Facile Charge Transfer Research Articles

Freeform Lithium Superionic Conductor

The key challenge in all-solid-state batteries (ASSBs) is establishing perfect physical contact between rigid components for facile interfacial charge transfer, especially between the solid electrolyte and cathode. Here, we introduce a new class of shapeable inorganic-based solid electrolytes with a liquid-like sublattice that can form intimate contact with the rigid cathode. The electrolyte exhibits extraordinary clay-like mechanical properties (storage and loss moduli < 1 MPa) at room temperature, high lithium ion conductivity (3.4 mS cm-1), and a glass transition below -50 ℃. The unique mechanical features provide liquid-like penetration into the porous cathode and ionic conduction paths for all cathode particles, delivering a high energy density. We propose a design principle that the complex anion formation including Ga, F and a different halogen can induce the clay-like features. Our findings provide new opportunities in the search for solid electrolytes and suggest a new approach for resolving the issues caused by the solid electrolyte–cathode interface in ASSBs.

ZnO Nano-Rod Arrays Synthesized with Exposed {0001} Facets and the Investigation of Photocatalytic Activity

Zinc oxide (ZnO) possesses superior chemical and physical properties so that it can occupy an essential position in the application of nanostructures. In this paper, ZnO nano-rod arrays were synthesized by a simple one-step hydrothermal approach with the assistance of cetyl trimethyl ammonium bromide (CTAB). Exposure of the {0001} facets could be controlled by adjusting the amount of CTAB and the maximum exposure of the {0001} facets of ZnO nanorods is obtained at 1.2 g of CTAB. The photocurrent, EIS, and PL measurements support the facile charge transfer with minimum recombination of the photogenerated excitons of the ZnO nano-rod arrays obtained at 1.2 g of CTAB. Consequently, the obtained ZnO nano-rod arrays at the optimal CTAB of 1.2 g exhibit an excellent photocatalytic degradation rate of 99.7% for rhodamine B (RhB), while the degradation rate of RhB by the ZnO obtained without CTAB is only 35%.

Pliable Lithium Superionic Conductor for All-Solid-State Batteries

The key challenges in all-solid-state batteries (ASSBs) are establishing and maintaining perfect physical contact between rigid components for facile interfacial charge transfer, particularly betwe...

Aluminum textile-based binder-free nanostructured battery cathodes using a layer-by-layer assembly of metal/metal oxide nanoparticles

Despite considerable interest in textile-based battery electrodes with large surface areas and mechanical flexibility, issues have restricted further advances in the energy performance of textile electrodes. These issues include the ineffective incorporation of conductive and/or active components into textile frameworks, the poor charge transfer between energy materials, and the formation of numerous unstable interfaces within textile electrodes. Herein, we introduce an aluminum textile-based lithium-ion battery cathode with remarkable areal capacity, high rate performance, and good cycling stability. Ligand exchange reaction-induced layer-by-layer (LbL) assembly of metal nanoparticles and small molecule linkers, with subsequent metal electroplating, perfectly converted polyester textiles to 3D-porous aluminum textiles that can be used as current collectors and high-energy reservoirs. The consecutive LbL assembly of high-energy LiFePO4 and conductive indium tin oxide nanoparticles onto the aluminum textiles using small organic linkers significantly increased the areal capacity and cycling stability (at least 580 cycles) of the resultant cathode, allowing facile charge transfer within the textile electrodes. Furthermore, the areal capacity of these textile electrodes increased from 1.07 to 3.28 mA h cm−2, with an increase in the folding number from 0 to 2.

A thermodynamic approach toward selective and reversible sub-ppm H2S sensing using ultra-small CuO nanorods impregnated with Nb2O5 nanoparticles

CuO nanorods impregnated Nb2O5 composites have been thermodynamically designed for facile interfacial charge transfer, which favors CuO sulfidation and oxidation with reversible, selective, and stable sub-ppm H2S sensing at a constant temperature.

