Laser induced selective photo-catalytic reduction of CO 2 into methanol using In 2 O 3 -WO 3 nano-composite

A Review of the Effect of Defect Modulation on the Photocatalytic Reduction Performance of Carbon Dioxide

Constructive defect engineering has emerged as a prominent method for enhancing the performance of photocatalysts. The mechanisms of the influence of defect types, concentrations, and distributions on the efficiency, selectivity, and stability of CO2 reduction were revealed for this paper by analyzing the effects of different types of defects (e.g., metallic defects, non-metallic defects, and composite defects) on the performance of photocatalysts. There are three fundamental steps in defect engineering techniques to promote photocatalysis, namely, light absorption, charge transfer and separation, and surface-catalyzed reactions. Defect engineering has demonstrated significant potential in recent studies, particularly in enhancing the light-harvesting, charge separation, and adsorption properties of semiconductor photocatalysts for reducing processes like carbon dioxide reduction. Furthermore, this paper discusses the optimization method used in defect modulation strategy to offer theoretical guidance and an experimental foundation for designing and preparing efficient and stable photocatalysts.

Enhanced carbon dioxide adsorption and carrier separation over amine functionalized zirconium metal organic framework/gold/indium oxide for boosting photocatalytic carbon dioxide reduction

Photocatalytic CO2 conversion is a prospective way to mitigate greenhouse effect. In2O3 is widely used in the resource conversion of CO2, but still exists a few drawbacks containing limited CO2 capture and activation, narrow light absorption range, low charge separation and utilization. To overcome these disadvantages, an NH2-UiO-66/Au/In2O3 composite photocatalyst is built, with Au nanoparticles and NH2-UiO-66 decorated on the surface of In2O3 nanorods. Significantly, the improved carrier separation ability is attributed to the Schottky junction at the Au/In2O3 interface and the heterostructure between In2O3 and NH2-UiO-66. And the widened light absorption is attributed to the plasmon effect caused by Au nanoparticles. Moreover, the increase of CO2 adsorption and activation is mainly due to the porosity of NH2-UiO-66, thereby greatly improving photocatalytic CO2RR efficiency of NH2-UiO-66/Au/In2O3 nanorods. The CO yield of NH2-UiO-66/Au/In2O3 is 8.56 μmol g-1 h-1, which is nearly 45 times that of In2O3. This work will present a novel idea to design high-efficient composite photocatalysts for CO2 reduction by multifunctional component synergistic enhancement.

Advances in the Application of Bi-Based Compounds in Photocatalytic Reduction of CO2

Bi-based semiconductor materials have special layered structure and appropriate band gap, which endow them with excellent visible light response ability and stable photochemical characteristics. As a new type of environment-friendly photocatalyst, they have received extensive attention in the fields of environmental remediation and energy crisis resolution and have become a research hotspot in recent years. However, there are still some urgent issues that need to be addressed in the practical large-scale application of Bi-based photocatalysts, such as the high recombination rate of photogenerated carriers, limited response range to visible spectra, poor photocatalytic activity, and weak reduction ability. In this paper, the reaction conditions and mechanism of photocatalytic reduction of CO₂ and the typical characteristics of Bi-based semiconductor materials are introduced. On this basis, the research progress and application results of Bi-based photocatalysts in the field of reducing CO₂, including vacancy introduction, morphological control, heterojunction construction, and co-catalyst loading, are emphasized. Finally, the future prospects of Bi-based photocatalysts are prospected, and it is pointed out that future research directions should be focused on improving the selectivity and stability of catalysts, deeply exploring reaction mechanisms, and meeting industrial production requirements.

