Role of Post-Hydrothermal Treatment on the Microstructures and Photocatalytic Activity of TiO2-Based Nanotubes

The present study demonstrates the thermal stability and photocatalytic activity of TiO2-based nanotubes with respect to post-hydrothermal treatment. Titanate nanotubes were synthesized by adapting an alkali hydrothermal method from TiO2sol using NaOH as a catalyst. The effect of post-hydrothermal heating on the properties—such as structure, morphology, textural properties, and activity—of as-synthesized one-dimensional titania nanostructure is investigated in detail. The characterizations are carried out using SEM, EDX, TEM, XRD, and a BET surface area analyzer. When heated in the presence of water in an autoclave, the protonated titanate phase of the nanotubes converts to anatase phase. Meanwhile, the tubular morphology is gradually lost as the post-hydrothermal heating duration increases. The photocatalytic activity was assessed utilizing the photo-oxidation of an amaranth dye. It is discerned that the as-prepared nanotubes are photocatalytically inactive but become active after post-hydrothermal processing. The activity trend follows the formation of the active phase—the titanate phase crystallizes into a photocatalytically-active anatase phase during post-hydrothermal heating. The effect of experimental parameters, such as reaction pH, dye concentration, and amount of catalyst, on the dye removal is studied. The findings also highlight that the role of holes/OH•− is more prominent as compared to conduction band electron/O2•− for the removal of the dye. In addition, the photocatalyst exhibited excellent stability and reusability.Theauthorswouldliketoexpresstheir appreciation to Ministry of Higher Education Malaysia for Fundamental Research Grant SchemewithProject Code: FRGS/1/2019/STG07/USM/02/12

Mechanical performance of date palm fiber-reinforced concrete modified with nano-activated carbon

Date palm fiber (DPF) is an easily processed, low cost, and accessible natural fiber. It has mostly been used in composites for non-structural applications. For DPF to be utilized in cementitious composites for structural applications, ways to reduce its harmful effect on compressive strength must be devised. Therefore, in this study, nano-activated carbon (NAC), due to its filler effects, was used as an additive to produce the DPF-reinforced concrete (DPFRC). To produce the DPFRC, 0, 1, 2, and 3% by cement weight of DPF and NAC were added. The fresh properties, strength, and microstructure of the concrete were examined. The findings revealed that DPF decreased the consistency, density, and compressive strength. Additionally, it increases the porosity in the concrete microstructure. The addition of up to 1% NAC significantly improved the compressive, flexural, and split tensile strengths of the concrete, while it decreased the harmful impact of up to 2% DPF on the DPFRC’s strength. The split tensile and flexural strengths of the concrete were enhanced with the addition of up to 2% DPF without any NAC. The addition of up to 2% NAC densified the DPFRC’s microstructure by refining and filling the pores generated by the DPF. The multivariable statistical models developed to estimate the mechanical properties of the DPFRC containing DPF and NAC were very significant with a very high degree of precision

Surface plasmonic resonance and z-scheme charge transport synergy in three-dimensional flower-like ag-ceO2-znO heterostructures for highly improved photocatalytic CO2 reduction

The design and engineering of plasmonic metal nanocomposite photocatalysts offer an operative approach for highly efficient CO2 photoreduction. Herein, the authors report a plasmonic 3D flower-like (3DF) Ag-CeO2-ZnO nanocomposite catalyst with effective charge carrier separation/transfer and CO2 adsorption capacity exhibiting a considerable enhanced performance compared to pure ZnO and CeO2 for photocatalytic CO2 reduction to CO and CH4 under UV-vis light. The apparent quantum efficiency of the optimized sample is 4.47% at 420 nm, and the CO2 to CO selectivity reaches up to similar to 95%. The enhanced photocatalytic performance of 3DF Ag-CeO2-ZnO can be assigned to the prolonged absorption in the visible light region induced by the surface plasmon resonance (SPR) effect, the efficient separation of photogenerated charges, and the Z-scheme configuration. Furthermore, the photocatalyst displays excellent stability and reusability. The mechanism of the plasmon-mediated Z-scheme structure has been suggested in which Ag NPs act as both visible light absorber and electron mediator

Rational design of a 2D TiO2-MoO3 step-scheme heterostructure for boosted photocatalytic overall water splitting

The design of step-scheme (S-scheme) heterostructure photocatalysts is a promising strategy for the high utilization of photogenerated charge carriers. Herein, a novel S-scheme two-dimensional (2D) TiO2-MoO3 heterojunction photocatalyst is fabricated by a facile electrochemical method for high water splitting photocatalytic efficiency. According to X-ray photoelectron spectroscopy (XPS) assessment, electrons are transported from TiO2 to MoO3 upon close contact, creating an internal electric field (IEF) directed from TiO2 to MoO3. Hence, upon light irradiation, the photogenerated electrons in MoO3 move toward TiO2 under the IEF effect, as revealed by EPR analysis, implying that the S-scheme heterojunction was established in the TiO2-MoO3 heterostructure and significantly promoted the separation of electron-hole pairs to enhance efficient photocatalytic water splitting. Thanks to the 2D morphology of the TiO2-MoO3 heterojunction and the significantly improved redox capability of the charge carriers in the S-scheme system, the photocatalytic water splitting efficiency of the optimized TiO2-MoO3 is higher than those of both pure MoO3 and TiO2 and commercial TiO2-P25. This study, for the first time, presents the charge transfer pathways in the TiO2-MoO3 heterostructure photocatalyst via an S-scheme system. It will shed new light on the design and fabrication of novel step-scheme heterojunction photocatalysts for overall water splitting

