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The Au/TiO 2 model catalyst has been extensively studied across various applications, yet its utilization in electrochemical CO 2 and CO reduction (EC CO 2 R and COR) remains underexplored. In this study, we employed the Au/TiO 2 /Ti system, prepared via a two-step process: initially forming rutile TiO 2 on metallic Ti through laser-assisted methods, followed by sputtering Au onto the surface. The experimental conditions included varying concentrations of KHCO 3 and phosphate, applied potentials, Au overlayer thickness, and laser treatment parameters for the Ti-based catalysts. The major products detected were syngas (CO and H 2), which varied with experimental settings, along with liquid formate and other hydrocarbons. The study also examined the role of surface species like *CO and H* in facilitating C–C coupling, drawing parallels to traditional Fischer-Tropsch (F-T) synthesis. Spectroscopic analyses, including XPS and UPS, were utilized to investigate interfacial electronic structures, oxidation states, and overlayer stability post-electrochemical processing. This research contributes to a deeper understanding of EC CO 2 R and COR mechanisms on Au/Ti electrodes, providing valuable insights into optimizing electrode design and operational conditions for enhanced catalytic efficiency in syngas production and direct F-T chemistry. [Display omitted] • Au/TiO 2 /Ti system was prepared by laser-assisting TiO 2 formation on Ti, followed by sputtering Au. • A tunable H 2 /CO ratio was by varying electrolyte concentrations and applied potentials in electrochemical CO 2 reduction. • Fischer-Tropsch synthesis pathway was understood through the role of *CO and H* in facilitating C–C coupling. • XPS and UPS revealed the oxidation states, interfacial electronic structures, and stability of Au overlayer. [ABSTRACT FROM AUTHOR]

In this work, gold-photo-catalyzed CO2 transformation was conducted and the effect of three variables with two levels was investigated: support (TiO2 and hydroxyapatite from bovine bone (BB)), Au content (5 and 10%) and activation wavelength (254 and 380–700 nm). Reactions were conducted in a stirred tank reactor by bubbling CO2 (9 × 10−3 dm3/min) in 0.1 dm3 of 0.5 M NaOH solution. The catalysts were synthesized using AuCl3, TiO2 and BB. Au nanoparticles were obtained by reduction with Hetheroteca inuloides, thus eliminating calcination and hydrogenation to reduce the gold species. By TEM, the particle size distribution was determined, and the synthesized nanoparticle sizes varied in the range of 9 to 19 nm, depending on the support and Au content. By UV–Vis spectroscopy, the energy band gaps of the prepared materials were 2.18 eV (10% Au/BB), 2.38 eV (5% Au/BB), 2.42 eV (BB), 3.39 eV (5% Au/TiO2), 3.41 eV (10% Au/TiO2) and 3.43 eV for pure TiO2. Methanol and formic and acetic acids were identified during the process. Selectivity toward methanol was found to be improved with the 10% Au/BB catalytic system. [ABSTRACT FROM AUTHOR]

Growing hydrogen demand and progress in fuel cell technology contributed to renewed interest in water-gas shift (WGS) reaction. Supported gold catalysts attracted a special attention during the last three decades. Given the undisputed role of support nature in catalyst activity the purpose of this work was exploration of the effect of ceria amount (1, 3, and 5 wt%) and preparation approach as sol-gel (SG) or mechanochemical mixing (MM) to WGS activity of Au/TiO 2 catalyst. Thorough studies using textural measurements, X-ray fluorescence spectrometry, powder X-ray diffraction, transmission electron microscopy, UV–Vis diffuse reflectance, UV-Raman and X-ray photoelectron spectroscopy, electron paramagnetic resonance, and temperature-programmed reduction were carried out to explain the relationship among structure, electronic properties, and WGS performance. The catalysts showed a notably better performance as compared to Ce-free Au/TiO 2 counterpart by reaching a 90−93 % CO conversion at 180 °C vs. 75 % with unmodified sample. Formation of defective Ti 4 O 7 and Ce 11 O 20 phases occurred during sample preparation by SG. In addition, a distinct ceria phase was found in MM-prepared carriers to assist preferential gold deposition. All these structures contributed to improved WGS activity of the supported gold catalysts. Activity enhancement was related to Ce–Ti interactions and modification of structural and electronic properties that favor water dissociation. New insights into structure-to-function relationships of Au/Ce–TiO 2 catalysts for WGS reaction are provided. [Display omitted] • Effect of Ce doping in Au/TiO 2 and preparation route on WGS activity was explored. • Au/Ce-doped TiO 2 outperformed Au/TiO 2 by reaching a 93 % CO conversion at 180 °C. • Defective Ti 4 O 7 and Ce 11 O 20 phases occurred during sample preparation. • Modification of structural and electronic properties favored H 2 O dissociation. • Tuning physicochemical properties of TiO 2 enable higher WGS activity of Au catalysts. [ABSTRACT FROM AUTHOR]

A novel tandem reaction system formed with H 2 O 2 production and in situ fabric bleaching reaction was firstly designed and constructed with Au/TiO 2 photocatalyst. Results showed H 2 O 2 generated in situ achieved high-efficiency fabric bleaching under the sunlight excitation, thus successfully constructing a ready-to-use system.·OH was confirmed as the main active specie in the simultaneous fabric bleaching reaction. Herein, to ensure the sufficient H 2 O 2 production is a key factor. The different intensity of strong metal-support interaction (SMSI) was introduced into Au/TiO 2 by regulating the calcination atmosphere to boost the H 2 O 2 yield. H 2 /Ar calcination atmosphere imparted Au/TiO 2 the SMSI effect to make H 2 O 2 yield exceed that of counterpart under air atmosphere after 6 h of continuous reaction. The controllable capsulating overlayer on Au NPs provided relatively fewer exposed Au active sites to balance the H 2 O 2 generation and decomposition rates, thus giving a better final yield. This work not only offer a novel path to improve H 2 O 2 generation performance,but also propose new ideas for realizing in situ bleaching using sunlight as driving force and cleaning production of textile printing and dyeing industry. [ABSTRACT FROM AUTHOR]

The commercial feasibility of biodiesel production highly depends on the effective utilization of byproduct glycerol through an environmentally friendly process like photocatalytic reforming. However, the process should be possible under visible light if solar energy is used. In this work, this process was studied over Pt, Au, Au–Cu, and Cu on reduced TiO 2 (by NaBH 4), which is more effective under visible light than pristine TiO 2 , for the first time in literature. Au, Au–Cu, and Cu were loaded by deposition precipitation with urea, while Pt was loaded by impregnation. Although the performance under UV–vis and white TiO 2 is still higher, the visible light performance of Pt, Au–Cu, and Cu is much better over reduced TiO 2 (91, 36, and 27 μmol/h. gcat respectively) than those over pristine TiO 2 (9, 14 and 18 μmol/h. gcat respectively). This indicates that reduced TiO 2 has the potential for the visible light reforming of glycerol. • Photocatalytic glycerol reforming was studied on Pt, Au, Au–Cu, Cu/black TiO 2. • TiO 2 surface was chemically reduced using NaBH 4. • Bandgap of TiO 2 decreased and visible light absorption increased by reduction. • Visible light activity of Au based catalysts were higher. • Visible light activity on Pt, Au–Cu and Cu/black TiO 2 was higher than regular TiO 2. [ABSTRACT FROM AUTHOR]

In this work, gold-photo-catalyzed CO2 transformation was conducted and the effect of three variables with two levels was investigated: support (TiO2 and hydroxyapatite from bovine bone (BB)), Au content (5 and 10%) and activation wavelength (254 and 380–700 nm). Reactions were conducted in a stirred tank reactor by bubbling CO2 (9 × 10−3 dm3/min) in 0.1 dm3 of 0.5 M NaOH solution. The catalysts were synthesized using AuCl3, TiO2 and BB. Au nanoparticles were obtained by reduction with Hetheroteca inuloides, thus eliminating calcination and hydrogenation to reduce the gold species. By TEM, the particle size distribution was determined, and the synthesized nanoparticle sizes varied in the range of 9 to 19 nm, depending on the support and Au content. By UV–Vis spectroscopy, the energy band gaps of the prepared materials were 2.18 eV (10% Au/BB), 2.38 eV (5% Au/BB), 2.42 eV (BB), 3.39 eV (5% Au/TiO2), 3.41 eV (10% Au/TiO2) and 3.43 eV for pure TiO2. Methanol and formic and acetic acids were identified during the process. Selectivity toward methanol was found to be improved with the 10% Au/BB catalytic system.

