Co-doping Strategy Research Articles

Sensitive sensing of Hg(II) based on lattice B and surface F co-doped CeO2: Synergies of catalysis and adsorption brought by doping site engineering

Transition metal oxides are widely used in the detection of heavy metal ions (HMIs), and the co-doping strategy that introducing a variety of different dopant atoms to modify them can obtain a better detection performance. However, there is very little research on the co-doped transition metal oxides by non-metallic elements for electrochemical detection. Herein, boron (B) and fluorine (F) co-doped CeO2 nanomaterial (BFC) is constructed to serve as the electrochemically sensitive interface for the detection of Hg(II). B and F affect the sensitivity of CeO2 to HMIs when they were introduced at different doping sites. Through a variety of characterization, it is proved that B is successfully doped into the lattice and F is doped on the surface of the material. Through the improvement of the catalytic properties and adsorption capacity of CeO2 by different doping sites, this B and F co-doped CeO2 exhibits excellent square wave anodic stripping voltammetry (SWASV) current responses to Hg(II). Both the high sensitivity of 906.99 μA μM−1 cm−2 and the low limit of detection (LOD) of 0.006 μM are satisfactory. Besides, this BFC glassy carbon electrode (GCE) also has good anti-interference property, which has been successfully used in the detection of Hg(II) in actual water. This discovery provides a useful strategy for designing a variety of non-metallic co-doped transition metal oxides to construct trace heavy metal ion-sensitive interfaces.

Successive performance enhancement on a Ge-Ti codoped α-Fe2O3 with AlOOH modification photoanode for photoelectrochemical water splitting

The poor charge separation efficiency is the main limiting factor of the α-Fe2O3 photoanode for photoelectrochemical water splitting. In this study, we have discovered that the incorporation of Ge-Ti codoping and AlOOH modification strategies can greatly enhance the charge separation efficiency of the α-Fe2O3 photoanode. By introducing the Ti element, which possesses high conductivity, and further enhancing the charge transfer through Ge doping, we have achieved a synergistic inhibition of charge recombination in the Ge-Ti codoped α-Fe2O3. Additionally, the introduction of AlOOH through modification has led to an increase in the interface band bending, thereby enhancing charge separation by elevating the Fermi band level. Furthermore, through the secondary growth (shorted as SG) of undoped α-Fe2O3 and the incorporation of a NiFeOx cocatalyst, we have successfully adjusted the surface states and reduced the onset potential. Through the collaborative efforts of Ge-Ti codoping, SG, AlOOH modification, and NiFeOx catalysis, we have sequentially optimized the performance of the α-Fe2O3-based photoanode, resulting in an impressive photocurrent density of 3.46 mA cm−2 at 1.23 VRHE, as well as a low onset potential of 0.65 VRHE.

Preparation and properties of ternary rare earth co-stabilized zirconia ceramics for dental restorations

High fracture toughness and excellent hydrothermal aging resistance are the characteristics required for dental ceramic materials, but the widely used dental ceramic currently (3Y-TZP) does not exhibit. Aiming to solve this problem, a ternary rare earth co-stable zirconia ceramic (1.5Y5.5Ce0.3La-ZrO2) was prepared by a coating method based on a co-doping strategy. The sintering process, densification evolution, mechanical properties, resistance to hydrothermal aging and biocompatibility of 1.5Y5.5Ce0.3La-ZrO2 ceramic were studied. The results show that 1200 °C is the best pre-sintering temperature, and the machinability and controllability of shrinkage can meet the needs. When the final sintering temperature is 1600 °C, it has the best performance. Compared with 3Y-TZP, the bending strength is about 8.7% higher (912.48 MPa), and the fracture toughness is about 76.6% higher (10.49 MPa m1/2). Furthermore, its resistance to hydrothermal aging is significantly enhanced, greatly extending the service life of the material. The biosafety of 1.5Y5.5Ce0.3La-ZrO2 ceramics was evaluated, and the results showed that the material had no cytotoxicity. To sum up, 1.5Y5.5Ce0.3La-ZrO2 ceramics is a promising dental biomaterial, which has a broad application prospect in oral restoration.

