Synergistic effect of Ni–Ag–rutile TiO2 ternary nanocomposite for efficient visible-light-driven photocatalytic activity

P25 comprising of mixed anatase and rutile phases is known to be highly photocatalytically active compared to the individual phases. Using a facile wet chemical method, we demonstrate a ternary nanocomposite consisting of Ni and Ag nanoparticles, decorated on the surface of XTiO₂ (X: P25, rutile (R)) as an efficient visible-light-driven photocatalyst. Contrary to the current perspective, RTiO₂-based Ni–Ag–RTiO₂ shows the highest activity with the H₂ evolution rate of ∼86 μmol g⁻¹ W⁻¹ h⁻¹@535 nm. Together with quantitative assessment of active Ni, Ag and XTiO₂ in these ternary systems using high energy synchrotron X-ray diffraction, transmission electron microscopy coupled energy dispersive spectroscopy mapping evidences the metal to semiconductor contact via Ag. The robust photocatalytic activity is attributed to the improved visible light absorption, as noted by the observed band edge of ∼2.67 eV corroborating well with the occurrence of Ti³⁺ in Ti 2p XPS. The effective charge separation due to intimate contact between Ni and RTiO₂via Ag is further evidenced by the plasmon loss peak in Ag 3d XPS. Moreover, density functional theory calculations revealed enhanced adsorption of H₂ on Ti₈O₁₆ clusters when both Ag and Ni are simultaneously present, owing to the hybridization of the metal atoms with d orbitals of Ti and p orbitals of O leading to enhanced bonding characteristics, as substantiated by the density of states. Additionally, the variation in the electronegativity in Bader charge analysis indicates the possibility of hydrogen evolution at the Ni sites, in agreement with the experimental observations.

Robust photocatalytic activity of Ni–Ag–RTiO₂ is attributed to the improved visible light absorption and effective charge separation due to intimate contact between Ni and RTiO₂via Ag, as evidenced by Ti³⁺ in Ti 2p XPS and energy dispersive mapping.     

Hierarchically ordered macro–mesoporous anatase TiO2 prepared by pearl oyster shell and triblock copolymer dual templates for high photocatalytic activity

Hierarchically ordered macro–mesoporous anatase TiO₂ is prepared by combining the supramolecular-templating self-assembly of amphiphilic triblock copolymer P123 with a natural pearl oyster shell in a hard-templating process by a facile sol–gel reaction. The obtained materials are characterized by Raman spectroscopy, X-ray diffraction, N₂ adsorption–desorption analysis, scanning electron microscopy, and transmission electron microscopy. The results demonstrate that all TiO₂ materials obtained after calcination at various temperatures are in the anatase phase, and interestingly the resultant ordered structure of both macropores and mesopores are well-preserved after calcination at 350 °C or 450 °C, with the walls of macropores composed of ordered mesopores. However, upon calcination at 550 °C or 650 °C, while the ordered macroporous structures remain well-preserved, the mesoporous structures collapse. The photocatalytic activities of the resulting TiO₂ materials are also evaluated by photodegradation of rhodamine B under UV light irradiation. The prepared TiO₂ calcined at 450 °C shows the highest photocatalytic activity.

Hierarchically ordered macro–mesoporous anatase TiO₂ with photocatalytic activity was prepared using triblock copolymer P123 and natural pearl oyster shell as dual templates.     

Hydrogen induced interface engineering in Fe2O3–TiO2 heterostructures for efficient charge separation for solar-driven water oxidation in photoelectrochemical cells