Research Progress of Co-Catalysts in Photocatalytic CO2 Reduction: A Review of Developments, Opportunities, and Directions

With the development of the global economy, large amounts of fossil fuels are being burned, causing a severe energy crisis and climate change. Photocatalytic CO2 reduction is a clean and environmentally friendly method to convert CO2 into hydrocarbon fuel, providing a feasible solution to the global energy crisis and climate problems. Photocatalytic CO2 reduction has three key steps: solar energy absorption, electron transfer, and CO2 catalytic reduction. The previous literature has obtained many significant results around the first two steps, while in the third step, there are few results due to the need to add a co-catalyst. In general, the co-catalysts have three essential roles: (1) promoting the separation of photoexcited electron–hole pairs, (2) inhibiting side reactions, and (3) improving the selectivity of target products. This paper summarizes different types of photocatalysts for photocatalytic CO2 reduction, the reaction mechanisms are illustrated, and the application prospects are prospected.

Properties, optimized morphologies, and advanced strategies for photocatalytic applications of WO3 based photocatalysts

The development of WO₃ based photocatalysts has gained considerable attention across the world, especially in the realm of environmental remediation and energy production. WO₃ has a band gap of 2.5- 2.7 eV that falls under the visible region and is thus a potential candidate to utilize in various photocatalytic processes. As an earth-abundant metal oxide, WO₃ discovered in 1976 displayed excellent electronic and morphological properties, good stability, and enhanced photoactivity with diverse crystal phases. Also, it unveils non-toxicity, high stability in drastic conditions, biocompatibility, low cost, excellent hole mobility (10 cm² V^-1s^-1), and tunable band gap. This review provides a comprehensive overview of the different properties of WO₃ inclusive of crystallographic, electrical, optical, thermoelectrical, and ferroelectric properties. The different morphologies of WO₃ based on dimensions were obtained by adopting different fabrication methods including inspecting their effects on the efficiency of WO₃. Numerous strategies to construct an ideal photocatalyst such as engineering crystal facets, surface defects, doping, heterojunction formation explaining specifically type-II, Z-scheme, and S-scheme mechanisms with addition to carbonaceous based WO₃ nanocomposites are summed up to explore the photocatalytic performance. The typical application of WO₃ is deliberated in detail involving the role and efficiency of WO₃ in pollutant degradation, CO₂ photoreduction, and water splitting. Besides, other applications of WO₃ as gas-sensor, bio-sensor, decomposition of VOCs, heavy metals ions adsorption, and antimicrobial property are also included. Moreover, the numerous aspects responsible for the high efficiency of WO₃-based nanocomposites with their challenges, opportunities, and future aspects are summarized. Hopefully, this review may inspire researchers to explore new ideas to boost the production of clean energy for the next generation.

Laser Induced Anchoring of Nickel Oxide Nanoparticles on Polymeric Graphitic Carbon Nitride Sheets Using Pulsed Laser Ablation for Efficient Water Splitting under Visible Light

A visible-light-active nickel oxide-graphitic carbon nitride (NiO@g-CN) hetero-structured nanocomposite was synthesized for the first time by pulsed laser ablation in liquid and used as a photoanode material in photoelectrochemical water-splitting reaction with a solar simulator. It was found that the photoelectrochemical performance of PLAL synthesized NiO@g-CN nanocomposite as photoanode, compared to g-CN as photoanode showed fourfold enhancements in photocurrent density under visible light. FT-IR, XRD, FE-SEM, and EDX consistently showed the proper anchoring of nano-sized NiO on g-CN. UV-DRS and the band gap estimation showed the narrowing down of the band gap energy and consequent enhancement in the visible-light absorption, whereas photoluminescence spectroscopy confirmed the reduction of the recombination of photo-excited electron hole pairs as a result of the anchoring of NiO on g-CN. The photoelectrochemical performance of g-CN and the NiO@g-CN nanocomposite photoanodes was compared by linear sweep voltammetry (LSV), Chronoamperometry (I-t), and Electrochemical Impedance Spectroscopy (EIS). All of these results of the characterization studies account for the observed fourfold enhancement of photocurrent density of NiO@g-CN nanocomposite as photoanode in the photoelectrochemical reaction.