Electrochemical oxidation of boron-doped nickel-iron layered double hydroxide for facile charge transfer in oxygen evolution electrocatalysts.

The oxygen evolution reaction (OER) is the key reaction in water splitting systems, but compared with the hydrogen evolution reaction (HER), the OER exhibits slow reaction kinetics. In this work, boron doping into nickel–iron layered double hydroxide (NiFe LDH) was evaluated for the enhancement of OER electrocatalytic activity. To fabricate boron-doped NiFe LDH (B:NiFe LDH), gaseous boronization, a gas–solid reaction between boron gas and NiFe LDH, was conducted at a relatively low temperature. Subsequently, catalyst activation was performed through electrochemical oxidation for maximization of boron doping and improved OER performance. As a result, it was possible to obtain a remarkably reduced overpotential of 229 mV at 10 mA cm−2 compared to that of pristine NiFe LDH (315 mV) due to the effect of facile charge-transfer resistance by boron doping and improved active sites by electrochemical oxidation.

Self-standing SnS nanosheet array: a bifunctional binder-free thin film catalyst for electrochemical hydrogen generation and wastewater treatment.

Hydrogen generation during wastewater treatment has remained a long-standing challenge for the environment preservation welfare. In the present work, we have fabricated a promising bifunctional thin film-based catalyst for hydrogen generation with concurrent wastewater treatment. The prepared catalyst film is a vertically oriented thin SnS (tin monosulfide) nanosheet array on a Ni-foam (SnS/NF) obtained via a solution process, demonstrating a promising electrocatalytic activity towards the generation of green H2 fuel at the cathodic side and the decomposition of urea waste at the anodic side. Notably, while assembling two identical electrodes as cathode and anode together with a reference electrode (i.e., SnS/NF∥SnS/NF vs. RHE assembly) in 1 M KOH aqueous electrolyte containing 0.33 M urea, the electrolyzer electrolyzed urea at a lower cell potential of 1.37 and 1.43 V (vs. RHE) to deliver a current density of 10 mA cm-2 and 50 mA cm-2, respectively, for the decomposition of urea at the anodic SnS/NF electrode and green hydrogen fuel generation at the cathodic SnS/NF electrode. This activity on electrocatalytic urea decomposition lies within the best performance to those of the previously reported sulfide-based and other catalytic materials. The promising catalytic activities of the SnS catalyst film are attributed to its combined effect of self-standing nanosheet array morphology and high crystallinity, which provides abundant active sites and a facile charge transfer path between the nanosheet arrays and the electrolyte. Thus, the present work offers a green avenue to the waste-urea treatment in water and sustainable hydrogen energy production.

MnO Stabilized in Carbon‐Veiled Multivariate Manganese Oxides as High‐Performance Cathode Material for Aqueous Zn‐Ion Batteries

Aqueous Zn‐ion battery has emerged as one of the most prospective energy storage devices due to its low cost, high safety, and eco‐friendliness. However, Zn‐ion batteries are bottlenecked by significant capacity fading during long‐term cycling and poor performance at high current rates. Here, we report an available cooperation of multivariate manganese oxides@carbon hybrids (MnO2/MnO@C and MnO2/Mn3O4@C) via a plasma‐assisted design as an attractive Zn‐ion cathode. Among them, the MnO2/MnO@C cathode exhibits a reversible specific capacity of 165 mAh g−1 over 200 cycles at a high rate of 0.5 A g−1, and possesses great rate performance with high capacities of 110 and 100 mAh g−1 at a high rate of 0.8 and 1 A g−1, respectively. The good cathode performance significantly results from the facile charge transfer and ions (Zn2+ and H+) insertion in the manganese oxides/carbon hybrids featuring phase stability behavior in the available cooperation of multivalence and carbon conductive substrates. This work will promote the Zn‐manganese dioxide system for the design of low‐cost and high‐performance aqueous rechargeable Zn‐ion batteries.

