TiO2 Plane Research Articles

Lead-Free Cs2AgBiBr6/TiO2 S-Scheme Heterojunction for Efficient Photocatalytic Antibiotic Rifampicin Degradation.

Exploring efficient and stable halide perovskite-based photocatalysts is a great challenge due to the balance between the photocatalytic performance, toxicity, and intrinsic chemical instability of the materials. Here, the environmentally friendly lead-free perovskite Cs2AgBiBr6 confined in the mesoporous TiO2 crystal matrix has been designed to enhance the charge carrier extraction and utilization for efficient photocatalytic rifampicin degradation. The as-prepared Cs2AgBiBr6/TiO2 catalyst was stable in air for over 500 days. An S-scheme heterojunction was formed between the (004) plane of Cs2AgBiBr6 and the (101) plane of TiO2 through the Bi-O-Br bonds. The built-in electric field at the interface efficiently promoted the photoinduced charge separation and carrier extraction. The Cs2AgBiBr6/TiO2-200 showed a 92.83% degradation efficiency of rifampicin within 80 min under simulated sunlight illumination (AM 1.5G 100 mW cm-2). This work offers an effective way for the construction of halide perovskite-based photocatalysts with high photocatalytic performance, good stability, and low toxicity simultaneously.

650 ps SET speed in Ge2Sb2Te5 phase change memory induced by TiO2 dielectric crystal plane

AbstractCrystallization speed of phase change material is one of the main obstacles for the application of phase change memory (PCM) as storage class memory in computing systems, which requires the combination of nonvolatility with ultra‐fast operation speed in nanoseconds. Here, we propose a novel approach to speed up crystallization process of the only commercial phase change chalcogenide Ge2Sb2Te5 (GST). By employing TiO2 as the dielectric layer in phase change device, operation speed of 650 ps has been achieved, which is the fastest among existing representative PCM, and is comparable to the programing speed of commercial dynamic random access memory (DRAM). Because of its octahedral atomic configuration, TiO2 can provide nucleation interfaces for GST, thus facilitating the crystal growth at the determinate interface area. Ti–O–Ti–O four‐fold rings on the (110) plane of tetragonal TiO2 is critical for the fast‐atomic rearrangement in the amorphous matrix of GST that enables ultra‐fast operation speed. The significant improvement of operation speed in PCM through incorporating standard dielectric material TiO2 in DRAM paves the way for the application of phase change memory in high performance cache‐type data storage.image

Enhanced CO2 conversion with CH4 for greenfuel generation using coke-neutral nickel-loaded fibrous silica titania catalysts

This study reveals a groundbreaking advancement in utilizing carbon dioxide (CO2) for syngas production through methane (CH4) dry reforming using Fibrous Silica Titania (FST) as a support, loaded with different (1%, 3%, and 5%) nickel dosages. FST is distinguished by its fibrous structure, maintains a stable temperature, facilitates the confinement and dispersion of active metal, and is exceptionally effective at preventing carbon deposition. For a thorough examination of the new catalysts, characterization methods including XRD, FESEM, EDX mapping, N2 physisorption, FTIR-KBr, H2-TPR, and CO2-TPD were employed. Importantly, TEM lattice fringes verified the existence of XRD peaks and planes of Ni (111), Ni (200), and TiO2 (101). Aspects such as O-H stretching, Si-O-Si asymmetry, vibrations caused by external Si-OH groups, and Si-O-Si bending were identified using FTIR-KBr analysis. The study ingeniously identified the superior (3Ni/FST) catalyst, which exhibited moderate basicity sites on the CO2-TPD at approximately 350 °C. The catalyst converted nearly 100% CH4 at 750 °C with minimal coke production and 80% CO2 at 850 °C. Surprisingly, the 3Ni/FST catalyst demonstrated remarkable stability during a 72 h TOS stability test at 650 °C, effectively preventing coke-forming side reactions such as CO disproportionation, CO hydrogenation, CO2 and CH4 cracking with syngas ratio around unity and little coke production. The FST support exhibited exceptional attributes for low temperature carbon neutral CH4 reforming.

