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Ce3+ ions from the surface of CeO2 nanoparticles play a key role as active sites in various chemical reactions including silicate adsorption. However, the insufficient concentration of Ce3+ ions at the CeO2 surface is a limitation in the use of CeO2 nanoparticles. In the present study, we introduce hydrogenated CeO2 nanoparticles with plentiful Ce3+ concentration for high-efficiency silicate adsorption. Surface-modified CeO2 nanoparticles were prepared using heat treatment at 800 °C for 10 hours with 10% and 20% hydrogen atmospheres to increase oxygen vacancies. During the modification process, two excess electrons from the increased oxygen vacancy formation localized the 4f-state of cerium ions, leading to a valence change in the Ce ions from Ce4+ to Ce3+. As a result, the concentration of Ce3+ ions increased by 45%, from 16.59 to 24.01%, according to hydrogen reduction. The adsorption properties of silicate ions onto hydrogenated CeO2 surfaces were investigated through adsorption isothermal analysis. Finally, the adsorption isotherm results were fitted using the Langmuir and Freundlich equations to elucidate their improved adsorption behaviors. [ABSTRACT FROM AUTHOR]

The solvation sheath of Li+–glyme was modulated to enhance Li+–TFSI− association by adopting a highly polar solvent, especially water molecules, which affects the solid electrolyte interface (SEI) layer composition. By the Li+–TFSI− association, a TFSI− anion-derived SEI layer is formed on the Li metal anode, resulting in higher Li metal anode efficiency. [ABSTRACT FROM AUTHOR]

Lithium (Li) metal is considered an ideal anode for next-generation Li metal batteries (LMBs). However, Li dendrite formation and low coulombic efficiency (CE) are major obstacles for its practical use in LMBs. The engineering of the interface between Li metal and electrolytes is crucial for better Li ion kinetics and interface stability to overcome the above problems. In this study, we report a thin LiF/defluorinated polymer (LiF@Po) composite as an artificial SEI layer. The LiF@Po composite layer, formed by a facile and scalable roll-pressing process using polytetrafluoroethylene (PTFE) and Li metal, is composed of an inner (lithium side) LiF-rich layer and an outer (electrolyte side) polymer rich (polyene/fluoropolymer) layer. The free space between LiF particles could be conformally filled with a polymeric layer, improving the Li surface coverage properties of the protection layer. This novel LiF@Po protection layer enables highly stable cyclability even in a carbonate-based electrolyte for more than 1000 h at 1 mA cm−2 in a Li‖Li symmetric cell and a cycle retention of 80% capacity for >200 cycles with an extremely stable average CE of 99.7% in a Li‖LiCoO2 full cell. Furthermore, this LiF@Po protection layer could significantly enhance the cyclability and reversible capacity in a Li‖LiNi0.8Co0.1Mn0.1O2 (NCM-811) full cell. [ABSTRACT FROM AUTHOR]

The demand for green energy conversion and storage for various applications, such as portable electronics, electric vehicles, and large-scale power stations, has boosted the exploration of advanced energy storage technologies. Lithium-ion batteries (LIBs), sodium-ion batteries (SIBs), and liquid-metal batteries (LMBs) meet the different requirements of high-energy density, low cost, and large-scale energy storage, respectively. Currently, designing and synthesizing appropriate electrode materials with high performance, abundant natural availability, and low cost are the main challenges for rechargeable battery technology. Recent studies have demonstrated that Sb-based materials are promising electrode candidates for LIBs, SIBs, and LMBs because of their relatively low cost and high electrochemical performance. This review critically presents recent developments in Sb-based electrode materials, including storage mechanisms, synthesis strategies, and applications in LIBs, SIBs, and LMBs. It also presents challenges and prospects on further improving Sb-based electrode materials for real applications. [ABSTRACT FROM AUTHOR]