Highly efficient and air stable thermoelectric devices of poly(3-hexylthiophene) by dual doping of Au metal precursors

The electrical conductivity and doping stability of poly(3-hexylthiophene) (P3HT) in ambient air are significantly improved using a gold chloride dopant, where the coexistence of AuCl 4 − and Au nanoparticles contributes to high electrical conductivity and doping stability at the same time. The uniformly formed Au nanoparticles induce a facile charge transfer in a thin film of AuCl 3 -doped P3HT as examined by the crystallography and transmission electron microscopy. P3HT doped with AuCl 3 exhibits a high electrical conductivity of 207 S cm − 1 , a Seebeck coefficient of 73.9 μV K − 1 , and an optimized power factor of 110 μW m −1 K −2 . Importantly, AuCl 3 -doped P3HT shows excellent air stability. After exposure to the ambient condition for 300 h, the optimized power factor of the AuCl 3 -doped P3HT maintains over 80% of the initial, whereas that of the FeCl 3 -doped P3HT decreases to only 20% of the original. Finally, a flexible and organic thermoelectric generator (OTEG) is fabricated using the AuCl 3 -doped P3HT by slot-die coating. The OTEG shows a relatively high open-circuit voltage ( V oc ) of 7.96 mV and a short-circuit current ( I sc ) of 0.93 μA, resulting in a power density of 18.5 nW cm − 2 at a temperature gradient of 10 °C. Highly improved thermoelectric performance and doping stability of poly(3-hexylthiophene) by dual doping effect • Thermoelectric (TE) performance and doping stability of Poly(3-hexylthiophene) are highly improved. • A gold chloride with two different chemical states in the form of AuCl4− and Au nanoparticles enhances doping effect. • A flexible TE generator with high durability is successfully demonstrated.

Sulfidation of CoAl-layered double hydroxide on Ni foam for high-performance supercapacitors

The transition-metal sulfides (CoAl-S) as supercapacitor electrode materials were fabricated onto Ni foam via a simple and cost-effective two-step hydrothermal route. The sulfidation treatment significantly improved the electrical conductivity and accelerated the ion diffusion rate for the materials. By adjusting the S2−/Co2+ molar ratio during the sulfidation process, it was found that the CoAl-S8 sulfide with a 3D and loosely interconnected network mesoporous structure on the Ni foam was gained at S2−/Co2+ molar ratio of 8.0, and exhibited the highest specific capacitance. Benefiting from the unique network structural feature to facilitate active sites exposure and facile charge transfer, the optimized CoAl-S8 material displayed an enhanced specific capacitance of 575.3 C g−1 (1150.6 F g‒1) at 1.0 A g‒1 and cycling stability with 97.8% capacitance retention after 1000 cycles at 5.0 A g‒1 in the three-electrode system. Furthermore, the as-fabricated CoAl-S8//AC device delivered outstanding energy densities of 55.31 and 32.91 Wh kg−1 at a power density of 749.97 and 7498.48 W kg−1, respectively, and excellent rate capability and outstanding long-term cycle stability (92.45% of the initial value at 5 A g−1 after 10 000 cycles). This facile synthesis strategy provided a useful clue in designing novel and effective electrode materials for supercapacitors.

Template‐free synthesis of one‐dimensional cobalt sulfide nanorod array as an attractive architecture for overall water splitting

One-dimensional (1D) nanoarrays are beneficial for electrochemical reactions, including water splitting, due to their directional electron transport through the array, large effective surface area, and porosity. Fabrication of such array without a template is, however, extremely challenging. Herein, an ion-exchange approach is employed to fabricate a 1D cobalt sulfide nanorod array (1D-CoS) from Co3O4 on stainless steel. The 1D-CoS electrode works as a bifunctional electrocatalyst, attaining the current density of 10 mA cm−2 for hydrogen evolution reaction and oxygen evolution reaction at a low overpotential of 159 and 280 mV, respectively in a 1 M KOH solution. A full electrolyzer with the same two 1D-CoS electrodes assembly demonstrates a low cell voltage of 1.75 V at 10 mA cm−2 and this performance value is well maintained for 20 hours. The efficient catalytic performance can be due to the controlled CoS phase with a unique 1D nanoarchitecture, which allows facile electrolyte diffusion and charge transfer between electrode/electrolyte interface.

