Interfacial modification of titanium dioxide to enhance photocatalytic efficiency towards H2 production

Green Synthesis of NiFe2O4 Nano-Spinel Oxide-Decorated Carbon Nanotubes for Efficient Capacitive Performance-Effect of Electrolyte Concentration

Energy storage applications received great attention due to environmental aspects. A green method was used to prepare a composite of nickel-iron-based spinel oxide nanoparticle@CNT. The prepared materials were characterized by different analytical methods like X-ray diffraction, X-ray photon spectroscopy (XPS), scanning electron microscopy (SEM), and transmitted electron microscopy (TEM). The synergistic effect between nickel-iron oxide and carbon nanotubes was characterized using different electrochemical methods like cyclic voltammetry (CV), galvanostatic charging/discharging (GCD), and electrochemical impedance spectroscopy (EIS). The capacitances of the pristine NiFe2O4 and NiFe2O4@CNT were studied in different electrolyte concentrations. The effect of OH- concentrations was studied for modified and non-modified surfaces. Furthermore, the specific capacitance was estimated for pristine and modified NiFe2O4 at a wide current range (5 to 17 A g-1). Thus, the durability of different surfaces after 2000 cycles was studied, and the capacitance retention was estimated as 78.8 and 90.1% for pristine and modified NiFe2O4. On the other hand, the capacitance rate capability was observed as 65.1% (5 to 17 A g-1) and 62.4% (5 to 17 A g-1) for NiFe2O4 and NiFe2O4@CNT electrodes.

Testing of Sr-Doped ZnO/CNT Photocatalysts for Hydrogen Evolution from Water Splitting under Atmospheric Dielectric Barrier Plasma Exposure

Nonthermal plasma is a well-recognized environmentally advantageous method for producing green fuels. This work used different photocatalysts, including PZO, S_xZO, and S_xZC_x for hydrogen production using an atmospheric argon coaxial dielectric barrier discharge (DBD)-based light source. The photocatalysts were produced using a sol-gel route. The DBD discharge column was filled with water, methanol, and the catalyst to run the reaction under argon plasma. The DBD reactor was operated with a 10 kV AC source to sustain plasma for water splitting. The light absorption study of the tested catalysts revealed a decrease in the band gap with an increase in the concentration of Sr and carbon nanotubes (CNTs) in the Sr/ZnO/CNTs series. The photocatalyst S₂₅ZC₂ demonstrated the lowest photoluminescence (PL) intensity, implying the most quenched recombination of charge carriers. The highest H₂ evolution rate of 2760 μmol h^-1 g^-1 was possible with the S₂₅ZC₂ catalyst, and the lowest evolution rate of 56 μmol h^-1 g^-1 was observed with the PZO catalyst. The photocatalytic activity of S₂₅ZC₂ was initially high, which decreased slightly over time due to the deactivation of the photocatalyst. The photocatalytic activity decreased from 2760 to 1670 μmol h^-1 g^-1 at the end of the process.

Recent innovations in the technology and applications of low-dimensional CuO nanostructures for sensing, energy and catalysis

Low-dimensional copper oxide nanostructures are very promising building blocks for various functional materials targeting high-demanded applications, including energy harvesting and transformation systems, sensing and catalysis. Featuring a very high surface-to-volume ratio and high chemical reactivity, these materials have attracted wide interest from researchers. Currently, extensive research on the fabrication and applications of copper oxide nanostructures ensures the fast progression of this technology. In this article we briefly outline some of the most recent, mostly within the past two years, innovations in well-established fabrication technologies, including oxygen plasma-based methods, self-assembly and electric-field assisted growth, electrospinning and thermal oxidation approaches. Recent progress in several key types of leading-edge applications of CuO nanostructures, mostly for energy, sensing and catalysis, is also reviewed. Besides, we briefly outline and stress novel insights into the effect of various process parameters on the growth of low-dimensional copper oxide nanostructures, such as the heating rate, oxygen flow, and roughness of the substrates. These insights play a key role in establishing links between the structure, properties and performance of the nanomaterials, as well as finding the cost-and-benefit balance for techniques that are capable of fabricating low-dimensional CuO with the desired properties and facilitating their integration into more intricate material architectures and devices without the loss of original properties and function.

