Tuning oxygen vacancy content in TiO2 nanoparticles to enhance the photocatalytic performance

Environmental Charge-Mediated Nanopiezocatalysis for Sonodynamic Therapy

Piezocatalysis garners growing attention in sonodynamic therapy (SDT). However, its mechanism remains controversial due to the prominent but conflicting theories of energy band and piezoelectric effect. The former just focuses on the role of carriers, while the latter emphasizes only the contribution of screening charges. This divergence greatly hinders the development of piezocatalysis-mediated SDT. Here, we demonstrate the combined action of carriers (electrons/holes) and screening charges on piezocatalysis and propose a new piezocatalytic model (termed environmental charge-mediated nanopiezocatalysis) based on defective BaTiO3@TiO2 piezoelectric nanoparticles (D-B@T). The synergistic effect of carriers and screening charges endows D-B@T with superior reactive oxygen species generation capability under ultrasound stimulation and enables effective SDT treatment of bacterial pneumonia in vivo. This work offers an insightful understanding of piezocatalysis and guides the rational design of high-performance piezoelectric nanosonosensitizers for SDT.

A Supercapacitor Diode with High Rectification Ratio Induced by Carbon and Oxygen Vacancies

Supercapacitor-based ionic diode (CAPode) integrates ion-electron dual charge carriers in one device, thus possessing great potential in bioabiotic systems such as intelligent implantable devices and human-computer interfaces. Herein, we present a high-performance CAPode that takes carbon-modified anatase titania (C@TiO2-x) nanowires with abundant oxygen vacancies as the negative electrode. The modification of the thin carbon layer improves the conductivity and cycling stability of TiO2 nanowires, and more attractively, introduces a large amount of oxygen vacancies in them, enhancing the electrochemical kinetics and rectification capability of the C@TiO2-x nanowires. Consequently, the C@TiO2-x electrode exhibits a high rectification ratio I (RRI) of 204.6 and a rectification ratio II (RRII) of 98.3% at 1 mV s-1. Also, the assembled CAPode exhibits an RRI of 99.1 at 8 mV s-1 and a wide operating window of -1.0 to 1.4 V. Therefore, the assembled CAPodes successfully demonstrate the functionality of both "AND" and "OR" gates, revealing the potential to process information. The above results show that the rectification capability of CAPodes can be comparable to that of conventional ionic diodes and highlight the importance of modulating the electrochemical ion storage behavior to improve the rectification performance of CAPodes.

Interfacially engineered metal oxide nanocomposites for enhanced photocatalytic degradation of pollutants and energy applications

Escalating global energy demands and environmental pollution necessitate innovative solutions for sustainable development. Conventional methods often prove inadequate, driving research towards advanced materials and technologies. This review critically analyzes existing industrial wastewater treatment approaches, highlighting their merits and limitations, before focusing on the recent advancements in metal oxide-based nanocomposite photocatalysis for both pollutant degradation and energy generation. Moreover, the structural, electronic, and optical properties of metal oxides (MOx) are elucidated. The review discusses various MOx synthesis routes and their nanocomposites and elucidates the underlying photocatalytic mechanisms, emphasizing the influence of operational parameters on photocatalytic efficiency. Moreover, it explores how MOx can be utilized for photocatalytic energy generation, in addition to their role in pollutant degradation. Furthermore, it delves into the synergistic effects achieved by combining MOx with complementary nanomaterials (carbon-based structures, polymers, non-metals, semiconductors, and metal sulfides) to create hybrid nanocomposites with enhanced photocatalytic activity for both applications. A cost analysis and SWOT analysis are presented to assess the economic and technological feasibility of this trend. This comprehensive overview provides valuable insights for developing efficient, sustainable, and scalable wastewater treatment solutions using MOx-based nanocomposites, ultimately contributing to improved environmental remediation and water resource management while simultaneously exploring opportunities for energy production.

Ultrasensitive detection of doxycycline enabled by oxygen vacancy modulated TiO2 nanotubes

TiO2 nanotubes rich in oxygen vacancies (Ov), which were successfully fabricated on Ti foils, were used as the working electrode of a photoelectrochemical (PEC) sensor. The TiO2 nanotube electrode optimized with abundant Ov demonstrated a remarkable photocurrent density of 1.03 mA/cm2, which is approximately 2.9 times higher than that of the TiO2 nanotube electrode. When applied to the detection of DOC, this electrode exhibited a wide linear detection range spanning from 0.1 to 100 μM and achieved an exceptionally low detection limit of 0.043 μM with a signal-to-noise ratio of 3. Furthermore, comparative experiments indicated that the Ov-enriched TiO2 nanotube electrode exhibited excellent anti-interference capabilities and long-term stability, ensuring the accuracy and reliability of the detection outcomes. The superior detection performance is primarily attributed to two aspects: on one hand, Ov act as electron traps, facilitating the capture and transfer of photogenerated electrons, effectively prolonging the lifetime of these carriers; on the other hand, Ov also serves as active sites, enhancing the adsorption of DOC molecules and reaction kinetics, further amplifying the detection signal. This work offers a theoretical and experimental groundwork for the rapid monitoring of residual antibiotics.

Unique S-scheme structures in electrostatic self-assembled ReS2-TiO2 for high-efficiency perfluorooctanoic acid removal

Perfluorinated compounds (PFCs), recognized as persistent organic pollutants, resist degradation in the environment due to the high bond energy of the C-F. Increasing carrier density via adopting electrostatic self-assembly strategy has been shown to effectively cleave C-F bonds. In this work, a unique S-scheme structure was fabricated by combining oppositely charged semiconductors, TiO2 and ReS2, through electrostatic self-assembly. The resulting 2 % ReS2-TiO2 composite achieved a photodegradation efficiency of 98 % for perfluorooctanoic acid (PFOA), considerably higher than the 62 % efficiency observed for pure TiO2. Additionally, the 2 % ReS2-TiO2 composite demonstrated broad applicability for the removal of other PFCs. The introduction of ReS2, with a lower work function than TiO2, could generate an internal electric field (IEF) to facilitate electron transfer from TiO2 to ReS2 under continuous irradiation and thereby enhance charge separation efficiency.

Electron Beam Irradiation-Induced Defects Enhance Pt-TiO2 Photothermal Catalytic Degradation in PAEs: A Performance and Mechanism Study

Phthalic acid esters (PAEs), ubiquitous semi-volatile organic compounds (SVOCs) in indoor environments, pose adverse effects on human health. However, their degradation mechanisms and pathways remain unclear. Herein, we developed an efficient photothermal catalyst by introducing defects (oxygen vacancies, OVs) on TiO2 (P25) surfaces via electron beam irradiation technology with different irradiation doses (100, 300, 500, and 700 kGy). The TiO2 with defects was employed as a support to prepare Pt-TiO2 catalysts for the photothermal degradation of di (2-ethylhexyl) phthalate (DEMP) and dimethyl phthalate (DMP), two representative PAEs. TiO2 pre-treated with a 300 kGy irradiation dose supported the Pt catalyst (Pt-Ti-P-300) and presented the optimal catalytic performance for DEMP and DMP degradation. Characterization results confirmed that OVs were successfully introduced to the catalysts. Meanwhile, OVs induced by electron beam irradiation expanded the light absorption range and improved the generation and separation of photogenerated carriers, which significantly enhanced the catalytic activity of the catalysts for PAE degradation. Importantly, the degradation mechanism and pathway of DMP were further explored by using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and gas chromatography-mass spectrometry (GC-MS). These findings provide important insights into the electron beam irradiation-mediated regulation of catalysts and the photothermal catalytic removal of PAEs in indoor environments.