A photoelectrochemical molecular imprinting sensor based on Au/TiO2 nanocomposite was constructed for the detection of dibutyl phthalate. Firstly, TiO2 nanorods were grown on fluorine-doped tin oxide substrate by hydrothermal method. Then, gold nanoparticles were electrodeposited on TiO2 to fabricate Au/TiO2. Finally, molecular imprinted polymer was electropolymerized on the Au/TiO2 surface to construct MIP/Au/TiO2 PEC sensor for DBP. The conjugation effect of MIP accelerates the electron transfer between TiO2 and MIP, which can greatly improve the photoelectric conversion efficiency and sensitivity of the sensor. In addition, MIP can also provide sites for highly selective recognition of dibutyl phthalate molecules. Under optimal experimental conditions, the prepared photoelectrochemical sensor was used for the quantitative determination of DBP and the results showed a wide linear range (50 to 500 nM), a low limit of detection (0.698 nM), and good selectivity. The sensor was used in a study of real water samples to show that it has promising applications in environmental analysis. [ABSTRACT FROM AUTHOR]

TiO2-supported catalysts have been widely used for a range of both liquid-phase and gas-phase hydrogenation reactions. However, little is known about the effect of their different crystalline surfaces on their activity during the hydrodeoxygenation process. In this work, Au supported on anatase TiO2, mainly exposing 101 or 001 facets, was investigated for the hydrodeoxygenation (HDO) of guaiacol. At 300 °C, the strong interaction between the Au and TiO2-101 surface resulted in the facile reduction of the TiO2-101 surface with concomitant formation of oxygen vacancies, as shown by the H2-TPR and H2-TPD profiles. Meanwhile, the formation of Auδ−, as determined by CO-DRIFT spectra and in situ XPS, was found to promote the demethylation of guaiacol producing methane. However, this strong interaction was absent on the Au/TiO2-001 catalyst since TiO2-001 was relatively difficult to be reduced compared with TiO2-101. The Au on TiO2-001 just served as the active site for the dissociation of hydrogen without the formation of Auδ−. The hydrogen atoms spilled over to the surface of TiO2-001 to form a small amount of oxygen vacancies, which resulted in lower activity than that over Au/TiO2-101. The catalytic activity of the Au/TiO2 catalyst for hydrodeoxygenation will be controlled by tuning the crystal plane of the TiO2 support. [ABSTRACT FROM AUTHOR]

We designed an edge-sites 2D/0D/2D based TiO2@Au/g-C3N4 Z-scheme photocatalytic system consists of highly exposed (001) TNSs@Au edge-site heterojunction, and the Au/g-C3N4 interfacial heterojunction. The designed photocatalyst was prepared by a facile and controlled hydrothermal synthesis strategy via in-situ nanoclusters-to-nanoparticles deposition technique and programable calcination in N2 atmosphere to get edge-site well-crystalline interface, followed by chemically bonded thin overlay of g-C3N4. Photocatalytic performance of the prepared TNSs@Au/g-C3N4 catalyst was evaluated by the photocatalytic degradation of organic pollutants in water under visible light irradiation. The results obtained from structural and chemical characterization conclude that the inter-facet junction between highly exposed (001) and (101) TNSs surface, and TNSs@Au interfacial heterojunction formed by a direct contact between highly crystalline TNSs and Au, are the key factors to enhance the separation efficiency of photogenerated electrons/holes. On coupling with overlay of g-C3N4 2D NSs synergistically offer tremendous reactive sites for the potential photocatalytic dye degradation in the Z-scheme photocatalyst. Particularly in the designed photocatalyst, Au nanoparticles accumulates and transfer the photo-stimulated electrons originated from anatase TNSs to g-C3N4via semiconductor-metal heterojunction. Because of the large exposed reactive 2D surface, overlay g-C3N4 sheets not only trap photoelectrons, but also provide a potential platform for increased adsorption capacities for organic contaminants. This work establishes a foundation for the development of high-performance Z-scheme photocatalytic systems.

TiO2-supported catalysts have been widely used for a range of both liquid-phase and gas-phase hydrogenation reactions. However, little is known about the effect of their different crystalline surfaces on their activity during the hydrodeoxygenation process. In this work, Au supported on anatase TiO2, mainly exposing 101 or 001 facets, was investigated for the hydrodeoxygenation (HDO) of guaiacol. At 300 °C, the strong interaction between the Au and TiO2-101 surface resulted in the facile reduction of the TiO2-101 surface with concomitant formation of oxygen vacancies, as shown by the H2-TPR and H2-TPD profiles. Meanwhile, the formation of Auδ−, as determined by CO-DRIFT spectra and in situ XPS, was found to promote the demethylation of guaiacol producing methane. However, this strong interaction was absent on the Au/TiO2-001 catalyst since TiO2-001 was relatively difficult to be reduced compared with TiO2-101. The Au on TiO2-001 just served as the active site for the dissociation of hydrogen without the formation of Auδ−. The hydrogen atoms spilled over to the surface of TiO2-001 to form a small amount of oxygen vacancies, which resulted in lower activity than that over Au/TiO2-101. The catalytic activity of the Au/TiO2 catalyst for hydrodeoxygenation will be controlled by tuning the crystal plane of the TiO2 support.

[Display omitted] • Inactive Au/TiO 2 can be activated by Cl radicals. • Once Cl is consumed, the reaction will be terminated, although a large amount of supported cationic Au remains. • The Au(I)–Au(III) redox couple is responsible for triggering the reaction. Supported cationic gold (Au) has been recognized as an active site of acetylene hydrochlorination for decades; however, it remains ambiguous why its loading on carbon-based materials is active but that on metal oxides (e.g., titania, TiO 2) is virtually inactive. For the inactive Au/TiO 2 catalyst, the Au(I)–Au(III) redox couple cannot be constructed in the presence of oxidizing gas (NO, N 2 O, and NO 2), which is thermally desorbed from the catalyst synthesis when aqua regia is used. Surprisingly, the inactive Au/TiO 2 can be activated when it is impregnated with trichloromethane, CHCl 3 , which releases the radical (Cl) to trigger the Au(I)–Au(III) redox couple. Once Cl radicals are consumed, the reaction will be terminated, although a large amount of supported cationic Au remains. The terminated Au/TiO 2 catalyst can be reactivated by adding Cl again. In contrast to the carbon-supported cationic Au system, the inability to build Au(I)–Au(III) redox couples is the dominant reason for the inactivity of metal-oxide-supported Au catalysts and provides a new perspective on activating metal-oxide-supported metal-based hydrochlorination catalysts. [ABSTRACT FROM AUTHOR]

