting multifunctional exciton emission.

Metal-doped amorphous microporous carbon for isotope separation: Pore size modulation and selective deuterium adsorption

Efficient hydrogen isotope separation is crucial for applications in energy production and advanced scientific research, but separation of these poses significant challenges. In this study, we developed amorphous microporous carbon (AMC) derived from a zeolite template and explored hydrogen isotope separation using quantum sieving. Thermal desorption spectroscopy (TDS) technique was used to evaluate the selectivity of hydrogen (H2) and deuterium (D2) isotope separation. The doping of metal ions, such as Ca2⁺, Mg2⁺, Ni2⁺, and Cu2⁺, in the porous carbon modulates the physicochemical properties of the pores. The metal-doped carbon samples demonstrated D2vs H2 selectivity (SD2/H2) of over 10, compared to the pristine carbon's SD2/H2 of less than 8. Density functional theory (DFT) calculation infers that pore modulation through metal doping enhanced the binding affinity of materials towards D2 resulting in increased separation selectivity compared to pristine carbon samples. This approach not only boosts separation efficiency but also provides a scalable and cost-effective solution for industrial applications.

Composition and Structure of the solid electrolyte interphase on Na-Ion Anodes Revealed by Exo- and Endogenous Dynamic Nuclear Polarization─NMR Spectroscopy.

Sodium ion batteries (SIB) are among the most promising devices for large scale energy storage. Their stable and long-term performance depends on the formation of the solid electrolyte interphase (SEI), a nanosized, heterogeneous and disordered layer, formed due to degradation of the electrolyte at the anode surface. The chemical and structural properties of the SEI control the charge transfer process at the electrode-electrolyte interface, thus, there is great interest in determining these properties for understanding, and ultimately controlling, SEI functionality. However, the study of the SEI is notoriously challenging due to its heterogeneous nature and minute quantity. In this work, we present a powerful approach for probing the SEI based on solid state NMR spectroscopy with increased sensitivity from dynamic nuclear polarization (DNP). Utilizing exogenous (organic radicals) and endogenous (paramagnetic metal ion dopants) DNP sources, we obtain not only a detailed compositional map of the SEI but also, for the first time for the native SEI, determine the spatial distribution of its constituent phases. Using this approach, we perform a thorough investigation of the SEI formed on Li4Ti5O12 used as a SIB anode. We identify a compositional gradient, from organic phases at the electrolyte interface to inorganic phases toward the anode surface. We find that the use of fluoroethylene carbonate as an electrolyte additive leads to performance degradation which can be attributed to formation of a thicker SEI, rich in NaF and carbonates. We expect that this methodology can be extended to examine other titanate anodes and new electrolyte compositions, offering a unique tool for SEI investigations to enable the development of effective and long-lasting SIBs.

Surface-doped perovskite electrolyte for low-temperature ceramic electrochemical cells

Protonic ceramic electrochemical cells (PCECs) can be employed for power generation and sustainable hydrogen production. Lowering the PCEC operating temperature to >500 °C can facilitate its scale-up and commercialization. However, achieving high energy efficiency and long-term durability at low operating temperatures is a long-standing challenge. Here, we report a simple and scalable approach for fabricating metal ion doping into perovskite (Li-doped SrTiO3 (STO)) using the sol-gel approach and presented as a proton conducting electrolyte with lower ohmic and polarization resistance for low-temperature ceramic fuel cells. The prepared electrolyte with symmetrical electrodes attains high power densities in fuel-cell mode (∼0.65 W cm−2 at 520 °C and ∼0.20 W cm−2 at 420 °C) and exceptional current densities in steam electrolysis mode (−0.94 A cm−2 at 1.4 V and 520 °C). Additionally, five-layer devices (Ni-NCAL/BCZYYb/Li-STO/BCZYYb/NCAL-Ni) demonstrate the proton fuel cell performance of 0.55 W cm−2 at 520 °C.

