Effect of titania synthesis conditions on the catalytic performance of mesoporous Ni/TiO2 catalysts for carbon dioxide reforming of methane

The catalytic performance of 5 wt% Ni/TiO₂ catalysts with different physicochemical properties was studied for the CO₂ reforming of methane reaction. The TiO₂ supports were prepared by the evaporation-induced self-assembly method using three different titania metal precursors. The catalysts were characterized by XRD, BET, TGA, and TEM techniques. The results showed that the phase composition of TiO₂ support plays a crucial role in catalyst performance. Furthermore, the variation of synthesis conditions significantly affects the physicochemical properties of TiO₂ support. NH₃-treatment helped maintain the higher surface area by retaining a significant fraction of the amorphous content of titania support. Catalysts deactivation was caused by the phase transformation of TiO₂ from anatase to rutile and the sintering of Ni metal. Phase transformation into rutile was more significant, with the catalysts possessing a higher content of amorphous TiO₂. Ni/TiO₂ catalyst prepared using the titanium ethoxide precursor performed better in the dry reforming reaction. Anatase titania offers strong metal-support interaction, whereas weak metal-support interaction was observed in the amorphous and rutile phase.     

Fabrication of graphene/Titania nanograss composite on shape memory alloy as photoanodes for photoelectrochemical studies: Role of the graphene

In this study, hierarchical composites of Titania-graphene nanograss arrays (TiO₂@Gr) on shape memory alloy were prepared via chemical vapor deposition-controlled growth process (camphor as source) and subsequent hydrothermal method. The TiO₂@Gr composite composition was optimized by varying the concentrations of graphene on TiO₂ nanograss grown over shape memory alloy. The optical, surface, and structural studies of as-prepared TiO₂@Gr composite were performed under UV–vis spectroscopy, Field Emission Scanning Electron Microscope, Transmission Electron Microscope, Raman, X-ray diffraction and X-ray photoelectron spectroscopy. The result revealed the formation of pure rutile phase Titania nanograss with the impregnation of graphene sheets. Further, the impregnated graphene-Titania composite samples were used as photoanodes (photoelectrode) in 1 M potassium hydroxide solution for photoelectrochemical application. The results revealed an enhancement in photocurrent density of 1.82 mA/cm² at 1.23 V vs. reversible hydrogen electrode, signifying excellent photoelectrochemical performance superior to that of pure rutile titania (nearly 3.5 times), which is attributed to a synergetic effect of the improved electron-hole pair separation rate leading to superior charge transfer due to the presence of graphene nanosheets. Transient photo-response studies (TPS) and Electrochemical impedance spectroscopy (EIS) were used to study the effective charge transfer response and interfacial charge transfer process respectively. The approach for the fabrication of the hierarchical nanocomposite in this study may drive the way for designing innovative composite materials for enhanced photoelectrochemical performance.     

Degradation of methylene blue-ciprofloxacin and hydrogen production simultaneously using combination of electrocoagulation and photocatalytic process with Fe-TiNTAs

The study reported in this paper combines the electrocoagulation and photocatalysis for the simultaneous degradation of methylene blue dyes (MB)-antibiotic ciprofloxacin (CP) and production of hydrogen. The pollutant removal process was conducted by combining adsorption by electrocoagulation and degradation by photocatalysis. Meanwhile, H₂ was produced by reducing the H⁺ on the cathode and the photocatalyst surface in a reactor made of acrylic equipped with aluminum as the anode, stainless steel 316 plates as a cathode, Fe-doped titania nanotube arrays (TiNTAs) as a photocatalyst, and a 250-W mercury lamp as the light source. TiNTAs were synthesized via anodization and followed by the successive ionic layer adsorption and reaction (SILAR) method to incorporate Fe as the dopant. In particular, the effects of Fe loading in the composite photocatalyst are investigated. XRD results showed that TiO₂ nanotubes arrays comprise a 100% anatase phase. FESEM, EDX, TEM, and HRTEM analysis confirmed the formation of the nanotubular structure of TiO₂ and the presence of Fe deposited on the surface. The UV–Vis DRS indicated that the bandgap of Fe-TiNTAs reduced with Fe introduction, as compared to that of the undoped TiNTAs. The results showed that accumulation of the produced hydrogen from the combination of electrocoagulation-photocatalytic system is greater than that which is obtained using individual electrocoagulation or photocatalytic system. The combined process exhibited an enhanced degradation ability of methylene blue and ciprofloxacin, as well as in the H₂ production.     