A high response humidity sensor based on Au nanoparticles (AuNPs) modified TiO 2 (Au/TiO 2) was designed for real-time monitoring of human respiration. Effects of Ti3+ defect content on the performance of TiO 2 humidity sensor was further explored. Experiments show that AuNPs can make more Ti3+ defects to appear on TiO 2 surface to enhance hydrophilicity of the materials, which can greatly enhance response of the humidity sensor. AuNPs can also increase oxygen vacancy and hydroxyl content on the surface of TiO 2 to promote decomposition of water molecules into conductive ions and to accelerate the process of proton conduction. Such an Au/TiO 2 humidity sensor shows high response (84366.9), good linearity, low hysteresis (4.76%) and high reliability in the range of RH from 11% to 95%. In addition, Au/TiO 2 humidity sensor can effectively detect different breathing states and skin surface moisture, showing strong application potential in real-time respiratory monitoring and non-contact sensing. This research has further enriched factors that affect the performance of TiO 2 humidity sensors, and also provides a possibility for the development of high-performance TiO 2 respiration sensors. [ABSTRACT FROM AUTHOR]

In this work, an Au modified Bi2O3-TiO2 (Au/Bi2O3-TiO2) hybrid is developed as a simple and effective photocatalyst for the production of H2O2. The modification of Bi2O3 improves the charge separation of photocatalyst and significantly enhances the photocatalytic activity of Au/TiO2 for H2O2 production. In-situ electron spin resonance studies shows stepwise single-electron oxygen reduction reaction (ORR) on the Au/Bi2O3-TiO2 photocatalyst for the production of H2O2. This work demonstrates the importance of heterojunction structure photocatalyst for improved performance of TiO2 in order to produce concentrated H2O2.

An effective improvement of hydrogen evolution from water splitting under solar light irradiation was investigated using quantum dots (QDs) compounds loaded onto a Au/TiO 2 photocatalyst. First, Au/TiO 2 was prepared by the deposition-precipitation method, and then sulfide QDs were loaded onto the as-prepared Au/TiO 2 by a hydrothermal method. QDs were loaded onto Au/TiO 2 to enhance the energy capture of visible light and near-infrared light of the solar spectrum. The results indicated that the as-prepared heterojunction photocatalysts absorbed the energy from the range of ultraviolet light to the near-infrared light region and effectively reduced the electron-hole pair recombination during the photocatalytic reaction. Using a hydrothermal temperature of 120 °C, the as-prepared (ZnS–PbS)/Au/TiO 2 photocatalyst had a PbS QDs particle size of 5 nm, exhibited an energy gap of 0.92 eV, and demonstrated the best hydrogen production rate. Additionally, after adding 20 wt % methanol as a sacrificial reagent to photocatalyze for 5 h, the hydrogen production rate reached 5011 μmol g−1 h−1. [Display omitted] • Sulfide QDs loaded onto Au/TiO 2 prepared by a hydrothermal method. • QDs onto Au/TiO 2 enhance energy capture of the solar spectrum. • (ZnS–PbS)/Au/TiO 2 prepared at 120 °C demonstrated the best hydrogen production rate. [ABSTRACT FROM AUTHOR]

[Display omitted] • High efficiency Au/TiO 2 for CTH of 4-nitrostyrene by NH 3 BH 3 is reported. • The presence of Au-OH accelerates dehydrogenation of NH 3 BH 3. • The existence of Au-OH could promote the adsorption of 4-nitrostyrene. • Low-coordinated Au also promotes the adsorption of 4-nitrostyrene. Transfer hydrogenation of unsaturated nitro compounds by NH 3 BH 3 is an important hydrogenation reaction. Among them, Au/TiO 2 catalysts could achieve good activity for this reaction, but often have problem such as the selectivity decline. In this study, we prepare PVA-wrapped Au nanoparticles, and then load them onto TiO 2 support to obtain Au/TiO 2 catalyst. We demonstrate that the prepared catalyst after calcination has achieved high activity (>99 %) and high selectivity (99 %) in the transfer hydrogenation of 4-nitrostyrene (4-NS) within 30 min by NH 3 BH 3 under ambient temperature and pressure. In addition, the catalyst can still maintain high selectivity (>97 %) after being recycled for 5 times, showing its remarkable stability and reusability. Characterization results and density functional theory (DFT) calculations showed that the presence of Au-OH species accelerates the dehydrogenation of NH 3 BH 3 and thus enhances the catalytic activity. Meanwhile, Au-OH species and low-coordinated Au are beneficial to enhance nitro adsorption and improve the selectivity of transfer hydrogenation reaction. This study provides new ideas for the rational design of high-performance green gold catalytic transfer hydrogenation reactions. [ABSTRACT FROM AUTHOR]

This study compares the impact of two reduction techniques, thermal reduction (TR) and photocatalytic reduction (PR), on Au/TiO 2 photocatalysts synthesized using the deposition-precipitation with urea method. Characterization methods, including temperature-programmed reduction, UV-Vis diffuse reflectance spectroscopy, electrochemical assessments (open-circuit potential and linear sweep voltammetry), and transmission electron microscopy, were employed. The 2-h. PR treatment yielded a highly effective photocatalyst (0.5Au-PR2), with 93.6% of gold nanoparticles below 4 nm, outperforming the TR counterpart (76.8%). All Au-loaded samples exhibited an absorption band between 400 and 800 nm, indicating the localized surface plasmon resonance (LSPR) effect. Interestingly, the TR catalyst had a broader LSPR band than the PR catalyst. Additionally, the 0.5Au-PR2 sample showed higher photocurrent and superior photocatalytic activity in the degradation of methyl orange and hydrogen production, which is attributed to its smaller particle size (2.9 nm) and weaker metal-support interaction. This smaller particle size emphasizes the crucial role of reduction techniques in tailoring Au/TiO 2 photocatalysts for enhanced performance. [Display omitted] • Photocatalytic (PR) and thermal reduction (TR) of Au on TiO 2 was performed. • PR led to smaller Au nanoparticle size and a more uniform size distribution. • 0.5Au-PR2 sample exhibited higher photocurrent than TR sample. • 0.5Au-PR2 showed higher photocatalytic activity in H2 production by photoreforming. • Increase in activity was attributed to a smaller Au particle size. [ABSTRACT FROM AUTHOR]

A floating catalyst was developed by immobilizing Au/TiO 2 photocatalyst on porous Zein polymer, which showed good photocatalytic activity for degradation of a range of organic dyes under natural sunlight. [Display omitted] • Developed polymer-Au/TiO 2 floating photo-catalyst for dye degradation under sunlight. • Catalyst includes Au/TiO 2 on low-density Zein-based polymer, enabling easy recovery and reusability. • Thorough spectroscopic, thermo-gravimetric, and imaging analysis confirms catalyst's identity and stability. • Catalyst shows high photocatalytic activity, simple fabrication, suitable for water pollution treatment. Floating catalysts for photocatalytic dye degradation under sunlight is very useful for large-scale real-world application. The strategy of immobilizing semiconductor photo-catalysts to a variety of low-density floating material is demonstrated with the objective of easy recovery, low catalyst loss and long reusability. In this study a polymer-Au/TiO 2 (Z@Au/TiO 2) floating photo-catalyst was developed using Au/TiO 2 as a visible light active photo-catalyst immobilized on Zein based low density polymer material. The synthesized floating catalyst was meticulously characterized by a range of spectroscopic, thermo gravimetric and imaging techniques to confirm its chemical identity and stability. Under either artificial or natural sunlight conditions, a variety of dye molecules (Auramine (Aur), Congo red (CR), Jakazol red (JR), and Methyl violet (MV)) could be degraded through photocatalytic degradation with floating Z@Au/TiO 2. Additionally, it was demonstrated that it could be collected easily after the catalysis and can be reused for several cycles. Due to its ease of fabrication and high photocatalytic activity, Z@Au/TiO 2 floating photo-catalyst may be helpful in treating water pollution for environmental remediation. [ABSTRACT FROM AUTHOR]

