Uniform TiO2 Research Articles

Enhanced solar hydrogen evolution by laminated integration of n+p-SiIP/TiO2/Pt inverted pyramid black Si photocathode

The nano/microstructuring of silicon (Si) via chemical methods has garnered significant attention due to its excellent light-trapping capabilities across a wide spectral range. Current research has predominantly focused on the synthesis of pyramidal-shaped microtextures, which enable two reflections on the surface, while largely overlooking the superior light-trapping potential of inverted pyramid silicon (SiIP) microtextures, which theoretically allow for three reflections. Moreover, there has been limited investigation into the application of inverted pyramid black silicon for solar-driven hydrogen evolution. This study reports the synthesis of uniformly arranged inverted pyramid-textured black silicon using the copper-assisted chemical etching (Cu-ACE) method to enhance the efficiency of solar-driven water splitting for hydrogen production. The formation mechanism and the influence of copper-localized surface plasmon resonance (Cu-LSPR) from Cu nanoparticle (NP) byproducts on photoelectrochemical (PEC) activity were systematically analyzed. To reduce sidewall defects and minimize photogenerated carrier recombination, the surface of the SiIP was treated with tetramethylammonium hydroxide (TMAH). A vertical PN junction was developed through ion implantation to reduce the external bias of the SiIP. Additionally, a uniform TiO₂ antireflective layer was deposited via atomic layer deposition (ALD), reducing the average reflectance of the SiIP-T4 to 5.78 % over the 300–1100 nm wavelength range. MoSₓ and Pt NPs were electrodeposited to improve the fill factor and enhance HER kinetics. With optimized catalyst loading, the n+p-SiIP-T4/TiO₂/Pt 80 mC electrode achieved a photocurrent density of 8.0 mA cm−2 at 0 V vs. RHE, an applied bias photon-to-current efficiency (ABPE) of 0.93 % at 0.24 V vs. RHE, and a double-layer capacitance (Cdl) of 91 μF cm−2. The onset potential (Von) was positively shifted by ∼1.13 V to 0.49 V vs. RHE compared to a SiIP photocathode, and the photocathode operated continuously at 0 V vs. RHE for 27 h in an acidic electrolyte. These results demonstrate that SiIP has significant potential for PEC hydrogen evolution, with further performance optimization achievable through structural and surface engineering.

Realization of Atomically Uniform ALD-Al2O3 and TiO2 on SiO2 and GeO2 by UV-Ozone Treatment

