Synthesis and characterization of zeolite NaY from rice husk silica

Rice husk silica (RHS) in amorphous phase with 98% purity was prepared from a waste rice husk from rice milling by leaching with hydrochloric acid and calcination. The RHS was used effectively as a silica source for the synthesis of zeolite Y in sodium form (NaY). The zeolite in pure phase was obtained from a two-step synthetic route in which the starting gels were mixed, aged for 24 h at room temperature and crystallized for 24 h at 90 °C. The diameter of single crystal particles from a scanning electron microscope was approximately 1.0 μm, whereas the average particle diameter from laser diffraction particle size analyzer was approximately 10 μm because of the agglomeration of small crystals. Longer crystallization time in this route resulted in a mixed phase containing NaY and zeolite P in sodium form (NaP). In addition, a one-step synthetic route (no aging) was studied and the product was also a mixed phase zeolite.     

Comparison between cobalt and cobalt–platinum supported on zeolite NaY: Cobalt reducibility and their catalytic performance for butane hydrogenolysis

This work investigated reducibility of cobalt species in monometallic Co/NaY and bimetallic CoPt/NaY catalysts with various Co loading (1, 6 and 10 wt.%) and fixed Pt loading (1 wt.%). The form and environment of Co species after reduction was determined by X-ray absorption spectroscopy including X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopies. The cobalt species in the mono- and bimetallic catalyst with Co loading of 1 wt.% was not reducible whereas those with Co loading of 6 and 10 wt.% were partially reduced. The extent of reduction increased with Co loading and enhanced by the presence of Pt. Catalytic performance for n-butane hydrogenolysis mono- and bimetallic catalysts were compared. The higher extent of Co reduction in 6CoPt/NaY and 10CoPt/NaY resulted in higher conversions than the monometallic counterpart. Sequential hydrogenolysis was favored on the monometallic catalysts because methane was the only product. The presence of Pt suppressed such reaction resulting in ethane and propane. The effect of Pt on such effect was most prominent in 6CoPt/NaY.     

2D Porous TiO2 Single‐Crystalline Nanostructure Demonstrating High Photo‐Electrochemical Water Splitting Performance

Porous single crystals are promising candidates for solar fuel production owing to their long range charge diffusion length, structural coherence, and sufficient reactive sites. Here, a simple template‐free method of growing a selectively branched, 2D anatase TiO₂ porous single crystalline nanostructure (PSN) on fluorine‐doped tin oxide substrate is demonstrated. An innovative ion exchange–induced pore‐forming process is designed to successfully create high porosity in the single‐crystalline nanostructure with retention of excellent charge mobility and no detriment to crystal structure. PSN TiO₂ film delivers a photocurrent of 1.02 mA cm^?2 at a very low potential of 0.4 V versus reversible hydrogen electrode (RHE) for photo‐electrochemical water splitting, closing to the theoretical value of TiO₂ (1.12 mA cm^?2). Moreover, the current–potential curve featuring a small potential window from 0.1 to 0.4 V versus RHE under one‐sun illumination has a near‐ideal shape predicted by the Gartner Model, revealing that the charge separation and surface reaction on the PSN TiO₂ photoanode are very efficient. The photo‐electrochemical water splitting performance of the films indicates that the ion exchange–assisted synthesis strategy is effective in creating large surface area and single‐crystalline porous photoelectrodes for efficient solar energy conversion.     

Photocatalytic degradation of benzene,toluene, ethylbenzene,and xylene (BTEX) using transition metal-doped titanium dioxide immobilized on fiberglass cloth

Transition metal (Fe, V and W)-doped TiO₂ was synthesized via the solvothermal technique and immobilized onto fiberglass cloth (FGC) for uses in photocatalytic decomposition of gaseous volatile organic compounds—benzene, toluene, ethylbenzene and xylene (BTEX)—under visible light. Results were compared to that of the standard commercial pure TiO₂ (P25) coated FGC. All doped samples exhibit higher visible light catalytic activity than the pure TiO₂. The V-doped sample shows the highest photocatalytic activity followed by the W- and Fe-doped samples. The UV-Vis diffuse reflectance spectra reveal that the V-doped sample has the highest visible light absorption followed by the W- and Fe-doped samples. The X-ray diffraction (XRD) patterns indicate that all doped samples contain both anatase and rutile phases with the majority (>80%) being anatase. No new peaks associated with dopant oxides can be observed, suggesting that the transition metal (TM) dopants are well mixed into the TiO₂ lattice, or are below the detection limit of the XRD. The X-ray absorption near-edge structure spectra of the Ti K-edge transition indicate that most Ti ions are in a tetravalent state with octahedral coordination, but with increased lattice distortion from Fe- to V- and W-doped samples. Our results show that the TM-doped TiO₂ were successfully synthesized and immobilized onto flexible fiberglass cloth suitable for treatment of gaseous organic pollutants under visible light.     