Porous transition metal oxides are widely used in energy storage applications owing to their unique physicochemical properties. However, the development of simple synthetic routes using cheap precursors without sacrificial templates still remains challenging. Herein we report a synthesis of hierarchical porous TiNb2O7 nanotubes via dual nozzle electrospinning as a high power anode material for LIBs. The porosity and dimensions of the nanotubes were controlled by varying the molar concentration ratio of Ti/Nb metal precursors to acetic acid and adjusting the degree of formation of Ti/Nb hydroxides in electrospun fibers. The TiNb2O7 nanotubes have a diameter of ∼300 nm with tunable wall thickness and a surface area in the range of 52–151 m2 g−1. Moreover, the nanotubes have a hierarchical porous structure consisting of micropores below 2 nm and mesopores in the range of 5–60 nm in their walls that are connected to the macroscale inner hole with a diameter of 150 nm. The unique structure of the nanotubes enables a high discharge capacity of ∼294 mA h g−1, a stable cycle performance of 86% capacity retention over 700 cycles, and a superior rate capability of ∼230 mA h g−1 at high 50C, which is the highest retention ever reported to the best of our knowledge. Our strategy demonstrates a facile synthesis of hierarchical porous TiNb2O7 nanotubes without templates and their potential as a high power anode material for LIBs. [ABSTRACT FROM AUTHOR]

We demonstrate the dual advantages of graded photoabsorbers in mesoporous metal oxide-based hetero interfacial photoanodes in improving photogenerated charge carrier (e−/h+) separation for the solar light-driven water-oxidation process. The pre-deposition of sol–gel-derived, tungsten-doped bismuth vanadate (W:BiVO4) onto a primary BiVO4 water oxidation layer forms graded interfaces, which facilitate charge transfer from the primary photoabsorber to the charge transport layer, thereby superseding the thickness-controlled charge recombination at the BiVO4 water oxidation catalyst. As a result, the WO3/BiVO4 hetero photoanode containing the photoactive W:BiVO4 interfacial layer showed 130% higher photocurrent than that of the interfacial layer-free hetero photoelectrode owing to the enhanced charge separation led water oxidation process. [ABSTRACT FROM AUTHOR]

Sn is a promising anode material for sodium ion batteries due to its high capacity. However, the fast capacity fading caused by large volume changes limits the employment of Sn anodes. Graphene has been considered as a host for Sn anode materials to improve the cycle performance. However, graphene scaffold preparation with large free spaces is challenging due to the need for a sacrificial template and etching process. Here, we prepared a porous scaffold composed of both reduced graphene oxide and graphene via a camera flash reduction as the host for Sn. The camera flash induces the reduction of the graphene oxide and pores generated by the c-axis popping of the graphene. The mechanical strength of the scaffold is also achieved by adjusting the concentration of graphene which does not react with the flash light. The porosity and mechanical properties of the reduced graphene oxide–graphene scaffold could be controlled by flash irradiation conditions and the mixing ratio between the graphene oxide and graphene. The porous scaffold enables a uniform Sn loading and an improvement in the sodium ion battery performance due to a sufficient free space for accommodating the Sn volume change and mechanical stability. [ABSTRACT FROM AUTHOR]

We first demonstrate a facile and effective strategy to directly deposit a Nafion nanoweb onto a sulfur cathode to address the challenges underlying in Li–S batteries. The Nafion nanoweb not only blocks the diffusion of polysulfides by electrostatic repulsion but also allows fast Li-ion exchange with the sulfur cathode through the selective protection layer. The Nafion nanoweb-sulfur cathode retained an excellent cycle performance over 200 cycles and delivered an improved rate capability, as compared to a sulfur cathode and a Nafion layer-sulfur cathode. [ABSTRACT FROM AUTHOR]

Co3O4 microframes are synthesized through a template-engaged strategy via the etching of Co–Co Prussian blue analogue microcubes with ammonia solution and subsequent annealing treatment. Benefitting from their unique structural merits including 3D open structure and high porosity, these Co3O4 microframes exhibit enhanced electrochemical properties for both lithium-ion batteries and water oxidation. [ABSTRACT FROM AUTHOR]