Purification and Value-Added Conversion of NOx under Ambient Conditions with Photo-/Electrocatalysis Technology

As primary air pollutants from fossil fuel combustion, the excess emission of nitric oxides (NOx) results in a series of atmospheric environmental issues. Although the selective catalytic reduction technology has been confirmed to be effective for NOx removal, green purification and value-added conversion of NOx under ambient conditions are still facing great challenges, especially for nitrogen resource recovery. To address that, photo-/electrocatalysis technology offers sustainable routes for efficient NOx purification and upcycling under ambient temperature and pressure, which has received considerable attention from scientific communities. In this review, recent advances in photo-/electrocatalysis technology for the purification and value-added conversion of NOx are critically summarized. The target products and reaction mechanisms for NOx conversion systems, together with the responsible active sites, are discussed, respectively. Then, the realistic environmental practicability is proposed, including strict performance evaluation criteria and application in realistic conditions for NOx purification and upcycling by the application of photo-/electrocatalysis. Finally, the current challenges and future opportunities are proposed in terms of catalyst design, NOx conversion enhancement, reaction mechanism understanding, practical application conditions, and product separation techniques.

Solid CaCO3 Formation in Glioblastoma Multiforme and its Treatment with Ultra-Nanoparticulated NPt-Bionanocatalysts

BACKGROUND

Glioblastoma multiforme (GBM), the most prevalent form of central nervous system (CNS) cancer, stands as a highly aggressive glioma deemed virtually incurable according to the World Health Organization (WHO) standards, with survival rates typically falling between 6 to 18 months. Despite concerted efforts, advancements in survival rates have been elusive. Recent cutting-edge research has unveiled bionanocatalysts with 1% Pt, demonstrating unparalleled selectivity in cleaving C-C, C-N, and C-O bonds within DNA in malignant cells. The application of these nanoparticles has yielded promising outcomes.

OBJECTIVE

The objective of this study is to employ bionanocatalysts for the treatment of Glioblastoma Multiforme (GBM) in a patient, followed by the evaluation of obtained tissues through electronic microscopy.

METHODS

Bionanocatalysts were synthesized using established protocols. These catalysts were then surgically implanted into the GBM tissue through stereotaxic procedures. Subsequently, tissue samples were extracted from the patient and meticulously examined using Scanning Electron Microscopy (SEM).

RESULTS AND DISCUSSION

Detailed examination of biopsies via SEM unveiled a complex network of small capillaries branching from a central vessel, accompanied by a significant presence of solid carbonate formations. Remarkably, the patient subjected to this innovative approach exhibited a three-year extension in survival, highlighting the potential efficacy of bionanocatalysts in combating GBM and its metastases.

CONCLUSION

Bionanocatalysts demonstrate promise as a viable treatment option for severe cases of GBM. Additionally, the identification of solid calcium carbonate formations may serve as a diagnostic marker not only for GBM but also for other CNS pathologies.

Antibiofilm Activity of PDMS/TiO2 against Candida glabrata through Inhibited Hydrophobic Recovery

Coatings with antibiofilm properties are desirable for biomedical applications. Titanium dioxide (TiO2) has been explored as an antimicrobial agent in materials development primarily due to it being an excellent photocatalyst. Candida glabrata (C. glabrata) is an emerging human fungal pathogen with known high resistance to oxidative stress. Here, we fabricated a polydimethylsiloxane/titanium dioxide (PDMS/TiO2) nanocomposite coating and tested its antibiofilm activities against C. glabrata. The resulting nanocomposite exhibited >50% reduction in C. glabrata biofilm formation with 2.5 wt % TiO2 loading, even in the dark. Through ROS detection and surface characterization, the antibiofilm activity was attributed to the synergistic interaction of TiO2 nanoparticles with the PDMS matrix, which resulted in the impediment of hydrophobic recovery. This work provides a design strategy to develop antibiofilm coatings against C. glabrata.

An enhanced non-enzymatic electrochemical sensor based on the Bi2S3-TiO2 nanocomposite with HNTs for the individual and simultaneous detection of 4-nitrophenol and nitrofurantoin in environmental samples

In the current era of rapid population growth, there has been an increase in resource consumption and the subsequent release of organic pollutants into water bodies by various industries. To address this issue, we have developed a nanocomposite material, Bi2S3-TiO2/HNTs, for electrochemical sensors capable of simultaneously detecting nitrofurantoin (NFT) and 4-nitrophenol (4-NP) contaminants. The nanocomposite material was synthesized using a novel one-pot sol-gel method, and its structural morphology was characterized using techniques such as FE-SEM, FT-IR, HR-TEM, and XRD. The electrochemical sensor exhibited a remarkably low limit of detection (3.2 nM for NFT and 3.5 nM for 4-NP) and a wide concentration range from 0 μM to 260 μM for both NFT and 4-NP, demonstrating their high sensitivity and accuracy for pollutant detection, and furthermore its potential for real-world application was assessed considering pond and tap water as real samples.

Nano-TiO2/TiN Systems for Electrocatalysis: Mapping the Changes in Energy Band Diagram across the Semiconductor|Current Collector Interface and the Study of Effects of TiO2 Electrochemical Reduction Using UV Photoelectron Spectroscopy

TiO2 is the most widely used material in photoelectrocatalytic systems. A key parameter to understand its efficacy in such systems is the band bending in the semiconductor layer. In this regard, knowledge on the band energetics at the semiconductor/current collector interface, especially for a nanosemiconductor electrode, is extremely vital as it will directly impact any charge transfer processes at its interface with the electrolyte. Since direct investigation of interfacial electronic features without compromising its structure is difficult, only seldom are attempts made to study the semiconductor/current collector interface specifically. This work utilizes ultraviolet photoelectron spectroscopy (UPS) to determine the valence band maximum (EVBM) and Fermi level (EF) at different depths in a nano-TiO2/TiN thin-film system reached using an Ar gas-clustered ion beam (GCIB). By combining UPS with GCIB depth profiling, we report an innovative approach for truly mapping the energy band structure across a nanosemiconductor/current collector interface. By coupling it with X-ray photoelectron spectroscopy (XPS), correlations among chemistry, chemical bonding, and electronic properties for the nano-TiO2/TiN interface could also be studied. The effects of TiO2 in situ electrochemical reduction in aqueous electrolytes are also investigated where UPS confirmed a decrease in the semiconductor work function (WF) and an associated increase in n-type Ti3+ centers of nano-TiO2 electrodes post use in a 0.2 M potassium chloride solution. We report the use of UPS to precisely determine the energy band diagrams for a nano-TiO2/TiN thin-film interface and confirm the increase in TiO2 n-type dopant concentrations during electrocatalysis, promoting a much more comprehensive and intuitive understanding of the TiO2 activation mechanism by proton intercalation and therefore further optimizing the design process of efficient photocatalytic materials for solar conversion.