The performance of CO oxidation over plasmonic Au/TiO2 photocatalysts is largely determined by the electric discharge characteristics and physicochemical properties of discharge gas. To explore the activation mechanism of Au/TiO2, an O2 and Ar mixture gas as a discharge gas was employed to activate Au/TiO2. The photocatalytic activity in CO oxidation over activated Au/TiO2 was obtained, and the electric discharge characteristics, Au nanoparticle size, surface chemical state, optical property and CO chemisorption were thoroughly characterized. As the O2 content increases from 10% to 50%, the amplitude of the current pulses increases, but the number of pulses and the discharge power decrease. The photocatalytic activity of Au/TiO2 rises rapidly at first and then remains constant at 75% when the O2 content is above 50%. Compared with the discharge gas of 10% and 30% O2/Ar, the sample activated by 50% O2/Ar plasma possesses less metallic Au and more surface oxygen species and carbonate species by X-ray photoelectron spectroscopy, which is consistent with UV-vis diffuse reflectance spectra and CO chemisorption. The CO chemisorption capacities of the activated samples are the same at a long exposure time due to the approximate Au nanoparticle size observed by transmission electron microscopy. An increase in carbonate species generated from the oxygen species on the surface of TiO2 is discovered.

Surface plasmon resonance (SPR) is proved to induce catalysis and generate surface‐enhanced Raman scattering (SERS) effect. However, it remained a significant challenge in developing the efficient approach to in situ monitor the surface reaction and extending the SPR catalysis as a general approach in surface organic synthesis, especially for the C–C coupling. Herein, SPR from the Au nanoparticles played the bifunctional roles to induce the surface catalysis reaction and enhance the surface Raman signal. The SPR and electrochemical potential became two necessary external fields for the surface coupling reaction to produce 2,2′‐bipyridine, which was explored by SERS. The adsorbed pyridine molecules underwent a dimerization to produce cis‐configuration 2,2′‐bipyridine at the −0.7 V by appropriate laser irradiation. It demonstrated that the surface dimerization efficiency was critically dependent on the laser, potential, the solution properties, and so on. It was improved significantly at the relative negative potential and by 638 nm laser. The solvent with oxygen facilitated the surface dimerization reaction. Pd nanoparticles played the assistant role to capture the hydrogen released from the pyridine to accelerate the breaking of C–H bond and C–C coupling reaction. The surface reaction mechanisms involved the electrons transfer from Au to TiO2 and injected electron delivery to α‐H of pyridine for activation and the formation of carbon free radicals and coupling together to produce 2,2′‐bipyridine. This strategy is expected to further provide an alternative approach to the C–C coupling reaction and to extend the SPR and electrochemical catalysis to a practical application in surface modification as well as organic synthesis, and SERS is anticipated to be a promising in situ technique for the surface chemical reaction. [ABSTRACT FROM AUTHOR]

The development of advanced catalyst integration strategy is of great importance and promising for long‐term and stable gas catalysis in environmental processing. However, conventional catalyst fabrication techniques including spray method and spin coating cannot overcome the key problems of catalyst peeling off from substrate and related severe performance degradation. In this work, an in situ integration strategy of monolithic Au/TiO2 catalysts on Ti mesh for efficient and stable low‐temperature CO oxidation is reported. Plasma electrolytic oxidation technology can create a porous TiO2 seeding layer with strong substrate adherence. Subsequent hydrothermal reaction, ion exchange, and calcination processes can induce the in situ nucleation of sodium titanate nanosheets and their follow‐up conversion to TiO2 nanosheets with huge surface area. The oxygen defects generated in anatase TiO2 nanosheet supports can not only provide sufficient anchoring sites for the deposition and attachment of gold nanoparticles (Au NPs) during deposition–precipitation process, but also absorb and activate oxygen species. Meanwhile, the strong interactions between Au NPs and TiO2 support make the catalysts more chemically active. As a result, the Au/TiO2 monolithic catalysts can eliminate CO completely at low temperature and exhibit considerably high stability, suggesting their potential in practical applications. [ABSTRACT FROM AUTHOR]

This study proposes a new and sustainable approach for the aerobic oxidation of furfural to furoic acid, the precursor of 2,5-furandicarboxylic acid (FDCA), a key monomer in the development of green polyethylene terephthalate substitutes. This work presents an alternative method for conducting this reaction utilizing a buffer solution to maintain a constant pH of 8. Au/TiO 2 is identified as the optimal catalyst, its high capacity to activate oxygen being the key factor to explain the favorable results obtained. The mechanistic and kinetic study of experimental results corroborates that the Cannizzaro route (which co-produces furfuryl alcohol) is suppressed. Thus, furoic acid is the only compound detected in the liquid phase when working at temperatures below 120ºC and 20 bar O 2. The pH control has also a double positive effect on the stability, with a significant reduction in the humins formation and preventing the catalytic deactivation observed in base-free reactions by the permanent adsorption of the acids obtained. To sum up, this new approach represents a significant improvement in terms of activity, selectivity, and stability. These three aspects are crucial to ensure sustainability and to facilitate the process scale-up. [Display omitted] • Furfural to furoic acid oxidation performed at controlled pH = 8. • Cannizaro-type side reactions are supressed at these conditions. • Au/TiO 2 presents the better furoic acid yields (>35 % yield). • Operation at these conditions minimize the formation of humins. • A mechanistic kinetic model, useful for reactor design purposes is proposed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Au-modified TiO 2 nanorod arrays were synthesized via a two-step method. • The Au/TiO 2 exhibited excellent n-butanol sensing performances. • The enhanced sensitivity mechanism of Au/TiO 2 was discussed detailed. • The experimental results are verified by first-principles calculation. In this paper, TiO 2 nanorod arrays were grown on FTO via a simple hydrothermal method. Then Au nanoparticles with an average size of ∼ 6 nm were modified on the surface of TiO 2 nanorods (NRs) using magnetron sputtering technology. The gas-sensing performance of pristine TiO 2 and Au-modified TiO 2 samples were systematically tested. The Au/TiO 2 -based sensors exhibited better gas-sensing properties to n-butanol gas than pristine TiO 2 sensors, including high sensitivity, lower working temperature, and faster response and recovery time. And 10 s-Au/TiO 2 sensor showed the highest response (S = 25) to 100 ppm n-butanol gas at 240 °C, which was 5 times higher than that of pristine TiO 2. Furthermore, the adsorption energies of TiO 2 and Au/TiO 2 surface to n-butanol molecules were calculated using first-principles calculations. It is revealed that the enhanced n-butanol sensing performance of Au/TiO 2 sensor is mainly attributed to the catalytic effects and chemical sensitization of Au toward n-butanol gas. The study confirms that Au-modified TiO 2 nanorods have great potential for application in n-butanol sensors. [ABSTRACT FROM AUTHOR]