Semiconductor heterostructure junctions are known to improve the water oxidation performance in photoelectrochemical (PEC) cells. Depending on the semiconductor materials involved, different kinds of junctions can appear, for instance, type II band alignment where the conduction and valence bands of the semiconductor materials are staggered with respect to each other. This band alignment allows for a charge separation of the photogenerated electron–hole pairs, where the holes will go from low-to-high valance band levels and vice versa for the electrons. For this reason, interface engineering has attracted intensive attention in recent years. In this work, a simplified model of the Fe₂O₃–TiO₂ heterostructure was investigated via first-principles calculations. The results show that Fe₂O₃–TiO₂ produces a type I band alignment in the heterojunction, which is detrimental to the water oxidation reaction. However, the results also show that interstitial hydrogens are energetically allowed in TiO₂ and that they introduce states above the valance band, which can assist in the transfer of holes through the TiO₂ layer. In response, well-defined planar Fe₂O₃–TiO₂ heterostructures were manufactured, and measurements confirm the formation of a type I band alignment in the case of Fe₂O₃–TiO₂, with very low photocurrent density as a result. However, once TiO₂ was subjected to hydrogen treatment, there was a nine times higher photocurrent density at 1.50 V vs. the reversible hydrogen electrode under 1 sun illumination as compared to the original heterostructured photoanode. Via optical absorption, XPS analysis, and (photo)electrochemical measurements, it is clear that hydrogen treated TiO₂ results in a type II band alignment in the Fe₂O₃–H:TiO₂ heterostructure. This work is an example of how hydrogen doping in TiO₂ can tailor the band alignment in TiO₂–Fe₂O₃ heterostructures. As such, it provides valuable insights for the further development of similar material combinations.

Approximate energy band diagram and charge transfer mechanism for the Fe₂O₃–TiO₂ photoanode (left) and Fe₂O₃–H:TiO₂ photoanode (right) with external applied anodic potential under illumination.     

Crystalline phase regulation of anatase–rutile TiO2 for the enhancement of photocatalytic activity

Biphasic TiO₂ with adjustable crystalline phases was prepared by the hydrothermal-calcination method assisted by nitric acid (HNO₃) and hydrogen peroxide (H₂O₂), using potassium titanate oxalate (K₂TiO(C₂O₄)₂) as the titanium source. The influences of H₂O₂ volume on anatase and rutile contents and photocatalytic activity of biphasic TiO₂ were investigated and the photocatalytic mechanism was explored. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (UV-vis DRS) and specific surface area (BET) were employed to characterize crystal structure, physical morphology, absorbable light, chemical composition, specific surface area and pore size distribution. The photocatalytic degradation efficiency towards a methylene blue (MB) solution under xenon light was tested, and the photocatalytic stability of the sample was investigated by photocatalytic cycle experiments. The prepared biphasic TiO₂ was nanorod-shaped and had a large specific surface area. The results showed the anatase TiO₂ content increased and the photocatalytic efficiency was enhanced as the H₂O₂ volume solution increased. Among the catalysts, the biphasic TiO₂ prepared with 30 mL of H₂O₂ had the best photocatalytic effect and could entirely degrade the MB solution after 30 minutes under irradiation. After three repeated degradations, the photocatalytic degradation rate was still estimated to be as high as 95%. It is expected that the work will provide new insights into fabricating heterophase junctions of TiO₂ for environmental remediation.

Biphasic TiO₂ with adjustable crystalline phases was prepared by the hydrothermal-calcination method assisted by nitric acid (HNO₃) and hydrogen peroxide (H₂O₂), using potassium titanate oxalate (K₂TiO(C₂O₄)₂) as the titanium source.     

Room temperature ferromagnetism in D–D neutron irradiated rutile TiO2 single crystals

Room temperature ferromagnetism (RTFM) was observed in unirradiated rutile TiO₂ single crystals prepared by the floating zone method due to oxygen vacancy (V_O) defects. D–D neutrons mainly collide elastically with TiO₂, producing V_O, titanium vacancies (V_Ti) and other point defects; the density and kind of defect is related to the neutron irradiation fluence. D–D neutron irradiation is used to regulate the concentration and type of defect, avoiding impurity elements. As the irradiation fluence increases, the saturation magnetization (M_s) first increases, then decreases and then increases. To verify the origin of RTFM, the CASTEP module was used to calculate the magnetic and structural properties of point defects in TiO₂. V_O induces a 2.39 μ_B magnetic moment, Ti³⁺ and F⁺ induce 1.28 μ_B and 1.70 μ_B magnetic moments, respectively, while V_Ti induces a magnetic moment of ∼4 μ_B. Combining experimental and theoretical results, increases in V_O concentration lead to M_s increases; more V_O combine with electrons to form F⁺, inducing a smaller magnetic moment. V_O and V_Ti play a key role and M_s changes accordingly with larger fluence. V_O, F⁺ and V_Ti are the most likely origins of RTFM.

