Ultrathin TiO2 Research Articles

Surface-dominated sodium storage enabled by TiO2 nanosheets with 84 % exposure of (0 0 1) facets for high-performance Na-ion battery anodes

Anatase titanium dioxide (TiO2) has garnered enormous attention as a promising anode material for sodium-ion batteries (SIBs), owing to its non-toxicity, superior structural stability, and cost-effectiveness. Nevertheless, its intrinsic low electrical conductivity poses a substantial challenge to its practical applications. Here, the ultrathin TiO2 nanosheets were obtained. The TiO2 nanosheets with a thickness of ∼8 nm and exposed 84 % (001) facet. The exposed (001) crystal facets and ultrathin nanosheet structure provide abundant active sites for Na-ion adsorption, shortens ion diffusion pathways, enhances reaction kinetics, and significantly boosts the pseudocapacitive effect. This synergistic strategy of exposed (001) facet with nanosheets structure leads to an exceptional capacity of 177.1 mAh/g at 0.1 A/g, and 59 % capacity retention at 5 A/g. This work will contribute to the understanding of facet-dependent electrochemical behavior anode materials for high-performance SIBs.

Sunflower-disc-inspired vertical growth of 2D ZnIn2S4 on ultra-thin TiO2: Constructing a 3D porous photocatalytic glass film for ultra-efficient organic pollutant degradation

Thin-film catalysts show immense potential for photocatalytic applications due to their versatility and ease of recovery. However, their stability is often compromised by detachment and poor surface utilization. In this study, inspired by the architecture of sunflower discs, we present a novel 3D porous photocatalytic film by vertical growth of 2D ZnIn2S4 on ultra-thin TiO2/glass for ultra-efficient degradation of organic pollutants. Crucially, ZnIn2S4 nanosheets were vertically grown on the stable TiO2/glass substrate to form a 3D porous structure, and the vertical growth mechanism is demonstrated by DFT. In contrast, when directly grown on glass, only aggregated ZnIn2S4 spheres formed. The enhanced surface area of the 3D ZnIn2S4 structure allows for maximum light absorption, while the rapid separation and transfer of photogenerated charges follow a Z-scheme charge transfer mechanism in the ZnIn2S4/TiO2 heterojunction. This synergy significantly improves the photocatalytic performance, surpassing most previously reported semiconducting films.

S/N Co-Doped Ultrathin TiO2 Nanoplates as an Anode Material for Advanced Sodium-Ion Hybrid Capacitors.

Anatase titanium dioxide (TiO2) has emerged as a potential anode material for sodium-ion hybrid capacitors (SICs) in terms of its nontoxicity, high structure stability and cost-effectiveness. However, its inherent poor electrical conductivity and limited reversible capacity greatly hinder its practical application. Here, ultrathin TiO2 nanoplates were synthesized utilizing a hydrothermal technique. The electrochemical kinetics and reversible capacity were significantly improved through sulfur and nitrogen co-doping combined with carbon coating (SN-TiO2/C). Sulfur and nitrogen co-doping generated oxygen vacancies and introduced additional active sites within TiO2, facilitating accelerated Na-ion diffusion and enhancing its reversible capacity. Furthermore, carbon coating provided stable support for electron transfer in SN-TiO2/C during repeated cycling. This synergistic strategy of sulfur and nitrogen co-doping with carbon coating for TiO2 led to a remarkable capacity of 335.3 mAh g-1 at 0.1 A g-1, exceptional rate property of 148.3 mAh g-1 at 15 A g-1 and a robust cycling capacity. Thus, the SN-TiO2/C//AC SIC delivered an impressive energy density of 177.9 W h kg-1. This work proposes an idea for the enhancement of reaction kinetics for energy storage materials through a synergistic strategy.