Recently, Interface Dipole Modulation (IDM) has been observed in amorphous HfO2/1-Monolayer (ML) TiOx/SiO2 stack structures [1]. To fabricate IDM devices, the thickness of the modulation layer, which is at the atomic layer level, must be precisely controlled to produce a uniform film with high-quality. Therefore, Atomic Layer Deposition (ALD) is one of the promising methods. However, it is difficult to form very thin oxide films on thermally oxidized SiO2/Si or GeO2/Ge by ALD because the oxide film surface is chemically inert. In fact, deposition delays, which is called incubation cycles, and island growth have been observed in the 0-20 cycle range for Al2O3 with Trimethylaluminum (TMA) and H2O as precursors [2, 3]. This is thought to depend on the time it takes for -OH bonds to form on the surface, so surface modification with low damage is necessary. Several surface modification methods exist, especially UV-Ozone (UVO) treatment [4], which has been reported to modify the surface of oxide films such as SiO2 and Al2O3 and has the advantage of being environmentally harmless and compatible with CMOS processes. In this study, the effect of surface modification of insulating films by the UVO method on ALD deposition was investigated for the purpose of controlling atomic layer thickness and producing a uniform oxide film.The samples for the measurement were prepared by the following procedure. First, the chemically cleaned Si or Ge substrate was thermally oxidized to form a ~10 nm thick oxide film. Next, after 15 min of UVO treatment in air at room temperature, the oxide films of Al2O3 or TiO2 were deposited using ALD method on two kinds of substrate. The precursor used for Al2O3 deposition and for TiO2 deposition were TMA and Tetrakis(dimethylamido)titanium (TDMAT), respectively. The oxidant is H2O. The samples were evaluated by Atomic Force Microscopy (AFM), Spectroscopic Ellipsometry (SE) and X-ray Photoelectron Spectroscopy (XPS).Al 2p photoelectron spectra from Al2O3 films deposited after UVO treatment were measured by XPS to confirm the composition of Al2O3. As shown in Fig. 1(a), fitting is possible with two peaks of Al 2p 3/2 and 2p 1/2, which can be said to be stoichiometric Al2O3. Next, Fig. 1(b) shows the photoelectron spectrum of the TiO2 film used as the modulation layer in the IDM device. The Ti 2p spectra, as same as the Al 2p spectra, can be fitted with two peaks, and the photoelectron intensity increases almost in proportion to the number of cycles. The thickness of the ALD film was then calculated from the photoelectron intensity ratio from the Al2O3, TiO2 and the lower oxide film. As shown in Fig. 1(c), there is a delay of one-cycle for the deposition of Al2O3 on SiO2, but it can be seen that the film thickness increases in proportion to the increase in the number of cycles. This is thought to have occurred by the following mechanism. First, UVO treatment breaks the Si-O or Ge-O bonds on SiO2 or GeO2 surface. This dangling bond is the starting point for precursor formation during initial layer formation. Therefore, the H2O during the ALD process is thought to have formed a Si-OH or Ge-OH bond and improved reactivity with methyl groups. The growth per cycle (GPC) can be calculated to be about 0.10 nm/cycle, which is in close agreement with the literature value [5]. Furthermore, SE measurements of Al2O3 films deposited on SiO2 at 50 and 200 cycles yielded thicknesses of 4.83 and 19.97 nm, respectively, which were in close agreement with the GPC calculated using XPS. The TiO2 film deposited on SiO2 also experienced a one-cycle delay similar to that of the Al2O3 film, and the GPC could be calculated to be 0.046 nm/cycle. Furthermore, as shown in Fig. 1(d), UVO treatment increased the average film thickness and reduced the surface roughness from the AFM images. These results indicate that UVO treatment is effective for surface modification of SiO2 and GeO2, and it can be concluded that the ALD method can deposit uniform oxide films without delay.This work was partly supported by TOKYO CITY UNIVERSITY Interdisciplinary Research Center for Nano Science and Technology for instrumental analysis.[1] N. Miyata, Sci. Rep., 8, pp. 8486, 2018.[2] H. Fukumizu et al., Jpn. J. Appl. Phys. 59 016504, 2020.[3] E. Shigesawa et al., Semicond. Sci. Technol. 33 124020, 2018.[4] D. Guo et al., Chem. Phys. Lett., 429, 124–128, 2006.[5] A.W. Ott et al., Thin Solid Films, 292, pp. 135-144, 1997. Figure 1

TiO2 Nanotube Arrays Inside Ultrafine Ti Tubes with an Aspect Ratio of 2500 for Sensing Needles: The Bubble Effect in a Confined Space.

Capillary metal tubes have attracted considerable interest for flexible electronics, portable devices, trace sampling, and detection. Tailoring the microstructure and wettability inside the capillary tubes is of paramount importance, yet it presents great difficulty because of the spatial confinement. Here, the coupling effect is revealed between the fluidic and electric field induced by bubble motion in a confined space during anodic oxidation. By controlling the bubble regeneration and flow rate, uniform and superhydrophilic TiO2 nanotube arrays are developed throughout the inner surface of an ultrafine Ti tube with a diameter of 0.4mm and length of 1000mm, equivalent to an aspect ratio of 2500 that is the largest value being ever reported. The inner surface of a capillary tube is further coated with a polytetrafluoroethylene layer and explored as a sensing needle for liquid detection in terms of concentration and species. This study provides an innovative approach to tailor the microstructure and wettability in a confined space for functional capillary tubes.

Ultrathin Titanium Dioxide Coating Enables High-Rate and Long-Life Lithium Cobalt Oxide.