• The reactivity of Au/TiO 2 -1 0 1 was higher than Au/TiO 2 -0 0 1 during CO oxidation. • Diverse gold status induced different CO adsorption behavior. • The crystal plane of support strongly affected the surface carbonate species. • Different ability of CO adsorption and CO 2 desorption led to disparate reactivity. Supported gold catalysts exhibit very high activity for CO oxidation. However, there is lack of systematic study for supports effect on reactants adsorption and products desorption. Herein, we successfully prepared supported gold catalysts on TiO 2 matrix exposing either {1 0 1} or {0 0 1} crystal plane (labeled as Au/TiO 2 -1 0 1 and Au/TiO 2 -0 0 1 respectively) by deposition-precipitation (DP) method. It is found that the reactivity of Au/TiO 2 -1 0 1 was much higher than Au/TiO 2 -0 0 1 in CO oxidation reaction (9.33 × 10−3 mol CO g Au −1 s−1 vs. 6.23 × 10−4 mol CO g Au −1 s−1 at 30 °C). The gold nanoparticles (∼2 nm) were detected as sole gold species in Au/TiO 2 -1 0 1, while not only gold nanoparticles (∼4 nm) but also clusters (∼1.3 nm) were present in Au/TiO 2 -0 0 1. The difference in gold status induced different CO adsorption situations that CO was more effectively adsorbed on gold nanoparticles in Au/TiO 2 -1 0 1 which existed more Au0 site. Meanwhile, we revealed that the bidentate carbonate, which could either block active sites for the reaction or hinder access of reactants, were adsorbed much more strongly on TiO 2 -0 0 1. While on TiO 2 -1 0 1, bicarbonate was the main surface species which was easier decomposed to form CO 2. Therefore, the differences between Au/TiO 2 -1 0 1 and Au/TiO 2 -0 0 1 in the efficiency of CO adsorption and the ability of CO 2 desorption resulted in disparate reactivity. We reasonably gave the deep insight into the support effect that was intrinsically related to the adsorption and desorption behavior of surface species on the catalyst. [ABSTRACT FROM AUTHOR]

Here, in Part B of this Series, we take a critical look at the reaction mechanisms of low temperature CO oxidation reactions over nanoscale gold, including adsorption, surface reaction, and desorption of key substrates, viz., CO and O2. Based on a concerted analysis of reactivity data of Au nanoparticles, physicochemical surface characterization, and theoretical first principles calculations, we conclusively prove that out of the 2 most commonly invoked reaction mechanisms, gold-only vs. gold-assisted, the latter is the only mechanism operative for supported gold particles in the quantum size range of 2–5 nm. The Au-MOx support perimeter interface is a structural motif that is very rich in small metallic particles, and extremely low-coordinated Au sites (with N ∼4–5), and some in presence of atomic bonding with Zn atoms. There is both charge and species transfer at this perimeter interface, which also provides highly active sites for adsorption of CO and O2. [ABSTRACT FROM AUTHOR]

Graphical abstract A new strategy to enhance catalytic performance by manipulating surface charges of Au in the timescale of chemical reaction. Highlights • We provide a new strategy to increase quantum efficiency of hydrogen evolution. • The surface charges of Au have been modified within μs to ms timescale. • The lifetime of surface charges is crucial for the catalytic performance. Abstract Here we reported a novel method for manipulating the surface charge of Au/TiO 2 (Gold/Titanium Dioxide) photocatalysts within chemical reaction timescales by using our home-modified LED light source. We further demonstrate that the alternation of negative charge and neutral charge on Au surface would affect the photocatalytic performance, in which the suitable timescale of switching surface charge on Au benefits for the enhanced quantum efficiency in the photo-mediated hydrogen evolution. We believe that our results will help a deeper understanding of the kinetics process in the photocatalytic reaction and pave the way for achieving highly efficient photocatalytic systems. [ABSTRACT FROM AUTHOR]

Abstract A label- and amplification-free photoelectric immunosensor based on well-defined layer-by-layer sandwich-structured AuNP/TNW/AuNP composite is proposed for direct and ultrasensitive detection of α-fetoprotein (AFP). The AuNP/TNW/AuNP composite is produced by assembling an Au nanoparticle underlayer and anatase TiO 2 nanowires (TNW) onto the FTO substrate, followed by decorating Au nanoparticles onto the TNW surface, through a simple sputtering and hydrothermal process. The resulting AuNP/TNW/AuNP electrode exhibits a 14-fold and 2-fold enhancement in photocurrent density under simulated sunlight compared with that of bare TNW and AuNP/TNW, respectively, which benefits from the SPR-induced photoabsorption increment and charge separation improvement in Au nanoparticle and interfacial charge transfer promotion at the TiO 2 /substrate interface in the Au underlayer. As a proof of concept, the AFP antigen can be quantitatively detected by the proposed AuNP/TNW/AuNP coupled with anti-AFP through the analysis of the photocurrent change. This novel AFP photoelectric immunosensor exhibited sensitive detection of AFP with an ultrahigh sensitivity of 0.001 ng mL−1 and good specific selectivity. Moreover, the practical determination of AFP in human serum is also investigated, demonstrating its applicability and potential attraction for clinical tests and disease diagnosis. Highlights • Design, synthesis, and application of a label- and amplification-free photoelectric immunosensor. • The layer-by layer sandwich-type AuNP/TNW/AuNP sensing electrode could evidently enhance the photocurrent response. • Allowed sensitive and specific detection of α-fetoprotein (AFP). • Ultralow detection limit of the proposed photoelectric immunosensor for AFP is estimated to be 0.001 ng mL−1. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • In situ DRIFTS is employed to study CO oxidation on Au/TiO 2 catalysts with various TiO 2 facets. • Dual-perimeter-sites catalysis of Au/TiO 2 catalysts depends sensitively on TiO 2 facets. • CO migration from TiO 2 to Au–TiO 2 perimeter sites depends on the catalytic activity of perimeter sites. • Dual-perimeter-sites catalysis occurs on Au/TiO 2 {1 0 0} and Au/TiO 2 {1 0 1} but not on Au/TiO 2 {0 0 1}. Abstract Au/TiO 2 catalysts for low-temperature CO oxidation exhibit dual-perimeter-sites catalysis in which CO molecules adsorbed at both Au and TiO 2 surfaces diffuse to Au–TiO 2 perimeters and are oxidized into CO 2. Via a comprehensive in situ DRIFTS study of CO adsorption and oxidation on Au/TiO 2 catalysts with different TiO 2 morphologies predominantly exposing {0 0 1}, {1 0 0}, and {1 0 1} facets, we report that such dual-perimeter-sites catalysis depends sensitively on TiO 2 morphology and facets. Adsorbed CO molecules remain stable on TiO 2 surfaces up to 223 K. The migration of CO molecules from TiO 2 to Au–TiO 2 perimeter sites depends on the catalytic activity of Au–TiO 2 perimeter sites. Dual-perimeter-sites catalysis occurs within Au/TiO 2 {1 0 0} and Au/TiO 2 {1 0 1} catalysts with catalytically active Au–TiO 2 perimeter sites that exhibit large coverage gradients between CO molecules adsorbed at Ti and Au sites, facilitating the migration of CO molecules from TiO 2 to the Au–TiO 2 perimeter sites, but seldom within Au/TiO 2 {0 0 1} catalysts with catalytically inactive Au–TiO 2 perimeter sites that exhibits few coverage gradients between CO molecules adsorbed at Ti and Au sites. These results provide novel insights into the structure–activity relationship in Au/TiO 2 catalysts for low-temperature CO oxidation. [ABSTRACT FROM AUTHOR]

• Gold supported titania catalyst for sonochemical parallel synthesis of 1,2,3-triazoles. • The effect of ultrasonics on catalyst in liquids was studied. • The Work shows synergetic effect of Au/TiO 2 catalysts and the ultrasound irradiation. • SEM was used to distinguish the observed synergetic effect of fresh and spent catalysts. • HMBC 2D NMR was used as a valuable tool to unambiguously assign the obtained structures. A lower carbon society can be achieved with innovative recycling and parallel organic and pharmaceutical synthesis practices that reduce the chemical industry's environmental footprint; this is crucial to fulfilling the principles of green chemistry and engineering. Regioselective azide-alkyne cycloadditions were investigated using heterogeneous catalysts based on gold supported on titania (Au/TiO 2) and ultrasonic irradiation. The catalysts were used in the base-free synthesis of 1,2,3-triazoles via azide-alkyne click reactions. The catalyzed azide-alkyne cycloaddition reaction protocol was completed in a short amount of time (5 min) with high product yields in parallel synthesis design The superior catalytic efficacy of Au/TiO 2 catalysts for achieving the highest product yield emphasizes the ultimate sympathetic of the catalyst structure and role. The scanning electron microscope (SEM) was used to distinguish the synergetic effect of Au/TiO 2 catalysts, and the ultrasound irradiation tool for fresh and spent catalysts. Furthermore, the Heteronuclear Multiple Bond Correlation (HMBC) 2D NMR technique was used as a valuable tool to unambiguously assign the obtained structures. [Display omitted] [ABSTRACT FROM AUTHOR]