Catalytically ultrathin titania coating to enhance energy storage and release of aluminum hydride via atomic layer deposition

Aluminum hydride (AlH3) has attracted much attention owing to its extraordinary hydrogen storage performance, yet AlH3 is prone to hydrogen release reaction during long-term storage, leading to a decrease in energy and hindering its practical application. Herein, AlH3 particles are stabilized by catalytically ultrathin TiO2 coating via atomic layer deposition (ALD), the hydrogen content of which is controllable and reduces only 0.0026 wt% per ALD cycle of TiO2 coating. 30 cycles of TiO2 (2.4 nm) coated AlH3 exhibits a peak decomposition temperature of 203.42 ℃ and decomposition activation energy of 112.21 kJ/mol, which are 7.83 ℃ and 22.64 kJ/mol higher than those of bare AlH3. The hydrogen content loss of TiO2 coated AlH3 under hydrothermal aging conditions is much lower than that of bare AlH3 due to the passivation of defects on native Al2O3 by forming inert Al2O3 and catalytic TiO2 double-shell coating structure. TiO2 coated AlH3 exhibits enhanced combustion performance with stronger flame radiation intensity compared to bare AlH3. The density functional theory calculations indicate that the contact between AlH3 and TiO2 can weaken the strength of Al-H ion bond and promote the release of hydrogen. Our work offers a feasible method for simultaneously improving the stability and energy release of AlH3.

Mass Transport Limitations in Plasmonic Photocatalysis.

The interpretation of mechanisms governing hot carrier reactivity on metallic nanostructures is critical, yet elusive, for advancing plasmonic photocatalysis. In this work, we explored the influence of the diffusion of molecules on the hot carrier extraction rate at the solid-liquid interface, which is of fundamental interest for increasing the efficiency of photodevices. Through a spatially defined scanning photoelectrochemical microscopy investigation, we identified a diffusion-controlled regime hindering the plasmon-driven photochemical activity of metallic nanostructures. Using low-power monochromatic illumination (<2 W cm-2), we unveiled the hidden influence of mass transport on the quantum efficiency of plasmonic photocatalysts. The availability of molecules at the solid-liquid interface directly limits the extraction of hot holes, according to their nature and energy, at the reactive spots in Au nanoislands on an ultrathin TiO2 substrate. An intriguing question arises: does the mass transport enhancement caused by thermal effects unlock the reactivity of nonthermal carriers under steady state?

Accelerated Charge Transfer through Interface Chemical Bonds in MoS2/TiO2 for Photocatalytic Conversion of Lignocellulosic Biomass to H2.

Solar photocatalytic H2 production from lignocellulosic biomass has attracted great interest, but it suffers from low photocatalytic efficiency owing to the absence of highly efficient photocatalysts. Herein, we designed and constructed ultrathin MoS2-modified porous TiO2 microspheres (MT) with abundant interface Ti-S bonds as photocatalysts for photocatalytic H2 generation from lignocellulosic biomass. Owing to the accelerated charge transfer related to Ti-S bonds, as well as the abundant active sites for both H2 and ●OH generation, respectively, related to the high exposed edge of MoS2 and the large specific surface area of TiO2, MT photocatalysts demonstrate good performance in the photocatalytic conversion of α-cellulose and lignocellulosic biomass to H2. The highest H2 generation rate of 849 μmol·g-1·h-1 and apparent quantum yield of 4.45% at 380 nm was achieved in α-cellulose aqueous solution for the optimized MT photocatalyst. More importantly, lignocellulosic biomass of corncob, rice hull, bamboo, polar wood chip, and wheat straw were successfully converted to H2 over MT photocatalysts with H2 generation rate of 10, 19, 36, 29, and 8 μmol·g-1·h-1, respectively. This work provides a guiding design approach to develop highly active photocatalysts via interface engineering for solar H2 production from lignocellulosic biomass.

Optical and photocatalytic properties of sol-gel AuNPs@TiO2 ultrathin film

The optical and photocatalytic properties of ultrathin TiO2 layers were investigated in order to stress out the effect of nanoscale thickness on the film properties. The method relies on monitoring localized surface plasmon resonance (LSPR) through UV–visible spectroscopy and enhanced Raman spectroscopy (SERS). To achieve this, TiO2 thin films were prepared using the sol–gel method on high density gold nanoparticles arrays (AuNPs). TiO2 anatase phase was obtained by thermal annealing and confirmed by XRD, HRTEM, and SERS. Our results reveal that the thinnest TiO2 layers consist of compact TiO2NPs of small dimensions and lower porosity compared to the thicker TiO2NPs layers. Subsequently, these thin TiO2 layers functionalizing AuNPs were applied in plasmonic photocatalysis, specifically for the N-demethylation of methylene blue in the visible range. When comparing layers with the same thickness (a single deposition layer with layers prepared by stacking various thin layers), the stacked layers demonstrated enhanced photocatalytic activity. This novel, stable form of TiO2 has the potential to open numerous opportunities in the fields of photocatalysis and detection.