Lithium cobalt oxide (LCO) has been widely used as a leading cathode material for lithium-ion batteries in consumer electronics. However, unstable cathode electrolyte interphase (CEI) and undesired phase transitions during fast Li+ diffusivity always incur an inferior stability of the high-voltage LCO (HV-LCO). Here, an ultra-thin amorphous titanium dioxide (TiO2) coating layer engineered on LCO by an atomic layer deposition (ALD) strategy is demonstrated to improve the high-rate and long-cycling properties of the HV-LCO cathode. Benefitting from the uniform TiO2 protective layer, the Li+ storage properties of the modified LCO obtained after 50 ALD cycles (LCO-ALD50) are significantly improved. The results show that the average Li+ diffusion coefficient is nearly tripled with a high-rate capability of 125 mAh g-1 at 5C. An improved cycling stability with a high-capacity retention (86.7%) after 300 cycles at 1C is also achieved, far outperforming the bare LCO (37.9%). The in situ XRD and ex situ XPS results demonstrate that the dense and stable CEI induced by the surface TiO2 coating layer buffers heterogenous lithium flux insertion during cycling and prevents electrolyte, which contributes to the excellent cycling stability of LCO-ALD50. This work reveals the mechanism of surface protection by transition metal oxides coating and facilitates the development of long-life HV-LCO electrodes.

Realization of Atomically Uniform ALD-Al2O3 and TiO2 on SiO2 and GeO2 by UV-Ozone Treatment

Thermally oxidized SiO2/Si and GeO2/Ge are difficult to form very thin oxide films by atomic layer deposition (ALD) due to the chemical inertness of the oxide film surface. In this study, the effect of surface modification of insulating films by the UV-Ozone (UVO) method on ALD was investigated with the aim of controlling the atomic layer thickness and producing a uniform oxide film. The results show that UVO treatment can deposit atomic layer-thick films on SiO2 or GeO2 without delay. This may be due to the formation of dangling bonds on the oxide film surface, which improves the reactivity between the surface and the precursor during initial layer formation.

Experimental studies on mechanical properties of Al-7075/TiO2 metal matrix composite and its tribological behaviour

This study explores the fabrication and characterization of an Al-7075/TiO2 metal matrix composites (MMCs) through stir casting, varying TiO2 contents from 2% to 10%. Various tests, including tensile, hardness, and elastic indentation modulus testing, dynamic mechanical analysis, microstructural evaluation, and XRD, were conducted. Tribological analysis involved tribo-pairs of an EN31 disc and a smooth MMCs pin, using a high-temperature Pin-on-disc setup. Microstructural analysis of Al-7075/TiO2 MMCs revealed uniform TiO2 distribution, grain refinement, and enhanced mechanical properties, with XRD confirming structural changes. Tensile tests showed improved ultimate force and stress with increasing TiO2 content, indicating potential for high-strength applications. Hardness assessments demonstrated progressive improvements in Martens, Elastic Indentation, and Vickers Hardness, highlighting the material's suitability for critical wear and tribology applications. The composites exhibited enhanced damping flexural characteristics, especially with 8% TiO2. Maximum and minimum modulus values are reported as 98.9 GPa at 25 °C and 77.3 GPa at 350 °C for 8% TiO2 mix MMC. Tribological performance was improved with lower COF values and wear rates. At elevated temperatures, the wear behavior varied with TiO2 content, influenced by factors such as heat generation and localized welding.

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.

MoSe2 in flower spheres provides abundant active sites for TiO2 photocatalytic degradation of RhB

In this paper, a MoSe2/TiO2 composite photocatalyst was constructed by modifying TiO2 with MoSe2 as a group catalyst. The results showed that pure TiO2 and MoSe2 had no degradation activity for RhB, and the composite catalyst of 0.03 g MoSe2 had the best photocatalytic degradation activity for RhB. Through SEM, TEM, UV-VIS absorption spectrum, transient photocurrent curve, photoluminescence spectrum, and electrochemical impedance spectrum analysis, it can be seen that the excellent performance of 0.03 g MoSe2 composite sample is due to its excellent nanostructure, and uniform TiO2 nanosheets are attached to MoSe2 flower spheres. The active site of RhB photocatalytic degradation was increased, the visible light response and photobiological carrier separation were enhanced, and TiO2 had photocatalytic activity under simulated sunlight.