Interface engineering combined with nitrogen and phosphorus co-doped synergistic optimization strategies for designing hollow/porous N, P-CoWO4@Co3O4 heterojunction nanocubes for superior-performance supercapacitor and oxygen evolution reaction

Co3O4 possesses high activity and desirable capacitance, which is widely applied in the field of oxygen evolution reaction (OER) and supercapacitor (SCs). Nevertheless, the serious challenges of limited active sites and poor electrical conductivity still hinder its commercial application. Herein, the hollow/porous N, P co-doped nanocubes with heterogeneous structure (denoted as N, P-CoWO4@Co3O4 HNCs) are prepared by in situ ion-exchange and co-doping strategies. The heterogeneous structure could change electron density and facilitate electron transfer. Meanwhile, N, P co-doping could enhance the metallicity significantly. Furthermore, the hollow/porous structure could furnish more electrochemical active sites and accelerate the adsorption and desorption between active sites and charged particles. Based on these advantages, N, P-CoWO4@Co3O4 HNCs demonstrates an overpotential of 553.0 mV at 50 mA cm−2 for OER. On the other hand, N, P-CoWO4@Co3O4 HNCs exhibits outstanding specific capacitance (558.0 F g−1 at 0.5 A g−1) and cycling stability. Moreover, N, P-CoWO4@Co3O4 HNCs//AC delivers an ideal energy density (11.4 Wh kg−1 at 473.9 W kg−1), which surpasses most of the Co3O4-based materials. In general, this work furnishes a facile and pioneering strategy for designing the dual-functional electrode materials in the fields of supercapacitor and oxygen evolution reaction.

Effective calcium co-doping in Sm0.8Ca0.2Ba1-xCaxCo2O5+δ cathode materials for intermediate-temperature solid oxide fuel cells

High performance and durability of electrode materials are key requirements for intermediate-temperature solid oxide fuel cells (IT-SOFCs). Herein, a novel doubles perovskite oxides Sm0.8Ca0.2Ba1-xCaxCo2O5+δ (x=0.1 and 0.2; SCBCC) were prepared by A site calcium co-doping strategy. x=0.1 sample shows stabilized an orthorhombic structure with the space group Pmmm. Compared with parent SmBaCo2O5+δ, substitution of Ca for Sm and Ba effectively reduces the thermal expansion coefficient (TEC) (20.2 × 10−6 K−1 to 13.2 × 10−6 K−1). x=0.1 sample exhibits excellent chemical compatibility with CeO2-based electrolytes up to 1000 °C, the conductivity values reach 340–400 S cm−1 at 600–800 °C. The sample with x = 0.1 showed the best catalytic activity and carbon dioxide resistance. The area specific resistance and maximum power density of the x= 0.1 cathode are 0.022 Ω cm2 and 885 mW cm−2 at 800 °C. x = 0.1 double perovskite has good chemical compatibility and electrochemical properties while greatly reducing TEC, making this double perovskite a promising material for IT-SOFCs.

2D-COFs-derived heteroatom-doped carbon nanosheets as high-efficiency all-solid frustrated lewis pair metal-free hydrogenation catalyst

Metal-free catalysts without metal active sites participating in the reactions have obtained growing attraction under the drive of the economic and environmental problems. Here, 2D-COFs-drived B/N co-doped carbon nanosheets as metal-free catalyst was synthesized by Schiff-based coupling reaction and self-templated carbonization. It shows excellent catalytic performance in nitro compound hydrogenation reaction as all-solid FLP catalyst in H2 system (100 % conversion of nitrobenzene and 99.89 % selectivity to aniline) without any metal active species in the catalyst. This result is the most promising compared to the previous literatures. In the study, the high crystallinity of precursor 2D-COFs is imperative for catalytic stability, and the function of B atoms modification and the B-N synergism were investigated carefully. The formation of B-N bond as a fixed all-solid FLP active center was verified, and it also indicates that B atoms introduction can make the carbon nanosheets orderly and enhance the strength and amount of the acid and base sites. The catalytic mechanism of hydrogen activation was also studied by combining the characterization results and density functional theory (DFT) calculations. The results show that the B atoms doping and defects formation efficiently accelerate the charges aggregation between B-N bonds to form Lewis pairs, and the TS searching calculations shows the significant decrease of H2 dissociation barrier energy and the reaction energy, demonstrating the effectiveness of N and B co-doping strategy. This work is very promising and the metal-free catalyst is the potential alternative to traditional metal catalysts.