A closer look at the fabrication of some doped metal ions in borophosphate glass system and their structural, elastic, optical, and gamma-ray shielding characteristics

Borophosphate host glasses doped with zinc oxide (ZnO), titanium dioxide (TiO2), tellurium dioxide (TeO2), or cerium oxide (CeO2) were synthesized using rapid quenching techniques. Fourier transform infrared (FTIR) spectra, along with deconvoluted FTIR spectra, were recorded in the 400–4000 cm−1 range. Using the models of Tauc and Urbach, the optical energy band gaps of these glasses were found to be 3.212, 3.289, 3.262, 3.087, and 2.475 eV respectively. Due to the incorporation of different metal ions into the prepared glasses, the density increased and the molar volume decreased, making the glass structure highly compact. Since the elastic moduli are directly related to the average cross-link density, the shear and longitudinal moduli show a forward proportionality with the average cross-link density. Detailed reporting focused on the mass attenuation coefficients (μm) and exposure build-up factors (EBF), crucial for evaluating the shielding properties of the material within the energy range of 0.015–15 MeV and penetration depth up to 40 mean free paths (mfp). Glass samples doped with tellurium dioxide exhibited the highest gamma attenuation due to their higher effective atomic number compared to the other samples. Compared to Portland concrete, the prepared glass composites showed higher mass attenuation coefficients across the entire investigated energy range. These results suggest that although Borophosphate glasses doped with cerium oxide have preferred mechanical properties compared with the other prepared glasses, Borophosphate glasses doped with tellurium dioxide could serve as transparent shielding material for medical applications due to their higher attenuation coefficient.

Influence of metal ion doping for the electrochemical performance of NiCo layered double hydroxide nanostructures

Layered double hydroxide (LDH) is considered to be a potential energy storage material due to its high theoretical specific capacitance and microstructure. However, poor conductivity restricts their application and development in energy storage devices. Considering metal cations doping as an effective way to improve conductivity of semiconductors, metal cations doping can also be used to improve the conductivity of LDH. In the study, metal ions with different valence states are selected and doped into the NiCo LDH nanostructures. Indeed, metal cations doping can improve the conductivity of NiCo LDH, which can be confirmed by the results of EIS analysis. But the corresponding changes in electrode capacity are different. Compared with the Ag+ and Zn2+, Al3+ ion doped in NiCo LDH can achieve significant improvement of capacity. The capacity can reach 2130 F/g at a current density of 2 A/g when the doping concentration of Al3+ is 0.02, which has 48 % improvement compared to the original NiCo LDH (1435 F/g). The improvement of conductivity dose not determine the increase of capacity, the type and valence states of elements are also key factors affecting material capacity. Therefore, this study provides an idea for the subsequent doping of metal cations in LDH materials.

Metal ions guide the production of silkworm silk fibers

Silk fibers’ unique mechanical properties have made them desirable materials, yet their formation mechanism remains poorly understood. While ions are known to support silk fiber production, their exact role has thus far eluded discovery. Here, we use cryo-electron microscopy coupled with elemental analysis to elucidate the changes in the composition and spatial localization of metal ions during silk evolution inside the silk gland. During the initial protein secretion and storage stages, ions are homogeneously dispersed in the silk gland. Once the fibers are spun, the ions delocalize from the fibroin core to the sericin-coating layer, a process accompanied by protein chain alignment and increased feedstock viscosity. This change makes the protein more shear-sensitive and initiates the liquid-to-solid transition. Selective metal ion doping modifies silk fibers’ mechanical performance. These findings enhance our understanding of the silk fiber formation mechanism, laying the foundations for developing new concepts in biomaterial design.

Photon–carrier–spin coupling in a one-dimensional Ni(II)-doped ZnTe nanostructure

Transition metal (TM) ion doping in II–VI semiconductors can produce exciton magnetic polarons (EMPs) and localized EMPs containing longitudinal optical (LO) phonon coupling, which will be discussed in this paper. TM ion doping in II–VI semiconductors for a dilute magnetic semiconductor show emission via magnetic polarons (MPs) together with hot carrier effects that need to be understood via its optical properties. The high excitation power that is responsible for hot carrier effects suppresses the charge trapping effect in low exciton binding energy (8.12 meV) semiconductors, even at room temperature (RT). The large polaron radius exhibits strong interaction between the carrier and MP, resulting in anharmonicity effects, in which the side-band energy overtone to LO phonons. The photon-like polaritons exhibit polarized spin interactions with LO phonons that show strong spin–phonon polaritons at RT. The temperature-dependent photoluminescence spectra of Ni-doped ZnTe show free excitons (FX) and FXs interacting with 2LO phonon–spin interactions, corresponding to 3T1(3F) → 1T1(1G) and EMP peaks with ferromagnetically coupled Ni ions at 3T1(3F) → 1E(1G). In addition, other d–d transitions of single Ni ions (600–900 nm) appear at the low-energy side. RT energy shifts of 14–38 meV are observed due to localized states with density-of-states tails extending far into the bandgap-related spin-induced localization at the valence band. These results show spin–spin magnetic coupling and spin–phonon interactions at RT that open up a more realistic new horizon of optically controlled dilute magnetic semiconductor applications.