A template-engaged strategy is used to synthesize nanostructured metal phosphides with different compositions. Among the as-synthesized metal phosphides, nickel cobalt phosphides quasi-hollow nanocubes exhibit the best electrocatalytic activity for hydrogen evolution reaction in terms of lower overpotential and smaller Tafel slope in alkaline solution. [ABSTRACT FROM AUTHOR]

TiO2 has received significant research interest as an anode material for lithium ion batteries due to its robustness and safe operation. However, poor rate capabilities limit its practical use. Various strategies have been explored to address this issue by improving the electronic conductivity and enhancing the Li ion kinetics. Especially, surface facet control, doping and surface treatment of TiO2 enable significant improvement in kinetics associated with the electron and the Li ion without employing other foreign materials. Recent reports show that the unique physicochemical properties and well established technologies on engineering of TiO2 properties have opened up further possibilities in the next generation Li batteries and advanced Li ion batteries as a supplemental material. This review discusses recent scientific and technological advances in (i) the improvement in rate capabilities of TiO2 anodes from the engineering of their structural or electronic properties (ii) TiO2 as a supplemental material in Li–S and Li–O2 batteries and advanced Li ion batteries. In addition to highlighting recent progress, the limitations and challenges of TiO2 for Li ion batteries and next generation Li batteries have also been discussed. [ABSTRACT FROM AUTHOR]

We report a stackable all-solid-state supercapacitor based on three dimensional PPy–NiO/RGO–CNT electrodes. The electrodes were prepared by growing NiO nanowalls (NWs) on both sides of a freestanding RGO–CNT film with the hydrothermal method, followed by coating with conductive polypyrrole. The double-sided architecture of the NiO NWs on a carbon-based current collector suggests that the novel approach addresses the issue of low areal capacitance in supercapacitors. Furthermore, conductive polypyrrole renders fast electron transport through the two-dimensional structure of NiO NWs. With our 3D-designed electrodes, we successfully fabricated a stackable all-solid-state supercapacitor and thus achieved a high areal capacitance of 1948 mF cm−2. [ABSTRACT FROM AUTHOR]

Hydroxylated multi-walled carbon nanotubes were introduced into sulfur cathodes to utilize the hydrophilic attraction between the OH group and polysulfides as well as to increase the utilization of sulfur. This approach shows a promising strategy for diminishing the polysulfides shuttling behavior and improving the electrochemical performance of lithium–sulfur batteries. [ABSTRACT FROM AUTHOR]

Porous LiMnPO4/C composite nanofibers between 150 and 250 nm have been synthesized as a cathode material for lithium ion batteries via electrospinning. The porous LiMnPO4/C composite nanofibers show excellent electrochemical performance including a high reversible capacity of 112.7 mA h g−1 at 0.2C, a stable cycle retention of 95% after 100 cycles at 1C, and excellent rate capability (73.1 mA h g−1 at 5C) in constant current mode between 2.0 and 4.5 V. These improved electrochemical properties are attributed to the one-dimensional geometry and porous structure, which significantly enhanced kinetics associated with electrons and Li ions. [ABSTRACT FROM AUTHOR]