Simultaneously activating molecular oxygen and surface lattice oxygen on Pt/TiO2 for low-temperature CO oxidation

Developing high-performance Pt-based catalysts with low Pt loading is crucial but challenging for CO oxidation at temperatures below 100 °C. Herein, we report a Pt-based catalyst with only a 0.15 wt% Pt loading, which consists of Pt-Ti intermetallic single-atom alloy (ISAA) and Pt nanoparticles (NP) co-supported on a defective TiO2 support, achieving a record high turnover frequency of 11.59 s-1 at 80 °C and complete conversion of CO at 120 °C. This is because the coexistence of Pt-Ti ISAA and Pt NP significantly alleviates the competitive adsorption of CO and O2, enhancing the activation of O2. Furthermore, Pt single atom sites are stabilized by Pt-Ti ISAA, resulting in distortion of the TiO2 lattice within Pt-Ti ISAA. This distortion activates the neighboring surface lattice oxygen, allowing for the simultaneous occurrence of the Mars-van Krevelen and Langmuir-Hinshelwood reaction paths at low temperatures.

Synergistic effects of oxygen vacancies and mesoporous structures in amorphous C@TiO2 for photocatalytic CO2 reduction

In this study, the theoretical calculations proves that the combination of oxygen vacancy and amorphous carbon films in TiO2 (VO-CT) can effectively reduce the energy bandgap and work function. The minimum Gibbs free energies required for the CO2RR reaction of VO-CT are 0.20 eV, which is lower than pure TiO2. The amorphous c@TiO2 nanomaterials with oxygen vacancy and mesoporous structures (VO-MCT) are prepared with the P123 surfactant as the template and oxalic acid as an inducer. The electron paramagnetic resonance indicates the presence of abundant oxygen vacancy defects in the samples. UV-vis spectra indicate that the mesoporous structure enhances light absorption capacity. The photocatalytic CO2 reduction tests show that the highest conversion rates for CH4 and CO of VO-MCT are 14 μmol g-1 h-1 and 10.66 μmol g-1 h-1, respectively. The electron consumption rate of VO-MCT is 12.43 times higher than that of commercial TiO2 (P200).

Oxygen Vacancy-Enriched CoFe2O4 for Electrochemically Sensitive Detection of the Breast Cancer CD44 Biomarker

Enhancing the selectivity of detection methods is essential to distinguish breast cancer biomarker cluster of differentiation 44 (CD44) from other species and reduce false-positive or false-negative results. Here, oxygen vacancy-enriched CoFe2O4 (CoFe2O4-x) was crafted, and its implementation as an electrochemical electrode for the detection of CD44 biomarkers has been scrutinized. This unique electrode material offers significant benefits and novel features that enhance the sensitivity and selectivity of the detection process. The oxygen vacancy density of CoFe2O4-x was tuned by adjusting the mass ratios of iron to cobalt precursors (iron-cobalt ratio) and changing annealing atmospheres. Electrochemical characterization reveals that, when the iron-cobalt ratio is 1:0.54 and the annealing atmosphere is nitrogen, the as-synthesized CoFe2O4-x electrode manifests the best electrochemical activity. The CoFe2O4-x electrode demonstrates high sensitivity (28.22 μA (ng mL)-1 cm-2), low detection limit (0.033 pg mL-1), and robust stability (for 11 days). Oxygen vacancies can not only enhance the conductivities of CoFe2O4 but also provide better adsorption of -NH2, which is beneficial for stability and electrochemical detection performance. The electrochemical detection signal can be amplified using CoFe2O4-x as a signal probe. Additionally, it is promising to know that the CoFe2O4-x electrode has shown good accuracy in real biological samples, including melanoma cell dilutions and breast cancer patient sera. The electrochemical detection results are comparable to ELISA results, which indicates that the CoFe2O4-x electrode can detect CD44 in complex biological samples. The utilization of CoFe2O4-x as the signal probe may expand the application of CoFe2O4-x in biosensing fields.

S-scheme heterojunction Cu-porphyrin/TiO2 nanosheets with highly efficient photocatalytic reduction of CO2 in ambient air

Directly capturing CO2 in ambient air and converting it into value-added fuels using photocatalysis is a potentially valuable technology. In this study, Cu-porphyrin (tetrakis-carboxyphenyl porphyrin copper, CuTCPP) was innovatively anchored on the surface of TiO2 (titanium dioxide) nanosheets to form an S-scheme heterojunction. Based on this, a photocatalytic reaction system for stably converting CO2 in ambient air into value-added fuels at the gas-solid interface was constructed without addition of sacrificial agents and alkaline liquids. Under the illumination of visible light and sunlight, the evolution rate of CO is 56 μmol·g-1·h-1 and 73 μmol·g-1·h-1, respectively, with a potential CO2 conversion rate of 35.8 % and 50.4 %. The enhanced of photocatalytic performance is attributed to the introduction of CuTCPP, which provides additional active sites, significantly improves capture capacity of CO2 and the utilization of electrons. Additionally, the formation of S-scheme heterojunction expands the redox range and improves the separation efficiency of photo-generated charges.

Mechanocatalytic Synthesis of Ammonia by Titanium Dioxide with Bridge-Oxygen Vacancies: Investigating Mechanism from the Experimental and First-Principle Approach

Mechanochemical ammonia (NH3) synthesis is an emerging mild approach derived from nitrogen (N2) gas and hydrogen (H) source. The gas-liquid phase mechanochemical process utilizes water (H2O), rather than conventional hydrogen (H2) gas, as H sources, thus avoiding carbon dioxide (CO2) emission during H2 production. However, ammonia yield is relatively low to meet practical demand due to huge energy barriers of N2 activation and H2O dissociation. Here, six transition metal oxides (TMO) such as titanium dioxide (TiO2), iron(III) oxide (Fe2O3), copper(II) oxide (CuO), niobium(V) oxide(Nb2O5), zinc oxide (ZnO), and copper(I) oxide (Cu2O) are investigated as catalysts in mechanochemical N2 fixation. Among them, TiO2 shows the best mechanocatalytic effect and the optimum reaction rate constant is 3.6-fold higher than the TMO-free process. The theoretical calculations show that N2 molecules prefer to side-on chemisorb on the mechano-induced bridge-oxygen vacancies in the (101) crystal plane of TiO2 catalyst, while H2O molecules can dissociate on the same sites more easily to provide free H atoms, enabling an alternative-way hydrogeneration process of activated N2 molecules to release NH3 eventually. This work highlights the cost-effective TiO2 mechanocatalyst for ammonia synthesis under mild conditions and proposes a defect-engineering-induced mechanocatalytic mechanism to promote N2 activation and H2O dissociation.