The nature of crystal facet effect of TiO2-supported Pd/Pt catalysts on selective hydrogenation of cinnamaldehyde: electron transfer process promoted by interfacial oxygen species.

Supported noble metal nanocatalysts typically exhibit strong crystal plane dependent catalytic behavior, but their working mechanism is still unclear. Herein, using anatase TiO2 with well-exposed crystal facets of {101}, {100} and {001} as a prototype support, Pd- and Pt-based supported TiO2 nanocatalysts (TiO2-Pd and TiO2-Pt) were prepared by chemical reduction with NaBH4 as reducer, and they showed a distinct metal-dependent crystal facet effect in the selective hydrogenation of cinamaldehyde (CAL). For Pd-based nanocatalysts, most Pd species on the {100} plane of TiO2 are present in the oxidized form with positive charges and unexpectedly show higher reactivity than the Pd species in the zero-valence state on the {101} and {001} planes. On the contrary, Pt species on all three crystal planes of TiO2 show zero-valence state, with relatively low conversion, but much better selectivity for hydrogenation of a CO bond than Pd-based catalysts. Well-designed experiments manipulating the stability and type of surface oxygen species confirmed that the essence of the crystal facet effect of the catalyst support actually creates a unique nanoconfined interface at the molecular level to construct a surface p-band intermediate state (PBIS), which provides a new alternative channel for surface electron transfer and consequently accelerates the reaction kinetics.

Can HOCl be superficially stabilized on an electrocatalyst as proposed in the active chlorine mechanism involving •OH radicals?: Beyond the Cl2 evolution

According to Comninellis’ proposal on water oxidation, anodes physisorbing active oxygen readily form •OH radicals to develop electrocombustion processes, while electrode surfaces forming the so-called higher oxide MO x+1 chemisorb active oxygen, being more prone to perform the O2 evolution reaction (OER). Here, we adopt a similar premise to account for the active chlorine mechanism (ACM), assuming that the capacity of an electrocatalyst to physisorb/chemisorb active oxygen determines the type of chlorine species formed and stabilized. Density Functional Theory (DFT) calculations are conducted to evaluate the stability of HOCl, OCl and OCl --H+ species oxidant species on Boron Doped Diamond (BDD), and rutile-type surfaces (110 plane) of SnO2, TiO2, PbO2, RuO2, and IrO2, in the absence and presence of H2O molecules. The computed relaxed models reveal that SnO2 and PbO2 physisorbing active oxygen are only able to stabilize OCl-ads species on pentacoordinated transition metal atoms (M5c); whereas RuO2, and IrO2 chemisorbing active oxygen produce Clads- on an adjacent M5c active site. The BDD surface is the only surface able to maintain the HOCl stability with and without H2O solvation. Thus, it is proposed that BDD and TiO2, physisorbing active oxygen, preferentially adopt a 2-electron transfer step to generate (HOCl)ads; while SnO2 and PbO2, with moderate physisorption, also follow a 2-electron transfer step but produced (OCl-)ads and (H+)ads, thus dissociating (HOCl)ads. RuO2 and IrO2, preferentially forming the so-called higher oxide MOx+1, adopt a 3-electron transfer step to either produce (OCl)ads, or (O)ads + (Cl)ads, where there is a more equal competition towards the oxygen evolution.

Selective hydrogenation of crotonaldehyde over Ir/TiO2 catalysts: Unraveling the metal-support interface related reaction mechanism

For the supported catalysts for the selective hydrogenation of α, β - unsaturated aldehyde with H2, tailoring of metal - support interfacial effect to improve reaction performance is a significant but challenging subject. In this work, we regulated both the size regimes of the Ir deposits (single atom, nanocluster and nanoparticle) and the crystal plane of anatase TiO2 (TiO2(101), TiO2(100) and TiO2(001)) so as to alter the Ir-TiOx interfacial properties, in order to unravel reaction mechanism of selective hydrogenation of crotonaldehyde over the Ir/TiO2 catalysts. Both the activity and selectivity to crotyl alcohol increased as the Ir size grew from single atom to nanoparticle, ascribed to high Ir0 content, high concentration of surface defects and prominent H-spillover effect on the Ir nanoparticles. Moreover, the in situ Fourier transform infrared spectroscopy (FTIR) and density functional theory (DFT) calculations demonstrated that an end-on CO adsorption mode for crotonaldehyde molecule was favored at the Ir-TiOx interface particularly at high H coverage, which thus facilitated the hydrogenation of CO bond to form crotyl alcohol. Moreover, the highest reactivity of the Ir nanoparticles was evidenced by the lowest reaction barrier. These results explicitly demonstrate that larger metal nanoparticles and adsorption geometry of the reactant at the metal - support interface are vital for improved catalytic performance, which would shed light on the ingenious catalyst design.

