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Bismuth oxide, tin oxide and Pd metal (Pd/SnBi3SG) hybrids, synthesized via sol–gel technique while employing polyethylene glycol template at a ratio of 3 (Bi/Sn = 3) were tested toward the photocatalytic oxidation of fluorene under ultraviolet and visible light irradiations in comparison with Pd/BiSG and Pd free SnBi3SG photocatalysts. These catalysts were characterized using X-ray diffraction (XRD), UV–vis diffuse reflectance (DRUV–vis), N2 sorptiometry, Raman spectroscopy, transmission electron microscopy (TEM) and GC–MS technique, which used for analyzing the photo-oxidation products. The actual photocatalyst exhibited the highest activity (100% conversion, TOF ≈ 9.4 × 10−6 s−1, fluorenone/fluorenol = 3/1) following oxygen flushing for 30 min (35 ml/min) before UV irradiation. This was mainly due to the close proximity between β-Bi2O3 and Bi2Sn2O7 heterojunction as well as increasing the mesoporosity margin comparatively. On the other hand, the Pd/BiSG catalyst that exhibited smaller crystallite size (20 nm vs. 44 nm) and higher surface area (21.0 vs. 12.0 m2/g) than Pd/SnBi3SG indicated lower activity (Pd/BiSG, 72% conv.). This highlights the importance of the modified electronic structure of Pd/SnBi3SG in designing efficient charge separation as well as high quantum yield value (Φ ∼ 0.1 ± 0.05) exceeding that of Pd/BiSG (3 × 10−2) and SnBi3SG (10−2) photocatalysts. The catalytic behavior and mechanism, reactivity–structure relationship and recyclable use of the hybrid photocatalysts have been thoroughly examined. An indirect chemical probe method using active species scavengers elucidated that the photo-oxidation mechanism was proceeded via holes and O2 − moieties rather than singlet oxygen moieties.

A simple deposition method for synthesizing different loadings of Ag2O@Ag (0.4%–8.5%) coated oxygen functionalized carbon nanotubes (CNT); using a triblock copolymer template, is adopted followed by annealing at different temperatures (250 °C and 400 °C). These synthesized materials are characterized by XRD, TEM-SAED, N2 sorptiometry, XPS and photoluminescence spectroscopy. The catalysts electrode surfaces are electrochemically characterized by cyclic voltammetry, galvanostatic charge/discharge and impedance spectroscopy. Remarkably, the photocatalyst 4%Ag2O@Ag/CNT annealed at 400 °C (7 nm) exhibits the highest reduction rate constant of 4-nitrophenol (4-NP) under dark (0.0112 s−1) and visible light illumination (0.028 s−1), followed by 8.5%Ag2O@Ag/CNT (dark, 0.008 s−1) annealed at 250 °C. The generation of Ag2O p-type on the annealed CNT surface establishes the formation of p–n junction; confirmed by the Mott-Schottky analysis, mediated by Ag nanoparticles of surface plasmon resonance bands at 460 and 555 nm. The 8.5%Ag2O@Ag/CNT250 electrode shows a specific capacitance of 225 F g−1 exceeding that of 4%Ag2O@Ag/CNT400 (186 F g−1) at a current density of 1.0 A g−1, achieving lower internal resistance at the former electrode. This proposes that the charge storage and its transfer rate are not the only factor affecting the reduction of 4-NP. This emphasizes the importance of the reactants facile adsorption as well as the facile creation of the reductive reactive species. The kinetics of the reduction reaction as well as the reaction mechanism are well elucidated and discussed.