Tailored Metal-Organic Frameworks for Water Purification: Perfluorinated Fe-MOFs for Enhanced Heterogeneous Catalytic Ozonation

An industrially viable catalyst for heterogeneous catalytic ozonation (HCO) in water purification requires the characteristics of good dispersion of active species on its surface, efficient electron transfer for ozone decay, and maximum active species utilization. While metal-organic frameworks (MOFs) represent an attractive platform for HCO, the metal nodes in the unmodified MOFs exhibit low catalytic activity. Herein, we present a perfluorinated Fe-MOF catalyst by substituting H atoms on the metalated ligands with F atoms (termed 4F-MIL-88B) to induce structure evolution. The Lewis acidity of 4F-MIL-88B was enhanced via the formation of Fe nodes, tailoring the electron distribution on the catalyst surface. As a result of catalyst modification, the rate constant for degradation of the target compounds examined increased by ∼700% compared with that observed for the unmodified catalyst. Experimental evidence and theoretical calculations showed that the modulated polarity and the enhanced electron transfer between the catalyst and ozone molecules contributed to the adsorption and transformation of O3 to •OH on the catalyst surface. Overall, the results of this study highlight the significance of tailoring the metalated ligands to develop highly efficient and stable MOF catalysts for HCO and provide an in-depth mechanistic understanding of their structure-function evolution, which is expected to facilitate the applications of nanomaterial-based processes in water purification.

Tunable structure of TiO2 deposited by DC magnetron sputtering to adsorb Cr (VI) and Fe (III) from water

TiO2 thin films with mixtures of the anatase, rutile, and brookite phases were deposited on glass substrates via magnetron sputtering. Based on XRD and Raman results, the TiO2-0.47 and TiO2-3.47 films principally contained the brookite phase, while the TiO2-1.27 and TiO2-2.13 films were primarily anatase. The capacities of the TiO2 films to adsorb heavy metals were tested with Cr(VI) and Fe(III) solutions, and the maximum Cr(VI) and Fe(III) adsorption capacities were realized with the TiO2-0.47 film (334.5 mg/g) and TiO2-3.47 film (271.3 mg/g), respectively. SEM‒EDS results revealed the presence of Cr and Fe on the surfaces of the films, thus corroborating the ability of the TiO2 films to adsorb and remove heavy metals. They are strong candidates for use in wastewater treatment plants.

Flame Spray Pyrolysis Synthesis of Vo-Rich Nano-SrTiO3-x

Engineering of oxygen vacancies (Vo) in nanomaterials allows diligent control of their physicochemical properties. SrTiO3 possesses the typical ABO3 structure and has attracted considerable attention among the titanates due to its chemical stability and its high conduction band energy. This has resulted in its extensive use in photocatalytic energy-related processes, among others. Herein, we introduce the use of Flame Spray Pyrolysis (FSP); an industrial and scalable process to produce Vo-rich SrTiO3 perovskites. We present two types of Anoxic Flame Spray Pyrolysis (A-FSP) technologies using CH4 gas as a reducing source: Radial A-FSP (RA-FSP); and Axial A-FSP (AA-FSP). These are used for the control engineering of oxygen vacancies in the SrTiO3-x nanolattice. Based on X-ray photoelectron spectroscopy, Raman and thermogravimetry-differential thermal analysis, we discuss the role and the amount of the Vos in the so-produced nano-SrTiO3-x, correlating the properties of the nanolattice and energy-band structure of the SrTiO3-x. The present work further corroborates the versatility of FSP as a synthetic process and the potential future application of this process to engineer photocatalysts with oxygen vacancies in quantities that can be measured in kilograms.

Enhanced Photocatalysis of Electrically Polarized Titania Nanosheets

Titania (TiO2) nanosheets are crystals with controlled, highly ordered structures that improve the functionality of conventional TiO2 nanoparticles. Various surface modification methods have been studied to enhance the effectiveness of these materials as photocatalysts. Surface modifications using electrical polarization have attracted considerable attention in recent years because they can improve the function of titania without changing its composition. However, the combination of facet engineering and electrical polarization has not been shown to improve the functionality of TiO2 nanosheets. In the present study, the dye-degradation performance of polarized TiO2 nanosheets was evaluated. TiO2 nanosheets with a F/Ti ratio of 0.3 were synthesized via a hydrothermal method. The crystal morphology and structure were evaluated using transmission electron microscopy and X-ray diffraction. Then, electrical polarization was performed under a DC electric field of 300 V at 300 °C. The polarized material was evaluated using thermally stimulated current measurements. A dye-degradation assay was performed using a methylene blue solution under ultraviolet irradiation. The polarized TiO2 nanosheets exhibited a dense surface charge and accelerated decolorization. These results indicate that electrical polarization can be used to enhance the photocatalytic activity of TiO2.

In vitro long-term antibacterial performance and mechanism of Zn-doped micro-arc oxidation coatings

Micro-arc oxidation (MAO) coatings containing 2.86 wt%, 5.83 wt% and 8.81 wt% Zn (Zn-2.86 wt%, Zn-5.83 wt% and Zn-8.81 wt%) were separately fabricated on Ti6Al4V alloys using EDTA-ZnNa2 electrolytes. In vitro antibacterial examination exhibits that the antibacterial rates of Zn-2.86 wt%, Zn-5.83 wt% and Zn-8.81 wt% against Staphylococcus aureus (S. aureus) are 76.0 %, 100.0 % and 99.2 %, respectively. Reactive oxygen species (ROS) level of MAO samples is significantly higher than that of the untreated Ti6Al4V. Zn-containing coatings especially Zn-5.83 wt% induces the strongest oxidative stress on S. aureus due to relatively high released Zn2+ concentration. Moreover, qPCR analysis shows that MAO samples inhibit the icaADBC transcription and result in the down-regulation of PIA production, thereby mitigating biofilm formation. After immersion in simulated body fluid (SBF) for 3, 8 and 14 d, the antibacterial rate of Zn-5.83 wt% is 84.7 %, 63.2 % and 12.5 % respectively, and ROS level of MAO samples is also significantly higher than that of the untreated Ti6Al4V even after 14 d of immersion, suggesting that the antibacterial performance of MAO samples can last a relatively long immersion period and exhibit large application potential in orthopedic clinic.

Surface Hydrogen Bond-Induced Oxygen Vacancies of TiO2 for Two-Electron Molecular Oxygen Activation and Efficient NO Oxidation

Defect engineering can provide a feasible approach to achieving ambient molecular oxygen activation. However, conventional surface defects (e.g., oxygen vacancies, OVs), featured with the coordinatively unsaturated metal sites, often favor the reduction of O2 to •O2- rather than O22- via two-electron transfer, hindering the efficient pollutant removal with high electron utilization. Herein, we demonstrate that this bottleneck can be well discharged by modulating the electronic structure of OVs via phosphorization. As a proof of concept, TiO2 nanoparticles are adopted as a model material for NaH2PO2 (HP) modification, in which HP induces the formation of OVs via weakening the Ti-O bonds through the hydrogen bond interactions. Additionally, the formed Ti-O-P covalent bond refines the electronic structure of OVs, which enables rapid electron transfer for two-electron molecular oxygen activation. As exemplified by NO oxidation, HP-modified TiO2 with abundant OVs achieved complete NO removal with high selectivity for benign nitrate, superior to that of pristine TiO2. This study highlights a promising approach to regulate the O2 activation via an electronic structure modulation and provides fresh insights into the rational design of a photocatalyst for environmental remediation.