The quality and assessment of a catalyst can be documented in detail by the application of pore size. This research aims to calculate fractal dimension from the relationship among pore size, maximum pore size and wetting phase saturation and to confirm it by the fractal dimension derived from the relationship among the ratio between surface area per unit pore volume, entry surface area per unit pore volume and wetting phase saturation. In this research, pore size was measured on Au/TiO2 using Brunauer–Emmett–Teller (BET) surface area. Two equations for calculating the fractal dimensions have been employed. The first one describes the functional relationship between wetting phase saturation, pore size, maximum pore size and fractal dimension. The second equation implies to the wetting phase saturation as a function of surface area per unit pore volume, entry surface area per unit pore volume and the fractal dimension. Two procedures for obtaining the fractal dimension have been utilized. The first procedure was done by plotting the logarithm of the ratio between pore size and maximum pore size versus logarithm wetting phase saturation. The positive slope of the first procedure = 3 − Df (fractal dimension). The second procedure for obtaining the fractal dimension was determined by plotting the logarithm of the ratio between surface area per unit pore volume, entry surface area per unit pore volume versus the logarithm of wetting phase saturation. The negative slope of the second procedure = Df − 3. It was found that the plasma + thermally treated Au/TiO2 has the highest fractal dimension value owing to possibility of having holes and channels. The results also show similarity between pore size fractal dimension and surface area per unit pore volume fractal dimension. In our case, as conclusions, the higher the fractal dimension, the better the catalytic activity. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Ni/P25 TiO 2 and Au/P25 TiO 2 afford similar H 2 production rates in alcohol-water mixtures. • Ni/P25 TiO 2 outperforms Au/P25 TiO 2 in methanol-water mixtures under UV excitation. • H 2 production rates depend on the alcohol hole scavenger and alcohol concentration. • At 10 vol%, rates follow the order glycerol > ethylene glycol > methanol > ethanol. • At 40 vol%, rates follow the order methanol > ethylene glycol > glycerol > ethanol. Abstract This study systematically compares the performance of 0.5 wt% Ni/P25 TiO 2 and 2 wt% Au/P25 TiO 2 photocatalysts for H 2 production in alcohol-water mixtures under UV excitation. HRTEM, XANES and EXAFS confirmed the presence of 5–8 nm Ni0 and Au0 nanoparticles on the surface of the photocatalysts. H 2 production tests were conducted in various alcohol-water systems (0–100 vol%), using methanol, ethanol, ethylene glycol and glycerol. The Ni/P25 TiO 2 and Au/P25 TiO 2 photocatalysts demonstrated remarkably similar performance for hydrogen production in all the alcohol-water systems tested. At low alcohol concentrations (15 vol% or less), H 2 production rates followed the order glycerol > ethylene glycol > methanol > ethanol, whilst at higher alcohol concentrations methanol (optimum 40 vol%) and ethanol (optimum 80–90 vol%) afforded the highest rates. Rates depended on the polarity and oxidation potential of the alcohol. Further, anatase-rutile heterojunctions in P25 TiO 2 were found to greatly enhance H 2 production. [ABSTRACT FROM AUTHOR]

Abstract A series of Au-Pd/TiO 2 catalysts were synthesized in different weight % using sol-immobilization method. Of the range studied 1%Pd/TiO 2 catalyst achieved 86.4% conversion of phenol to CO 2 in a standard batch-slurry system utilizing UV. However under recycle or continuous operation Pd leaching from catalyst surface led to gradual deactivation. Au-Pd nanoparticles supported on TiO 2 P25 were stable and recyclable, here Au species were found to help to anchor Pd species on TiO 2 , and no observable Pd leaching occurred. Utilizing UV, 1%Pd/TiO 2 showed faster rate of phenol degradation in comparison to Au-Pd/TiO 2 , while 1%Au/TiO 2 and 0.5%Au-0.5%Pd/TiO 2 showed faster phenol degradation rates under visible light. The TiO 2 P25 support was also found to be active, stable and recyclable in phenol degradation utilizing UV; and was hence considered suitable for continuous operation. However poor oxygen mass transfer led to the formation and lay-down of polymeric species when using a Trickle bed approach. Operation in the Taylor flow regime was demonstrated to increase oxygen saturation and significantly reduced deactivation. Hence continuous photocatalytic degradation of phenol could be achieved using TiO 2 under Taylor Flow conditions. [ABSTRACT FROM AUTHOR]

Au/TiO 2 catalytic coatings have been developed onto the inner surface of a quartz tube for photocatalytic applications. Gold nanoparticles with diameter 3–5 nm were synthesised using the citrate method, with sodium borohydride as a reducing agent. The nanoparticles were characterised by UV–vis spectroscopy, small angle X-ray scattering (SAXS), dynamic light scattering (DLS), and transmission electron microscopy (TEM). The photocatalytic activity of gold nanoparticles and Au/TiO 2 catalytic coatings was studied in the reduction of 4-nitrophenol (4-NP) with green LEDs. The reaction rate follows Langmuir-Hinshelwood kinetics and increases with the light intensity until a plateau at 3 mW cm−2. The photocatalytic activity of gold nanoparticles was fully preserved in the Au/TiO 2 coatings. [Display omitted] • Efficient visible light Au/TiO 2 photocatalytic coatings with a thickness of 2 mm were developed for 4-nitrophenol reduction. • Gold nanoparticles retain their photocatalytic activity upon incorporation into titania coatings. • The catalyst has a low saturation power density with green light of 3 mW cm−2 • Aggregation of Au in the coating shifts the plasmonic peak from 520 to 560 nm. [ABSTRACT FROM AUTHOR]

Strong Metal−Support Interaction (SMSI) is a well-known phenomenon of heterogeneous catalysis that have not been extensively investigated in photocatalytic applications. Moreover, the reactions previously studied for photocatalysts under SMSI state are mainly restricted to energy related uses. The present work seeks to explore the effect of SMSI induced by soft wet-chemistry in a Au/TiO 2 photocatalyst with specific focus on photocatalytic environmental remediation. With this aim, the developed photocatalyst has been evaluated considering liquid, gas and solid pollutants in order to represent the wide range of environmental photocatalysis applications. These photooxidation scenarios were methylene blue dissolved in water, gaseous NO, and soot directly deposited on the photocatalyst. The results revealed that the SMSI induction has a generally positive effect on photoactivity promoting the MB and soot removal by 53% and 60%, respectively. However, the SMSI did not provide any additional benefit in the NO x elimination compared to the non-SMSI Au/TiO 2 photocatalyst, because the enveloping of AuNPs limits the gold-pollutant interaction. [Display omitted] • Strong Metal−Support Interaction (SMSI) induced in Au/TiO 2 by soft wet-chemistry. • Photocatalytic removal of water (MB), air (NO x) and solid (soot) pollutants. • SMSI increases the Au/TiO 2 photocatalytic pollutants removal by 50–60%. • TiO x overlayer hinders the Au adsorption capacity diminishing the NO removal. [ABSTRACT FROM AUTHOR]

The purification of drinking water is one of the most urgent challenges in developing countries, for which the efficient removal of traces of heavy metals, e.g., Cr(IV), represents a key technology. This can be achieved via photocatalysis. In this study, we compare the performance of Au/TiO2 to bare TiO2 P25 catalysts. Furthermore, the influence of the sacrificial reagent citric acid under UV-Vis and Vis excitation was investigated and a detailed investigation of the catalysts before and after reaction was performed. During the photocatalytic reduction of Cr(IV) under acidic conditions, both leaching of Au, as well as absorption of Cr, occur, resulting in new catalyst systems obtained in situ.