D–D neutron irradiation is used to regulate the concentration and type of defect in rutile TiO₂. Room temperature ferromagnetism was observed after irraidiation. Combining experimental and theoretical results, we elucidate the likely origins of RTFM.     

Unbiased spontaneous solar hydrogen production using stable TiO2–CuO composite nanofiber photocatalysts

We report on the optimization of electrospun TiO₂–CuO composite nanofibers as low-cost and stable photocatalysts for visible-light photocatalytic water splitting. The effect of different annealing atmospheres on the crystal structure of the fabricated nanofibers was investigated and correlated to the photocatalytic activity of the material. The presence of CuO resulted in narrowing the bandgap of TiO₂ and shifting the absorption edge into the visible region of the light spectrum. The effect of incorporating CuO within TiO₂ nanofibers on the crystal structure and composition was also investigated using X-ray diffraction (XRD), electron paramagnetic resonance (EPR), and X-ray photoelectron spectroscopy (XPS) techniques. The fabricated TiO₂–CuO composite nanofibers showed 117% enhancement in the amount of hydrogen evolved during the photocatalytic water splitting process compared to pure TiO₂. This enhancement was related to the created shallow defect states that facilitate charge transfer from TiO₂ to CuO and distinct characteristics of the composite nanofibers, such as the high surface area and directional charge transfer. The study showed that Cu is a promising alternative to noble metals as a catalyst in photocatalytic water splitting, with the advantage of being an Earth abundant element and a relatively cheap material.

We report on the optimization of electrospun TiO₂–CuO composite nanofibers as low-cost and stable photocatalysts for visible-light photocatalytic water splitting.     

Green and facile sol–gel synthesis of the mesoporous SiO2–TiO2 catalyst by four different activation modes

The most environmentally friendly protocol for obtaining mesoporous SiO₂–TiO₂ catalysts has been sought. Water has been employed as a green solvent, the energy input has been minimized, and three further principles (1, 3, and 12) of Green Chemistry have been considered. Four different modes for promoting the reaction have been comparatively evaluated, namely near-infrared and microwave electromagnetic irradiations, ultrasound, and traditional mantle heating. Brunauer–Emmett–Teller (BET) analyses of the catalysts produced revealed that the non-conventional activation modes afforded both large surface areas (335–441 m² g⁻¹) and smaller crystal sizes (7.2–15.3 nm) than the mantle heating process. These modes also generated the catalysts in shorter reaction times than traditional mantle heating, 10–30 min versus 3 h, with anatase as the sole crystalline phase. The photocatalytic degradation of 4-chlorophenol has been carried out to assess the catalytic efficiencies of the hybrid materials. The catalyst synthesized with microwave assistance showed the best mineralization activity (97%), followed by those prepared with ultrasound, near-infrared, and mantle heating. The materials have been extensively characterized by FTIR, XRD, DRS-UV/Vis, SEM, ²⁹Si MAS NMR, and BET analyses. To the best of our knowledge, this is the first such comparative assessment of green energetic alternatives in developing a sol–gel process.

The most environmentally friendly protocol for obtaining mesoporous SiO₂–TiO₂ catalysts has been sought.     

Comparison of Fe2TiO5/C photocatalysts synthesized via a nonhydrolytic sol–gel method and solid-state reaction method

Fe₂TiO₅/C photocatalysts were synthesized by a solid-state reaction method (Fe₂TiO₅/C_(S)) and nonhydrolytic sol–gel (NHSG) method (Fe₂TiO₅/C_(N)), where C was introduced by external carbon and in situ carbon sources, respectively. The Fe₂TiO₅/C_(N) photocatalyst with in situ carbon has much better photocatalytic degradation efficiency than that of Fe₂TiO₅/C_(S) synthesized by doping external carbon. The superiorities of in situ carbon were demonstrated by SEM, EDS, BET and photoelectrochemical analysis. Compared with Fe₂TiO₅/C_(S) using external carbon as a carbon source, Fe₂TiO₅/C_(N) with in situ carbon exhibits more uniform elemental distribution, much larger surface area, higher photocurrent density and lower resistivity of interfacial charge transfer. The results show that the introduction of in situ carbon via the NHSG method more easily promotes the separation of photogenerated electron–hole pairs, owing to the uniformity of the carbon element, thereby improving the photocatalytic activity of the photocatalyst.

