Porosity-dependent photoelectrochemical activity of double-layered TiO2 thin films deposited by spin-coating method

Photoelectrochemical (PEC) cells made of low-cost, chemically stable, and abundant materials are crucial for green hydrogen production. In this regard, the fabrication of porous films with high light trapping ability and a large contact area is crucial for the production of efficient PEC cells. In this report, anatase TiO2 thin films with a porous double-layered structure were successfully prepared using a conventional spin-coating deposition method. Various amounts of polystyrene spheres were used as a pore-templating agent to control the porosity of the films. A range of characterization techniques, such as scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and photoluminescence were employed to assess the morphology, structural and optical properties of prepared TiO2 films. PEC measurements revealed that prepared double-layered TiO2 thin films exhibit porosity-dependent photocatalytic activity. For example, TiO2 films with an optimized porous structure demonstrated an increase in photocurrent density by a factor of ∼2.23 (to 141.7 μA cm-2) and photoconversion efficiency improvement by a factor of ∼2.14 as compared to non-porous double-layered TiO2 reference films. Absorbance and photoluminescence analysis confirmed that improved PEC activity can be attributed to increased light absorption by the porous structure and reduced charge carrier recombination.

Photocatalytic Degradation of Phenol Red in Water on Nb(x)/TiO2 Nanocomposites

In this paper, the photocatalytic effect of Nb(x)/TiO2 nanocomposites on the degradation of phenol red (PR) was studied. Nb(x)/TiO2 nanocomposites are fabricated by a simple sol-gel route with new experimental conditions. The structural and optical properties were determined using high transmission electron microscopy (HRTEM), X-ray diffraction, Raman spectroscopy, photoluminescence, and UV-vis absorbance spectroscopy. Compared to pure anatase TiO2, the recently fabricated Nb(x)/TiO2 nanocomposite has a shift in the optical band edge to the visible wavelength. Consequently, it has high performance in adsorption capacity and photocatalytic activities. A time of 160 min has been observed to be suitable for mostly degradable 20 mgL−1 of phenol red on Nb(2.0)/TiO2 composite. The kinetic results were in good agreement with the first-order kinetic model at different concentrations. In addition, the results showed that the addition of Nb led to a significant degradation process. The decomposition of phenol red pollutants showed a synergistic effect of the Nb(2.0)/TiO2 nanocomposites on wastewater treatment.

Preparation of a Ti0.7W0.3O2/TiO2 nanocomposite interfacial photocatalyst and its photocatalytic degradation of phenol pollutants in wastewater

A Ti_0.7W_0.3O₂/TiO₂ nanocomposite interfacial photocatalyst was designed and prepared for the photocatalytic degradation of phenol pollutants in wastewater. The detailed properties of the Ti_0.7W_0.3O₂/TiO₂ nanocomposite interface (NCI) were analyzed by XRD, SEM, EDX, DRS, UPS and XPS technologies, showing that anatase TiO₂ nanospheres (NSs) were uniformly dispersed on the surface of rutile Ti_0.7W_0.3O₂ nanoparticles (NPs) and formed the nanocomposite interface. The DRS and UPS results of 5 wt% Ti_0.7W_0.3O₂/TiO₂ NCI indicated a greatly broadened light response range with a wavelength shorter than 527 nm and a shorter band gap energy of 2.37 eV. The conduction band of TiO₂ NSs, Ti_0.7W_0.3O₂ NPs and 5 wt% Ti_0.7W_0.3O₂/TiO₂ NCI were measured based on the results of the valence band and band gap energy obtained via XPS and DRS, and then the energy level diagram of Ti_0.7W_0.3O₂/TiO₂ NCI was proposed. The photocatalytic degradation of phenol at Ti_0.7W_0.3O₂/TiO₂ NCI with different loading ratios of Ti_0.7W_0.3O₂ NPs was investigated under optimum conditions (i.e., pH of 4.5, catalyst dosage of 0.45 g L^-1 and phenol initial concentration of 95 ppm) under the illumination of ultraviolet visible light. Also, 5 wt% Ti_0.7W_0.3O₂/TiO₂ NCI exhibited the highest photocatalytic activity, with the initial rate constant (k) calculated as 0.09111 min^-1. After recycling six times, Ti_0.7W_0.3O₂/TiO₂ NCI showed good stability and recyclability. The involvement of superoxide radicals in the initial reaction at Ti_0.7W_0.3O₂/TiO₂ NCI was evidenced by the use of a terephthalic acid (TA) fluorescent probe. Besides, UV-Vis spectroscopy, UHPLC-MS and GC-MS technologies were used to analyze the main intermediates in the photocatalytic degradation of phenol. The probable photocatalytic degradation mechanism of phenol at Ti_0.7W_0.3O₂/TiO₂ NCI was also proposed.