Aiming at model systems with close-to-realistic transport properties, we have prepared and studied planar Au/TiO2 thin-film model catalysts consisting of a thin mesoporous TiO2 film of 200–400 nm thickness with Au nanoparticles, with a mean particle size of ~2 nm diameter, homogeneously distributed therein. The systems were prepared by spin-coating of a mesoporous TiO2 film from solutions of ethanolic titanium tetraisopropoxide and Pluronic P123 on planar Si(100) substrates, calcination at 350 °C and subsequent Au loading by a deposition–precipitation procedure, followed by a final calcination step for catalyst activation. The structural and chemical properties of these model systems were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption, inductively coupled plasma ionization spectroscopy (ICP–OES) and X-ray photoelectron spectroscopy (XPS). The catalytic properties were evaluated through the oxidation of CO as a test reaction, and reactivities were measured directly above the film with a scanning mass spectrometer. We can demonstrate that the thin-film model catalysts closely resemble dispersed Au/TiO2 supported catalysts in their characteristic structural and catalytic properties, and hence can be considered as suitable for catalytic model studies. The linear increase of the catalytic activity with film thickness indicates that transport limitations inside the Au/TiO2 film catalyst are negligible, i.e., below the detection limit.

Supported gold nanoparticle catalysts show extraordinarily high activity in many reactions. While the relative poor thermal stability of Au nanoparticles against sintering at elevated temperatures severely limits their practical applications. Here atomic layer deposition (ALD) of TiO2 and Al2O3 was performed to deposit an Au/TiO2 catalyst with precise thickness control, and the thermal stability was investigated. We surprisingly found that sub-nanometer-thick Al2O3 overcoat can sufficiently inhibit the aggregation of Au particles up to 600 °C in oxygen. On the other hand, the enhancement of Au nanoparticle stability by TiO2 overcoat is very limited. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) of CO chemisorption and X-ray photoelectron spectroscopy measurements both confirmed the ALD overcoat on Au particles surface and suggested that the presence of TiO2 and Al2O3 ALD overcoat on Au nanoparticles does not considerably change the electronic properties of Au nanoparticles. The catalytic activities of the Al2O3 overcoated Au/TiO2 catalysts in CO oxidation increased as increasing calcination temperature, which suggests that the embedded Au nanoparticles become more accessible for catalytic function after high temperature treatment, consistent with our DRIFTS CO chemisorption results. [ABSTRACT FROM AUTHOR]

Commercial gold nanoparticles supported on titanium dioxide (TiO2) were found to be a highly efficient catalyst for alkyne hydroamination. Terminal alkynes could easily undergo intermolecular hydroamination with low catalyst loadings (0.2 mol% Au) under solvent-free conditions. Indoles were efficiently synthesized using microwave heating through intramolecular hydroamination. [ABSTRACT FROM AUTHOR]

The use of heterogeneous catalysis to upgrade biomass wastes coming from lignocellulose into higher value-added chemicals is one of the most explored subjects in the prospective vision of bio-refinery. In this frame, a lot of interest has been driven towards biomass-derived building block molecules, such as furfural. Gold supported catalysts have been successfully proven to be highly active and selective in the furfural oxidative esterification to methyl-2-furoate under mild conditions by employing oxygen as benign oxidant. Particular attention has been given to the studies in which the reaction occurs even without base as co-catalyst, which would lead to a more green and economically advantageous process. The Au catalysts are also stable and quite easily recovered and represent a feasible and promising route to efficiently convert furfural to methyl-2-furoate to be scaled up at industrial level. [ABSTRACT FROM AUTHOR]

Aiming at an improved mechanistic understanding of the preferential oxidation of CO on supported Au catalysts, we have investigated the competition between CO and H2 for stable, active oxygen (Oact) species on a Au/TiO2 catalyst during the simultaneous exposure to CO and H2 with various CO/H2 ratios at 80℃ and 400℃ by quantitative temporal analysis of products (TAP) reactor measurements. It is demonstrated that, at both higher and lower temperature, the maximum amount of active oxygen removal is (i) independent of the CO/H2 ratio and (ii) identical to the amount of active oxygen removal by CO or H2 alone. Hence, under preferential CO oxidation (PROX) reaction conditions, in the simultaneous presence of CO and H2, CO and H2 compete for the same active oxygen species. In addition, also the dependency of the selectivity towards CO oxidation on the CO/H2 ratio was evaluated from these measurements. Consequences of these findings on the mechanistic understanding of the PROX reaction on Au/TiO2 will be discussed. [ABSTRACT FROM AUTHOR]

The efficient remediation of pharmaceuticals, including wastewater, remains a remarkably challenging issue for water regeneration. Herein, porous Au/TiO 2 synthesized by pyrolysis of NH 2 -MIL-125(Ti) was utilized to be an efficient photocatalyst for mineralization of trimethoprim (TMP) and Metronidazole (MNZ) as the parent compound. The effects of different factors, including TMP and MNZ concentrations, light intensity, H 2 O 2 concentration, Au/TiO 2 dosage, and pH value of reaction solution on the degradation and mineralization performances during UV and visible light (VIS), were addressed. The porous Au/TiO 2 photocatalyst exhibited superior photocatalytic degradation of TMP and MNZ under UV and VIS illumination. The optimum pH values were 4; the optimum dosage of Au/TiO 2 was 1.5 g/L, H 2 O 2 concentration was 9.8 mM, TMP and MNZ concentrations was 10 ppm, and their photodegradation efficiency was 100% after 30 min illumination time and mineralization efficiency 98.2% after 3 h illumination for TMP and MNZ, respectively under UV illumination, however, the photodegradation efficiency was 100% after 50 min illumination and mineralization efficiency 96.3% after 4.5 h illumination time for TMP and MNZ, respectively under VIS illumination. The real wastewater matrix with 10 mg/L of TMP and MNZ were subjected to 60 min of illumination under similar optimum conditions of synthetic solution. The results indicated that photodegradation efficiency was determined to be 100% after 70 min illumination time for removal of both TMP (k = 3.4 × 10−2 min−1) and MNZ (k = 2.87 × 10−2 min−1). This is ascribed to the incorporation of Au NPs onto TiO 2, reducing the photoinduced electron-hole recombination, thus promoting the photocatalytic performance. The possible mechanism for photodegradation of antibiotics was also discussed. The demonstration of photocatalysis mechanism over Au/TiO 2 photocatalyst can provide some directing in the enhancement of novel photocatalysts based on MOFs doped by noble metal. [Display omitted] • Porous TiO 2 NPs was derived from NH 2 -MIL-125(Ti) through pyrolysis strategy. • 0.1%Au/TiO 2 was assessed for mineralization of two antibiotics in real wastewater. • The reaction process over Au/TiO 2 was optimized by investigating different factors. • Complete mineralization of two antibiotics (100%) was achieved by UV and VIS light. • 0.1% Au/TiO 2 photocatalyst showed high stability and recyclability for four cycles. [ABSTRACT FROM AUTHOR]

The use of heterogeneous catalysis to upgrade biomass wastes coming from lignocellulose into higher value-added chemicals is one of the most explored subjects in the prospective vision of bio-refinery. In this frame, a lot of interest has been driven towards biomass-derived building block molecules, such as furfural. Gold supported catalysts have been successfully proven to be highly active and selective in the furfural oxidative esterification to methyl-2-furoate under mild conditions by employing oxygen as benign oxidant. Particular attention has been given to the studies in which the reaction occurs even without base as co-catalyst, which would lead to a more green and economically advantageous process. The Au catalysts are also stable and quite easily recovered and represent a feasible and promising route to efficiently convert furfural to methyl-2-furoate to be scaled up at industrial level.