Two different methods were used to prepare Fe₂TiO₅/C photocatalysts, demonstrating the superiorities of in situ carbon introduced by a NHSG method.     

Enhanced charge separation in TiO2/nanocarbon hybrid photocatalysts through coupling with short carbon nanotubes

The interfacial contact between TiO₂ and graphitic carbon in a hybrid composite plays a critical role in electron transfer behavior, and in turn, its photocatalytic efficiency. Herein, we report a new approach for improving the interfacial contact and delaying charge carrier recombination in the hybrid by wrapping short single-wall carbon nanotubes (SWCNTs) on TiO₂ particles (100 nm) via a hydration-condensation technique. Short SWCNTs with an average length of 125 ± 90 nm were obtained from an ultrasonication-assisted cutting process of pristine SWCNTs (1–3 μm in length). In comparison to conventional TiO₂–SWCNT composites synthesized from long SWCNTs (1.2 ± 0.7 μm), TiO₂ wrapped with short SWCNTs showed longer lifetimes of photogenerated electrons and holes, as well as a superior photocatalytic activity in the gas-phase degradation of acetaldehyde. In addition, upon comparison with a TiO₂–nanographene “quasi-core–shell” structure, TiO₂-short SWCNT structures offer better electron-capturing efficiency and slightly higher photocatalytic performance, revealing the impact of the dimensions of graphitic structures on the interfacial transfer of electrons and light penetration to TiO₂. The engineering of the TiO₂–SWCNT structure is expected to benefit photocatalytic degradation of other volatile organic compounds, and provide alternative pathways to further improve the efficiency of other carbon-based photocatalysts.

The interfacial contact between TiO₂ and graphitic carbon in a hybrid composite plays a critical role in electron transfer behavior, and in turn, its photocatalytic efficiency.     

Mechanistic pathways for the degradation of SMX drug and floatation of degraded products using F–Pt co-doped TiO2 photocatalysts

This work presents smart pathways to enhance the photocatalytic activity of TiO₂via co-doping with fluorine (F) and platinum (Pt) to form F–Pt co-doped TiO₂ photocatalysts and investigates the unique and unusual fluorination of the floated products. Our investigations indicate that the crystalline structure of the photocatalysts was a mixture of anatase and brookite phases and that the nanoparticles of the synthesized nanocomposites had nanometric sizes (4–25 nm). The F–Pt co-doped TiO₂ nano-photocatalysts demonstrated degradation of sulfamethoxazole (SMX) drug of >93% within 90 min under direct solar light and 58% degradation within 360 min under a solar simulator. Thus, co-doping TiO₂ with F and Pt atoms to form F–Pt co-doped TiO₂ nanocomposite is an efficient pathway to achieve high photocatalytic performance escorted with the formation of floating metal-fluoropolymer, unlike pristine TiO₂ which has less photocatalytic degradation and no generation of a floating polymer. Our photocatalytic protocol demonstrates that the degradation of SMX started with redox reactions of oxygen and water absorbed on the surface of the prepared nanocomposites to form superoxide anions (O₂˙⁻) and hydroxy radicals (˙OH) which have oxidation superpower. The resultant products were subsequently fluorinated by fluoride radical ions and floated as metal-fluoropolymer.

This work presents smart pathways to enhance the photocatalytic activity of TiO₂via co-doping with fluorine (F) and platinum (Pt) to form F–Pt co-doped TiO₂ photocatalysts and investigates the unique and unusual fluorination of the floated products.     

SILP materials based on TiO2–SiO2 and TiO2–SiO2/lignin supports as new catalytic materials for hydrosilylation reaction – synthesis,physicochemical characterization and catalysis

The oxide system TiO₂–SiO₂ as well as a TiO₂–SiO₂/lignin system have been obtained by the sol–gel synthesis method and applied as supports in Supported Ionic Liquid Phase (SILP) materials. In total 24 SILP systems were obtained with ionic liquids containing imidazolium, pyridinium, phosphonium or sulfonic cations and bis(trifluoromethylsulfonyl)imide or methylsulfate anions, and homogeneous complexes of rhodium or platinum as the active phase. The supports and catalytic materials were subjected to thorough characterization by elemental analysis, XRD, SEM-EDX, IR, and TGA, and their particle size distribution and porous properties were assessed. The new SILP materials were used in hydrosilylation of 1-octene with 1,1,1,3,5,5,5-heptamethyltrisiloxane. The effectiveness of hydrosilylation reaction catalyzed by the obtained SILP materials for the polar and nonpolar reagents was assessed. All the catalytically active materials were proved to be easy to isolate and reuse, and the best SILP systems have been shown to be active in 10 or more subsequent catalytic cycles.