Enhanced photoelectrochemical performance of NiS-modified TiO2 nanorods with a surface charge accumulation facet.

Photoelectrochemical (PEC) water splitting for hydrogen production technology is considered as one of the most promising solutions to energy shortage and environmental remediation. TiO2/NiS nanorod arrays were successfully prepared using hydrothermal deposition followed by the successive ionic layer adsorption and reaction (SILAR) method. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and photoluminescence (PL) spectra characterization studies indicate the successful deposition of NiS on TiO2 NRs. The NiS deposition on TiO2 was optimized by controlling the impregnation cycle. The optimal sample exhibits a photocurrent density of 1.16 mA cm-2 at 0.6 V vs. Ag/AgCl, which is a 1.9-fold enhancement over that of pristine TiO2 nanorod arrays. The enhanced photoelectrochemical performance can be attributed to two aspects. On the one hand, the (101) crystal plane of rutile TiO2 is the facet where photogenerated holes accumulate and is an efficient active plane for the oxygen evolution reaction; on the other hand, NiS is a narrow band gap semiconductor, and its deposition on TiO2 nanorods can further promote the separation and transport of photogenerated charge carriers.

100% N2O inhibition in photocatalytic NOx reduction by carbon particles over Bi2WO6/TiO2 Z-scheme heterojunctions

The chemically inert property of nitrous oxide (N2O) has made it difficult to be reduced to benign dinitrogen during (photo) selective catalytic reduction (SCR) of NOx. The introduction of oxygen vacancies and BrØnsted acid sites to thermal catalysts is found to effectively inhibit N2O formation. However, the efficiency is still far from satisfactory and the inhibition of N2O in photocatalytic selective reduction of NOx has not been investigated yet. Herein, 100% inhibition of N2O formation during photo-SCR of NOx with carbon particles is successfully achieved via the fabrication of Bi2WO6/TiO2 Z-scheme heterojunction photocatalyst. The completely inhibited N2O formation is attributed to the rapid charge separation and stronger N2O adsorption on the (101) plane of TiO2 according to the density functional theory calculations and experimental results. The presence of water vapor prolongs the reaction time for NOx photo-reduction of carbon particles but has no significant effect on carbon oxidation rate. Introduction of heterostructure interface effectively accelerates photo-induced charge carrier separation and transfer, thereby enhancing photocatalytic efficiency for NOx reduction with carbon particles. The optimized 0.2 Bi2WO6/TiO2 (molar ratio) composite achieves the highest formal electron/photon quantum efficiency of 0.036, which is 3.3 times that of TiO2. The results provide an alternative perspective on the catalyst fabrication via the simple heterojunction materials for toxic byproduct control in the field of pollutants removal.

The Preparation of {001}TiO2/TiOF2 via a One-Step Hydrothermal Method and Its Degradation Mechanism of Ammonia Nitrogen.