Recent Advances in Niobium-Based Materials for Photocatalytic Solar Fuel Production

The search for renewable and clean energy sources is a key aspect for sustainable development as energy consumption has continuously increased over the years concomitantly with environmental concerns caused by the use of fossil fuels. Semiconductor materials have great potential for acting as photocatalysts for solar fuel production, a potential energy source able to solve both energy and environmental concerns. Among the studied semiconductor materials, those based on niobium pentacation are still shallowly explored, although the number of publications and patents on Nb(V)-based photocatalysts has increased in the last years. A large variety of Nb(V)-based materials exhibit suitable electronic/morphological properties for light-driving reactions. Not only the extensive group of Nb2O5 polymorphs is explored, but also many types of layered niobates, mixed oxides, and Nb(V)-doped semiconductors. Therefore, the aim of this manuscript is to provide a review of the latest developments of niobium based photocatalysts for energy conversion into fuels, more specifically, CO2 reduction to hydrocarbons or H2 evolution from water. Additionally, the main strategies for improving the photocatalytic performance of niobium-based materials are discussed.

High-throughput HSE study on the doping effect in anatase TiO2

Systematic study on the doping effects of anatase TiO₂ doped with 40 kinds of elements by high-throughput HSE06 calculations.

Surface chemistry and growth mechanism of highly oriented, single crystalline Nb-doped TiO2 nanorods

The effect of the Nb doping on morphological changes in TiO₂ nanorods by hydrothermal growth and its enhanced carrier transport were investigated. The nanorod diameter, film thickness, nucleation density, and photocurrent are discussed.

Synthesis of LaFeO3/Ag2CO3 Nanocomposites for Photocatalytic Degradation of Rhodamine B and p-Chlorophenol under Natural Sunlight

Novel LaFeO₃/Ag₂CO₃ nanocomposites are synthesized by co-precipitation method for photocatalytic degradation of Rhodamine B (RhB) and p-chlorophenol under visible light irradiation. Heterostructures between LaFeO₃ and Ag₂CO₃ semiconductors are formed during the synthesis of these nanocomposites. Among the nanocomposites prepared with different ratios of LaFeO₃ and Ag₂CO₃, 1% LaFeO₃/Ag₂CO₃ shows the highest photocatalytic activity for the degradation of RhB. Maximum electron-hole pair decoupling efficiency is observed in 1% LaFeO₃/Ag₂CO₃, which causes the greater activity of the heterostructure. Degradation efficiency of 99.5% for RhB and 59% for p-chlorophenol has been obtained under natural sunlight within 45 min. Interestingly, the stability of Ag₂CO₃ is improved dramatically after making nanocomposite, and no decomposition of the catalyst was observed even after several photocatalytic cycles. Reactive oxygen species scavenging experiments with p-benzoquinone, isopropyl alcohol, and ammonium oxalate suggest that a major degradation process is caused by holes. Degradation of RhB into small organic moieties is detected using LC-MS technique. Further, the efficient mineralization of the degradation products occurs during the catalytic process.

Tuning mixed-phase Nb-doped titania films for high-performance photocatalysts with enhanced whole-spectrum light absorption

Heterojunction of rutile and anatase phase enhanced photocatalytic performance of mixed-phase Nb doped titania films to degrade pollutants under visible (vis) light.