Investigation of the survival viability of cervical cancer cells (HeLa) under visible light induced photo-catalysis with facile synthesized WO3/ZnO nanocomposite

The photo catalytic degradation, a proven chemical process used for the decontamination of organic/inorganic pollutants and microorganisms in water was implemented. In this work for the selective killing of cervical cancer cells (HeLa cells) by using nano-composite of ZnO (Zinc Oxcide), WO₃ (tungsten oxide) and (n-WO₃/ZnO) as a photo-catalyst under the irradiation of visible light. All the three nanostructured semiconducting materials (WO3, ZnO and n-WO3/ZnO) were synthesized by facile chemical precipitation method and their morphological and optical characterization studies were carried out to elucidate the observed enhancement in the photo-catalytic killing of HeLa cancer cells with n-WO3/ZnO as a photo-catalyst. After 60 min of photo-catalytic reaction with n-WO₃/ZnO as a photo-catalyst, a survival viability of HeLa cancer cells as low as 15% was achieved (nearly 85% of killing), as compared to 65% of HeLa cancer cell survival viability (nearly 35% of killing) with individual use of WO₃ and ZnO as photo-catalysts under the same irradiation and experimental conditions. This improved photo-catalytic killing of HeLa cancer cells using n-WO₃/ZnO in the visible spectral region is attributed to the enhanced visible light absorption and reduced electron hole recombination, characteristically brought about in the n-WO₃/ZnO composite material. As photo-catalytic killing of the cancer cells can be selective, localized and reasonably efficient, in principle, this method can be considered as a non-invasive targeted treatment option for killing any type of cancer cells. HeLa cells, in particular are the cervical cancer cell and the tumors in and around cervix, containing HeLa cells can be non-surgically accessed and photo-catalytically treated with appropriate photo-catalyst and light source.

Single step production of high-purity copper oxide-titanium dioxide nanocomposites and their effective antibacterial and anti-biofilm activity against drug-resistant bacteria

In the present research work, copper oxide-titanium dioxide nanocomposites were synthesized for the first time using advanced pulsed laser ablation in liquid (PLAL) technique for disinfection of drug-resistant pathogenic waterborne biofilm-producing bacterial strains. For this, a series of copper oxide-titanium dioxide nanocomposites were synthesized by varying the composition of copper oxide (5%, 10%, and 20%) with titanium dioxide. The pure titanium dioxide and copper oxide-titanium dioxide nanocomposites were characterized by advanced instrumental techniques. XRD, TEM, FE-SEM, EDX, elemental mapping and XPS analysis results consistently revealed the successful formation of copper oxide-titanium dioxide nanocomposites using PLAL technique. The antibacterial and antibiofilm activities of pure titanium dioxide and copper oxide-titanium dioxide nanocomposites were investigated against biofilm-producing strains of Methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa by various methods. Our results revealed that the PLAL synthesized copper oxide-titanium dioxide nanocomposites showed enhanced anti-biofilm and antibacterial activity compared to pure titanium dioxide in a dose-dependent manner against targeted pathogens. Furthermore, the effects of pure titanium dioxide and copper oxide-titanium dioxide nanocomposites on bacterial morphology, biofilm formation, aggregation and their colonization by targeted pathogens were also examined using scanning electron microscopy. Microscopic images clearly showed that the cell envelope of almost all the cells were rumples, rough, had irregularities and abnormal appearance with the major damage being characterized by the formation of "pits". Many depressions and indentations were also seen in their cell envelope and the original shape of Pseudomonas aeruginosa cells changed from normal rod to swollen, large and elongated which indicates the loss of membrane integrity and damage of cell wall and membrane. The findings suggested that PLAL synthesized copper oxide-titanium dioxide nanocomposites have good potential for removal of biofilm or killing of pathogenic bacteria in water distribution network and for wastewater treatment, hospital and environmental applications. In addition, cytotoxic activity of pure TiO₂ and PLAL synthesized copper oxide-titanium dioxide nanocomposites against normal and healthy cells (HEK-293) and cancerous cells (HCT-116) were also evaluated by MTT assay. The MTT assay results showed no cytotoxic effects on HEK-293 cells, which suggest TiO₂ and PLAL synthesized copper oxide-titanium dioxide nanocomposites are non-toxic to the normal cells.