{001}TiO2/TiOF2 photocatalytic composites with a high activity {001} crystal plane were prepared by one-step hydrothermal methods using butyl titanate as a titanium source and hydrofluoric acid as a fluorine source. X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), raman spectroscopy, N2 adsorption-desorption curve (BET), UV-Vis diffuse absorption spectroscopy (UV-Vis DRS), X-ray photoelectron spectroscopy (XPS), and fluorescence spectroscopy (PL) were used to evaluate the structure, morphology, specific surface area, optical properties, and photocarrier separation ability of {001}TiO2/TiOF2. Ammonia nitrogen was taken as the target pollutant, and the degradation performance of the catalyst was investigated. The results show that hydrofluoric acid improves the content of {001} crystal plane of TiO2 with high activity; it also improves the specific surface area and dispersion of the composite material and adjusts the ratio of {001}TiO2 to TiOF2 in the composite material to enhance the absorption capacity of the composite material and reduce the band gap width of the composite material. The degradation rate of ammonia nitrogen by 100 mg F15 is 93.19% when the initial concentration of ammonia nitrogen is 100 mg/L and pH is 10. Throughout the reaction process, the {001}TiO2/TiOF2 composite produces superoxide anion radical (·O2−) and hydroxyl radical (·OH) to oxidize NH3·H2O and generate N2 accompanied by a small amount of NO3− and NO2−.

Effect of B2O3, K2O and Li2O as modifiers on crystal phase transition and crystallite growth of TiO2 in calcination of titanyl sulfate

Thermal phase transformation and crystal growth in calcination of titanyl sulfate with addition of B2O3, K2O and Li2O have been studied, and the structure and morphology of TiO2 product has been characterized by XRD, SEM, TEM and size analyzer. It is found that B3+ ions being doped interstitially into crystal lattice of rutile TiO2 tend to form compound of TiB0.024O2 with TiO2, which leads to increase in unit cell volume and henceforth, an increase in growth rate of the crystal plane (110) or reduction in growth rate of crystal plane (001). Change in growth rate in different crystal planes contributes to development of the plate shape and rod shape microcrystals and improvement in grain sphericity. Doping of K2O tends to inhibit the transformation of crystal form and inhibit particle sintering at high temperatures mainly by adsorption of the dopants onto crystal plane (110) and plane (100) of rutile TiO2. Li2O, which is mainly adsorbed on the surface of rutile TiO2, is found to have a weak effect on crystal phase transformation. The apparent activation energy for crystal growth of rutile TiO2 doped with B2O3, K2O and Li2O has been calculated to be 73.16 ​kJ/mol, 103.21 ​kJ/mol, and 187.24 ​kJ/mol respectively.

MIL-101(Cr)-decorated Ti/TiO2 anode for electrochemical oxidation of aromatic pollutants from water

Hydroxyl radicals (•OH) generated on anode play a vital role in electrochemical oxidation (EO) of organic pollutants for water treatment. Inspired by the four-electron oxygen evolution reaction (OER), we supposed an anode-selection strategy to stabilize deeply oxidized states (*O and *OOH) which are beneficial to generating •OH. To verify the hypothesis, a candidate anode component (MIL-101(Cr), a well-known metal-organic framework with active variable-valence transition metal centers) was used to coat Ti/TiO2 plate to fabricate anodes. Compared to TiO2(101) plane on undecorated anode surface, fast and complete removal of aniline and phenol, and improved energy utilization were achieved on MIL-101(Cr)-coated-Ti/TiO2 anode. Mechanism investigation, including pollutant degradation pathways, showed the predominate contribution (69.60%–75.13%) of •OH in pollutant mineralization. Density functional theory (DFT) computations indicated Cr site in MIL-101(Cr) was more conducive to stabilizing *O and *OOH, leading to thermodynamical spontaneous generation of •OH. This work opens up an exciting avenue to explore •OH production, and supplies a useful guidance to the development of anode materials for EO process.

General embedded cluster protocol for accurate modeling of oxygen vacancies in metal-oxides.

The O vacancy (Ov) formation energy, EOv, is an important property of a metal-oxide, governing its performance in applications such as fuel cells or heterogeneous catalysis. These defects are routinely studied with density functional theory (DFT). However, it is well-recognized that standard DFT formulations (e.g., the generalized gradient approximation) are insufficient for modeling the Ov, requiring higher levels of theory. The embedded cluster method offers a promising approach to compute EOv accurately, giving access to all electronic structure methods. Central to this approach is the construction of quantum(-mechanically treated) clusters placed within suitable embedding environments. Unfortunately, current approaches to constructing the quantum clusters either require large system sizes, preventing application of high-level methods, or require significant manual input, preventing investigations of multiple systems simultaneously. In this work, we present a systematic and general quantum cluster design protocol that can determine small converged quantum clusters for studying the Ov in metal-oxides with accurate methods, such as local coupled cluster with single, double, and perturbative triple excitations. We apply this protocol to study the Ov in the bulk and surface planes of rutile TiO2 and rock salt MgO, producing the first accurate and well-converged determinations of EOv with this method. These reference values are used to benchmark exchange-correlation functionals in DFT, and we find that all the studied functionals underestimate EOv, with the average error decreasing along the rungs of Jacob's ladder. This protocol is automatable for high-throughput calculations and can be generalized to study other point defects or adsorbates.