Continuous hydrogen production activity over finely dispersed Ag2O/TiO2 catalysts from methanol:water mixtures under solar irradiation: A structure–activity correlation

Ag₂O/TiO₂ catalysts with varying amounts of Ag₂O 0.5, 1, 2, and 5 wt% loadings are prepared by impregnation method and Ag/TiO₂ catalyst is prepared by photo deposition method. These catalysts are characterized by XRD, SEM-EDAX, DRS, XPS and TEM techniques. DRS studies clearly showing the expanded photo response of TiO₂ into visible region on impregnation of Ag⁺ ions on surface layers of TiO₂ due to the increased number of energy states created by the silver ions in TiO₂ surface lattice. TEM images are showing the fine dispersion of silver particles on TiO₂ surface. XPS of Ag₂O/TiO₂ calcined and used catalysts along with Ag₂O/TiO₂ reduced and Ag/TiO₂ photo deposited catalysts are compared and the binding energy values of Ti 2p, O1s and Ag 3d are confirming that silver ions are in interaction with TiO₂ in Ag₂O/TiO₂ calcined catalysts. EDAX analysis supports the presence of silver species on the surface layers of TiO₂. Photocatalytic hydrogen production activity studies are conducted over Ag₂O/TiO₂, Ag₂O/TiO₂ reduced and Ag/TiO₂ photo deposited catalysts in pure water and methanol:water mixtures under solar irradiation. Maximum hydrogen production of 145 μmoles/h is observed on 0.5wt% Ag₂O/TiO₂ catalyst in pure water and the maximum hydrogen production of 3350 μmoles/h is observed on 1wt% Ag₂O/TiO₂ catalyst in methanol:water mixtures. Whereas Ag₂O/TiO₂ reduced and Ag/TiO₂ photo deposited catalysts are not showing any hydrogen production activity either in water or in methanol:water mixtures under solar irradiation. Based on the XPS, DRS, TEM, SEM-EDAX studies and the hydrogen production activity on these catalysts, a structure–activity correlation has been proposed wherein the interacted Ag⁺ ions on the surface layers of TiO₂ are playing an important role in maintaining the hydrogen production activity under solar irradiation.     

Photocatalytic hydrogen production from glycerol–water mixture over Pt‐N‐TiO2 nanotube photocatalyst

The effects of several modifications on TiO₂ P25 in producing hydrogen from glycerol–water mixture have been investigated. Prior to further modification, TiO₂ underwent hydrothermal treatment at 130°C for several hours to obtain nanotube shape. TiO₂ nanotubes (TiNT) was then doped with platinum (Pt) and nitrogen (N) by employing photo‐deposition and impregnation method, respectively. SEM and XRD results showed that Pt‐N‐TiNT was successfully obtained as pure anatase crystal structure. The effects of glycerol content to photocatalytic activity of hydrogen production have also been studied, result in 50%v of glycerol as the optimum concentration correspond to the stoichiometric volume ratio of glycerol reforming. The results of photo‐production test showed that TiNT (nanotube) could enhance hydrogen generation by two times compared with unmodified P25 (nanoparticle). Meanwhile, simultaneous modification of TiNT by Pt and N dopants (Pt‐N‐TiNT) lead to activity improvement up to 13 times compared with P25. The output of this study may contribute toward finding an alternative pathway to produce H₂ from renewable resources. Copyright © 2012 John Wiley & Sons, Ltd.     

Photo-induced reforming of alcohols with improved hydrogen apparent quantum yield on TiO2 nanotubes loaded with ultra-small Pt nanoparticles

Photo-induced reforming of methanol, ethanol, glycerol and phenol at room temperature for hydrogen production was investigated with the use of ultra-small Pt nanoparticles (NPs) loaded on TiO₂ nanotubes (NTs). The Pt NPs with diameters between 1.1 and 1.3 nm were deposited on TiO₂ NTs by DC-magnetron sputtering (DC-MS) technique. The photocatalytic hydrogen rate achieved an optimum value for a loading of about 1 wt% of Pt. Apparent quantum yield for hydrogen generation was measured for methanol and ethanol water solutions reaching a maximum of 16% under irradiation with a wavelength of 313 nm in methanol/water solution (1/8 v/v). Pt NPs loaded on TiO₂ NTs represented also a true water splitting catalyst under UV irradiation and pure distilled water. DC-MS method appears to be a technologically simple, ecologically benign and potentially low-cost process for production of an efficient photocatalyst loaded with ultra-small NPs with precise size control.     