Tungsten and fluorine co-doping induced morphology change and textured growth of spray-pyrolyzed SnO2 thin films viable for photocatalytic application

Physicochemical aspects of numerous metal oxide based thin films are crucial for various optoelectronic applications. Cationic (W) and anionic (F) co-doping strategy into SnO2 thin film has been adapted in order to tune the optoelectronic parameters. X-ray diffraction pattern reveals successful doping of ‘W’ and ‘F’ into the SnO2 lattice and textured growth along (111) plane direction at the expense of suppression of the (211) plane. X-ray photoelectron spectroscopy confirmed the charge states of Sn4+, W6+, O2− and F1− elements present in the films. Scanning electron microscopy shows that tetragonal morphology of pure and F-doped SnO2 changes to a network-like feature upon ‘W’ co-doping and the elemental composition is also ensured. The contact angle measurement gives the surface wettability nature, which indicates all the films are hydrophilic. The 10 wt.% F-doped SnO2 shows a maximum transmittance of 89.36 % at 550 nm with a direct band gap of 3.82 eV. Electrical transport parameters are measured using linear four-probe and Hall effect techniques. Photocatalytic activity of methylene blue dye degradation showing a maximum efficiency for pure and solely F-doped SnO2 thin films are explained based on the obtained optoelectronic parameters.

Regulating the tip effect on urchin-like N-NiCoP/NF as high-performance electrocatalyst for hydrogen evolution reaction

Transition metal phosphides (TMPs) have emerged as highly promising electrocatalysts for the hydrogen evolution reaction (HER) due to their earth-abundance reserves, rich electrochemical active sites and high stability. Herein, to cope with the inert atoms on the basal plane and sluggish electrochemical kinetics, we propose a novel strategy involving the in-situ conversion of urchin-like NiCo-LDH into a nitrogen-doped NiCoP electrocatalyst on nickel foam (N-NiCoP/NF) via a hydrothermal-phosphorylation approach. In this structure, NiCoP nanoneedles are assembled into a tip-rich urchin-like structure on NF substrates, delivering abundant mismatched active sites for capturing catalytic intermediates, accelerating charge transport and constructing an optimized heterogeneous interface. Additionally, heterogeneous N-atom doping can further regulate the charge distribution of NiCoP needles, and significantly contribute to enhancing the electrocatalytic performance for HER. Benefitting from the synergistic effect of the abundant active sites provided by tip-rich NiCoP nano-urchin, electronic modulation by heterogeneous N-species and optimized interfacial coupling, the N-NiCoP/NF electrocatalyst displays low overpotentials of 75 mV and obtains 10 mA cm−2 in alkaline electrolyte without significant decrease even after 5000 cycles, indicating high catalytic activity and stability. This study provides a low-cost and controlled approach for developing novel heteroatom-doped TMPs for HER applications.The various properties of the materials surprisingly demonstrate that our diatomic codoping strategy prepared by facile hydrothermal phosphatization with annealing can effectively enhance the HER properties of the materials. The unique morphology possessed by the material provides advantages such as active sites and accelerated charge transport that can further enhance the catalytic performance of the material, which is further formalized by our DFT calculations. Our theoretical and experimental studies provide a good case for the development of simple and low-cost electrocatalytic materials.

The performance tuning of NaCaTiTaO6:Dy3+, Eu3+ phosphor by employing the co-doping strategy for white LED application