An innovative strategy towards highly efficient flame-retardant silk

As a luxurious textile raw material, silk fiber (SF) and its products are widely favored by consumers because of their elegant appearance and excellent comfort. However, their flammability causes potential fire risks and hazards in daily fires and has gained significant attention in recent years. In this work, an ultrathin and uniform TiO2, Al2O3, and ZnO nanofilms with thicknesses of 1 ∼ 200 nm (less than one in a hundred of SF diameter) were deposited on the surface of a silk fabric (SFR) by atomic layer deposition (ALD). By tuning the types of metal oxides and nanofilm thickness, the modified SFR quickly self-extinguished, and its pristine weave was completely preserved after exposure to a flame in a torch burn test, representing superior performance compared to numerous conventional coating technologies reported with higher loadings. An expanded charcoal residue formed on the surface of the modified SFR, acting as a physical barrier that enhanced flame retardancy. Furthermore, the modified SFR showed excellent laundering durability, which helps improve the service life of the fabric. Most importantly, the nanofilms had a negligible impact on the intrinsic comfort and other comprehensive properties of the silk.

Activation of polyimide by oxygen plasma for atomic layer deposition of highly compact titanium oxide coating

Titanium oxide (TiO2) coated polyimide has broad application prospects under extreme conditions. In order to obtain a high-quality ultra-thin TiO2 coating on polyimide by atomic layer deposition (ALD), the polyimide was activated by in situ oxygen plasma. It was found that a large number of polar oxygen functional groups, such as carboxyl, were generated on the surface of the activated polyimide, which can significantly promote the preparation of TiO2 coating by ALD. The nucleation and growth of TiO2 were studied by x-ray photoelectron spectroscopy monitoring and scanning electron microscopy observation. On the polyimide activated by oxygen plasma, the size of TiO2 nuclei decreased and the quantity of TiO2 nuclei increased, resulting in the growth of a highly uniform and dense TiO2 coating. This coating exhibited excellent resistance to atomic oxygen. When exposed to 3.5 × 1021 atom cm−2 atomic oxygen flux, the erosion yield of the polyimide coated with 100 ALD cycles of TiO2 was as low as 3.0 × 10−25 cm3/atom, which is one order less than that of the standard POLYIMIDE-ref Kapton® film.

Silver-infused TiO2 nanowires and unveiling their potential for superior wastewater dye remediations.

Silver infused ultrathin TiO2 nanowires (NWs) were synthesized via a single step solvothermal approach. The crystallinity, structure, and morphology were determined to understand the physicochemical nature of the nanocomposites. The catalytic efficiency of the newly synthesized nanocatalysts was tested for the textile waste treatment taking methylene blue (MB) as model pollutant under solar light irradiations. Nearly 96% photodegradation efficiency for MB was achieved within 20 min. Furthermore, the recyclability of the photocatalyst was also studied, and the material remained stable and effective up to four consecutive runs. RESEARCH HIGHLIGHTS: Precise size-controlled synthesis of Ag-incorporated titania nanowires (ATNWs) Controlled aspect ratios, with tunable lengths and diameters (100-3 nm) via precursor and surfactant optimization Demonstrated ATNWs' efficiency in degrading toxic dye, methylene blue (MB) 96% photodegradation efficiency for MB achieved within 20 min using 3 nm thick annealed TiO2 NWs Recyclability efficiency of photocatalyst, which remained stable and effective for up to four consecutive runs.