Hydrodeoxygenation of Oxygenates Derived from Biomass Pyrolysis Using Titanium Dioxide-Supported Cobalt Catalysts

Bio-oil upgrading to produce biofuels and chemicals has become an attractive topic over the past decade. However, the design of cost- and performance-effective catalysts for commercial-scale production remains a challenge. Herein, commercial titania (TiO2) was used as the support of cobalt (Co)-based catalysts (Co/TiO2) due to its low cost, high availability, and practicability for commercialization in the future. The Co/TiO2 catalysts were made with two different forms of TiO2 (anatase [TiO2-A] and rutile [TiO2-R]) and comparatively evaluated in the hydrodeoxygenation (HDO) of 4-propylguaicol (4PG), a lignin-derived model compound. Both Co/TiO2 catalysts promoted the HDO of 4PG following a similar pathway, but the Co/TiO2-R catalyst exhibited a higher activity in the early stages of the reaction due to the formation of abundant Ti3+ species, as detected by X-ray photoelectron spectroscopy (XPS) and hydrogen-temperature programed reduction (H2-TPR) analyses. On the other hand, the Co/TiO2-A catalyst possessed a higher acidity that enhanced propylcyclohexane production at prolonged reaction times. In terms of reusability, the Co/TiO2-A catalyst showed a higher stability (less Co leaching) and reusability compared to Co/TiO2-R, as confirmed by transmission electron microscopy (TEM) and inductively coupled plasma optical emission spectroscopy (ICP-OES) analyses. The HDO of the real bio-oil derived from pyrolysis of Leucaena leucocephala revealed that the Co/TiO2-A catalyst could convert high oxygenated aromatics (methoxyphenols, dimethoxyphenols, and benzenediols) to phenols and enhanced the phenols content, hinting at its potential to produce green chemicals from bio-feedstock.

Oxygen-Deficient Bioceramics: Combination of Diagnosis, Therapy, and Regeneration

The journey of ceramics in medicine has been synchronized with an evolution from the first generation-alumina, zirconia, etc.-to the third -3D scaffolds. There is an up-and-coming member called oxygen-deficient or colored bioceramics, which have recently found their way through biomedical applications. The oxygen vacancy steers the light absorption toward visible and near infrared regions, making the colored bioceramics multifunctional-therapeutic, diagnostic, and regenerative. Oxygen-deficient bioceramics are capable of turning light into heat and reactive oxygen species for photothermal and photodynamic therapies, respectively, and concomitantly yield infrared and photoacoustic images. Different types of oxygen-deficient bioceramics have been recently developed through various synthesis routes. Some of them like TiO2- x , MoO3- x , and WOx have been more investigated for biomedical applications, whereas the rest have yet to be scrutinized. The most prominent advantage of these bioceramics over the other biomaterials is their multifunctionality endowed with a change in the microstructure. There are some challenges ahead of this category discussed at the end of the present review. By shedding light on this recently born bioceramics subcategory, it is believed that the field will undergo a big step further as these platforms are naturally multifunctional.

Synergistic material modification-induced optimization of interfacial charge transfer and surface hydrogen adsorption

Being chemically stable, low cost and made from abundant resources, titanium dioxide (TiO2) possesses the most desired advantages for photocatalytic applications. However, the intrinsic limits of high surface hydrogen adsorption energy, wide band gap, low separation rate and rapid recombination of the photogenerated charge carriers greatly hamper its utilization. To address these issues, the present work combines density functional theory (DFT) calculations with rational modifications of TiO2 with nickel doping and an ultra-thin shield of fluorinated carbon (FNT) for application in the photocatalytic hydrogen evolution reaction (HER). Comprehensive studies imply that the synergistic modifications not only optimize the surface H adsorption, but also facilitate the interfacial charge transfer and simultaneously prevent the photochemical and chemical corrosion of the catalysts. In good agreement with the theoretical predictions, the resulting FNT photocatalysts demonstrate an optimal HER efficiency of 13.0 mmol g-1 h-1, nearly 33-times and over three-times beyond that of the pristine TiO2 (0.4 mmol g-1 h-1) and the Ni-doped TiO2 (4.2 mmol g-1 h-1), respectively. Moreover, the composite also exhibits excellent stability with a well-reproducible HER performance over a 66-hour cyclic HER test of 15 cycles.

Oxygen vacancies induced band gap narrowing for efficient visible-light response in carbon-doped TiO2

The band gap of rutile TiO2 has been narrowed, via the formation of oxygen vacancies (OVs) during heat treatment in carbon powder (cHT) with embedding TiO2 coatings. The narrowed band gap efficiently improves the visible light response of TiO2 coatings, to further enhance the visible-light-driven photocatalytic activity. The change in OVs during cHT has been studied by manipulation of cHT temperature and time. The effect of OVs on the band structure of nonstoichiometric TiO2-x has been further calculated by first-principles calculations. With raising the temperature, SEM images show that the nano-size fiber-like structure forms on the surface of TiO2 coatings, and the amount of the fiber-like structure significantly increases and their size changes from nano to micro under 800 °C, contributing to cause an increase in accessible surface area. The UV-Vis results reveal that the band gap of TiO2 has been narrowed during cHT, due to the formed oxygen vacancies. The XPS results further confirm that the formation of surface defects including OVs, and the XPS depth profile further shows the decreased relative amount of O whereas increased relative amount of carbon. Notably, after cHT for TiO2 coatings, the photocatalytic activity first increases then decreases with raising the temperature, achieving approximately 3 times at 850 °C. The first-principles calculation suggest that the OVs in TiO2 coatings with localized electrons could facilitate the band gap narrowing, further favoring to enhance the photocatalytic activity under visible light.

Fabrication of optimal oxygen vacancy amount in P/Ag/Ag2O/Ag3PO4/TiO2 through a green photoreduction process for sustainable H2 evolution under solar light

Defects engineering on photocatalysts such as oxygen vacancies (OVs) is an effective approach for improving photocatalytic hydrogen (H₂) evolution efficiency. In this study, OVs modified P/Ag/Ag₂O/Ag₃PO₄/TiO₂ (PAgT) composite was successfully fabricated via a photoreduction process by controlling the ratio of PAgT to ethanol (16, 12, 8, 6 and 4 g·L^-1) under simulated solar light irradiation for the first time. Characterization methods confirmed the presence of OVs in the modified catalysts. Meanwhile, the OVs amount and their effects on the light absorption ability, charge transfer rate, conduction band and H₂ evolution efficiency of the catalysts were also investigated. The results indicated that the optimal OVs amount endowed OVs-PAgT-12 with the strongest light absorption, the fastest electron transfer rate and suitable band gap for H₂ evolution, leading to the highest H₂ yield (863 μmol·h^-1·g^-1) under solar light irradiation. Moreover, OVs-PAgT-12 exhibited a superior stability during cyclic experiment, indicating its great potential for practical application. Furthermore, a sustainable H₂ evolution process was proposed based on a combination of sustainable bio-ethanol resource, stable OVs-PAgT, abundant solar energy and recyclable methanol. This study would provide new insights into the design of defects modified composite photocatalyst for enhanced solar-to-hydrogen conversion.