Synthesis of nanosized TiO2 using different molecular weight polyethylene glycol (PEG) as capping agent and their performance as photoanode in dye-sensitized solar cells

In this study, synthesis of nanosized TiO2 in which hydrolysis and polycondensation of precursor, Ti(OC4H9)4, has been performed in presence of different molecular weight polyethylene glycol (PEG) polymer as a capping agent is reported. Three different capped materials (TN-P400, TN-P4000, and TN-P8000) were synthesized along with un-capped TiO2 (TiO2 synthesized without using PEG, TN) for the sake of comparison. The structure and morphology of the synthesized TiO2 were characterized by XRD, FTIR, SEM, and DLS analyses. The X-ray diffraction spectrums show the presence of anatase phase TiO2. The as-synthesized PEG-capped TiO2 were used as photoanode material for dye-sensitized solar cells (DSSC) after coating with sensitizer dye N719, and photoelectric conversion efficiency (PCE) of 2.52%, under the illumination of 100 mW cm−2, has been achieved with TN-P8000, which was much improved compared with DSSC performance with un-capped TiO2 (PCE = 1.02%). EIS analyses revealed that TN-P8000 photoanode–based cell exhibited facile charge transfer, enhanced electron lifetime, and greater charge collection efficiency that contributed better photovoltaic performance. The results demonstrated that using PEG as a capping agent is a potential approach for improving the efficiency of DSSC and current conversion efficiency was increased as the molecular weight of PEG was increased.

Nickel incorporated graphitic carbon nitride supported copper sulfide for efficient noble-metal-free photo-electrochemical water splitting

Solar hydrogen generation through photo-electrochemical (PEC) water splitting is potential technology but equally challenging to address the growing energy demand as well as the concerns related to the use of fossil fuels, and several strategies have been devised to address these concerns. Herein, we report a nanohybrids of copper sulfides supported on nickel-incorporated graphitic carbon nitride (Ni/g-C3N4@CuS) sheets for enhanced activity towards PEC water oxidation. The TEM images confirm the presence of intimate contact between nickel doped graphitic carbon nitride and CuS, forming an interface which is favorable for an effective separation of charge-carriers. The electrochemical properties of the prepared samples are investigated through linear sweep voltammetry, electrochemical impedance spectroscopy, Mott-Schottky analysis, and chopped photo-current measurements. The Ni/g-C3N4@CuS nanohybrids depicts almost three-fold enhancement in current density under light illumination reaching to 15.5 mA cm−2 at an over potential of ca. 600 mV than in the dark and almost fifteen-fold enhancement as compared to its parent materials, CuS and g-C3N4. The enhanced activity towards PEC water splitting is assigned to the larger extent of band bending as illustrated by larger space charge region width, formation of p-n junction between CuS and g-C3N4, lowering of effective band gap of the resulting hetero-structures, and facile charge transfer kinetics due to Ni-incorporation into the g-C3N4 matrix.