Lattice origin of few-layer edge-on MoS2@TiO2 octahedral clusters for piezoelectric enhancement

Imaging the lattice origin of few-layer edge-on MoS2/TiO2 heterostructure at different growth stages could provide direct information for understanding the mechanism of its enhanced piezoelectric property. Via modifying the substrate surface to grow anatase TiO2 nanoparticles with truncated octahedron structure, few-layer MoS2 was exquisitely grown along the {101} basal planes of TiO2 by Van der Waals contact, and finally form an edge-on structure at the top edge of TiO2 nanoparticles due to steric hindrance. The vertical growth of few-layer MoS2 on the TiO2 surface endows not only better electronic contact between MoS2 and TiO2 substrate for fast electrons transfer but also high structure stability of piezoelectric properties. The piezocatalytic degradation ability is enhanced with the increase of hydrothermal reaction time, and the MoS2/TiO2-24 h sample exhibits the highest piezocatalytic activity under dark condition which demonstrates a high removal efficiency of 96.0% Rhodamine B within 60 min. This study establishes a relationship between the piezoelectric property of few-layer edge-on MoS2/TiO2 heterostructure and its growth mechanisms, and sheds light on the rational design of electric contact between transition metal dichalcogenide and semiconductor with specific crystal plane which is significant to the improvement of carrier separation and transport.

Significant Improvement of Photocatalytic Activity of TiO2/g–C3N4 Composite Synthesized by the Aiding of Hydrothermal Method

g–C3N4 nanosheets were first synthesized by calcining the mixture of hydrochloric acid-pretreated melamine and ammonium chloride. Then, by the aiding of solvothermal method and hydrofluoric acid as morphology modifier, 001-TiO2/g–C3N4 (TCN-X, [Formula: see text], 3, 2, 1) nanocomposites were synthesized using g–C3N4 nanosheets and tetrabutyl titanate, with the mass ratio of g–C3N4 to TiO2 was 5:1, 3:1, 2:1 and 1:1, respectively. The as-synthesized samples were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscopy, Fourier transform infrared spectroscopy, nitrogen adsorption–desorption method, ultraviolet–visible diffuse reflectance spectrum, photoluminescence spectrum, etc. Their photocatalytic properties were evaluated under visible light irradiation with rhodamine B (RhB) as the target pollutant. The results reveal that the TCN-3 composites had a large specific surface area of 67.38[Formula: see text]m2/g and consisted of g–C3N4 nanosheets and anatase TiO2 crystals about 10–20[Formula: see text]nm in size. The (001) crystal planes of TiO2 can be easily observed in TCN-X composites. All TiO2/g–C3N4 composites exhibited excellent photocatalytic activity compared with the pure g–C3N4 did. The photocatalytic property of TCN-X samples varied with the mass ratio of g–C3N4to TiO2, and TCN-3 presented the optimum photocatalytic performance. In total, 50[Formula: see text]mg of TCN-3 completely degraded 50[Formula: see text]mL and 100[Formula: see text]mL of RhB solution (10[Formula: see text]mg/L) in 15[Formula: see text]min and 40[Formula: see text]min, respectively. The reaction rate constant of TCN-3 was 6.7 times as large as that of pure g–C3N4. TCN-3 also presented outstanding activity for the photocatalytic degradation of the colorless tetracycline solution. The significant improvement in photocatalytic activity of TCN-3 was attributed to the evenly distribution of TiO2 on g–C3N4, the enhanced specific surface area and the construction of 001-TiO2/g–C3N4 heterojunction between the g–C3N4 nanosheets and the (001) crystal planes of anatase TiO2, which greatly reduced the recombination rate of the photo-generated electron and hole.