Titania - Supported transition metals sulfides as photocatalysts for hydrogen production from propan-2-ol and methanol

A series of transition metals sulfides deposited on anatase titania (MS_x/TiO₂) were prepared by precipitation of transition metals salts with thioacetamide in aqueous medium under reflux. The solids were characterized by XRD, XPS, temperature programmed reduction and transmission electron microscopy. The properties of as obtained catalysts were compared for the photocatalytic hydrogen evolution reaction (PHER) in pure methanol and water-isopropanol mixture. The sequences of PHER activity were compared with electrochemical HER and thiophene hydrodesulfurization (HDS) activity of the corresponding sulfides prepared by the same technique. For PHER, in both alcohols the most active photocatalysts contain hydrogenating sulfides of Co and Ru. However the PHER activity does not follow the same trend as electrocatalytic HER and thiophene HDS. Some sulfides, such as HgS or CuS, show poor activity in HDS and electrocatalytic HER, but have the PHER activity comparable with that of the best samples. This difference suggests that the PHER rate is not merely related to the hydrogen activating properties of the co-catalyst, but is enhanced by the transfer of photogenerated electrons from TiO₂ towards the sulfide. The ranking of the co-catalysts and the PHER activity depend also on the nature of the alcohol molecule, the overall PHER rates in water-isopropanol mixture being lower than in methanol.     

Effect of heat treatment on crystal phase and photocatalytic activity of Tm doped TiO2 nanoparticles

Abstract

Abstract

Tm doped TiO₂ nanoparticles have been synthesised by hydrolysis-precipitation method. The effect of heat treatment on the crystal phase and photocatalytic activity of Tm doped TiO₂ nanoparticles has been studied. The prepared samples were characterised by transmission electron microscopy, X-ray diffraction, Fourier transformed infrared and diffuse reflection spectrum analysis. The results show that Tm³⁺ doping can effectively inhibit the phase transformation from antase to rutile and decrease the crystallite size of nano-TiO₂ particles. There is an optimal Tm doping (1·4?mol.-%) after calcination at 550°C for the photocatalytic activity of methylene blue degradation.     

Thermally stable Pt/Ti mesh catalyst for catalytic hydrogen combustion

In this study, platinum (Pt) supported on titanium (Ti) mesh catalysts for catalytic hydrogen combustion were prepared by depositing Pt as a thin-layer on metallic or calcined Ti mesh. The Pt thin-layer could be stabilized as uniformly distributed, near nano-sized particles on the surface of calcined Ti mesh by exposing the freshly sputtered Pt to hydrogen. Temperatures between 478 and 525 °C were reached during hydrogen combustion and could be maintained at a hydrogen flow rate of 0.4 normal liter (Nl)/min for several hrs. It was determined that Ti mesh calcination at ≥900 °C formed an oxide layer on the surface of Ti wires, which prevented significant Pt aggregation. X-ray photoelectron spectroscopy revealed that the surface of Ti mesh was fully converted to TiO₂ at ≥900 °C. Raman spectroscopy showed that the majority of TiO₂ was present in the rutile phase, with some minor contribution from anatase-TiO₂. The calcined Ti support was stable through all investigations and did not indicate any signs of degradation.     

Characterization and visible light photocatalytic properties of nanocrystalline TiO2 synthesized by reactive plasma processing

Nanocrystalline titanium oxide powder has been synthesized by reactive plasma processing. The precursor powder of TiH₂ is oxidized ‘in-flight’ in a thermal plasma reactor to generate nanocrystalline titania powder. The synthesized powder consists of nano-sized particles of anatase and rutile phases of titanium dioxide. Photocatalytic activity of the plasma-synthesized powder was evaluated by studying the degradation of methylene blue dye solution under direct sunlight as well as UV irradiation. FTIR spectroscopy and X-ray photoelectron spectroscopy have been used to analyze the catalytic activity of the plasma-synthesized powder. UV-visible diffused reflectance spectra of the plasma-synthesized TiO₂ samples showed that they absorb in the visible region leading to effective photocatalytic activity in sunlight. The results corroborated that the plasma-synthesized powder can be effectively used for outdoor applications.     