A series of Dy3+ doped and Dy3+, Eu3+ co-doped NaCaTiTaO6 (NCTT) phosphors with the orthorhombic perovskite-type structures were prepared by a solid-state reaction method. The successful synthesis of the target samples was confirmed through various characterization techniques, such as XRD and Rietveld refinement, SEM, EDX spectroscopy, as well as elemental mapping. The optimal Dy3+ doping concentration of NCTT:xDy3+ under n-UV excitation was 0.10 mol. The phenomenon of efficient energy transfer between Dy3+ and Eu3+ ions was observed in the NCTT:0.1Dy3+/yEu3+ samples, as evidenced by the shortened lifetimes. Meanwhile, in the NCTT:0.1Dy3+/0.15Eu3+ sample, the PL intensity of Eu3+ ion at 420 K still maintained at 72.41% of that at 300 K, while that of Dy3+ ion is 82.35%, displaying its brilliant thermal stability. The performance of the fabricated white LED device using NCTT:0.1Dy3+/0.15Eu3+ as red phosphor was found to be outstanding, with Ra of 88, CCT of 5868 K, as well as excellent CIE chromaticity coordinates (0.325, 0.333), suggesting that NCTT:0.1Dy3+/0.15Eu3+ can be used as reddish-orange phosphors for w-LEDs in lightings and displays.

Zr/Ti trace Co-doping induced disordered structure to enhance the cycling stability of Li-rich Mn-based layered oxide cathodes

Due to the ultrahigh energy density, Li-rich Mn-based layered oxide cathodes have attracted great attentions. However, the irreversible structural transformation usually leads to long-cycled capacity decay, which severely restricts their practical applications. Here, a Zr/Ti trace co-doping strategy is proposed to stabilize the structure and obtain excellent electrochemical performance by constructing bulk phase disorder and surface Zr-enriched structures. The designed Li1.2Mn0.53Ni0.13Co0.13Zr0.005Ti0.005O2 (ZT-LRM) not only shows a higher specific capacity but also achieves an excellent long-cycle performance. The capacity retention of ZT-LRM is 69 % after 500 cycles at 5C (1250 mA g−1), which is much higher than that (34 %) of the Li1.2Mn0.54Ni0.13Co0.13O2 cathode. Neutron powder diffraction and transmission electron microscopy are used to demonstrate the disordered structure in the particles and the line scanning proves the surface Zr enrichment. In-situ X-ray diffraction verifies the more stable structural evolutions of the ZT-LRM during cycling. This simple modification method provides a reference for commercial applications of Li-rich Mn-based layered oxide cathodes.

KNN-Based Lead-Free Piezoelectric Ceramics with High Qm and Enhanced d33 via a Donor-Acceptor Codoping Strategy.

The wide application of KNN-based lead-free piezoelectric ceramics is constrained by the contradictory relationship between its mechanical quality factor and piezoelectric constant. From an application point of view, searching for chemical composition with enhanced piezoelectric constant (d33) and mechanical quality factor (Qm) is one of the key points of KNN-based ceramics. In this work, KNN-based ceramics with enhanced d33 and high Qm values were obtained by the solid solution method via a donor-acceptor codoping strategy. The donor dopant Ho3+ enhanced d33 values by refining the domain size, while the acceptor dopant (Cu1/3Nb2/3)4+ improved Qm by the formation of defect dipoles. The composition (KNN-5Ho-4CN) exhibits optimal integrated performances, of which d33, Qm, and TC values are 120 pC/N, 850, and 392 °C, respectively. Moreover, the temperature coefficient of resonant frequency (TCF = -429 ppm/K) indicates that KNN-5Ho-4CN ceramic has good temperature stability. This work provides a new insight for developing KNN-based ceramics with enhanced d33 and high Qm.

Exploration of Bifunctionality in Mn, Co Codoped CuO Nanoflakes for Overall Water Splitting