Comparison of SiO2/TiO2 photocatalysts with different thicknesses synthesized by fluidized bed atomic layer deposition

SiO2/TiO2 core/shell particles are effective photocatalysts, whose performance strongly depends on TiO2 film thicknesses. Fluidized bed atomic layer deposition (FBALD) can precisely control film thickness at the sub-nanometer scale. In this work, TiO2 films with different thicknesses are deposited on SiO2 particles via different ALD cycles at 180 °C in a fluidized bed reactor. TEM images indicate that complete and uniform nanoscale TiO2 films (0.7–6.4 nm, corresponding to 5–50 ALD cycles) are formed on SiO2 surface. The TiO2 film with about 3.9 nm is found to exhibit the highest photocatalytic characteristics by degrading rhodamine-B (RhB) and tetracycline (TC), and the photocatalytic activity is further maintained above 90% after 6 cycles of photocatalytic reaction. Suitable TiO2 film thickness shows minimal charge transfer resistance, resulting in enhanced photon adsorption and separation of electrons and holes, thus improving photocatalytic performance. This work provides an effective way to tune the photocatalytic performance via FBALD.

Self-Cleaning Highly Porous TiO2 Coating Designed by Swelling-Assisted Sequential Infiltration Synthesis (SIS) of a Block Copolymer Template.

Photocatalytic self-cleaning coatings with a high surface area are important for a wide range of applications, including optical coatings, solar panels, mirrors, etc. Here, we designed a highly porous TiO2 coating with photoinduced self-cleaning characteristics and very high hydrophilicity. This was achieved using the swelling-assisted sequential infiltration synthesis (SIS) of a block copolymer (BCP) template, which was followed by polymer removal via oxidative thermal annealing. The quartz crystal microbalance (QCM) was employed to optimize the infiltration process by estimating the mass of material infiltrated into the polymer template as a function of the number of SIS cycles. This adopted swelling-assisted SIS approach resulted in a smooth uniform TiO2 film with an interconnected network of pores. The synthesized film exhibited good crystallinity in the anatase phase. The resulting nanoporous TiO2 coatings were tested for their functional characteristics. Exposure to UV irradiation for 1 h induced an improvement in the hydrophilicity of coatings with wetting angle reducing to unmeasurable values upon contact with water droplets. Furthermore, their self-cleaning characteristics were tested by measuring the photocatalytic degradation of methylene blue (MB). The synthesized porous TiO2 nanostructures displayed promising photocatalytic activity, demonstrating the degradation of approximately 92% of MB after 180 min under ultraviolet (UV) light irradiation. Thus, the level of performance was comparable to the photoactivity of commercial anatase TiO2 nanoparticles of the same quantity. Our results highlight a new robust approach for designing hydrophilic self-cleaning coatings with controlled porosity and composition.

Enhancing Li‐ion Battery Performance through the Integration of Si@TiO2 Core‐Shell Nanoparticles with Natural Graphite

AbstractIn this study, Si@TiO2 core‐shell nanoparticles are synthesized using the peptization technique, resulting in a thin and uniform TiO2 coating layer over silicon nanoparticles. This coating layer serves the purpose of controlling the structural degradation of the silicon nanoparticles. These core‐shell nanoparticles are then reinforced into the natural graphite with the potential to be used as a composite anode material (Graphite/Si@TiO2) for Li‐ion batteries. The developed composite material exhibits an initial specific capacity of ≈675 mAh/g at 0.5 A/g, and after 100 cycles it retains the capacity of 75 %. Compared with Graphite/Si composite anode, the developed composite anode material shows improved cyclic stability. The pre‐and post‐cycling morphological analysis of Graphite/Si and Graphite/Si@TiO2 composite anode reveals the degradation behavior. It is assumed that the TiO2 coating provides a protective shield for the silicon particles, preventing their interaction with the electrolyte and causing less material to deposit over the anode surface. Electrochemical Impedance Spectroscopy (EIS) analysis supports these findings, with the Graphite/Si composite anode exhibiting higher resistance than the Graphite/Si@TiO2 anode. In conclusion, the study demonstrates the potential of using Si@TiO2 core‐shell nanoparticles as a reinforcing agent for natural graphite to develop high‐performance composite anode material for Li‐ion batteries.