The interaction strength of Au nanoparticles with pristine and nitrogen doped TiO2 nanowire surfaces was analysed using density functional theory and their significance in enhancing the solar driven photoelectrocatalytic properties was elucidated. In this article, we prepared 4-dimethylaminopyridine capped Au nanoparticle decorated TiO2 nanowire systems. The density functional theory calculations show {101} facets of TiO2 as the preferred phase for dimethylaminopyridine–Au nanoparticles anchoring with a binding energy of −8.282 kcal mol−1. Besides, the interaction strength of Au nanoparticles was enhanced nearly four-fold (−35.559 kcal mol−1) at {101} facets via nitrogen doping, which indeed amplified the Au nanoparticle density on nitrided TiO2. The Au coated nitrogen doped TiO2 (N–TiO2–Au) hybrid electrodes show higher absorbance owing to the light scattering effect of Au nanoparticles. In addition, N–TiO2–Au hybrid electrodes block the charge leakage from the electrode to the electrolyte and thus reduce the charge recombination at the electrode/electrolyte interface. Despite the beneficial band narrowing effect of nitrogen in TiO2 on the electrochemical and visible light activity in N–TiO2–Au hybrid electrodes, it results in low photocurrent generation at higher Au NP loading (3.4 × 10−7 M) due to light blocking the N–TiO2 surface. Strikingly, even with a ten-fold lower Au NP loading (0.34 × 10−7 M), the synergistic effects of nitrogen doping and Au NPs on the N–TiO2–Au hybrid system yield high photocurrent compared to TiO2 and TiO2–Au electrodes. As a result, the N–TiO2–Au electrode produces nearly 270 μmol h−1 cm−2 hydrogen, which is nearly two-fold higher than the pristine TiO2 counterpart. The implications of these findings for the design of efficient hybrid photoelectrocatalytic electrodes are discussed. [ABSTRACT FROM AUTHOR]

Sn-doped LiTi2(PO4)3/C composite nanofibers are synthesized by a facile electrospinning process. The unique one dimensional nanostructure combined with a uniform electrically conductive carbon matrix allows high-rate transportation of lithium ions and electrons. Besides, Sn-doping could further decrease the electrochemical resistance. Sn-doped LiTi2(PO4)3/C composite nanofibers exhibit excellent electrochemical performance, especially ultra-fast charging/discharge capability. At a charging rate of about 600 C (64 A g−1, 6 s), 66.2% capacity (68.9 mA h g−1) could be obtained when matched with a Li metal counter electrode. They also exhibit excellent electrochemical properties as an anode material for aqueous rechargeable lithium batteries. Sn-doped LiTi2(PO4)3/C composite nanofibers are promising electrode materials for both nonaqueous and aqueous lithium ion batteries. [ABSTRACT FROM AUTHOR]

Titanium niobium oxide (TiNb2O7) has been reported recently as an attractive anode material for lithium ion batteries due to its practical capacity of ∼280 mA h g−1, which is much higher than those of well-known metal oxide materials such as TiO2 and Li4Ti5O12. However, low electronic conductivity and poor lithium diffusivity limit its practical use as the active material in lithium ion batteries. Here, we synthesized porous TiNb2O7 nanofibers decorated with Ti1−xNbxN bumps via electro-spinning and thermal ammonia gas treatment. As-prepared nanofibers have one-dimensional geometry with an average diameter of ∼110 nm, and consist of ∼70 nm crystallites and pores in the range of 0–40 nm, shortening pathways for Li+ ion migration into the host material. Furthermore, conductive Ti1−xNbxN bumps with a particle size of ∼5 nm were formed on the surface via thermal ammonia gas treatment which render fast electron transport along the longitudinal direction. The fibers have a specific discharge capacity of ∼254 mA h g−1 at 1 C and a superior rate capability (∼183 mA h g−1 at 100 C). They also show a robust cycle performance over 500 cycles. These dramatic achievements are attributed to heterogeneous nano-structuring creating a porous structure, and the conductivity of the metal nitride achieved by optimal synthetic conditions. [ABSTRACT FROM AUTHOR]

Si nanotubes for reversible alloying reaction with lithium are able to accommodate large volume changes and offer improved cycle retention and reliable response when incorporated into battery anodes. However, Si nanotube electrodes exhibit poor rate capability because of their inherently low electron conductivity and Li ion diffusivity. Si/Ge double-layered nanotube electrodes show promise to improve structural stability and electrochemical kinetics, as compared to homogeneous Si nanotube arrays. The mechanism explaining the enhancement in the rate capabilities is revealed here by means of electrochemical impedance methods. The Ge shell efficiently provides electrons to the active materials, which increase the semiconductor conductivity thereby assisting Li+ ion incorporation. The charge transfer resistance which accounts for the interfacial Li+ ion intake from the electrolyte is reduced by two orders of magnitude, indicating the key role of the Ge layer as an electron supplier. Other resistive processes hindering the electrode charge–discharge process are observed to show comparable values for Si and Si/Ge array electrodes. [ABSTRACT FROM AUTHOR]