24 new easily isolated and reusable Pt-SILP and Rh-SILP materials with TiO₂–SiO₂ and TiO₂–SiO₂/lignin supports, with improved durability and stability, as effective catalysts for hydrosilylation reactions.     

Solar-light-active mesoporous Cr–TiO2 for photodegradation of spent wash: an in-depth study using QTOF LC-MS

A dark-coloured effluent called “spent wash” is generated as an unwanted product in sugarcane-based alcohol distilleries. Most distilleries discharge this effluent into soil or water without any treatment, causing water and soil pollution. Herein, we report chromium-doped TiO₂ (Cr–TiO₂) as a photocatalyst for the degradation of spent wash colour under natural sunlight. Cr-doped TiO₂ nanoparticles were prepared using an aqueous titanium peroxide-based sol–gel method with titanium isopropoxide as the Ti precursor and chromium nitrate as the Cr precursor. To observe the effect of dopant on sol–gel behaviour and physicochemical properties, the Cr concentration was varied in the range 0.5–5 wt%. The crystallization temperature and time were optimized to obtain the required phase of Cr–TiO₂. The physicochemical characteristics of the Cr-doped TiO₂ catalyst were determined using X-ray diffraction, FE-SEM, FETEM, TG, XPS, the Brunauer–Emmett–Teller (BET) method, FT-IR, Raman, PL, ICP-MS, and UV visible spectroscopy. A shift in the absorption edge of TiO₂ by doping with chromium suggested an increase in visible light absorption due to a decrease in the effective band gap. The application potential of the Cr–TiO₂ catalyst was studied in the degradation of sugar-based alcohol distillery waste under natural sunlight, and the results were compared with those of undoped TiO₂ and Degussa P25 TiO₂. Degradation of the spent wash solution was monitored using UV-visible, gel permeation chromatography (GPC), and QTOF LC-MS. GPC and LC-MS showed significant changes in the molecular weight of spent wash colour-forming compounds due to the degradation reaction. QTOF LC-MS analysis suggested that acids, alcohols, glucosides, ketones, lipids, peptides, and metabolites were oxidized to low-molecular-weight counterparts. From the results, 5% Cr–TiO₂ showed the highest degradation rate among all Cr–TiO₂ samples, undoped TiO₂, and Degussa P25 TiO₂ under identical reaction conditions, with nearly 68–70% degradation achieved in 5 h.

A dark coloured effluent called “spent wash” is generated as an unwanted product in sugar based alcohol distillery which is degraded to less toxic compounds using visible light active Cr–TiO₂ photocatalyst under natural sunlight.     

Dual-scale TiO2 and SiO2 particles in combination with a fluoroalkylsilane and polydimethylsiloxane superhydrophobic/superoleophilic coating for efficient solvent–water separation

Surfaces that have unique wettabilities and are simultaneously superhydrophobic with water contact angles > 150°, and superoleophilic with oil contact angles < 5°, are of critical importance in the oil/solvent–water separation field. This work details the facile preparation of highly efficient oil–water separation devices that successfully combine hierarchical surface roughening particles and low surface energy components with porous substrates. Coatings were generated using TiO₂ and hydrophobic-SiO₂ micro/nanoparticle loadings which were then embedded within polydimethylsiloxane, commercially known as Sylgard® 184, and 1H,1H,2H,2H-perfluorooctyltriethoxysilane (FAS) polymer mixtures. The resulting slurries were dip coated onto copper meshes with varying pore diameters (30, 60 and 100 meshes had 595, 250 and 149 μm pore dimensions respectively). Functional testing proved that mesh substrates coated in the lowest Sylgard® 184 : FAS polymer ratio formulations displayed heightened water repellency and retained their superoleophilic properties upon repeat testing. The largest average water contact angle of 145 ± 1°, was recorded on a copper 30 mesh substrate with a coating comprising H-SiO₂ microparticles and TiO₂ nanoparticles in a 1 : 9 polymer mixture of Sylgard® and FAS. The coating''s extreme oil affinity was supported by high solvent–water separation efficiencies (≥99%) which withstood numerous testing/washing cycles.