(Zn/Co)-ZIFs@TiO2 composite catalysts for oxidative desulfurization: Impacts of Zn2+/Co2+ on TiO2 interactions

Zeolitic imidazolate frameworks (ZIFs)-based catalysts with a high surface area and structural features have received great attention for potential use in complete eliminating refractory thiophenes from fuels. In this study, new composite frameworks of Zn/Co-based ZIFs@TiO2 were investigated for catalytic oxidative desulfurization (ODS) of dibenzothiophene (DBT). The effect of the type of metal centers (Zn2+ or Co2+) in the ZIF-8 and ZIF-67 frameworks on the coordination with TiO2 and eventually on the catalytic performance was targeted to be studied. The results verified that the intensity of effective N-Ti-O bond was influenced by the size of ZIF crystals and the type of metal ions. Over the ZIF-8-M with small size, the aggregation of TiO2 layer decreased the intensity of N-Ti-O bonds. Meanwhile, the lower energy of Zn-N bond and controlled particle size of ZIF-8-W were favorable for partially replacing Zn2+ with Ti4+ and forming extra N-Ti-O species which are supposed to enrich active Ti-peroxo intermediates for the ODS progress. In the case of ZIF-67, unsaturated Co-N bonds further improved DBT uptake. The maximum ODS efficiency of 98.6% was achieved using ZIF-8-W@TiO2 due to the high surface area (SBET=1548 m2/g), uniform TiO2 distribution, and further N-Ti-O bonds. A good recyclability was also verified for the proposed composite catalyst.

Mesoporous TiO2 Single-Crystal Particles from Controlled Crystallization-Driven Mono-Micelle Assembly as an Efficient Photocatalyst.

Mesoporous materials with crystalline frameworks have been widely explored in many fields due to their unique structure and crystalline feature, but accurate manipulations over crystalline scaffolds, mainly composed of uncontrolled polymorphs, are still lacking. Herein, we explored a controlled crystallization-driven monomicelle assembly approach to construct a type of uniform mesoporous TiO2 particles with atomically aligned single-crystal frameworks. The resultant mesoporous TiO2 single-crystal particles possess an angular shape ∼80 nm in diameter, good mesoporosity (a high surface area of 112 m2 g-1 and a mean pore size at 8.3 nm), and highly oriented anatase frameworks. By adjusting the evaporation rate during assembly, such a facile solution-processed strategy further enables the regulation of the particle size and mesopore size without the destruction of the oriented crystallites. Such a combination of ordered mesoporosity and crystalline orientation provides both effective mass and charge transportation, leading to a significant increase in the hydrogen generation rate. A maximum hydrogen evolution rate of 12.5 mmol g-1 h-1 can be realized, along with great stability under solar light. Our study is envisaged to extend the possibility of mesoporous single crystal growth to a range of functional ceramics and semiconductors toward advanced applications.

Fabrication of iron doped titanium dioxide photocatalytic nanocomposite supported by water-quenched blast furnace slag and photocatalytic degradation of wastewater