Hydrothermally synthesized mesoporous titania containing silver; at weight percentages ratio of 1.6 and 3.2, nanoparticles either assembled by polyoxyethylene laurel ether (POL) or sodium dodecylsulphate (SDS) were characterized with XRD, N2 sorptiometry, DRUV–vis, FTIR and TEM. The photocatalytic performance of the catalysts was tested for the oxidation of 2,4-dichlorophenoxyacetic acid (2,4-D; herbicide); through comparison with P25, under visible (λ > 420 nm) and UV light irradiation. Our results show that TEM measurements evince that dispersed Ag nanoparticles with diameter of 7 and 5 nm are deposited on titania surfaces synthesized using POL and SDS, respectively. XRD and N2 sorptiometry measurements advocate that Ag atoms were present inside titania pores; as confirmed from decreasing both surface area and pore volume values, as well as attending on titania surfaces upon increasing Ag content prohibiting the growth of anatase phase. The UV–vis absorbance spectra indicated that Ag nanoparticles can shift the absorption maximum to the visible light region as confirmed by the presence of surface plasmon bands at 634 and 700 nm. The apparent rate constants calculated under visible-light illumination for all catalysts were 0.0335 and 0.0289 min−1; for 1.6 wt.% and 3.2 wt.% Ag/TiO2 templated from POL, as well as 0.0263 and 0.0251 min−1; for 1.6 wt.% and 3.2 wt.% Ag/TiO2 templated from SDS. The direct involvement of the Ag particles in mediating the electron transfer from the photoexcited TiO2 under band gap excitation is considered to carry out the efficient photo-catalytic oxidation of the 2,4-D besides, the higher efficiency of generation, mobility, and separation of photoinduced electrons and holes.

Silica synthesized from raw rise husks (white particles) through submission to consecutive chemical treatment using NaOH and HCl solutions was well incorporated with other components forming zeolites; under hydrothermal conditions, to synthesize two series of ZSM-5 (Z) of different Si/Al ratios, namely Z40 and Z80. Transition metal oxides (V, Co) were incorporated with Z samples by in situ synthesis and by impregnation. Various techniques were employed for samples characterization including XRD, FTIR, SEM, N 2 adsorption and pyridine-FTIR. The photocatalytic activity of V and Co incorporated Z zeolites in addition to neat ZSM-5 samples towards degradation of acid green (AG) dye were well investigated and compared under similar conditions. The characterization results of the catalysts indicated that Z80 measured higher surface area (616 m 2 /g) and crystallites size (44.4 nm) than Z40 (536 m 2 /g and 35.8 nm) besides, Z40 signifies the presence of distinct phase of silica capable of decreasing the pore radius and volume of this particular sample (22.9 A, 0.49 cm 3 /g) when compared with the former (25.3 A, 0.623 cm 3 /g). The degradation rate of Z40 was 16 times higher than Z80 in presence of UV irradiation reflecting the importance of absorbability of silica phase present on Z40 as well as acidity and decreased crystallites size. V and Co impregnated Z (VZ imp , CoZ imp ) samples were found to exhibit higher and unique photocatalytic activities for AG degradation than in situ incorporated ones. CoZ80 imp exhibited the highest activity (0.14 min −1 ) among all samples exceeding CoZ40 imp (0.11 min −1 ) and VZ40 imp (0.043 min −1 ). The enhanced photocatalytic activity of CoZ80 imp is attributed to charge transfer excited complex between Co in Z along with AG ligand in addition to increasing the percentages of Co 3 O 4 and cobalt silicate moieties over those in CoZ40 imp and to the higher surface area of CoZ80 imp , comparatively. More informations on local structures of metal oxides inside zeolites and their photocatalytic activities towards AG were deduced, correlated and discussed.

Nano-structured titanium dioxide materials were synthesized hydrothermally (TiCl4, 353 K, 5 days) via assembling through cationic surfactants in particular cetyltrimethylammonium bromide (CTAB) and cetylpyridinum bromide (CPB). The bulk chemical and phase compositions, crystalline structure, particle morphology, thermal stability and surface texturing were determined by means of X-ray powder diffractometry (XRD), Infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermal analyses (DTA/TGA) and N2 sorptiometry. The acidity of synthesized materials was studied by FTIR spectroscopy of adsorbed pyridine as a probe molecule. The results revealed that the crystallites size of all materials lie in the range of 10.1–18.2 nm and organized in a morphological structure that change from nano-sized spheres to cotton fibrils shape. Surfaces thereon exposed were found to assume high specific areas (240–418 m2 g−1) and micro–mesoporous surfaces with pore size in the range 23.2–43.7 A. Rutile phase was only produced for all TiO2 materials assembled by cationic surfactants following heating up to 623 K. The transformation of rutile to anatase TiO2 was coincided with the developed interaction between vanadia and titania assembled by CPB template. The V in the resulting vanado-titanate was entirely incorporated in TiO2 structure. The as-synthesized phases of either rutile or anatase were maintained after calcining at 973 K exhibiting a significant thermal stability. Pyridine adsorption at RT indicated the involvement of acid–base site pair on all TiO2 assembled by cationic templates where that prepared by conventional method only exposed Lewis and Bronsted acid sites with a higher tendency to the latter comparatively.