Herein, bimetal (Mn, Co) codoping on a CuO host is aimed at enhancing oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) activity. Codoping of Mn and Co on CuO to enhance bifunctional action in electrochemical water splitting has not yet been investigated to the best of our knowledge. Literatures are focused on unary Mn-doped CuO or Co-doped CuO nanostructures. Mn, Co codoped CuO through an easy chemical coprecipitation method has been successfully attempted and is more beneficial which is the novelty of the present work. Defect-enriched ample active sites (Mn2+/Mn3+ and Co2+/Co3+) along with Cu2+ in the host CuO achieved high current density (100 mA/cm2) in OER and HER with low overpotential such as 468 mV and 271 mV, respectively. Faster charge transfer and diffusion ability was stimulated by the bimetal codoping CuO. Reasonable Tafel plot values (OER: 199 mV/dec, and HER: 21 mV/dec) with improved water-splitting reaction kinetics were achieved for the Mn, Co codoped CuO nanoflakes. The double-layer capacitance ( C dl ) value of 27.5 mF/cm2 for Mn, Co codoped CuO nanoflakes was achieved. Similarly, the increasing order of an electrochemically active surface area (EASA) was exhibited by the consequent addition of bimetal doping on CuO, denoted as Mn , Co / CuO > Co / CuO > Mn / CuO > CuO . The evidence shows that the codoping strategy could facilitate rapid reaction kinetics to develop overall water splitting. The charge transfer resistances ( R ct ) of 3.6 Ω and 1.2 Ω for the Mn, Co codoped CuO nanostructure corresponding to the OER and HER, respectively, were reported. The long-term stability over 16 h with negligible loss was reported for both the OER and the HER performance. Thus, this work contributes to better insight and analysis of the successful codoping of bimetal elements in earth-abundant electrocatalysts to enhance and make practical the electrocatalytic water-splitting activity.

Nitrogen-sodium co-doping improves cycle performance of lithium titanate anode materials at high rate

Li4Ti5O12 is a lithium-ion battery cathode material with great potential for development because of its “zero-strain” characteristics, but its low lithium ion diffusion and conductivity rate lead to poor rate and cycling performance. NaN-LTO, a nanorod-like material with oxygen vacancies on the surface, was prepared by calcination after hydrothermal reaction using sodium molybdate as the sodium source and L-cysteine as the nitrogen source and structural guiding agen, while achieving co-doping of N and Na at the O and Li positions in situ respectively. The effects of N and Na co-doping on the crystal and electronic structures were revealed. The electrochemical test results show that rate and cycle performance of NaN-LTO are greatly improved, which can reach 126.0 mAh/g at 20C (1C = 175 mAh/g), 126.9 mAh/g after 1000 cycles with a capacity retention rate of 100.7% and the capacity retention rate is 74.0% after 3000 cycles. The co-doping strategy of Li-site and O-site provides a new modification idea to enhance the electrochemical performance of lithium titanate. Meanwhile, the preparation cost of lithium titanate can be reduced by the partial replacement of Li by inexpensive Na.

Influence of Mn2+ and Eu3+ Concentration on Photoluminescence and Thermal Stability Properties in Eu3+-Activated ZnMoO4 Red Phosphor Materials.

The integration of trivalent europium ion (Eu3+)-doped zinc molybdate (ZnMoO4) as red phosphors in next-generation solid-state lighting (SSL) is impeded by their extended electron lifetime and suboptimal thermal stability. To overcome these limitations, we propose a co-doping approach by incorporating Mn2+ and Eu3+ in ZnMoO4, aiming to improve thermal reversibility and reduce the lifetime of electron transitions. A series of Eu3+-doped ZnMoO4 and Mn2+/Eu3+-co-doped ZnMoO4 phosphor materials were synthesized via the conventional sol-gel method, and their photoluminescence properties were compared under high-temperature conditions. Experimental results indicate that the introduction of Mn2+ into Eu3+-doped ZnMoO4 leads to a decrease in quantum efficiency and electron lifetime, primarily attributed to defects within the crystal lattice and energy transfer from Eu3+ to Mn2+, resulting in enhanced non-radiative transitions. However, the addition of a small quantity of Mn2+ remarkably improves the thermal stability and reversibility of the phosphors. Consequently, this co-doping strategy presents a promising avenue for expanding the application possibilities of phosphor materials, particularly for high-power SSL applications subjected to elevated temperatures. Hence, Eu3+-only doped samples are well-suited for lighting applications due to their high IQE and excellent thermal stability. Conversely, Eu3+/Mn2+-co-doped samples show promise in applications that require a shorter electron lifetime and good reversibility.