Impact of three different TiO2 morphologies on hydrogen evolution by methanol assisted water splitting: Nanoparticles, nanotubes and aerogels

Increasing the activity of a photocatalyst goes through the improvement of both its absorption (light) and adsorption (reactant) properties. For a given semiconducting material, the charge carrier separation is also a very important step. Properly combining chosen phases is one option to improve this separation (example of the commercial P25) and depositing platinum on the surface of the catalyst, another one. In some cases, coupling both may nevertheless lead to a decrease of photoactivity or at least limit the potentiality of the catalyst. A third option, consisting in modifying the morphology of the photoactive phase, has shown very promising results.In this study, we have elaborated, characterized and evaluated the hydrogen evolution potentiality (through methanol assisted water splitting) of different TiO₂ morphologies: nanoparticles, nanotubes and aerogels. These materials have shown different behaviours depending on both their composition and morphology. Different types of separation processes have been claimed to account for the observed different photoactivities, with more or less pronounced synergetic effects, due to: the use of Pt as a co-catalyst, the mixture of different TiO₂ phases (anatase and TiO₂(B) or rutile) and the specific morphology of the samples (nanotubes or aerogels). Among all the tested samples, the TiO₂ aerogel supported Pt one exhibited very promising performances, three times as active as P25 supported Pt, which is already much more active than pure P25 in our testing conditions.     

Low temperature ionothermal synthesis of TiO2 nanomaterials for efficient photocatalytic H2 production,dye degradation and photoluminescence studies

The photocatalytic hydrogen generation is a novel, eco-friendly and favourable method for production of green and clean energy using light energy. In this direction, we report low-temperature ionothermal method for the preparation of TiO₂ nanoparticles (NPs) using methoxy ethyl methyl imidazolium tris (pentafluoroethyl) trifluoro phosphate (MOEMINtf₂) as an ionic liquid (IL) at 120°C for 1 day. The synthesized nanomaterials were examined using different spectrochemical methods like UV-DRS, XRD, FT-IR, TEM, BET and TGA-DTA techniques. The mixed phase TiO₂ is obtained with 81.7% of anatase and 18.3% of rutile phase by the XRD studies, and average crystallite size is found to be ∼7 nm. The stretching of Ti-O bond (∼555 cm⁻¹) and few other bands related to ionic liquid were confirmed by FTIR spectrum. The band gap energy was observed to be ∼3.38 eV by UV-DRS analysis. TEM images reveal spherical shape with an average particles size of about 10 nm. Photocatalytic H₂ generation was carried out using TiO₂ NPs and observed the generation of 553 μmol h⁻¹ g⁻¹ via water splitting reaction. Furthermore, the prepared TiO₂ NPs employed for the photocatalytic degradation of methylene blue dye (84.54%), and photoluminescence studies confirms the obtained material can be used in optoelectronic applications with green emission.     

Influence of metal oxides on Pt catalysts for methanol electrooxidation using electrochemical impedance spectroscopy

Carbon nanotubes used as supports for platinum catalysts deposited with metal oxides (CeO₂, TiO₂, and SnO₂) were prepared for their application as anode catalysts in a direct methanol fuel cell. Cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy measurements were carried out in a solution of 0.5 M CH₃OH and 0.5 M H₂SO₄. Catalysts with the addition of CeO₂, TiO₂, and SnO₂ presented higher catalytic activity than pure platinum catalysts, and the catalysts with CeO₂ were the best among them. Electrochemical impedance spectra indicated that methanol electrooxidation on these catalysts had different impedance behaviors at different potential regions. The mechanism of methanol electrooxidation changed with increases of the potential. The promotion effect of the metal oxides lies in the oxidation of intermediate CO_ads on Pt at low potential regions.     