Nanoflower-like TiO2/CoAl-layered double hydroxide direct Z-scheme for boosted photocatalytic CO2 conversion

Direct Z-scheme heterojunction (DZH) has promising potential in photocatalytic carbon dioxide reduction (PCR) owing to its unusual charge transfer pathway, exceptional charge separation efficiency, and high redox ability. Herein, ultrathin TiO2 nanosheets (NSs) have been employed as a substrate for the in-situ growth of CoAl layered double hydroxide (LDH) NSs to fabricate nanoflower-like TiO2/CoAl-LDH (TCA) DZH. The unconsolidated heterostructure is beneficial for active site exposure and mass transfer, and the inherent alkalinity of CoAl-LDH promoted the adsorption of CO2, synergistically boosting the process of PCR reaction in the TCA system. Simulated calculation and in-situ analysis jointly demonstrate the unique electron transfer processes during hybridization and photoexcitation. The resulting (-)TiO2/(+)CoAl-LDH interfacial electric field and DZH further lead to efficient separation of photogenerated charges of TCA. In the solid–gas system, the optimized TCA heterojunction exhibits a competitive PCR activity (76.18 μmol g−1h−1 for CO production rate) increase of 31.6 and 20.3 times compared to TiO2 and CoAl-LDH, respectively.

Ultrathin TiO2 Coatings via Atomic Layer Deposition Strongly Improve Cellular Interactions on Planar and Nanotubular Biomedical Ti Substrates.

This work aims to investigate the chemical and/or structural modification of Ti and Ti-6Al-4V (TiAlV) alloy surfaces to possess even more favorable properties toward cell growth. These modifications were achieved by (i) growing TiO2 nanotube layers on these substrates by anodization, (ii) surface coating by ultrathin TiO2 atomic layer deposition (ALD), or (iii) by the combination of both. In particular, an ultrathin TiO2 coating, achieved by 1 cycle of TiO2 ALD, was intended to shade the impurities of F- and V-based species in tested materials while preserving the original structure and morphology. The cell growth on TiO2-coated and uncoated TiO2 nanotube layers, Ti foils, and TiAlV alloy foils were compared after incubation for up to 72 h. For evaluation of the biocompatibility of tested materials, cell lines of different tissue origin, including predominantly MG-63 osteoblastic cells, were used. For all tested nanomaterials, adding an ultrathin TiO2 coating improved the growth of MG-63 cells and other cell lines compared with the non-TiO2-coated counterparts. Here, the presented approach of ultrathin TiO2 coating could be used potentially for improving implants, especially in terms of shading problematic F- and V-based species in TiO2 nanotube layers.

High photocatalytic performance over ultrathin 2D TiO2 for CO2 reduction to alcohols.

We report a noble-metal-free photocatalyst, ultrathin TiO2 with atomic layer thickness, which is a potential catalyst for CO2 photoreduction. An excellent liquid-product yield of 463.9 μmol gcat-1 in 8 h with 98% selectivity to alcohols was achieved, owing to sufficient surface defects favoring CO2 adsorption/activation.

Dual active sites of single-atom copper and oxygen vacancies formed in situ on ultrathin TiO2(B) nanosheets boost the photocatalytic dehalogenative C–C coupling synthesis of bibenzyl

The combination of photocatalytic dehalogenation of halogenated aromatics and C–C coupling synthesis of valuable organics is an interesting method for the elimination of pollutants and synthesis of valuable chemicals.

A road for macroporous silicon stabilization by ultrathin ALD TiO2 coating

Ultrathin TiO2 layers deposited by ALD can successfully passivate macroporous silicon while keeping photocatalytic activity.

Asymmetric iron–titanium pairs within ultrathin TiO2 nanosheets enable high-efficiency nitrate reduction to ammonia

Monodispersed iron atoms were integrated into ultrathin TiO2 nanosheets, resulting in the formation of asymmetric Fe–Ti pairs. The asymmetric Fe–Ti pairs, characterized by delocalized electrons, synergistically promote the nitrate reduction process.