V-Doping Strategy Induces the Construction of the CoFe-LDHs/NF Electrodes with Higher Conductivity to Achieve Higher Energy Density for Advanced Energy Storage Devices.

Doping of metal ions shows promising potential in optimizing and modulating the electrical conductivity of layered double hydroxides (LDHs). However, there is still much room for improvement in common metal ions and conventional doping methods. In contrast to previous methodologies, a hollow triangular nanoflower structure of CoFeV-LDHs is devised, which is enriched with a greater number of oxygen vacancies. This resulted in a significant enhancement in the conductivity of the LDHs, leading to an increase in energy density following the appropriate doping of V. To investigate the impact of V-doping on the energy density of the LDHs, in situ XPS and in situ X-ray spectroscopy is employed. Regarding electrochemical performance, the CoFeV-LDHs/NF electrode with optimal doping ratio exhibited a specific capacitance of 881Fg-1 at a current density of 1Ag-1. The capacitance remained at 90.53% after 3000 cycles. In addition, the constructed battery-type supercapacitor CoFeV-LDHs/NF-2//AC exhibited an impressive energy density of 124.7Whkg-1 at a power density of 850Wkg-1 and capacitance remained almost unchanged at 95.2% after 3000 cycles. All the above demonstrates the great potential of V-doped LDHs and brings a new way for the subsequent research of LDHs.

Cs-Doped WO3 with Enhanced Conduction Band for Efficient Photocatalytic Oxygen Evolution Reaction Driven by Long-Wavelength Visible Light.

Cesium doped WO3 (Cs-WO3) photocatalyst with high and stable oxidation activity was successfully synthesized by a one-step hydrothermal method using Cs2CO3 as the doped metal ion source and tungstic acid (H2WO4) as the tungsten source. A series of analytical characterization tools and oxygen precipitation activity tests were used to compare the effects of different additions of Cs2CO3 on the crystal structure and microscopic morphologies. The UV-visible diffuse reflectance spectra (DRS) of Cs-doped material exhibited a significant red shift in the absorption edge with new shoulders appearing at 440-520 nm. The formation of an oxygen vacancy was confirmed in Cs-WO3 by the EPR signal, which can effectively regulate the electronic structure of the catalyst surface and contribute to improving the activity of the oxygen evolution reaction (OER). The photocatalytic OER results showed that the Cs-WO3-0.1 exhibited the optimal oxygen precipitation activity, reaching 58.28 µmol at 6 h, which was greater than six times higher than that of WO3-0 (9.76 μmol). It can be attributed to the synergistic effect of the increase in the conduction band position of Cs-WO3-0.1 (0.11 V) and oxygen vacancies compared to WO3-0, which accelerate the electron conduction rate and slow down the rapid compounding of photogenerated electrons-holes, improving the water-catalytic oxygen precipitation activity of WO3.

Efficient electrocatalytic reduction of nitrate to ammonia using Cu–CeO2 solid solution

Electrocatalytic nitrate reduction reaction (EC-NITRR) is expected to replace Haber-Bosch process for green ammonia (NH3) production. Currently, many catalysts often result in low NH3 yields and low faraday efficiencies due to the lack of active sites. In this study, Cu-doped CeO2 solid solution catalyst was prepared for EC-NITRR using transition metal ions doping. The addition of Cu significantly improved the oxygen vacancy (Ov) concentration of CeO2 and provided more active sites for NO3− catalysis. Meanwhile, the internal charge transfer capability and surface catalytic kinetics of the catalyst are enhanced by the excellent redox capability of Ce3+ and Cu+. Compared with bare CeO2, the NH3 yield of 7% Cu–CeO2 increased by 1.88 times. This work provides new ideas for the design of green and efficient catalysts for EC-NITRR by identifying the role of Cu in the mechanism of doping regulation of CeO2.

Engineering the electrochemical performance of CoWO4 composites of MXene by transitional metal ion doping for high energy density supercapacitors

Engineering the electrochemical performance of CoWO4 composites of MXene by transitional metal ion doping for high energy density supercapacitors