Visible light-irradiated degradation of alachlor on Fe-TiO<Subscript>2</Subscript> with assistance of H<Subscript>2</Subscript>O<Subscript>2</Subscript>

0.1 Fe/Ti mole ratio of Fe-TiO₂ catalysts were synthesized via solvothermal method and calcined at various temperatures: 300, 400, and 500 °C. The calcined catalysts were characterized by XRD, N₂-adsorption-desorption, UV-DRS, XRF, and Zeta potential and tested for photocatalytic degradation of alachlor under visible light. The calcined catalysts consisted only of anatase phase. The BET specific surface area decreased with the calcination temperatures. The doping Fe ion induced a red shift of absorption capacity from UV to the visible region. The Fe-TiO₂ calcined at 400 °C showed the highest photocatalytic activity on degradation of alachlor with assistance of 30 mM H₂O₂ at pH 3 under visible light irradiation. The degradation fitted well with Langmuir-Hinshelwood model that gave adsorption coefficient and the reaction rate constant of 0.683 L mg⁻¹ and 0.136 mg/L·min, respectively.     

Effect of Fe<Superscript>3+</Superscript> doping on the performance of TiO<Subscript>2</Subscript> mechanocoated alumina bead photocatalysts

Ferric ion was introduced to the commercial photocatalyst P25 (Degussa) by ultrasonic wet impregnation technique. The concentration of the dopant was varied from 0.0 to 3.0% Fe/Ti ratio. The doped TiO₂ was then loaded to alumina balls using mechanical coating technique and followed by calcination in air at 400, 450, 500 and 550 °C. The fabricated photocatalyst was characterized by X-ray diffraction, N₂ adsorption-desorption isotherms, scanning electron microscopy, UV-Vis diffuse reflectance spectroscopy, X-ray adsorption near edge structure and photoluminescence spectroscopy. The photocatalytic activity was tested by following the degradation of methylene blue (MB). It was found that the Fe³⁺ doped TiO₂/Al₂O₃ has a combination of anatase and rutile phase and free of iron oxide phases. The optimum calcination temperature is 400 °C with 0.1% Fe³⁺ concentration. The catalyst addresses the entrainment in photocatalytic reactors, eliminating the need for a post filtration process.     

Structural properties of CuO/TiO2 nanorod in relation to their catalytic activity for simultaneous hydrogen production under solar light

CuO was introduced into porous TiO₂ nanorod through impregnation method. Before the impregnation step, TiO₂ nanorod was hydrothermally synthesized from TiO₂ powder in aqueous NaOH solution and followed by thermal treatment at 450 °C. The structures and properties of impregnated samples were characterized using various techniques, including XRD, BET, XAS, TEM, and UV-DRS. Their photocatalytic performance on simultaneous hydrogen production from pure water and aqueous methanol solution was also investigated under solar light. It was found that CuO/TiO₂ nanorod possessed a high surface area, good photocatalytic property and excellent hydrogen generation activity. Incorporation of Cu ions into the lattice framework of anatase TiO₂ nanorod enhanced the efficiency in visible region at 438–730 nm. Moreover, the XAS results showed that some Cu ions formed solid solution in the TiO₂ nanorod (Cu_xT_1−xO₂). However, the excessive incorporation of Cu ions did not improve any ability of anatase TiO₂ nanorod for production of hydrogen from pure water splitting. This could be due to the excessive CuO agglomeration at outside-pores which blocked the sensitization of TiO₂ nanorod. Only 1% Cu/TiO₂ nanorod was found to be a remarkable and an efficient photocatalyst for hydrogen production under solar light from both pure water and sacrificial methanol splitting. The highest rate of hydrogen production of 139.03 μmol h⁻¹ g_catalyst⁻¹ was found in sacrificial methanol which was 3.24% higher than in pure water.     

The Role of N and S Doping on Photoluminescent Characteristics of Carbon Dots from Palm Bunches for Fluorimetric Sensing of Fe3+ Ion

This work aims to enhance the value of palm empty fruit bunches (EFBs), an abundant residue from the palm oil industry, as a precursor for the synthesis of luminescent carbon dots (CDs). The mechanism of fIuorimetric sensing using carbon dots for either enhancing or quenching photoluminescence properties when binding with analytes is useful for the detection of ultra-low amounts of analytes. This study revealed that EFB-derived CDs via hydrothermal synthesis exceptionally exhibited luminescence properties. In addition, surface modification for specific binding to a target molecule substantially augmented their PL characteristics. Among the different nitrogen and sulfur (N and S) doping agents used, including urea (U), sulfate (S), p-phenylenediamine (P), and sodium thiosulfate (TS), the results showed that PTS-CDs from the co-doping of p-phenylenediamine and sodium thiosulfate exhibited the highest PL properties. From this study on the fluorimetric sensing of several metal ions, PTS-CDs could effectively detect Fe³⁺ with the highest selectivity by fluorescence quenching to 79.1% at a limit of detection (LOD) of 0.1 µmol L⁻¹. The PL quenching of PTS-CDs was linearly correlated with the wide range of Fe³⁺ concentration, ranging from 5 to 400 µmol L⁻¹ (R² = 0.9933).