We demonstrate one-step gold nanoparticle (AuNP) coating and the surface nitridation of TiO2 nanowires (TiO2-NWs) to amplify visible-light photon reflection. The surface nitridation of TiO2-NW arrays maximizes the anchoring of AuNPs, and the subsequent reduction of the band gap energy from 3.26 eV to 2.69 eV affords visible-light activity. The finite-difference time-domain (FDTD) simulation method clearly exhibits the enhancement in the strengths of localized electric fields between AuNPs and the nanowires, which significantly improves the photocatalytic (PC) performance. Both nitridation and AuNP decoration of TiO2-NWs result in beneficial effects of high (e−/h+) pair separation through healing of the oxygen vacancies. The combined effect of harvesting visible-light photons and reducing recombination in Au/N-doped TiO2-NWs promotes the photocatalytic activity towards degradation of methyl orange to an unprecedented level, ∼4 fold (1.1 × 10−2 min) more than does TiO2-NWs (2.9 × 10−3 min−1). The proposed AuNP decoration of nitridated TiO2-NW surfaces can be applied to a wide range of n-type metal oxides for photoanodes in photocatalytic applications. [ABSTRACT FROM AUTHOR]

Robust composite nanofibers (NFs) are prerequisite for highly efficient electrochemical sensors. We report the electrochemical application of gold nanoparticle (Au NP)-composite Nafion NFs using a facile electrospinning technique. Owing to the uniform distribution and large surface area of the Au NPs in the NFs, the Au NP-composite electrodes gave rise to greatly improved electrochemical properties, compared to AuNP-free composite electrodes. When they were employed as reservoirs for immobilizing horseradish peroxidase (HRP), reliable and sensitive electrochemical detection by the enzyme reaction was achieved. The detection sensitivity for H2O2 was determined to be as low as 38 nM, which was one order higher than that of previous electrochemical sensors. In addition, there was no change in the enzyme stability over three weeks. In this regard, the developed NP/NF-based electrochemical sensors are anticipated to be very suitable for monitoring other enzyme reactions with high sensitivity and stability. [ABSTRACT FROM AUTHOR]

We present a new synthetic approach, viahydrothermal process with the use of polystyrene (PS) colloids, to fabricate vertically aligned, single crystalline ZnO nanotube arrays. Electron microscopy images revealed that single crystalline nanotubes with inner diameters of ∼15–20 nm and wall thicknesses of ∼10–15 nm were formed just below the PS colloids, whereas solid nanorods were grown in the absence of PS colloids. In addition, nanorods enclosing the PS colloids exhibited much faster growth rates than those on the area not covered with PS colloids. These results indicate that the introduction of PS colloids affected the formation and diffusion of adatoms. The growth behavior of ZnO crystals with regards to the PS colloids was exploited to convert the ZnO nanostructures from solid to nanotube-nanorod hybrid networks by introducing hexagonally close-packed PS colloidal monolayers. Moreover, we demonstrated further conversion to complete tubular forms by reducing the aperture size between adjacent PS colloids with thermal annealing. [ABSTRACT FROM AUTHOR]

Facile synthesis of TiO2 nanotube branched (length ∼0.5 μm) thin hollow-nanofibers is reported. The hierarchical three dimensional photoanodes (H-TiO2-NFs) (only ∼1 μm thick) demonstrate their excellent candidature as photoanodes in QD-sensitized solar cells, exhibiting ∼3-fold higher energy conversion efficiency (η = 2.8%, Jsc = 8.8 mA cm−2) than that of the directly grown nanotube arrays on a transparent conducting oxide (TCO) substrate (η = 0.9%, Jsc = 2.5 mA cm−2). [ABSTRACT FROM AUTHOR]