Carbon nitride quantum dots (CNQDs)/TiO2 nanoparticle heterojunction photocatalysts for enhanced ultraviolet-visible-light-driven bisphenol a degradation and H2 production

The extension of the absorption band of solar energy is an efficient strategy to dramatically enhance the application value of TiO₂. Based on this, we have prepared carbon nitride quantum dots (CNQDs)/TiO₂ nanoparticle heterojunctions by mixing TiO₂ and the as-prepared CNQDs by the simple mechanical stirring method. The synthesized CNQDs-x/TiO₂ composites were systematically characterized in term of their physicochemical properties, the performance of photocatalytic degradation of Bisphenol A, and their photocatalytic hydrogen evolution performance under stimulated sunlight. The CNQDs/TiO₂ nanoparticle exhibited a lattice spacing of 0.352 nm, assigning to the (101) crystal plane of anatase phase TiO_2. Intriguingly, the modification of TiO₂ nanoparticle with CNQDs can indeed get a narrower optical band gap of 3.02 eV, with a wider absorption range extending to visible light region and could enhance their overall photocatalytic performance over the commercially TiO₂ nanoparticles. In Addition, it was demonstrated that the ratios of CNQDs to TiO₂ exhibited obvious influence on the photocatalytic performance of the obtained composite catalysts.By contrast to the pure TiO₂, all the CNQDs-x/TiO₂ composites displayed higher photocatalytic activities, and the CNQDs-2/TiO₂ possessed the highest photocatalytic degradation capacity towards bisphenol A with a reaction rate constant 0.30 (0.17 for pure TiO₂). Meanwhile, the H₂ production rate of CNQDs-2/TiO₂ sample is about 30 μmol g⁻¹ h⁻¹ higher than that of the pure TiO₂ nanoparticles. Moreover, the photocurrent intensity of CNQDs-2/TiO₂ was about 25 times higher compared to that of pure TiO₂ nanoparticles. Therefore, our research results can provide valuable guidance for exploring high-performance photocatalytic materials.     

Electrocatalytic performance of Ba-doped TiO2 hollow spheres in water electrolysis

Barium doped titania hollow sphere catalysts of various compositions were prepared and their electrocatalytic performance was evaluated in acidic media. Titania hollow sphere particles were prepared using poly (styrene–methacrylic acid) latex as template material, and BaCl₂ was used precursor material during barium doping over spheres. The morphology and structure of Ba/TiO₂ hollow spheres were characterized by BET, XRD, TGA and TEM analysis. XRD results had confirmed the presence of rutile TiO₂ and BaTiO₃ phases in the catalysts. The catalysts have shown almost similar surface area values (around 97 m²/g) irrespective of their compositions. On the other hand, surface area values were diminished remarkably with rise in the calcination temperatures. In TEM images, hollow sphere formation with uniform layer of barium over the spheres could clearly be observed. Diameter of Ba-doped TiO₂ hollow sphere was found 0.4–0.5 μm irrespective of the variation in calcination temperatures. In cyclic voltammograms, both the hydrogen and oxygen evolution peaks were present for all the hollow sphere samples; although the peak positions had changed to some extent for few samples. Anodic polarization curves have shown 60 mA cm⁻² current density for 20 wt% Ba/TiO₂ hollow sphere sample. Tafel slope is revealed as 122 mV for the same electrocatalyst. Barium doped titania hollow spheres have also shown long time electrocatalytic stability in acid solution.     

TiO2 photocatalyst with single and dual noble metal co-catalysts for efficient water splitting and organic compound removal

Photocatalysts can be used both for air cleaning and solar energy harvesting through water splitting. However, pure TiO₂ photocatalysts are often inefficient and therefore co-catalysts are needed to improve the yield. To achieve this goal, we prepared TiO₂ and deposited Pt, Ir and Ru co-catalysts on its surface. Two base TiO₂ nanoparticles were used: P25 and rutile TiO₂ synthesized via hydrothermal method. Co-catalysts were deposited by wet impregnation technique using single element and a combination of two elements (Pt and Ir or Pt and Ru), followed by annealing in either air or H₂/Ar. Annealing in reducing atmosphere increased the photocatalytic activity of oxidation of isopropanol compared to annealing in air. We demonstrated a clear influence of the co-catalysts on the photocatalytic degradation of isopropanol and on electrochemical water-splitting reaction. The platinum-containing samples showed the best HER activity.     

Degradation of formic acid over semiconducting membranes supported on glass: effects of structure and electronic doping

The photocatalytic oxidation of solutions of formic acid over supported semiconducting ceramic membranes has been investigated. Sol-gel techniques were employed to coat pyrex glass supports with colloidal solutions. Subsequent firing leads to supported ceramic membranes suitable for use as photocatalysts. The structure of these membranes affects the rate of photocatalytic oxidation of formic acid. The most active titania photocatalysts are those membranes characterized by the least number of boundaries between particles. Titania membranes doped with vanadium, molybdenum, yttrium, magnesium, lithium and rutherium oxides and platinum metal have been prepared. Only those titania membranes doped with magnesium oxide, lithium oxide or platinum metal were characterized by higher activities for the degradation of formic acid than the original titania membranes. The rate of this degradation reaction can be characterized by an expression of the Langmuir-Hinshelwood-Hougen-Watson form.     