Surfaces that have unique wettabilities and are simultaneously superhydrophobic with water contact angles > 150°, and superoleophilic with oil contact angles < 5°, are of critical importance in the oil/solvent–water separation field.     

The effect of heat treatment on the anatase–rutile phase transformation and photocatalytic activity of Sn-doped TiO2 nanomaterials

Sn-doped TiO₂ nanomaterials with different amounts of Sn (1, 2.5, 5, 10, and 15 at%) were prepared by a sol–gel method and characterized by XRD, TG, DTA, EDS, XPS, DRS, SEM, BET, and PL. The photocatalytic activity of the prepared samples was investigated by measuring the degradation of rhodamine B in aqueous solution under UV light. The experimental results indicate that doping with Sn promotes phase transformation from anatase to rutile. The photocatalytic activity of TiO₂ is influenced by both the heat treatment temperature and the Sn doping concentration. 1% Sn–TiO₂ exhibits the highest degradation rate at 350 °C and 5% Sn–TiO₂ exhibits the best photocatalytic activity at 500 °C and 650 °C. The enhancement of the photocatalytic activity can be ascribed to a larger surface area and a better hydration ability, as well as less recombination of the photogenerated pairs.

Sn incorporation into TiO₂ lattices promotes anatase/rutile transformation and Sn–TiO₂ exhibits better photocatalytic activity at different temperatures.     

Enhanced photoelectrochemical biosensing performance for Au nanoparticle–polyaniline–TiO2 heterojunction composites

A new photoelectrochemical (PEC) sensing platform comprising TiO₂ nanotube arrays (TiONTAs), polyaniline (PANI), and gold nanoparticles (AuNPs) was successfully fabricated. After loading the enzyme, this Au–PANI–TiONTA electrode showed excellent response to glucose at a linear range of 2–36 mM with a 0.02 mM detection limit. Good PEC performance was obtained due to the following advantages of the material: high visible-light harvesting ability for excellent light trapping capacity of PANI and AuNPs, good separation of the photo-induced charges related to the specific Au–PANI–TiONTA heterostructure, efficient electrode surface reaction kinetics derived from the large specific surface area of TiONTAs and improved electrode catalytic activity. This work proposed a new and general PEC enzymatic format and can be extended to prepare different PEC biosensors for biomolecules such as DNA, proteins and substrates of oxidases.

A novel photoelectrode for glucose PEC biosensing composed of TiONTAs, PANI, and AuNPs was successfully obtained. The GOx@Au–PANI–TiONTA electrode exhibited a wide response range (2–36 mM) with a low detection limit (0.02 mM) and good stability.     

CNT–TiO2 core–shell structure: synthesis and photoelectrochemical characterization

Porous composite coatings, made of a carbon nanotube (CNT)–TiO₂ core–shell structure, were synthesized by the hybrid CVD-ALD process. The resulting TiO₂ shell features an anatase crystalline structure that covers uniformly the surface of the CNTs. These composite coatings were investigated as photoanodes for the photo-electrochemical (PEC) water splitting reaction. The CNT–TiO₂ core–shell configuration outperforms the bare TiO₂ films obtained using the same process regardless of the deposited anatase thickness. The improvement factor, exceeding 400% in photocurrent featuring a core–shell structure, was attributed to the enhancement of the interface area with the electrolyte and the electrons fast withdrawal. The estimation of the photo-electrochemically effective surface area reveals that the strong absorption properties of CNT severely limit the light penetration depth in the CNT–TiO₂ system.

CNT–TiO₂ core–shell nanostructured coatings were made using a hybrid CVD/ALD process. The evaluation of these films as photoanodes for the photoelectrochemical water splitting reaction reveals a clear benefit from the involvement of CNTs.     