Confinement of defect-rich bimetallic In2O3/CeO2 nanocrystals in mesoporous nitrogen-doped carbon as a sensitive platform for photoelectrochemical aptasensing of Escherichia coli

The sensitive determination of food-borne pathogens from food products is essential to ensure food safety and to protect people's health. Herein, a novel photoelectrochemical (PEC) aptasensor was manufactured based on defect-rich bimetallic cerium/indium oxide nanocrystals confined in mesoporous nitrogen-doped carbon (denoted as In₂O₃/CeO₂@mNC) for sensitively detecting Escherichia coli (E. coli) from real samples. A new cerium-based polymer-metal-organic framework [polyMOF(Ce)] was synthesized using polyether polymer containing 1,4-benzenedicarboxylic acid unit (L8) as ligand, trimesic acid as co-ligand, and cerium ions as coordination centers. After adsorbing trace indium ions (In³⁺), the gained polyMOF(Ce)/In³⁺ complex was calcined at high temperature under nitrogen atmosphere, resulting in the production of a series of defect-rich In₂O₃/CeO₂@mNC hybrids. Benefitting from the advantages of high specific surface area, large pore size, and multiple functionality of polyMOF(Ce), In₂O₃/CeO₂@mNC hybrids showed enhanced visible light absorption ability, separation performance of the photo-generated electrons and holes, promoted electron transfer, as well as the strong bioaffinity toward E. coli-targeted aptamer. Accordingly, the constructed PEC aptasensor illustrated an ultralow detection limit of 1.12 CFU mL^-1, remarkably lower than most of the reported E. coli biosensors, along with high stability and selectivity, excellent reproducibility, and expected regeneration ability. The present work provides insight into the construction of a general PEC biosensing strategy based on MOF-based derivatives for the sensitive analysis of food-borne pathogens.

Extrinsic Point Defects in TiO2-Acetylacetone Charge-Transfer Complex and Their Effects on Optical and Photochemical Properties

TiO₂-based visible-light-sensitive nanomaterials are widely studied for photocatalytic applications under UV-Vis radiation. Among the mechanisms of visible-light sensitization, extrinsic oxygen vacancies have been introduced into TiO₂ and charge-transfer complexes (CTCs) have been formed between chelating ligands, such as acetylacetone, and nanocrystalline TiO₂ (TiO₂-ACAC). However, the influence of extrinsic oxygen vacancies on the photocatalytic performance of TiO₂-based CTCs is unknown. In this work, surface/bulk extrinsic oxygen vacancies were introduced into TiO₂-ACAC through calcination at 270 °C under static air, argon, and hydrogen atmospheres. TiO₂-ACAC CTCs were characterized by X-ray powder diffraction, thermogravimetric analysis, diffuse-reflectance spectroscopy, photoluminescence, electron paramagnetic resonance (EPR), and X-ray photoelectron spectroscopy techniques. The correlation between EPR-spin trapping and tetracycline (TC) photodegradation, using scavengers, highlighted the key role of the superoxide radical in TC degradation by TiO₂-ACAC CTCs under low-power visible-light radiation. The increased extrinsic oxygen vacancies concentration was not beneficial for the photocatalytic performance of TiO₂ CTCs, since bulk extrinsic oxygen vacancies additionally act as recombination centers. In fact, the TiO₂-ACAC CTC with the lowest extrinsic oxygen vacancies concentration exhibited the highest photocatalytic performance for TC degradation due to an adequate distribution of extrinsic bulk oxygen vacancies, which led to the trapped electrons undergoing repeated hopping, reducing the recombination rates and improving the efficiency in superoxide radicals production. Our findings indicated that TiO₂-ACAC CTCs are able to degrade pollutants via interactions with electronic holes and principally superoxide radicals and also, provided fundamental information about the influence of surface/bulk extrinsic oxygen vacancies on the photocatalytic performance, lattice parameters, and optical and photochemical properties of TiO₂-based CTCs.

Aldehyde Hydrogenation by Pt/TiO2 Catalyst in Aqueous Phase: Synergistic Effect of Oxygen Vacancy and Solvent Water

The aldehyde hydrogenation for stabilizing and upgrading biomass is typically performed in aqueous phase with supported metal catalysts. By combining density functional theory calculations and ab initio molecular dynamics simulations, the model reaction of formaldehyde hydrogenation with a Pt/TiO₂ catalyst is investigated with explicit solvent water molecules. In aqueous phase, both the O vacancy (Ov) on support and solvent molecules could donate charges to a Pt cluster, where the Ov could dominantly reduce the Pt cluster from positive to negative. During the formaldehyde hydrogenation, the water molecules could spontaneously protonate the O in the aldehyde group by acid/base exchange, generating the OH* at the metal-support interface by long-range proton transfer. By comparing the stoichiometric and reduced TiO₂ support, it is found that the further hydrogenation of OH* is hard on the positively charged Pt cluster over stoichiometric TiO₂. However, with the presence of Ov on reduced support, the OH* hydrogenation could become not only exergonic but also kinetically more facile, which prohibits the catalyst from poisoning. This mechanism suggests that both the proton transfer from solvent water molecules and the easier OH* hydrogenation from Ov could synergistically promote aldehyde hydrogenation. That means, even for such simple hydrogenation in water, the catalytic mechanism could explicitly relate to all of the metal cluster, oxide support, and solvent waters. Considering the ubiquitous Ov defects in reducible oxide supports and the common aqueous environment, this synergistic effect may not be exclusive to Pt/TiO₂, which can be crucial for supported metal catalysts in biomass conversion.

Facile Synthesis of Gram-Scale Mesoporous Ag/TiO2 Photocatalysts for Pharmaceutical Water Pollutant Removal and Green Hydrogen Generation

This work demonstrates a two-step gram-scale synthesis of presynthesized silver (Ag) nanoparticles impregnated with mesoporous TiO₂ and evaluates their feasibility for wastewater treatment and hydrogen gas generation under natural sunlight. Paracetamol was chosen as the model pharmaceutical pollutant for evaluating photocatalytic performance. A systematic material analysis (morphology, chemical environment, optical bandgap energy) of the Ag/TiO₂ photocatalyst powder was carried out, and the influence of material properties on the performance is discussed in detail. The experimental results showed that the decoration of anatase TiO₂ nanoparticles (size between 80 and 100 nm) with 5 nm Ag nanoparticles (1 wt %) induced visible-light absorption and enhanced charge carrier separation. As a result, 0.01 g/L Ag/TiO₂ effectively removed 99% of 0.01 g/L paracetamol in 120 min and exhibited 60% higher photocatalytic removal than pristine TiO₂. Alongside paracetamol degradation, Ag/TiO₂ led to the generation of 1729 μmol H₂ g^-1 h^-1. This proof-of-concept approach for tandem pollutant degradation and hydrogen generation was further evaluated with rare earth metal (lanthanum)- and nonmetal (nitrogen)-doped TiO₂, which also showed a positive response. Using a combination of ab initio calculations and our new theory model, we revealed that the enhanced photocatalytic performance of Ag/TiO₂ was due to the surface Fermi-level change of TiO₂ and lowered surface reaction energy barrier for water pollutant oxidation. This work opens new opportunities for exploiting tandem photocatalytic routes beyond water splitting and understanding the simultaneous reactions in metal-doped metal oxide photocatalyst systems under natural sunlight.