Binary elements (Si, Mo) co-doping strategy enhanced the tribological performance of diamond-like carbon films

To overcome the constraints posed by high internal stress and weak bonding forces, and achieve DLC films exhibiting exceptional tribological characteristics. Si and Mo co-doped DLC (Si-MoDLC) films were fabricated via the double-target co-sputtering technology. The results revealed that Si was mainly present in SiC and SiO forms, while Mo existed mostly in MoC and Mo forms. With an increase in Si content from 0 to 14.4 ± 0.2 at.%, the ratio of sp3/sp2 (peak area ratio) increase from 1.2 to 2.1. The hardness decreased first and then increased, while the adhesion increased first and then decreased. The Si-MoDLC film with 3.4 ± 0.2 at.% Si and 7.7 ± 0.2 at.% Mo exhibited the lowest hardness (13.4 GPa) and the highest adhesion (340 mN). The tribological properties of thin films were significantly affected by Si content and the testing environment. In the air, the Si-MoDLC film containing 14.4 ± 0.2 at.% Si displayed the lowest friction coefficient (0.07) and a low wear rate (1.1 × 10−7 mm3/N·m), while in a methanol environment, it showed the highest friction coefficient (0.21) and wear rate (14.6 × 10−7 mm3/N·m). These findings provide valuable insights into the microstructure and properties of Si-MoDLC films and offer guidance for the application of DLC films in alcoholic environments.

Suppressing halide phase segregation in wide-bandgap perovskite film by co-doping strategy for high-performance and stable perovskite solar cells

Wide-bandgap perovskites formed by tuning the iodine/bromine ratio can be combined with narrow-bandgap silicon materials to construct tandem solar cells, thus overcoming the Shockley-Queissel limit. However, light-induced halide ion migration causes poor perovskite film quality and detrimental halide phase segregation in it. Herein, a facile co-doping strategy for wide-bandgap (FA0.65MA0.2Cs0.15)Pb(I0·8Br0.2)3 film is demonstrated, that is, Pb(SCN)2 and PEACl are synergistically incorporated into perovskite film to break through this hurdle. The proposed strategy not only enables high-quality perovskite films with larger grains, fewer grain boundaries, and high crystallinity, but also the two-dimensional (2D) perovskite formed at grain boundaries effectively suppresses halide phase separation and improves the hydrophobicity of the films. As a result, we achieved a power conversion efficiency (PCE) of 19.92% for the small-area (0.07 cm2) perovskite solar cells (PSCs) and 17.70% for modules with an active area of 10.00 cm2. And, the operational and long-term storage stability of the modules are improved, maintaining 76% of their initial efficiency after 150 h of exposure to an environment with a relative humidity of ∼40% and a temperature of ∼20 °C. Furthermore, a semitransparent device with a PCE of 19.51% and a four-terminal (4T) perovskite/silicon tandem solar cell with a PCE of 30.53%, were successfully obtained.

Boosting high-rate capacity and long-cycle stability of spinel LiMn2O4 by the Cr[sbnd]Al co-doping strategy

Jahn-Teller distortion and Mn dissolution are easily generated at a high current density, whilst hindering the elevation of high-rate capacity and long-cycle performance of spinel LiMn2O4. Herein, a CrAl co-doping strategy is proposed for preparing a series of LiCr0.04AlxMn1.96-xO4 (0 ≤ x ≤ 0.08) cathode materials using facile solid-state combustion. Crystalline structure and particle morphology are regulated by changing the Al-doping contents. After optimizing the Al-doping, the LiCr0.04Al0.01Mn1.95O4 cathode shows a unique truncated octahedron with the preferred growth of {111} crystal surfaces, which is conducive to reducing the Mn dissolution. Meanwhile, the LiCr0.04Al0.01Mn1.95O4 also exhibits a relatively high Mn average valence (+3.53) and lattice shrinkage, which can stabilize the spinel structure of the LiMn2O4 by inhibiting the Jahn-Teller to improve the electrochemical performance. Therefore, the optimized LiCr0.04Al0.01Mn1.95O4 cathode delivers the high-rate discharge capacity of 103.0 mAh/g and maintains the capacity retention of 67.0 % after 2000 cycles at 10C. Even at an ultra-high current rate of 30C, a long cycle life with a capacity retention of 78.0 % is also obtained after 1000 cycles.