Nanostructured titanium dioxide and vanadium oxide supported over titanium dioxide was synthesized using a template synthesis route method under hydrothermal conditions (at 353 K for 5 days) via sodium dodecyl sulfate surfactant. The influence of pH (2.0–9.0) and thermal treatment (623 and 773 K) on the structural, surface acidity and textural properties of TiO2 and V2O5/TiO2 materials was investigated using XRD, thermal analyses, SEM, FTIR, N2 adsorption and pyridine-FTIR measurements. The synthesized TiO2 and V2O5/TiO2 showed high mesoporosities with different pore sizes ranging from 24.6 to 40.6 A and exhibited nano-sized crystals varying from 7.5 to 15.1 nm. All templated samples exhibited very high surface areas; commencing from 263 to 465 m2/g, as well as pore volume up to 0.73 cm3/g. The synthesized samples exhibited a pure anatase crystalline phase for TiO2 in the pH range 4.8–9, in which substantial amounts of mesopores were developed where that prepared at pH = 2.0 showed the formation of only rutile phase with higher affinity to micropores. Surface acid strength was greater for highly dispersed V containing TiO2 due to a strong interaction of the VOx species with support centers that act as electron attractor centers creating Lewis acid sites. It was found that pH has a paramount effect influencing both the nature of pores and the type of TiO2 formed. The photocatalytic reduction of Hg2+ in water by UV irradiation was chosen to evaluate the activities of the synthesized materials.

Aqueous solutions of cerium nitrate of increasing concentrations (2.5, 5 and 7.5 wt.% Ce) have been contacted with the components forming Mordenite zeolite; during forming the gel under hydrothermal conditions, for allowing the accessibility of Ce ions to proceed into compensating positions in Mordenite structure. These materials were characterized by the methods of FTIR, XRD, N 2 adsorption and UV–vis diffuse reflectance spectroscopy. The interaction of NO and CO adsorptions; at room temperature, on thermally pre-treated (300 °C, 10 −5 Torr, 3 h) as well as pre-reduced (50 Torr, 500 °C, 1 h) samples were studied by in situ Fourier transform infrared spectroscopy. XRD and FTIR results indicate that the Ce atoms are mostly present in internal surfaces in Mordenites for 2.5 and 5CeMOR samples whereas for 7.5CeMOR, a decrease in diffusion of Ce to be in compensating positions is perceived; as conceived from lowering the lattice volume, pointing to the presence of discrete amounts of CeO 2 (582 cm −1 ) and cerium silicate (Si–O–Ce; 797 cm −1 ) species. All the samples indicate intra-crystalline mesopores as depicted from V l – t plots particularly the 7.5CeMOR sample that showed the highest wide-pore volume (0.073 cm 3 /g), lowest pore radius (21 A) and thus, revealed the highest S BET between all samples (363 m 2 /g). UV–vis characterization of 7.5CeMOR sample shows octahedral Ce species (345, 360 and 390 nm) in small clusters inside zeolite channels and most probably originated from cerium silicates having different coordination with NaMOR along with discrete amounts of CeO 2 (420 nm) species. CO readily adsorbs on the Ce 3+ sites of the pre-reduced 7.5CeMOR catalyst, rather than those on Ce 4+ , to display minor amounts of carboxylate and dominant amounts of monodentate carbonate that were amenable to decompose to produce CO 2 gas (2335 cm −1 ). On the other hand, the in situ interaction of nitric oxide (NO) gas on the 7.5CeMOR catalyst led to the formation of a series of nitrosyl species: N 2 O (2240 cm −1 ), NO (1908 cm −1 ), N 2 O 3 (1880 cm −1 ) and (NO) 2s,as (1844, 1734–1720 cm −1 ). Such nitrosyl complexes were favorably formed on Ce 3+ in 7.5CeMOR those exchanged Na ones.