Surface-redox sodium-ion storage in anatase titanium oxide

Sodium-ion storage technologies are promising candidates for large-scale grid systems due to the abundance and low cost of sodium. However, compared to well-understood lithium-ion storage mechanisms, sodium-ion storage remains relatively unexplored. Herein, we systematically determine the sodium-ion storage properties of anatase titanium dioxide (TiO₂(A)). During the initial sodiation process, a thin surface layer (~3 to 5 nm) of crystalline TiO₂(A) becomes amorphous but still undergoes Ti⁴⁺/Ti³⁺ redox reactions. A model explaining the role of the amorphous layer and the dependence of the specific capacity on the size of TiO₂(A) nanoparticles is proposed. Amorphous nanoparticles of ~10 nm seem to be optimum in terms of achieving high specific capacity, on the order of 200 mAh g^-1, at high charge/discharge rates. Kinetic studies of TiO₂(A) nanoparticles indicate that sodium-ion storage is due to a surface-redox mechanism that is not dependent on nanoparticle size in contrast to the lithiation of TiO₂(A) which is a diffusion-limited intercalation process. The surface-redox properties of TiO₂(A) result in excellent rate capability, cycling stability and low overpotentials. Moreover, tailoring the surface-redox mechanism enables thick electrodes of TiO₂(A) to retain high rate properties, and represents a promising direction for high-power sodium-ion storage.

Immobilization of photocatalytic materials for (waste)water treatment using 3D printing technology - advances and challenges

Photocatalysis has been considered a promising technology for the elimination of a wide range of pollutants in water. Various types of photocatalysts (i.e., homojunction, heterojunction, dual Z-scheme photocatalyst) have been developed in recent years to address the drawbacks of conventional photocatalysts, such as the large energy band gap and rapid recombination rate of photogenerated electrons and holes. However, there are still challenges in the design of photocatalytic reactors that limit their wider application for real (waste)water treatment, such as difficulties in their recovery and reuse from treated (waste)waters. 3D printing technologies have been introduced very recently for the immobilization of materials in novel photocatalytic reactor designs. The present review aims to summarize and discuss the advances and challenges in the application of various 3D printing technologies (i.e., stereolithography, inkjet printing, and direct ink writing) for the fabrication of stable photocatalytic materials for (waste)water treatment purposes. Furthermore, the limitations in the implementation of these technologies to design future generations of photocatalytic reactors have been critically discussed, and recommendations for future studies have been presented.

Preparation and modification methods of defective titanium dioxide-based nanoparticles for photocatalytic wastewater treatment-a comprehensive review

The rapid population growth and industrial expansion worldwide have created serious water contamination concerns. To curb the pollution issue, it has become imperative to use a versatile material for the treatment. Titanium dioxide (TiO₂) has been recognized as the most-studied nanoparticle in various fields of science and engineering due to its availability, low cost, efficiency, and other fascinating properties with a wide range of applications in modern technology. Recent studies revealed the photocatalytic activity of the material for the treatment of industrial effluents to promote environmental sustainability. With the wide band gap energy of 3.2 eV, TiO₂ can be activated under UV light; thus, many strategies have been proposed to extend its photoabsorption to the visible light region. In what follows, this has generated increasing attention to study its characteristics and structural modifications in different forms for photocatalytic applications. The present review provides an insight into the understanding of the synthesis methods of TiO₂, the current progress in the treatment techniques for the degradation of wide environmental pollutants employing modified TiO₂ nanoparticles, and the factors affecting its photocatalytic activities. Further, recent developments in using titania for practical applications, the approach for designing novel nanomaterials, and the prospects and opportunities in this exciting area have been discussed.

Au@Cu2O Core-Shell and Au@Cu2Se Yolk-Shell Nanocrystals as Promising Photocatalysts in Photoelectrochemical Water Splitting and Photocatalytic Hydrogen Production

In this work, we demonstrated the practical use of Au@Cu₂O core-shell and Au@Cu₂Se yolk-shell nanocrystals as photocatalysts in photoelectrochemical (PEC) water splitting and photocatalytic hydrogen (H₂) production. The samples were prepared by conducting a sequential ion-exchange reaction on a Au@Cu₂O core-shell nanocrystal template. Au@Cu₂O and Au@Cu₂Se displayed enhanced charge separation as the Au core and yolk can attract photoexcited electrons from the Cu₂O and Cu₂Se shells. The localized surface plasmon resonance (LSPR) of Au, on the other hand, can facilitate additional charge carrier generation for Cu₂O and Cu₂Se. Finite-difference time-domain simulations were carried out to explore the amplification of the localized electromagnetic field induced by the LSPR of Au. The charge transfer dynamics and band alignment of the samples were examined with time-resolved photoluminescence and ultraviolet photoelectron spectroscopy. As a result of the improved interfacial charge transfer, Au@Cu₂O and Au@Cu₂Se exhibited a substantially larger photocurrent of water reduction and higher photocatalytic activity of H₂ production than the corresponding pure counterpart samples. Incident photon-to-current efficiency measurements were conducted to evaluate the contribution of the plasmonic effect of Au to the enhanced photoactivity. Relative to Au@Cu₂O, Au@Cu₂Se was more suited for PEC water splitting and photocatalytic H₂ production by virtue of the structural advantages of yolk-shell architectures. The demonstrations from the present work may shed light on the rational design of sophisticated metal-semiconductor yolk-shell nanocrystals, especially those comprising metal selenides, for superior photocatalytic applications.

A review on TiO2-x-based materials for photocatalytic CO2 reduction

Photocatalytic CO₂ reduction technology has a broad potential for dealing with the issues of energy shortage and global warming. As a widely studied material used in the photocatalytic process, titanium dioxide (TiO₂) has been continuously modified and tailored for more desirable application. Recently, the defective/reduced titanium dioxide (TiO_2-x) catalyst has attracted broad attention due to its excellent photocatalytic performance for CO₂ reduction. In this perspective review, we comprehensively present the recent progress in TiO_2-x-based materials for photocatalytic CO₂ reduction. In detail, the review starts with the fundamentals of CO₂ photocatalytic reduction. Then, the synthesis of a defective TiO₂ structure is introduced for the regulation of its photocatalytic performance, especially its optical properties and dissociative adsorption properties. In addition, the current application of TiO_2-x-based photocatalysts for CO₂ reduction is also highlighted, such as metal-TiO_2-x, oxide-TiO_2-x and TiO_2-x-carbon-based photocatalysts. Finally, the existing challenges and possible scope of photocatalytic CO₂ reduction over TiO_2-x-based materials are discussed. We hope that this review can provide an effective reference for the development of more efficient and reasonable photocatalysts based on TiO_2-x.