Structure-tunable Mn3O4-Fe3O4@C hybrids for high-performance supercapacitor

Controlling the morphology and structure of nanomaterials is of great importance for enhancing the electrochemical properties. In the paper, Mn3O4-Fe3O4@C hybrids with different architectures were synthesized by incubation of electrospun FeOx-containing carbon fiber (Fe-CNF) in KMnO4 solution followed by annealing. The presence of FeOx on the CNF plays a vital role in determining the morphology and structure of the final hybrids, and the Mn3O4-Fe3O4@C hybrids with half-tube, tube and oolite-filled fibers are formed conveniently by tuning Fe content in the carbon fiber precursor. The good conductivity of fiber and various redox states of Mn and Fe afford the facile charge transfer and excellent reversible redox properties, thus enhancing the capacitor performance. The oolite-filled Mn3O4-Fe3O4@C with tubular structure exhibited a high specific capacitance of 178 F g−1 at a discharge rate of 1 A g−1. This capacitor electrode has an excellent cyclic stability with 95% capacitance retention after 1000 cycles at 3 A g−1. This work provides a very simple strategy to tune the unique nanostructures of metal oxide on Fe-CNF for high-performance supercapacitor application in the future.

Dual‐Phase Engineering of Nickel Boride‐Hydroxide Nanoparticles toward High‐Performance Water Oxidation Electrocatalysts

AbstractThe development of earth‐abundant and efficient oxygen evolution reaction (OER) electrocatalysts is necessary for green hydrogen production. The preparation of efficient OER electrocatalysts requires both the adsorption sites and charge transfer on the catalyst surface to be suitably engineered. Herein, the design of an electrocatalyst is reported with significantly enhanced water oxidation performance via dual‐phase engineering, which displays a high number of adsorption sites and facile charge transfer. More importantly, a simple chemical etching process enables the formation of a highly metallic transition boride phase in conjunction with the transition metal hydroxide phase with abundant adsorption sites available for the intermediates formed in the OER. In addition, computational simulations are carried out to demonstrate the water oxidation mechanism and the real active sites in this engineered material. This research provides a new material design strategy for the preparation of high‐performance OER electrocatalysts.

Surface engineered NiO–Co3O4 nanostructures as high-performance electrocatalysts for oxygen reduction reaction

The development of low-cost and high-performance oxygen reduction reaction (ORR) catalysts is important for renewable energy storage and conversion systems, such as fuel cell. Herein, we report a simple and facile surface engineering strategy for nickel and cobalt based (NiO–Co3O4) hybrid as efficient and robust ORR electrocatalyst. The surface nanostructure of NiO–Co3O4 nanohybrids can be easily tuned by controlling the precursor amounts of nickel and cobalt during a wet-chemical synthesis. With an optimal composition, an intriguing surface structure consisted of one dimensional (1D) nanorod with two dimensional (2D) nanosheet can be obtained for NiO–Co3O4 nanohybrids, which significantly boosts ORR electrocatalytic activity as well as stability. A facile charge or mass transfer within 1D and 2D open surface nanostructures is mainly responsible for an excellent catalytic performance of NiO–Co3O4 nanohybrids.

Molybdenum(VI) bis-imido Complexes of Dipyrromethene Ligands.

We report the synthesis of high-valent molybdenum(VI) bis-imido complexes 1-4 with dipyrromethene (DPM) supporting ligands of the general formula (DPMR)Mo(NR')2Cl (R, R' = mesityl (Mes) or tert-butyl (tBu)). The electrochemical and chemical properties of 1-4 reveal unexpected ligand noninnocence and reactivity. 15N NMR spectroscopy is used to assess the electronic properties of the imido ligands in the tert-butyl complexes 1 and 3. Complex 1 is inert toward ligand (halide) exchange with bulky phenolates such as KOMes or amides (e.g., KN(SiMe3)2), whereas the use of the lithium alkyl LiCH2SiMe3 results in a rare nucleophilic β-alkylation of the DPM ligand. While the reductions of the complexes occur at molybdenum, the oxidation is centered at the DPM ligand. Quantum-chemical calculations (complete active space self-consistent field, density functional theory) suggest facile (near-infrared) interligand charge transfer to the imido ligand, which might preclude the isolation of the oxidized complex [1]+ in the experiment.

