Modulation of Crystal Surface and Lattice by Doping: Achieving Ultrafast Metal-Ion Insertion in Anatase TiO2

Improvements in the Magnesium Ion Transport Properties of Graphene/CNT-Wrapped TiO2 -B Nanoflowers by Nickel Doping

Magnesium-ion batteries are widely studied for its environmentally friendly, low-cost, and high volumetric energy density. In this work, the solvothermal method is used to prepare titanium dioxide bronze (TiO2 -B) nanoflowers with different nickel (Ni) doping concentrations for use in magnesium ion batteries as cathode materials. As Ni doping enhances the electrical conductivity of TiO2 -B and promotes magnesium ion diffusion, the band gap of TiO2 -B host material can be significantly reduced, and as Ni content increases, diffusion contributes more to capacity. According to the electrochemical test, TiO2 -B exhibits excellent electrochemical performance when the Ni element doping content is 2 at% and it is coated with reduced graphene oxide@carbon nanotube (RGO@CNT). At a current density of 100 mA g-1 , NT-2/RGO@CNT discharge specific capacity is as high as 167.5 mAh g-1 , which is 2.36 times of the specific discharge capacity of pure TiO2 -B. It is a very valuable research material for magnesium ion battery cathode materials.

Mesoporogen free synthesis of CuO/TiO2 heterojunction for ultra-trace detection of catechol in water samples

Creating mesoporous architecture on the surface of metal oxides without using pore creating agent is significant interest in electrochemical sensors because these materials act as an efficient electron transfer process between the electrode interface and the analytes. Recent advances in mesoporous titanium dioxide (TiO₂)-based materials have acquired extraordinary opportunities because of their interconnected porous structure could act as a host for doping with various transition metals or heteroatoms to form a new type of heterojunction. Herein, a simple method is developed to synthesize mesoporous copper oxide (CuO) decorated on TiO₂ nanostructures in which homogenous shaped CuO nanocrystals act as dopants decorated on the mesoporous structure of TiO₂, resulting in p-n heterojunction nanocomposite. The TiO₂ particles exhibit a mesoporous structure with a pore volume of about 0.117 cm³/g is capable to load CuO nanocrystals on the surface. As a result, large pore volume 0.304 cm³/g is obtained for CuO-TiO₂ heterojunction nanocomposite with the loading of uniform-shaped CuO nanocrystals on the mesoporous TiO₂. The resulting CuO-TiO₂ nanocomposite on modified glassy carbon (GC) electrode exhibits good electrochemical performance for oxidation of catechol with the observation of strong enhancement in the anodic peak potential at +0.36 V. The decrease in the overpotential for the oxidation of catechol when compared to TiO₂/GC is attributed to the presence of CuO nanocrystals providing a large surface area, resulting in wide linear range 10 nM to 0.57 μM. Moreover, the resultant modified electrode exhibited good sensitivity, selectivity and reproducibility and the sensor could able to determine the presence of catechol in real samples such as lake and river water. Therefore, the obtained CuO-TiO₂ nanocomposite on the modified GC delivered good electrochemical sensing performance and which could be able to perform a promising strategy for designing various metal oxide doped nanocomposites for various photochemical and electrocatalytic applications.

Reversible Zn2+ Insertion in Tungsten Ion-Activated Titanium Dioxide Nanocrystals for Electrochromic Windows

Zinc-anode-based electrochromic devices (ZECDs) are emerging as the next-generation energy-efficient transparent electronics. We report anatase W-doped TiO₂ nanocrystals (NCs) as a Zn²⁺ active electrochromic material. It demonstrates that the W doping in TiO₂ highly reduces the Zn²⁺ intercalation energy, thus triggering the electrochromism. The prototype ZECDs based on W-doped TiO₂ NCs deliver a high optical modulation (66% at 550 nm), fast spectral response times (9/2.7 s at 550 nm for coloration/bleaching), and good electrochemical stability (8.2% optical modulation loss after 1000 cycles).

Confinement of PMo12 in hollow SiO2-PMo12@rGO nanospheres for high-performance lithium storage

High-performance lithium storage was achieved by the confinement of PMo12 in hollow SiO2-PMo12@rGO nanocomposites.

In Operando X-ray Studies of High-Performance Lithium-Ion Storage in Keplerate-Type Polyoxometalate Anodes

Polyoxometalates (POMs) have emerged as potential anode materials for lithium-ion batteries (LIBs) owing to their ability to transfer multiple electrons. Although POM anode materials exhibit notable results in LIBs, their energy-storage mechanisms have not been well-investigated. Here, we utilize various in operando and ex situ techniques to verify the charge-storage mechanisms of a Keplerate-type POM Na₂K₂₃{[(Mo^VI)Mo^VI₅O₂₁(H₂O)₃(KSO₄)]₁₂ [(V^IVO)₃₀(H₂O)₂₀(SO₄)_0.5]}·ca200H₂O ({Mo₇₂V₃₀}) anode in LIBs. The {Mo₇₂V₃₀} anode provides a high reversible capacity of up to ∼1300 mA h g^-1 without capacity fading for up to 100 cycles. The lithium-ion storage mechanism was studied systematically through in operando synchrotron X-ray absorption near-edge structure, ex situ X-ray diffraction, ex situ extended X-ray absorption fine structure, ex situ transmission electron microscopy, in operando synchrotron transmission X-ray microscopy, and in operando Raman spectroscopy. Based on the abovementioned results, we propose that the open hollow-ball structure of the {Mo₇₂V₃₀} molecular cluster serves as an electron/ion sponge that can store a large number of lithium ions and electrons reversibly via multiple and reversible redox reactions (Mo⁶⁺ ↔ Mo¹⁺ and V⁵⁺/V⁴⁺↔ V¹⁺) with fast lithium diffusion kinetics (D_Li⁺: 10^-9-10^-10 cm² s^-1). No obvious volumetric expansion of the microsized {Mo₇₂V₃₀} particle is observed during the lithiation/delithiation process, which leads to high cycling stability. This study provides comprehensive analytical methods for understanding the lithium-ion storage mechanism of such complicated POMs, which is important for further studies of POM electrodes in energy-storage applications.

Self-assembly of metal/semiconductor heterostructures via ligand engineering: unravelling the synergistic dual roles of metal nanocrystals toward plasmonic photoredox catalysis

Metal nanocrystals (NCs) have been recognized as an important class of nanomaterials by virtue of their unique surface plasmon resonance (SPR) effect and pivotal roles as electron traps in photocatalysis. Nevertheless, it is still challenging to unambiguously unravel and simultaneously harness the dual synergistic roles of metal NCs in a single photocatalytic system for solar-to-chemical energy conversion. Herein, an efficient ligand-triggered electrostatic self-assembly strategy was developed to achieve the spontaneous and monodispersed attachment of Au NCs onto 1D WO₃ nanorods (NRs) via pronounced electrostatic attractive interaction, in which tailor-made positively charged Au NCs were closely integrated with negatively charged WO₃ NRs. The intimate integration of Au NCs with WO₃ NRs at the nanoscale could significantly benefit the extraction, separation, and migration of plasmon-induced energetic hot carriers over Au NCs and promote the separation of photogenerated charge carriers over the WO₃ substrate. Such a cooperative synergy stemming from SPR and the electron-withdrawal effects of the Au NCs resulted in distinctly enhanced photoredox catalytic performances for plasmonic photocatalysis under both simulated solar and visible light irradiation. Our study highlights the significance of utilizing a rational interface design between metal NCs and semiconductors for excavating the multifarious roles of metal NCs in substantial solar energy conversion.