Metallurgical solid waste blast furnace water quenched slag (WBFS) was employed as carrier materials to prepare Fe–TiO2/WBFS composite photocatalyst using a sol-gel method for improving both the photocatalytic activity and the high-value utilization of metallurgical solid waste. The Fe3+ doping technology was adopted to increase the utilization of solar energy. The influencing factors and photocatalytic activity were systematically evaluated by thermogravimetry/differential thermal analyser (TG-DSC), X-Ray Diffraction (XRD), Brunauer-Emmett-Teller (BET) method, scanning electron microscopy-energy spectrometer (SEM-EDS), X-ray photoelectric spectroscopy (XPS), UV–Vis absorption spectrum and photoluminescence spectra technology through the degradation rate of methylene blue (MB) solution. The results showed that the Fe3+ ions were successfully incorporated into the TiO2 lattice, which had no effect on the crystalline phase of TiO2 and expanded the spectral response range of TiO2 from the ultraviolet region to the visible light region. When the calcination temperature was at 450 °C and the number of Fe–TiO2 sol loading cycles was two times, the photocatalytic activity of Fe–TiO2/WBFS presented the strongest, and the degradation ratio of MB reach the maximum value of 98.9 %. A uniform and dense anatase TiO2 thin film was wrapped on the surface of WBFS. The photocatalytic activity first improved and then weakened with an increase of calcination temperature, Fe3+ doping amounts and the loading cycles of sol. The TiO2 film changed from thin to thick and uneven to uniform, until cracking and spalling phenomenon finally occurred with an increase of Fe–TiO2 sol loading cycle from 1 to 3 times. When the Fe–TiO2/WBFS was reused for four times, the degradation rate of MB could still show 67.4 %, being far higher than that of TiO2/WBFS of 25.4 %.

Surface acoustic wave relative humidity sensor based on GO/TiO2 sensitive film

A surface acoustic wave (SAW) relative humidity (RH) sensor based on graphene oxide (GO)/TiO2 composite sensitive film was prepared. A uniform TiO2 film was deposited on the surface of a SAW resonator by DC reaction sputtering to get a TiO2/SAW sensor. The GO was coated onto the TiO2/SAW by drop-coated to construct the GO/TiO2/SAW sensor. The large specific surface area, abundant hydrophilic functional groups, and highly stable structure of the GO/TiO2 sensitive film are benefit to the improvement of the sensor performances. The prepared GO/TiO2/SAW sensor demonstrated excellent sensitive performances for practical applications, including high sensitivity, fast response and recovery, good repeatability, and good stability.

Vivid-Colored Electrorheological fluids with simultaneous enhancements in color clarity and Electro-Responsivity

HypothesisSurface modification of dielectric materials changes the dipole–dipole interactions under electric fields, thereby controlling the electrorheological (ER) response. The introduction of metal oxides onto mica templates and further coating of dyes is expected to simultaneously improve the color clarity and ER performance. ExperimentsDye-coated TiO2 platelets on mica are synthesized for high-performance colorful ER fluids. A sol–gel method is utilized to grow TiO2 on mica to prepare precursor light-colored mica/TiO2 materials, which are coated with appropriate dyes to enhance the vividness as determined by the Commission Internationale de clairage L*a*b* color system. The color expression and color clarity improvement are explained via the light interference effect and the presence of chromophores. FindingsThe uniform TiO2 layers can be obtained under low pH conditions with controlled nucleation kinetics. The addition of dyes to TiO2 increases the surface area and porosity of ER materials and introduces heteroatoms that act as positive factors. In practical ER applications, dye-coated TiO2-based ER fluids exhibit higher ER performances compared with the corresponding light-colored TiO2-based ER fluids. The vivid-colored ER fluids could provide an easy selection for a wide range of rheological systems requiring a specific magnitude of stress by confirming the color.

Optimal TiO2 Nanoparticles Electron Transporting Layer for Highly Efficient Ambient-atmosphere Fabricated Carbon-based Perovskite Solar Cells