We demonstrate the dual advantages of graded photoabsorbers in mesoporous metal oxide-based hetero interfacial photoanodes in improving photogenerated charge carrier (e - /h + ) separation for the solar light-driven water-oxidation process. The pre-deposition of sol-gel-derived, tungsten-doped bismuth vanadate (W:BiVO 4 ) onto a primary BiVO 4 water oxidation layer forms graded interfaces, which facilitate charge transfer from the primary photoabsorber to the charge transport layer, thereby superseding the thickness-controlled charge recombination at the BiVO 4 water oxidation catalyst. As a result, the WO 3 /BiVO 4 hetero photoanode containing the photoactive W:BiVO 4 interfacial layer showed 130% higher photocurrent than that of the interfacial layer-free hetero photoelectrode owing to the enhanced charge separation led water oxidation process.

The interaction strength of Au nanoparticles with pristine and nitrogen doped TiO2 nanowire surfaces was analysed using density functional theory and their significance in enhancing the solar driven photoelectrocatalytic properties was elucidated. In this article, we prepared 4-dimethylaminopyridine capped Au nanoparticle decorated TiO2 nanowire systems. The density functional theory calculations show {101} facets of TiO2 as the preferred phase for dimethylaminopyridine-Au nanoparticles anchoring with a binding energy of -8.282 kcal mol(-1). Besides, the interaction strength of Au nanoparticles was enhanced nearly four-fold (-35.559 kcal mol(-1)) at {101} facets via nitrogen doping, which indeed amplified the Au nanoparticle density on nitrided TiO2. The Au coated nitrogen doped TiO2 (N-TiO2-Au) hybrid electrodes show higher absorbance owing to the light scattering effect of Au nanoparticles. In addition, N-TiO2-Au hybrid electrodes block the charge leakage from the electrode to the electrolyte and thus reduce the charge recombination at the electrode/electrolyte interface. Despite the beneficial band narrowing effect of nitrogen in TiO2 on the electrochemical and visible light activity in N-TiO2-Au hybrid electrodes, it results in low photocurrent generation at higher Au NP loading (3.4 × 10(-7) M) due to light blocking the N-TiO2 surface. Strikingly, even with a ten-fold lower Au NP loading (0.34 × 10(-7) M), the synergistic effects of nitrogen doping and Au NPs on the N-TiO2-Au hybrid system yield high photocurrent compared to TiO2 and TiO2-Au electrodes. As a result, the N-TiO2-Au electrode produces nearly 270 μmol h(-1) cm(-2) hydrogen, which is nearly two-fold higher than the pristine TiO2 counterpart. The implications of these findings for the design of efficient hybrid photoelectrocatalytic electrodes are discussed.

We demonstrate one-step gold nanoparticle (AuNP) coating and the surface nitridation of TiO2 nanowires (TiO2-NWs) to amplify visible-light photon reflection. The surface nitridation of TiO2-NW arrays maximizes the anchoring of AuNPs, and the subsequent reduction of the band gap energy from 3.26 eV to 2.69 eV affords visible-light activity. The finite-difference time-domain (FDTD) simulation method clearly exhibits the enhancement in the strengths of localized electric fields between AuNPs and the nanowires, which significantly improves the photocatalytic (PC) performance. Both nitridation and AuNP decoration of TiO2-NWs result in beneficial effects of high (e(-)/h(+)) pair separation through healing of the oxygen vacancies. The combined effect of harvesting visible-light photons and reducing recombination in Au/N-doped TiO2-NWs promotes the photocatalytic activity towards degradation of methyl orange to an unprecedented level, ∼4 fold (1.1 × 10(-2) min) more than does TiO2-NWs (2.9 × 10(-3) min(-1)). The proposed AuNP decoration of nitridated TiO2-NW surfaces can be applied to a wide range of n-type metal oxides for photoanodes in photocatalytic applications.