A sustainable composite of rice-paper/BaMoO4 nanoparticles for the photocatalytic elimination of the recalcitrant 2,6-dichlorobenzamide (BAM) pesticide in drinking water and its mechanisms of degradation

This research reports the use of biodegradable and flexible composites for the removal of the 2,6-dichlorobenzamide (BAM) pesticide from drinking water. Rice paper (a biodegradable substrate) and Ag/BaMoO4 (MOBA) nanoparticles were employed to fabricate these composites. The SEM images showed that the MOBA nanoparticles with sizes of 300-800 nm decorated the surface of the biodegradable substrate and formed porous agglomerates, which have sizes of 1-3 μm. The MOBA powders were dispersed in drinking water polluted with BAM and were exposed to 4 h of UV-VIS irradiation, producing a maximum degradation of 82% for the BAM. Moreover, the flexible and biodegradable rice/MOBA composite produced a maximum removal percentage of 95% for the BAM. Also, we studied the effect of pH of the initial solution utilizing both powders and composites. From here, we found that a pH of 10 leads to a complete degradation of BAM after 4h, while a pH of 3 degraded only 37-47% of BAM for the same reaction time. According to the scavenger experiments, the •OH radical and the h+ were the main oxidizing agents for the BAM. Overall, the biodegradable photocatalytic composites are a reliable and a low-cost alternative to eliminate pesticides from the drinking water and can find application in water purification processes.

Photoelectrochemical Antibacterial Platform Based on Rationally Designed Black TiO2-x Nanowires for Efficient Inactivation against Bacteria

A hyphenated strategy for photoelectrochemical (PEC) disinfection is proposed with rationally designed black TiO_2-x as a photoresponsive material. The PEC method, a fusion of electrochemistry and photocatalysis, is an innovative and effective way to improve photocatalytic performance, which imparts certain properties to the photoelectrode and greatly promotes the charge transfer, thus effectively inhibiting the recombination of carriers and greatly promoting the catalytic efficiency. The oxygen vacancy (V_o) engineering on TiO₂ is conducted to obtain black TiO_2-x, which shows a much larger light absorption region in the full solar spectrum than the pristine white TiO₂ and presents excellent PEC sterilization performance. The bactericidal efficiency with the PEC method is 10 times higher than that with the photocatalytic method, inactivating 99% of bacteria within a short time of 30 min. In addition, the black titanium oxide nanowires (B-TiO_2-x NWs) are grown on flexible carbon cloth (CC) to form a sandwich structural self-cleaning face mask. The bacteria adhering to the surface of the mask will be sterilized quickly and efficiently under the illumination of visible light. The face mask with the characteristics of superior antibacterial effect and long service lifetime will be used for epidemic prevention and reduce the second pollution.

Engineering Bimodal Oxygen Vacancies and Pt to Boost the Activity Toward Water Dissociation

Water dissociation is the rate-limiting step of several energy-related reactions due to the high energy barrier required for breaking the oxygen-hydrogen bond. In this work, a bimodal oxygen vacancy (V_O ) catalysis strategy is adopted to boost the efficient water dissociation on Pt nanoparticles. The single facet-exposed TiO₂ surface and NiO_x nanocluster possess two modes of V_O different from each other. In ammonia borane hydrolysis, the highest catalytic activity among Pt-based materials is achieved with the turnover frequency of 618 min^-1 under alkaline-free conditions at 298 K. Theoretical simulation and characterization analyses reveal that the bimodal V_O significantly promotes the water dissociation in two ways. First, an ensemble-inducing effect of Pt and V_O in TiO₂ drives the activation of water molecules. Second, an electron promoter effect induced by the electron transfer from V_O in NiO_x to Pt further enhances the ability of Pt to dissociate water and ammonia borane. This insight into bimodal V_O catalysis establishes a new avenue to rationally design heterogeneous catalytic materials in the energy chemistry field.

Preparation of Ni-loaded oxygen-enriched vacancy TiO2−x hierarchical micro-nanospheres and the study of their photocatalytic hydrogen evolution performance

Ni-loaded oxygen-enriched vacancy TiO2−x hierarchical micro-nanospheres were prepared, and the photocatalytic hydrogen production properties were greatly improved due to the synergetic effect between THS, oxygen vacancies and Ni-based promoters.

N-doping TiO2 hollow microspheres with abundant oxygen vacancies for highly photocatalytic nitrogen fixation

Photocatalytic fixation of nitrogen to ammonia (NH₃) is a green but low-efficiency technology due to the high recombination of photo-generated carriers and poor light absorption of photocatalysts. Generally, the adsorption capacity for N₂ and the band position of TiO₂ are responsible for bandgap, light-adsorption, and the separation of photocarriers. Therefore, they play crucial roles to improve catalytic activity. Herein, N-doping TiO₂ hollow microspheres (NTO-0.5) with oxygen vacancies were synthesized via a hydrothermal method using phenolic resin microsphere as a template. The obtained NTO-0.5 achieves an impressive ammonia yield of 80.09 μmol g_cat^-1h^-1. Oxygen vacancies of NTO-0.5 were confirmed by ESR, Raman, XPS, Zeta potential, and H₂O₂ treatment for reducing oxygen vacancies. The ammonia yield of NTO-0.5 decreases to 34.78 μmol g_cat^-1h^-1 after reducing oxygen vacancies by H₂O₂ treatment, which demonstrates the importance of oxygen vacancies. The oxygen vacancies narrow the bandgap from 3.18 eV to 2.83 eV and impede the recombination of photo-generated carriers. The hollow microspheres structure is conducive to light absorption and utilization. Therefore, the synergistic effect between the oxygen vacancies and the hollow microspheres structure boosts the efficiency of photocatalytic nitrogen fixation. After four cycles, the ammonia production yield still maintains at 76.52 μmol g_cat^-1h^-1, meaning high stability. This work provides a new insight into the construction of catalysts with oxygen vacancies to enhance photocatalytic nitrogen fixation performance.

Modification of charge transport in nanostructured TiO2-xSchottky diodes via post fabrication annealing

An ordered, crack-free array of anatase TiO₂nanotubes were prepared via anodization and annealing at 550 °C. Oxygen vacancies are known to improve photocatalytic activity in TiO₂and were introduced using a facile low vacuum annealing. Stoichiometric and nonstoichiometric films were followed by a conformal Pt deposition at 250 °C using atomic layer deposition resulting in a current rectifying device, or Schottky diode. Here, we investigated the current-voltage effects of a post thermal treatment using 350 °C and 400 °C. This paper presents reproducible improvements in the charge transport behavior after a 350 °C post-fabrication annealing process. Oxygen vacancies resulted in the formation of a shunt resistance behavior of 10⁵Ω and no overall performance improvements compared to stoichiometric films. Additionally, thermal treatments offered trap-based shifts from multiple trap distributions to a single trap distribution. This work hereby provides valuable experimental observations into understanding the effects of oxygen vacancies and effectively modifying the electronic properties of a conformal Pt/TiO_2-xnanostructured junction using a facile post-thermal treatment.

Design of a dual-function photocatalyst for cracking water to produce hydrogen and degradation of o-phenylphenol

Titanium dioxide (TiO₂) has been widely studied because of its stable chemical properties, low cost and non-toxicity.