Oriented assembly of metal-organic frameworks and deficient TiO2 nanowires directed by lattice matching for efficient photoreversible color switching

The photoreversible color switching system (PCSS) is attracting increasing attention for use in alleviating energy crisis and environmental problems. We report a robust PCSS in which lattice matching enables bottom-up oriented assembly between metal-organic frameworks (MOFs) and inorganic nanocrystals (INCs), two distinct entities that differ drastically in structure and function. Specifically, cubic-phase Prussian blue (PB) of a framework backbone is spontaneously attached to rutile TiO2 nanowires in a defined orientation triggered by the lattice matching between the (001) plane of TiO2 and the (222) plane of PB. Ultraviolet light irradiation accelerates the photoelectron transport within the oriented TiO2/PB system and enables fast photo switching. The derived TiO2/PB paper can be ranked as one of the best light-printing papers in literature because of its high resolution (∼ µm) and capability to be repeatedly written for >100 times without significant loss of contrast. The ultrathin TiO2 nanowires are rich in oxygen and Ti vacancies, which allow visible- and sunlight-light printing. Density functional theory calculations suggest that the [Fe(CN)6]4− ligand from the PB attaches preferentially to the (110) surface of TiO2 to give the ordered TiO2/PB assembly. The findings demonstrate the strong versatility of particles-mediated assembly in advanced materials design.

Surprising stability of polar (001) surfaces of the Mott insulator GdTiO3

Using first-principles techniques based on hybrid density functional calculations, we study the stability, energetics, and electronic structure of the (001) surface of the Mott insulator GdTiO3 (GTO), which has an orthorhombic perovskite structure. Interestingly, we find the bare unreconstructed (but relaxed) polar surface terminated by a TiO2 plane to be very stable with a low surface energy (71 meV/Å2). As a test for stability of the TiO2 termination against reconstructions, we studied the influence of an H adatom. Hydrogen is known to form strong bonds with surface O atoms and passivate surface states, but contrary to expectations, hydrogen does not lead to a lowering of the GTO surface energy. We explain the energetics based on the surface electronic structure. We also address the interaction between the TiO2-terminated GTO surface and the high-density two-dimensional electron gas (2DEG) that can be formed at an SrTiO3 (STO)/GTO heterointerface. Unlike the situation in STO/LaAlO3 (LAO) heterostructures, where the LAO surface acts as a sink for electrons, the GTO surface does not drain electrons away from the 2DEG.

Design of rutile nanospheres decorated rGO/β-CD nanoflakes composite: A sustainable electrocatalyst for effective non-enzymatic determination of L-Tyrosine

A novel and facile electrochemical sensing device has fabricated based on TiO2@rGO/β-CD nanocomposite altered GCE for trace-level detection of L-Tyrosine. The crystalline nature, functional groups, shape morphology of nanocomposite were confirmed using various characterization techniques. The FE-SEM results expose TiO2 nanospheres were strongly bind with flake-like rGO/β-CD composite. The layer-like morphology of GO was modified to a flake-like structure with reduction in occurrence of dextrin linkages attached to GO layers with host-guest supramolecular interaction. These features further confirmed using HR-TEM analysis. The TiO2 nanospheres exist in flake-like surface of rGO/β-CD composite that significantly enhanced the active superficial area, conductivity of nanocomposite. The fabricated electrode shows superior and improved electrocatalytic oxidation, high sensitivity and low detection limits towards L-Tyr. It was ascribed to synergistic recombination between the edge planes of carbon-based materials and TiO2 exist in nanocomposite. The TiO2@rGO/β-CD modified GCE response over wide dynamic range (0.01–1920 μM), LOD (7.6 nM) for L-Tyr detection. Additionally, it displayed notable repeatability, reproducibility and storage stability. Moreover, the practicability of the proposed sensor in Apple juice, Tyr tablet and recovery results satisfactory. All strategies proposed TiO2@rGO/β-CD nanocomposite as sustainable electrocatalyst that could be explored as excellent candidate for detecting the L-Tyrosine in real sample analysis.