Ultra-thin MoS2 nanosheet for electron transport layer of perovskite solar cells

The structure and the physical dimension of the electron transport layer (ETL) in perovskite solar cell (PSC) determine the carrier transport characteristics to the electrode and then the overall performance of the device. ETL with ultimately thin and single-crystalline should facilitate enhanced photogenerated carrier transport to the electrode, inducing a highly dynamic charge transfer at the interface of ETL and perovskite absorber layer. Here, we demonstrated that a planar few atoms (5 monolayer or 5L) thick MoS2 nanosheets synthesized directly onto the ITO substrate allows a facile interfacial charge transfer and transport as judged from the open circuit voltage (Voc) value, steady-state photoluminescence and external quantum efficiency (EQE) analysis results. We found that the nanosheets crystallinity properties determines the photoelectrical process in the PSC device. The champion device in this study can produce a power conversion efficiency (PCE) as high as 3.36% with a short-circuit current density (Jsc), open circuit voltage (Voc) and fill-factor (FF) of as high as 16.24 mA cm−2, 0.56 V and 0.370, respectively. The champion device also exhibited a reasonable high stability properties that shows it can retain more than 90% of its initial PCE when operated under irradiation of 1 sun at maximum power-point. Due to the single crystallinity and the large area properties, the MoS2 nanosheets prepared using the present method may find extended application as high-performance ETL of perovskite solar cells.

Charge transfer enhancement in the surface-enhanced Raman scattering of Ta2O5 superstructures

Semiconductor nanomaterials with the surface-enhanced Raman scattering (SERS) sensitivity are gradually attracting more and more attention due to their particular advantages. However, the wider applications of semiconductor SERS-active substrates still require considerable effort to improve their SERS sensitivity. An excellent enhancement of Raman scattering is achieved by Ta2O5 superstructures with a mean diameter of 29 nm. The Ta2O5 superstructure is constructed by crystallized Ta2O5 quantum dots with an average diameter of 2.39 nm and exhibits a very low detection limit of 10−7 M for both methyl violet and methylene blue molecules under the irradiation of 532 nm laser. The chemical enhancement, originating from the precise matching of energy levels and the facile charge transfer between Ta2O5 superstructures and dye molecules, predominantly contributes to the Raman enhancement. The detailed band structure analysis in this work does a good demonstration for achieving the energy level matching and charge transfer enhancement in semiconductor SERS-active substrates with the probed molecules.

Altered crystal structure of nickel telluride by selenide doping and a poly(N-methylpyrrole) coating amplify supercapacitor performance

Nickel telluride doped with selenide (NiTe:Se) flakes show remarkably enhanced charge storage response compared to undoped NiTe. Se doping induces a morphological transformation from fibrillar NiTe to flaky NiTe:Se thereby endowing a two times higher surface roughness and an eight-fold increment in electrical conductivity to the latter, thus allowing facile charge transport and transfer across the material. Free charge carrier density available for conduction for NiTe:Se is also found to be double of that of NiTe. These beneficial effects combinedly translate into a capacity of 565 C g−1 (equivalent to a specific capacitance (SC) of 943 F g−1) for the single NiTe:Se electrode, which is 1.5 times greater than the NiTe electrode. The homogeneity of Se dispersion in the NiTe matrix is confirmed by magnetic force microscopy, where the prominent magnetic domains observed to be uniformly distributed across the surface of NiTe are obliterated homogeneously after Se doping. Asymmetric supercapacitor with activated carbon (AC//NiTe:Se) delivers a 300 C g−1 and this performance is bettered by coating a poly(N-methylpyrrole) (PMP) layer at the electrodes, where the polymer also contributes to charge storage and also assists in preserving the structural integrity of the active materials. The ensuing PMP@AC//PMP@NiTe:Se supercapacitor delivers a capacity of 404 C g−1, Emax and Pmax of 90 Wh kg−1, and 400 W kg−1, superior to the AC//NiTe:Se cell. Practical demonstration of the PMP@AC//PMP@NiTe:Se with a 3S (series), 4.5 V configuration, coupled with the ease of fabrication and scale-up open up avenues to develop this cell as a commercial product.