Synthesis, characterization and evaluation of visible light active cadmium sulfide-graphitic carbon nitride nanocomposite: A prospective solar light harvesting photo-catalyst for the deactivation of waterborne pathogen

Cadmium sulfide-graphitic carbon nitride nanocomposite was synthesized by pulsed laser ablation in liquid, and it was found from the results of optical and morphological characterizations that the proper anchoring of nanostructured cadmium sulfide on the nano-sheets of graphitic carbon nitride took place, which brought about the positive attributes such as enhanced visible light absorption and reduced photo-generated charge recombination, the key features required for an efficient photo-catalyst by solar light harvesting. The pulsed laser ablation in liquid method adopted for the synthesis of cadmium sulfide-graphitic carbon nitride has the following advantages: the shape and size of the synthesized particles can be controlled by altering the experimental parameters such as laser wavelength, pulse laser duration, the pH of the solution, the surfactants and the temperature of the solution, pulsed laser ablation in liquid method neither requires cumbersome equipment nor does it require intermediate chemicals and catalysts nor does it necessitate the post synthesis purification. The enhancement of photo-catalytic activity of cadmium sulfide-graphitic carbon nitride nanocomposite was tested for the photo-catalytic deactivation of Escherichia coli bacteria in water under visible light radiation. As anticipated, a significant improvement of photo-catalytic deactivation was observed, which is attributed to the enhanced and extended light absorption in the visible spectral region, and the formation of herterojunction between the semiconductors, which is instrumental in inhibiting the undesired recombination of photo-generated charge carriers. Quantitatively, the presence of cadmium sulfide on the graphitic carbon nitride surface contributed to a remarkable 129% increase of photo-catalytic degradation constant compared to pure graphitic carbon nitride, which resulted in the decrease of total depletion time of Escherichia coli from 156 min to 67 min with the cadmium sulfide-graphitic carbon nitride nanocomposite synthesized by pulsed laser ablation in liquid method. Our results on the efficient photo-catalytic deactivation of Escherichia coli under visible light assures that cadmium sulfide-graphitic carbon nitride nanocomposite can very well be used for photo-catalytic water purification by harvesting the abundant solar light.

WO3/Conducting Polymer Heterojunction Photoanodes for Efficient and Stable Photoelectrochemical Water Splitting

An efficient and stable heterojunction photoanode for solar water oxidation was fabricated by hybridization of WO₃ and conducting polymers (CPs). Organic/inorganic hybrid photoanodes were readily prepared by the electropolymerization of various CPs and the codeposition of tetraruthenium polyoxometalate (Ru₄POM) water-oxidation catalysts (WOCs) on the surface of WO₃. The deposition of CPs, especially polypyrrole (PPy) doped with Ru₄POM (PPy:Ru₄POM), resulted in a remarkably improved photoelectrochemical performance by the formation of a WO₃/PPy p-n heterojunction and the incorporation of efficient Ru₄POM WOCs. In addition, there was also a significant improvement in the photostability of the WO₃-based photoanode after the deposition of the PPy:Ru₄POM layer due to the suppression of the formation of hydrogen peroxide, which was responsible for corrosion. This study provides insight into the design and fabrication of novel photosynthetic and photocatalytic systems with excellent performance and stability through the hybridization of organic and inorganic materials.

A review on fabricating heterostructures from layered double hydroxides for enhanced photocatalytic activities

LDH is a controllable 2D material for fabricating heterostructures with another semiconductor.