Regulating the Electron Depletion Layer of Au/V₂O₅/Ag Thin Film Sensor for Breath Acetone as Potential Volatile Biomarker

Human exhaled breath has been utilized to identify biomarkers for diseases such as diabetes and cancer. The existence of these illnesses is indicated by a rise in the level of acetone in the breath. The development of sensing devices capable of identifying the onset of lung cancer or diabetes is critical for the successful monitoring and treatment of these diseases. The goal of this research is to prepare a novel breath acetone sensor made of Ag NPs/V2O5 thin film/Au NPs by combining DC/RF sputtering and post-annealing as synthesis methods. The produced material was characterized using X-ray diffraction (XRD), UV-Vis, Raman, and atomic force microscopy (AFM). The results revealed that the sensitivity to 50 ppm acetone of the Ag NPs/V2O5 thin film/Au NPs sensor was 96%, which is nearly twice and four times greater than the sensitivity of Ag NPs/V2O5 and pristine V2O5, respectively. This increase in sensitivity can be attributed to the engineering of the depletion layer of V2O5 through the double activation of the V2O5 thin films with uniform distribution of Au and Ag NPs that have different work function values

Fabrication of Z-scheme ZnO/g-C3N4/ZnS nanocomposites using high power laser for methylene blue degradation

Photocatalysis plays a vital role in addressing environmental challenges by harnessing solar energy for efficient pollutant degradation. In this study, we investigate the photocatalytic activity of a ZnO/g-C _3 N _4 /ZnS composite system in the degradation of methylene blue, a widely used dye with detrimental effects on aquatic ecosystems. The composite materials were synthesized using a facile and scalable approach, and their structural properties, morphologies, sizes, and elemental compositions were characterized using different analytical techniques. The ZnO/g-C _3 N _4 /ZnS composite exhibited enhanced photocatalytic performance compared to individual components. Remarkably, the degradation efficiency reached 80% for the composite with a 30% ZnO composition, surpassing the efficiencies of ZnS alone (29%) and ZnS/g-C _3 N _4 (65%). The composite’s higher degradation efficiency is due to synergistic semiconductor effects, enhancing charge transfer and reducing electron–hole recombination. ZnO incorporation increases active sites and surface area, improving interaction with methylene blue. The favorable band edge positions of ZnO aligned with ZnS and g-C _3 N _4 , facilitating the utilization of a broader spectrum of solar light. The composite’s photocatalytic activity was achieved under UV light irradiation, demonstrating its potential for sustainable and energy-efficient applications. This study highlights the significance of composite design and the Z-scheme concept in photocatalysis, offering insights into the development of advanced materials for environmental remediation. The findings contribute to the understanding of efficient solar-driven pollutant degradation and pave the way for the design and optimization of innovative photocatalytic systems for sustainable environmental solutions

One-Step Hydrothermal Synthesis of Anatase TiO2 Nanotubes for Efficient Photocatalytic CO2 Reduction

The hydrothermal dissolution-recrystallization process is a key step in the crystal structure of titania-based nanotubes and their composition. This work systematically studies the hydrothermal conditions for directly synthesizing anatase TiO2 nanotubes (ATNTs), which have not been deeply discussed elsewhere. It has been well-known that ATNTs can be synthesized by the calcination of titanate nanotubes. Herein, we found the ATNTs can be directly synthesized by optimizing the reaction temperature and time rather than calcination of titanate nanotubes, where at each temperature, there is a range of reaction times in which ATNTs can be prepared. The effect of NaOH/TiO2 ratio and starting materials was explored, and it was found that ATNTs can be prepared only if the precursor is anatase TiO2, using rutile TiO2 leads to forming titanate nanotubes. As a result, ATNTs produced directly without calcination have excellent photocatalytic CO2 reduction than titanate nanotubes and ATNTs prepared by titanate calcination

Construction of Bi2S3/TiO2/MoS2 S-Scheme Heterostructure with a Switchable Charge Migration Pathway for Selective CO2 Reduction

Switching between the redox potential of an appropriate semiconductor heterostructure could show critical applications in selective CO2 reduction. Designing a semiconductor photocatalyst with a wavelength-dependent response is an effective strategy for regulating the direction of electron flow and tuning the redox potential. Herein, the switching mechanism between two charge migration pathways and redox potentials in a Bi2S3/TiO2/MoS2 heterostructure by regulating the light wavelength is achieved. In situ irradiated X-ray photoelectron spectroscopy (ISI-XPS), electron spin resonance (ESR), photoluminescence (PL), and experimental scavenger analyses prove that the charge transport follows the S-scheme approach under UV–vis–NIR irradiation and the heterojunction approach under vis–NIR irradiation, confirming the switchable feature of the Bi2S3/TiO2/MoS2 heterostructure. This switchable feature leads to the reduction of CO2 molecules to CH3OH and C2H5OH under UV–vis–NIR irradiation, while CH4 and CO are produced under Vis–NIR irradiation. Interestingly, the apparent quantum efficiency of the optimal composite at λ = 600 nm is 4.23%. This research work presents an opportunity to develop photocatalysts with switchable charge transport and selective CO2 reduction.The authors are thankful to the DST National Single Crystal Diffractometer Facility Laboratory, DoS in Physics, UPE, IOE, and DST-PURSE, Vijnana Bhavana, University of Mysore, Mysuru, for providing the required facilities. The authors extend their appreciation to the Researchers Supporting Project number (RSP-2021/381), King Saud University, Riyadh, Saudi Arabia.Scopu