T he electron transporting layer (ETL) is a critical component for carbon-based planar Cs0.17FA0.83Pb(I0.83Br0.17)3 perovskite solar cells (C-PSCs), as it facilitates efficient charge transport between the perovskite material and the cathode. The low temperature processed TiO2 nanoparticles (TiO2 NPs) ETL (150°C) are widely employed in C-PSCs. However, the dispersion of commercial TiO2 NPs in colloid solution is often unstable, leading to particle agglomeration and sedimentation, which negatively affects the performance of C-PSCs. Therefore, it is crucial to achieve stable dispersion of TiO2 NPs in colloid solution before their application as ETL in C-PSCs. Furthermore, the surface properties of the TiO2 ETL such as the uniformity of film significantly impact the overall performance of C-PSCs. The objective of this study was to optimize the TiO2 ETL by investigating the dispersion of TiO2 NPs and varying their concentration in the solution for applying in ambient-atmosphere fabricated C-PSCs. The TiO2 NPs were dispersed in different solvents, including isopropanol, ethanol, and water. As a result, ethanol was the most effective solvent for dispersing TiO2 NPs, demonstrating the best dispersion stability. The concentration of TiO2 NPs in ethanol was then varied between 10-70 mg/ml. The results showed that the optimal concentration was 50 mg/ml, as it produced a high-quality ETL with a more uniform TiO2 film. This optimized TiO2 ETL in C-PSCs resulted in the highest power conversion efficiency (PCE) of 13.10% with FF, VOC, and JSC values of 65.50%, 1.02 V, and 19.52 mA/cm2, respectively.

Instant dispersion of titanium dioxide in waterborne coatings by pinning polyacrylate nanospheres

Titanium dioxide (TiO2) with 200–400 nm diameter is an important pigment in waterborne coatings. The effective dispersion of TiO2 is a significant factor in achieving outstanding coating performance. This paper presents a novel “Instant TiO2” powder by pinning a small number of polyacrylate nanospheres (less than 5 wt%) on TiO2, which can be rapidly dispersed in water within 4 s, similar to instant coffee. The polyacrylate nanospheres copolymerized with Methyl methacrylate (MMA) and 2-Hydroxyethyl methacrylate (HEMA), are connected to the surface of TiO2 via bridge linking of silane coupling agent. This technique prevents TiO2 particles from aggregation and enables rapid dispersion of TiO2 particles in water or waterborne coating. The hydrophilic groups on HEMA facilitate the nanospheres unfolding in water to form a uniform and stable TiO2 slurry, exhibiting a significantly low viscosity (101.2 mPa·s at 200 s−1) when the concentration of TiO2 as high as 70 wt%. The “instant TiO2” denoted as TiO2-MPS-PMH shows excellent coating performance, such as impressive hiding power, and long-term storage stability under 50 °C for 28 days. Pinning polyacrylate nanospheres offers a novel approach to increase dispersion and reduce energy consumption during production in waterborne coatings by the simplified coating process. This technique also provides a potential strategy for achieving the dispersion of TiO2 in various coatings by adjusting the copolymer's components with different wettability.

Synergetic effect of TiO2 coating and oxygen vacancy boosting LiMn2O4 cathode for stable aqueous zinc-ion batteries

LiMn2O4 cathode materials have been regarded as one of the promising candidates for aqueous zinc-ion batteries. However, their actual application is still hindered by the Mn2+ dissolution and structural transformation during the charge/discharge cycling. Herein, we synthesized LiMn2O4 cathode materials with octahedron morphologies and followed introducing oxygen vacancies by the calcination treatment in Ar. Octahedral shape is beneficial to the improvement of cycle stability of LiMn2O4 cathode materials. Oxygen vacancies contribute to the rate performance by improving the electronic conductivity. Nevertheless, the cycling stability of LiMn2O4 cathode materials with oxygen vacancies is not satisfactory. So, we proposed the synergistic strategy of TiO2-coating LiMn2O4 and oxygen vacancies. TiO2@(LMO-A0.5) sample with uniform thin TiO2 coating was obtained by regulating the hydrolysis reaction of tetrabutyl titanate. Consequently, TiO2@(LMO-A0.5) exhibits the impressive rate capability and cycling stability (as high as 85 mAh/g and 91.22% capacity retentions after 200 cycles at 0.1 A g−1) as the cathode materials for aqueous zinc-ion batteries. The synergetic development of multiple strategies may endow LiMn2O4 cathode materials with magical perspectives in aqueous zinc-ion batteries.