Enhanced performance of photocatalytic treatment of Congo red wastewater by CNTs-Ag-modified TiO2 under visible light.

In order to improve the treatment efficiency of printing and dyeing wastewater, the carbon nanotubes-silver-modified-titanium dioxide (CNTs-Ag-TiO2, CAT) ternary composite was prepared by a mechanical mixing method. It was found that the morphology of the prepared CAT sample was uniformly coated with strips of CNTs, speckled Ag, and lumpy TiO2. The (002) crystal plane of CNTs, the (101) crystal plane of TiO2, and the (111) crystal plane of Ag were observed, which possessed functional groups such as Ti-OH and Ti-O-C, indicating that the prepared CAT sample had photocatalytic reaction sites. The visible light utilization of titanium dioxide can be improved. The treatment effect of different proportions of CNTs-Ag-TiO2 on Congo red wastewater was tested, and the results showed that the optimum degradation effect of Congo red wastewater was CNTs: Ag = 10:1, and the doped amount of CNTs/Ag was 15%, and the removal rate of Congo red wastewater could reach 100% within 140 min. The excellent removal effect of CAT ternary composite on Congo red wastewater provided a new idea and way for the modification of TiO2 and its composites for the potential of organic dyes degradation.

UV illumination-enhanced ultrasensitive ammonia gas sensor based on (001)TiO2/MXene heterostructure for food spoilage detection

Ammonia has been used as an important marker to indicate the extent of food spoilage. However, current gas sensors for ammonia suffer from either insufficient sensitivity and selectivity or unsatisfactory levels of automation, impeding their practical application for on-site and real-time monitoring of food quality. To overcome these limitations, we propose here the design of a sensing material by in-situ growing (001)TiO2 onto a two-dimensional transition-metal carbide (Ti3C2Tx, MXene). In this design, TiO2 with a highly active (001) crystal plane provides efficient photogeneration under UV irradiation, while Ti3C2Tx can store holes through Schottky junction formed at the interface with TiO2, which greatly promotes the separation of electron-hole pairs, thereby enhancing ammonia sensing performance. By further introducing UV light for electron excitation, the (001)TiO2/Ti3C2Tx based sensor shows 34 times higher sensitivity for ammonia (30 ppm) than that of Ti3C2Tx. The density functional theory further revealed that the (001) plane of TiO2 and Ti3C2Tx composite configuration exhibited the highest adsorption affinity towards ammonia. Finally, an integrated circuit alarm system including near-field communication and a micro-controller system was designed to detect the decay process of fresh pork, fish, and shrimp. We believe such a sensing technology holds great promise in food quality monitoring.

The effects of TiO2 crystal-plane-dependent Ir-TiOx interactions on the selective hydrogenation of crotonaldehyde over Ir/TiO2 catalysts

Three supported Ir/TiO2 catalysts, containing anatase TiO2 nanocrystals with predominantly exposed {101}, {100}, and {001} planes, were subjected to various pre-treatments (H2 reduction at different temperatures and O2 re-oxidation) and then tested in the vapor phase selective hydrogenation of crotonaldehyde. The pre-treatments significantly altered the Ir-TiOx interactions, including the morphologies and electronic properties of the Ir species and their surface acidity. These interactions were also closely related to the crystal planes of TiO2, which further supported the observed reaction behaviors of the various Ir/TiO2 catalysts. The best performance was obtained using the Ir/TiO2-{101} catalyst pre-reduced at 300 °C, owing to its higher Ir0 surface concentration and moderate surface acidity compared to the other catalysts. Moreover, these findings indicated the synergistic role of the Ir-TiOx interface in the reaction, as the interfacial sites were responsible for the adsorption/activation of H2 and the C=O bond in the crotonaldehyde molecule. However, pre-reduction at 400 °C resulted in partial encapsulation of the Ir particles by TiOxvia strong metal-support interactions, which is unfavorable for the catalytic reaction owing to the loss of Ir-TiOx interfacial sites.