Fe/ZSM-5 samples (5 wt.% Fe) prepared by in situ incorporation using TPABr template under hydrothermal conditions (Fe–ZSM-5in), chemical liquid deposition (Fe–ZSM-5imp) and solid–solid (Fe–ZSM-5ss) interaction were characterized by N2 physisorption, TG/DSC, X-ray diffraction, FTIR spectroscopy, UV–Vis diffuse reflectance spectroscopy and 57Fe Mossbauer spectroscopy techniques. Calcination at 550 °C leads to almost complete removal of template that was associated with dislodgment of significant fraction of Fe to external positions as recognized for the in situ prepared sample (Fe–ZSM-5in). This sample showed an increase in lattice volume suggesting the presence of the majority of Fe ions in tetrahedral positions inside zeolite channels and offered as well the lowest crystallites size (75 nm) and maximum SBET (453 m2/g) between all samples. On the other hand, Fe–ZSM-5ssbef, resulting from solid–solid interaction and subjected to heat treatment in vacuum at 200 °C, measured the lowest mean pore radius (r−; 23 A), and pore volume (Vp; 0.3887 cm3/g), giving a hint about the probability of finding neutral iron oxide nanoparticles (α-Fe2O3) as a separate phase that has been validated by Mossbauer (IS = 0.3 mm/s, QS = −0.2 mm/s, Heff = 520 kOe) and UV–Vis (400 nm) investigations. This sample also demonstrated that the majority of Fe occupied framework positions beside a fraction identified as small oligonuclear oxo-iron ions ( Fe x 3 + – O ; 290 nm). Interestingly, Fe–ZSM-5ssaft, resulting from solid–solid interaction and subjected to air calcination at 550 °C, measured maximum Vp (0.6380 cm3/g) and r− (39 A) values, reflecting the enforced location of Fe in this sample leading to an effective pore widening and thus a pronounced mesoporosity is attained. IR bands due to νasT–O in ZSM-5 (1105 cm−1) showed a shift to lower wave numbers (1059 cm−1) following Fe incorporation reflecting the extent of exchanging Fe in this sample (Fe–ZSM-5ssaft), unlike the rest of the samples which showed splitting, which accounted for the presence of residual Al3+ beside Fe3+ ions in the same site. Mossbauer data of this sample confirmed the latter result and indicated the maximum lattice imperfection and showed as well the lowest degree of crystallinity. The Fe–ZSM-5impaft sample, subjected to heat treatment at 550 °C, showed α-Fe2O3 species where that heated at 110 °C presented the lowest SBET (361 m2/g). More correlations were evaluated and discussed on the effect of thermal treatment on the existence of various Fe species (either framework or non-framework), their electronic states and local structures.

High silica mordenite samples (Si/Al molar ratios 38 and 60) were synthesized hydrothermally at 433 K with the template route method using o -phenylenediamine and characterized with several techniques including XRD, FT-IR, TG/DTA, pyridine-FTIR and N 2 adsorption. The effects of Na 2 O/SiO 2 ratio, Si/Al ratio, temperature, crystallization time and various templates on mordenite crystallization as well as crystallite size that was smaller than 50 nm, irrespective of varying the parameters were thoroughly investigated. The effect of alkali cations such as Na + and K + on mordenite crystallization and on thermal stability of the produced mordenite was also investigated. Pyridine adsorption suggests an increase in Lewis acid sites particularly following hydrothermal treatment at 120 °C where at 160 °C both Lewis and Bronsted acid sites in addition to oxidation products, which are indicative of the existence of dual acid–base sites, were exposed. Surface texturing of the produced samples were correlated with their thermal analyses data.