Microwave synthesised Pd–TiO2 for photocatalytic ammonia production

Palladium doped anatase TiO₂ nanoparticles were synthesised by a rapid (3 min) one-pot microwave synthesis technique at low temperature and pressure. After being fully characterised by SEM, XRD, Raman, XPS and EDX, photocatalytic nitrate reduction and ammonia production were studied over various dopant levels between 0–3.97 wt% Pd and compared to similar previous literature. Improved yields of ammonia were observed with most dopant levels when compared to non-doped microwave synthesised TiO₂ with 2.65 wt% found to be the optimum dopant level producing 21.2 μmol NH₃. Electrochemical impedance spectroscopy of TiO₂ and Pd–TiO₂ photoelectrodes revealed improvements in charge transfer characteristics at high Pd dopant levels.

A rapid 3 minute one-pot microwave synthesis of Pd–TiO₂ showing improved activity for photocatalytic nitrate reduction into ammonia.     

Elucidation of the electron energy structure of TiO2(B) and anatase photocatalysts through analysis of electron trap density

A clear understanding of the electron energy structure of TiO₂(B)/anatase is needed to study the related catalytic reactions and design new composite photocatalysts. In this study, the electron energy structures of TiO₂(B) and anatase were estimated by analyzing the energy-resolved distribution of electron traps measured by reversed double-beam photoacoustic spectroscopy. In the mixture of TiO₂(B) and anatase, interfacial charge-transfer excitation from anatase to electron traps of TiO₂(B) was suggested. By analyzing this for TiO₂(B), the electron level with a relatively high density of states was found to be located ∼0.07 eV deeper than that for anatase. Furthermore, a similar electron energy structure was suggested for a composite photocatalyst having a mixed phase of TiO₂(B) and anatase.

The electron energy structures of TiO₂(B) and anatase were estimated by analyzing the energy-resolved distribution of electron traps.     

A flexible mesoporous Cu doped FeSn–G–SiO2 composite based biosensor for microalbumin detection

A new mesoporous Cu-doped FeSn–G–SiO₂ (CFSGS) based biosensor was developed for the detection of microalbumin in urine samples. The mechanically flexible FeSn modified sensor was fabricated at room temperature. These demonstrations highlight the unexplored potential of FeSn for developing novel biosensing devices. It is extremely sensitive and selective. Surfactant-aided self-assembly was used to synthesise the mesoporous CFSGS. The large surface area due to the mesopore presence in the CFSG surface that has been composited inside the mesoporous SiO₂ boosted the electrochemical detection. The linear range and detection limit of microalbumin under optimum circumstances were 0.42 and 1 to 10 μL, respectively. This easily fabricated mesoporous CFSGS provided a fast response with high sensitivity, and good selectivity. The sensor''s reusability and repeatability were also quite high, with just a 90 percent drop after 4 weeks of storage at ambient temperature. The biosensor also demonstrated high selectivity against typical potential interfering chemicals found in urine (ascorbic acid, urea, and sodium chloride). The good performance of the mesoporous CFSGS biosensor was validated by measuring microalbumin, and the findings indicated that this sensing device performed very well.

Microalbumin sensing mechanism with electrochemical performance system.     

Mesoporous TiO2 coating on carbon–sulfur cathode for high capacity Li–sulfur battery

In this paper, a meso-porous TiO₂ (titania) coating is shown to effectively protect a carbon–sulfur composite cathode from polysulfide dissolution. The cathode consisted of a sulfur impregnated carbon support coated with a few microns thick mesoporous titania layer. The carbon–sulfur cathode is made using activated carbon powder (ACP) derived from biomass. The mesoporous titania coated carbon–sulfur cathodes exhibit a retention capacity after 100 cycles at C/3 rate (433 mA g ⁻¹) and stabilized at a capacity around 980 mA h g⁻¹. The electrochemical impedance spectroscopy (EIS) of the sulfur cathodes suggests that the charge transfer resistance at the anode, (R_act) is stable for the titania coated sulfur electrode in comparison to a continuous increase in R_act for the uncoated electrode implying mitigation of polysulfide shuttling for the protected cathode. Stability in the cyclic voltammetry (CV) data for the first 5 cycles further confirms the polysulfide containment in the titania coated cathode while the uncoated sulfur electrode shows significant irreversibility in the CV with considerable shifting of the voltage peak positions. Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) studies confirm the adsorption of soluble polysulfides by mesoporous titania.

Mesoporous TiO₂ coating on carbon–sulfur cathode with simple electrical contact for high capacity Li–S battery.