Aiming at an improved mechanistic understanding of the preferential oxidation of CO on supported Au catalysts, we have investigated the competition between CO and H2 for stable, active oxygen (Oact) species on a Au/TiO2 catalyst during the simultaneous exposure to CO and H2 with various CO/H2 ratios at 80 °C and 400 °C by quantitative temporal analysis of products (TAP) reactor measurements. It is demonstrated that, at both higher and lower temperature, the maximum amount of active oxygen removal is (i) independent of the CO/H2 ratio and (ii) identical to the amount of active oxygen removal by CO or H2 alone. Hence, under preferential CO oxidation (PROX) reaction conditions, in the simultaneous presence of CO and H2, CO and H2 compete for the same active oxygen species. In addition, also the dependency of the selectivity towards CO oxidation on the CO/H2 ratio was evaluated from these measurements. Consequences of these findings on the mechanistic understanding of the PROX reaction on Au/TiO2 will be discussed.

Highlights: [•] PANI was well attached with Au/TiO2 catalyst. [•] PANI can remarkably promote CO oxidation over Au/TiO2. [•] A trace H2O could promote CO oxidation over Au/TiO2–PANI. [•] PANI could promote the electron transferring from TiO2 to Au surface. [•] Promoted electron transfer could be attributed to the interaction of PANI with TiO2 and Au nanoparticles. [Copyright &y& Elsevier]

The reaction of stable adsorbed, active surface oxygen (Oact) with H2 on Au/TiO2 catalysts with the same Au loading, but varying Au particle size was studied by quantitative Temporal Analysis of Products reactor measurements between 80 °C and 400 °C and compared to the Oact removal by CO. The absolute amount of Oact for H2 oxidation is identical to that in CO oxidation, and it also occurs at the Au-TiO2 interface perimeter, indicating that the Oact species for this reaction is identical to that for CO oxidation. Implications on the mechanism of the H2 oxidation and the origin of the selectivity during the preferential CO oxidation (PROX) are discussed. [ABSTRACT FROM AUTHOR]

Highlights: [•] Propylene undergoes gas-phase selective epoxidation with CO/O2 reactants over Au/TiO2. [•] The reaction is analogous to the known epoxidation of propylene with H2/O2 mixture. [•] Either CO and H2 are the necessary reducing co-reagents to perform the reaction. [•] CO and H2 induce a formation of the same active oxygen species. [ABSTRACT FROM AUTHOR]

Highlights: [•] Design a novel TPSR method to investigate the process of oxidizing CO over Au/TiO2. [•] CO is oxidized by the chemisorbed H2O over Au/TiO2 according to three different processes. [•] CO is probably oxidized by the physisorbed molecular O2 over Au/TiO2 at low temperature. [•] Water-gas shift reaction only occurs with the desorption of carbonate-like species at TiO2 sites. [ABSTRACT FROM AUTHOR]

Gold nanoparticles supported on TiO2 were probed by adsorption of methyl mercaptane (MM), and the process was quantified gravimetrically. This method allowed discrimination between weakly adsorbed (physisorbed) and strongly bound (chemisorbed) methyl mercaptane. Strong adsorption of MM occured on exposed Au faces, while low-temperature pre-treatment (30 °C) completely suppressed adsorption of MM on the TiO2 support. The thus obtained high selectivity of MM adsorption on Au enabled characterization of the gold surface area and the resulting values are comparable with other noble metal systems of similar average particle size. The estimated adsorption stoichiometry indicates that the entire Au surface is probed.

[Display omitted] • Au/TiO 2 hybrid nanosheets were fabricated with tunable SPR absorption from visible to NIR. • Broad spectrum light driven production of hot electrons and ROS were detected by ESR. • Au/TiO 2 displayed enhanced photocatalytic activity towards TMB oxidation and H 2 evolution. • SPR enhanced photocatalytic activity correlated with the generation of charge carriers and ROS. The coupling of semiconductor and plasmonic nanoparticles (NPs) has attracted significant attention due to improved light harvesting and charge separation for photocatalysis. However, the enhancement effect of surface plasmon resonance (SPR) has not been fully utilized, since it is related to a variety of factors, and the dominant factors remain unclear. It is realized that the spatial arrangement of semiconductor and plasmonic NPs may be of critically importance. To prove this concept, Au/TiO 2 plasmonic nanostructures were fabricated as model system by distributing Au nanorods (AuNRs) uniformly on TiO 2 nanosheets through mercaptopropionic acid assisted method. AuNRs/TiO 2 possesses tunable SPR induced light absorption centered at 520 nm and 795 nm, ranging from visible to NIR that depends on the shape of AuNPs. The sample exhibits simultaneously enhanced photocatalytic activity toward reduction of H 2 O to produce H 2 and oxidation of 3,3′,5,5′-tetramethylbenzidine when exposed to visible or NIR light. The production and reactive behaviors of electrons and ROS including ·OH, ⋅O 2 – and 1O 2 from irradiated Au/TiO 2 were detected by electron spin resonance, and correlated with SPR enhanced photocatalytic activity. These results unveil critical factor in SPR enhanced photocatalysis and suggest a highly preferred form of the hybrid nanostructures for their photocatalytic applications. [ABSTRACT FROM AUTHOR]

Conventionally supported nanoparticle (NP) of plasmonic Au/TiO 2 performs well under visible light, however the problem with cost, activity and durability inevitably remains. Here we demonstrate a semi-transparent nanofilm of plasmonic Au/TiO 2 by deposition-precipitation and atmospheric chemical vapor deposition methods. Onto a synthetic TiO 2 nanofilm (bottom layer), Au NP is allocated (top layer) for direct exposure to light with enhanced utilization efficiency (low cost). Compared to the conventional coating film from NPs, its growth nanofilm formed from molecular assembly is considered more durable. Effects of localized surface plasmon resonance (LSPR) and Fabry-Pérot (F–P) interference are evidenced by UV–vis absorption spectra. To identify and further utilize separation efficiency of charge carriers, photoluminescence spectra and visible-light photocurrent experiment in a three-electrode electrochemical cell were conducted. Using formaldehyde oxidation as reaction model, visible-light photocatalysis over plasmonic Au/TiO 2 nanofilm is conceptually verified. The presence and size of Au NP promotes light absorption, separation of charge carriers and photocurrent. Au/TiO 2 exhibits up to 10 times photocurrent at applied potential compared to TiO 2. Inspiringly, over Au/TiO 2 nanofilm, apparent rate constant, k app (ca. 0.49 s−1) is unprecedentedly achieved ca. 3-4 orders of magnitude larger than TiO 2 -based thin films reported in literatures. Our growth nanofilm of Au/TiO 2 , achieves reaction rate of 5.0 × 10−7 mol s−1·g cat −1 under green LED that is even higher than the conventional supported NP, which is of significance to be considered more durable with the improved interface. Consequently, our semi-transparent nanofilm of plasmonic Au/TiO 2 addresses cost, activity and durability for visible-light photocatalysis, for which it may pave a way to large-scale application from a practical perspective. [Display omitted] • Semi-transparent Nanofilms of Plasmonic Au/TiO 2 was developed. • Onto a synthetic TiO 2 nanofilm (bottom layer), Au NP is allocated (top layer). • Compared to conventional NP its growth nanofilm from molecule is more durable. • Au/TiO 2 has 10-fold photocurrent under light at applied potential compared to TiO 2. • Apparent rate constant on Au/TiO 2 is achieved, 103−4-fold TiO 2 -based ones reported. [ABSTRACT FROM AUTHOR]