Broadband near-infrared double-perovskite phosphor Sr2ScTaO6:Cr3+, Yb3+ for NIR pc-LED applications

The broadband near-infrared (NIR) phosphor converted light emitting diode (NIR pc-LED) has garnered unprecedented attention due to its crucial role in NIR applications. However, there remains a scarcity of efficient broadband NIR luminescence materials capable of emitting NIR light with wavelengths greater than 800 nm. This study reports the synthesis, crystal structure and photoluminescence (PL) properties for double perovskite Sr2ScTaO6:Cr3+ phosphors which exhibit a broadband NIR emission in the 650–1250 nm range, peaking at∼815 nm with the full width at half maximum (FWHM) of 161 nm. The observed broadband emission arises from two distinct Cr3+ centers, namely Sc3+ and Ta5+ octahedral sites within the Sr2ScTaO6 structure, as demonstrated by luminescence and decay kinetic analysis. A significant enhancement of the thermal stability and a remarkable broadening of the FWHM (from 161 to 275 nm) are achieved by employing Yb3+ co-doping strategy. The efficient energy transfer from Cr3+ to Yb3+ was confirmed through emission and excitation spectra, as well as luminescence decay measurements. Finally, Sr2ScTaO6:Cr3+-Yb3+ phosphor was integrated with a 470 nm blue LED chip to fabricate a NIR pc-LED device, and its potential application in night vision was evaluated.

A co-doping strategy to achieve high energy storage performance in BiFeO3-based ceramics

In this work, (Bi0.65-0.65xBa0.35-0.35xNdx)(Fe0.65-0.65xTi0.35-0.35xNbx)O3+x (abbreviated as: BFBT-xNN, x = 0, 0.04, 0.08 and 0.12) ceramics were fabricated through a solid-state reaction method, aiming to obtain high-performance capacitor materials. BFBT ceramics have attracted increasing attention as potential energy storage materials because of their excellent dielectric and ferroelectric properties. However, two handicaps limit the large improvement of their energy storage performance (ESP). One is the large hysteresis of their polarization (P)-electric field (E) loops; the other is the low dielectric breakdown strength (Eb), which has a close correlation with the inevitable defects present in BF-based ceramics. Herein, we designed a co-doping strategy to overcome the two handicaps in order to achieve high ESP in BFBT ceramics. In this strategy, the trivalent rare earth Nd3+ ions and high valence Nb5+ ions are simultaneously introduced at the perovskite A- and B-sites of BFBT ceramics, which is called NN co-doping. The NN co-doping enhances the relaxor properties of BFBT ceramics due to the enhanced composition and charge fluctuations and promotes the formation of the Bi-rich phases, which contribute to the appearance of a slim P-E loop. Meanwhile, the Eb of BFBT ceramics is enhanced, which is ascribed to the significantly decreased oxygen vacancy concentration, the reduced grain size and the Bi-rich phases. Benefitting from these factors, a high recoverable energy storage density (Wrec) of 3.64 J/cm3 and energy storage efficiency (η) of 88% are simultaneously obtained under an enhanced Eb of 330 kV/cm in BFBT-0.08NN ceramics. Moreover, the ESP of BFBT-0.08NN ceramics shows good thermal stability (30–150 °C) and charge-discharge properties. These results indicate that BFBT-0.08NN ceramics could be a promising capacitor material.

C2+ Selectivity for CO2 Electroreduction on Oxidized Cu-Based Catalysts.

Design for highly selective catalysts for CO2 electroreduction to multicarbon (C2+) fuels is pressing and important. There is, however, presently a poor understanding of selectivity toward C2+ species. Here we report for the first time a method of judiciously combined quantum chemical computations, artificial-intelligence (AI) clustering, and experiment for development of a model for the relationship between C2+ product selectivity and composition of oxidized Cu-based catalysts. We 1) evidence that the oxidized Cu surface more significantly facilitates C-C coupling, 2) confirm the critical potential condition(s) for this oxidation state under different metal doping components via ab initio thermodynamics computation, 3) establish an inverted-volcano relationship between experimental Faradaic efficiency and critical potential using multidimensional scaling (MDS) results based on physical properties of dopant elements, and 4) demonstrate design for electrocatalysts to selectively generate C2+ product(s) through a co-doping strategy of early and late transition metals. We conclude that a combination of theoretical computation, AI clustering, and experiment can be used to practically establish relationships between descriptors and selectivity for complex reactions. Findings will benefit researchers in designing electroreduction conversions of CO2 to multicarbon C2+ products.