(Poster Award - 3rd Place) Photocatalysis of TiO2 Nanosheets Prepared by the Cellulose Nanofiber Template

Two-dimensional material inspired tremendous research interest by its unique structure and specific property different from bulk material, which could benefit various applications such as optics, electronics, and chemistry. However, most documented processes for 2D materials are complicated with a lengthy process. We introduced the cellulose nanofiber (CNF) extracted from agricultural waste rice straws, which inherently possesses many functional groups, e.g., hydroxyl group, and carboxylate group, making it a terrific template method candidate. Besides, aerogel composed of cellulose nanofiber provides many surface and layered structures that facilitate the adhesion of titanium isopropoxide to form a uniform coating layer, which hydrolyzed to TiO2. The cellulose nanofiber serves as a template and could be removed entirely in an easy thermal process by thermogravimetric analysis; meanwhile, we can transform the original amorphous TiO2 nanosheet into an anatase phase which is flavored in the photocatalyst field. Atomic force microscopy (AFM) results spotted a stacked ultrathin TiO2 nanosheet with a thickness of less than 5 nm for each layer, and the lateral size could reach micron size. For the RhB dye degradation test, TiO2 nanosheets could decompose the 10 ppm RhB solution within 30 mins with a reaction rate of 0.065 min-1. In conclusion, we combine the CNF template and hydrolysis process, proposing a simple 2D TiO2 nanosheets

Effect of ethylene glycol chelated on ultrathin TiO2(B) nanosheets on the photocatalytic selective benzyl alcohol oxidation

The two-dimensional (2D) photocatalysts have been paid intensive attention in catalysis due to their excellent activity, which was greatly improved by the higher exposure of active sites and a facile reaction platform, and the separation efficiency of charge carriers. Herein, TiO2(B) nanosheets, which were synthesized via solvothermal method in ethylene glycol, could photocatalytically oxidize benzyl alcohol to benzaldehyde with high selectivity. The study revealed that the material's photocatalytic performance is highly influenced by the surface-chelated ethylene glycol. The pristine TiO2(B) was effective in selectively photocatalytic oxidizing benzyl alcohol, achieving a 94.5 % conversion, while the conversion decreased to 55 % after the elimination of the surface ethylene glycol. The presence of ethylene glycol on the surface of TiO2(B) nanosheets benefits the transfer of photogenerated charge carriers and improves charge separation efficiency. It is favorable for the selective formation of singlet oxygen (1O2) species, which results in enhanced photocatalytic activity and selectivity. We believe that our findings can shed light on the importance of the surface species and properties of photocatalysts in photocatalysis, and pave an avenue for the design and preparation of high-efficiency photocatalysts with unique surface properties.

Self-Organized Plasmonic Nanowire Arrays Coated with Ultrathin TiO2 Films for Photoelectrochemical Energy Storage

Self-Organized Plasmonic Nanowire Arrays Coated with Ultrathin TiO₂ Films for Photoelectrochemical Energy Storage

Ultrathin TiO2(B) nanosheets-decorated hollow CoFeP cube as PMS activator for enhanced photocatalytic activity

A novel TiO2(B)/phosphidated CoFe Prussian blue analogs (CoFeP) photocatalyst with core–shell structure was synthesized by hydrothermal method for the activation of peroxymonosulfate (PMS) to degrade TC under solar light. TiO2(B), an ultrathin two-dimensional (2D) layered material, is widely used in photocatalysis. However, the low light absorption efficiency and slow electron mobility limit the application of TiO2(B) in photocatalysis. Here, TiO2(B) was in-situ grown on the surface of phosphidated CoFe Prussian blue analogs (CoFeP). The composites with a core–shell structure can activate peroxymonosulfate (PMS) to degrade tetracycline (TC) under solar light. The optimized TiO2(B)/CoFeP heterojunction achieves a TC degradation rate of 94 % within 5 min, due to that it effectively suppresses the recombination of photogenerated charges and improves light absorption ability. The phosphorization of CoFePBA (CoFe Prussian blue analogs) not only promoted the formation of hollow structures but improved the carrier mobility between TiO2(B) and CoFeP. At the same time, the rapid redox cycle of Fe and Co metal ions promoted the activation of PMS and the rapid degradation of TC. This work provides a new core–shell TiO2(B)/CoFeP heterojunction for sustainable water purification via PMS activation.