Hydrothermally stabilized Fe(III) doped titania active under visible light for water splitting reaction

Fe³⁺ doped TiO₂ photocatalysts were prepared by hydrothermal treatment for the photocatalytic water splitting to produce stoichiometric hydrogen and oxygen under visible light irradiation. It was found that hydrothermal treatment at 110 °C for 10 h was essential for the synthesis of highly stabilized Fe³⁺ doped TiO₂ photocatalysts. The synthesized photocatalysts were characterized by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), ultraviolet–visible diffuse reflectance spectroscopy (UV–vis DRS) and BET surface area techniques. The doping of highly stabilized Fe³⁺ in the titania matrix leads to significant red shift of optical response towards visible light owing to the reduced band gap energy. Optimum amount of Fe³⁺ doped TiO₂, 1.0 wt% Fe/TiO₂, showed drastically improved hydrogen production performance of 12.5 μmol-H₂/h in aqueous methanol and 1.8 μmol-H₂/h in pure water, respectively. This Fe/TiO₂ photocatalyst was stable for 36 h without significant deactivation in the water splitting reaction.     

New nano-structured and interactive supported composite electrocatalysts for hydrogen evolution with partially replaced platinum loading

This work is concerned with preparation and characterization of nano-structured composite electrocatalytic material for hydrogen evolution based on CoPt hyper d-metallic phase and anatase (TiO₂) hypo d-phase, both deposited on multiwalled carbon nanotubes (MWCNTs) as a carbon substrate. The main goal is partially or completely to replace Pt as the electrocatalytic material. Four electrocatalytic systems were prepared with common composition 10% Me + 18% TiO₂ + MWCNTs, where Me = Co, CoPt (4:1, wt. ratio), CoPt (1:1, wt. ratio) and Pt. The structural changes and their influence on electrocatalytic activity were studied by means of XRD, TEM, SEM and FTIR. The electrocatalytic activity was assessed in aqueous alkaline and polymer acidic electrolytes by means of steady-state galvanostatic method. It was found that Co strongly affects the platinum particle size. The addition of Co reduces platinum particle's size from 11 nm (in pure Pt metallic system) to 4 nm (in both systems 4:1 and 1:1), i.e. almost by 3 times. The corresponding increase of the surface area and the number of the active catalytic centres improves the efficiency, despite the fact that the amount of used platinum was decreased up to 5 times. The catalyst based on CoPt (1:1) performed the best, while the activity of the pure platinum and CoPt (4:1) systems were very close. Generally, the studied electrocatalysts have shown good and stable performances for hydrogen evolution in PEM electrochemical cell. The influence of the hydrogen electrodes under investigation on the water electrolysis efficiency at current density of 0.3 A cm⁻² was assessed, using previous data oxygen evolution on IrO_x electrode. Related to the performances of commercial Pt (ELAT) electrode, when hydrogen electrodes with the prepared mixed electrocatalysts were used, the water electrolysis efficiency was only 5% lower for CoPt (1:1), nearly 10% lower for CoPt (4:1) and 13% lower in the case of pure Co-based electrocatalyst.     

Photocatalytic hydrogen production by reforming of methanol using Au/TiO2, Ag/TiO2 and Au-Ag/TiO2 catalysts

Abstract

We have investigated polyvinylalcohol stabilized Au and Ag based nanoparticles supported on titania prepared via sol immobilisation for the anaerobic, ambient temperature reforming of methanol with water for the photocatalytic production of hydrogen. The catalytic activity of the Au/TiO₂ catalysts was strongly affected by the metal loading and calcination temperature. Here, we report the preparation and use of supported Au–Ag nanoparticles, based on either the co-reduction or the consecutive reduction of the two metals. Au–Ag supported catalysts were more active than monometallic Au and Ag catalysts and the preparation methodology had a pronounced effect in terms of catalytic activity of the Au–Ag catalysts. In fact, using a consecutive reduction where Au was firstly reduced followed by reduction of Ag gave materials which exhibited the highest catalytic performance.