A Novel Photocatalytic Functional Coating Applied to the Degradation of Xylene in Coating Solvents under Solar Irradiation

A novel photocatalytic functional coating was prepared with g-C₃N₄/TiO₂ composites as the photocatalytic active component modified by dielectric barrier discharge (DBD), and it showed an efficient catalytic performance under solar light irradiation. The degradation of xylene released from fluorocarbon coating solvents by the g-C₃N₄/TiO₂ composite coatings was investigated under simulated solar irradiation. The degradation efficiency of the coating mixed with DBD-modified 10%-g-C₃N₄/TiO₂ showed a stable, long-lasting, and significantly higher activity compared to the coatings mixed with the unmodified catalyst. Ninety-eight percent of the xylene released from fluorocarbon coating solvents was successfully removed under solar light irradiation in 2 h. The properties of the catalyst samples before and after modification were evaluated using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible (UV-vis) spectroscopy, X-ray photoelectron spectroscopy (XPS), and other characterization techniques. The results suggested that DBD-modified g-C₃N₄/TiO₂ showed an improved capture ability and utilization efficiency of solar light with reduced band gap and lower complexation rate of electron-hole pairs. The prepared photocatalytic coating offers an environmentally friendly approach to purify the volatile organic compounds (VOCs) released from solvent-based coatings.

Functional nanomaterials, synergisms, and biomimicry for environmentally benign marine antifouling technology

Marine biofouling remains one of the key challenges for maritime industries, both for seafaring and stationary structures. Currently used biocide-based approaches suffer from significant drawbacks, coming at a significant cost to the environment into which the biocides are released, whereas novel environmentally friendly approaches are often difficult to translate from lab bench to commercial scale. In this article, current biocide-based strategies and their adverse environmental effects are briefly outlined, showing significant gaps that could be addressed through advanced materials engineering. Current research towards the use of natural antifouling products and strategies based on physio-chemical properties is then reviewed, focusing on the recent progress and promising novel developments in the field of environmentally benign marine antifouling technologies based on advanced nanocomposites, synergistic effects and biomimetic approaches are discussed and their benefits and potential drawbacks are compared to existing techniques.

Construction 0D/2D heterojunction by highly dispersed Ag2S quantum dots (QDs) loaded on the g-C3N4 nanosheets for photocatalytic hydrogen evolution

In recent years, the use of quantum dots (QDs) cocatalysts to improve the hydrogen evolution activity from the water splitting of photocatalysts has become a popular research topic. Herein, we successfully prepared a novel 0 dimension/2 dimension (0D/2D) heterojunction nanocomposite (denoted Ag₂S quantum dots (QDs)/g-C₃N₄) with excellent photocatalytic performance by anchoring the Ag₂S QDs cocatalyst on the surface of g-C₃N₄ through a self-assembly strategy. Ag₂S QDs with an average particle size of approximately 5.8 nm were uniformly and tightly modified on g-C₃N₄. The Ag₂S QDs/g-C₃N₄ composite with 0.5 wt% Ag₂S QDs loading achieved the highest hydrogen evolution rate of 471.1 μmol·g^-1·h^-1 with an apparent quantum efficiency (AQE) of 1.48% at 405 nm. Such remarkable hydrogen evolution activity far exceeded that of undoped g-C₃N₄ and Ag₂S nanoparticles (NPs)/g-C₃N₄. Moreover, it was 2.04 times the activity of Pt/g-C₃N₄ with Pt as the cocatalyst. The enhanced photocatalytic performance was attributed to the energy band broadening of Ag₂S QDs caused by the quantum size effect and the convenient and effective charge transfer between g-C₃N₄ and Ag₂S QDs cocatalysts. The mechanism underlying the enhanced photocatalytic H₂ evolution activity was further proposed. This study demonstrates that semiconductor-based quantum dots are strong candidates for excellent cocatalysts in photocatalysis.

Multifunctional oil-produced reduced graphene oxide - Silver oxide composites with photocatalytic, antioxidant, and antibacterial activities

Graphene-based nanomaterials that combine significant photocatalytic, antioxidant and antibacterial activity are very attractive candidates for biomedical and environmental applications. Conventional chemical synthesis routes may contaminate the resultant materials with toxic molecules, compromising their properties and limiting their use in biomedical applications. Ideally, to avoid any contamination, the nanomaterials should be synthesized from non-toxic precursors and reagents, e.g. foodstuff via a simple technology that does not rely on the use of hazardous chemicals yet produces materials of high quality. Here, we report an environmentally friendly, low cost reduced graphene oxide-silver-silver oxide nanocomposite with strong photocatalytic, antioxidant and antibacterial activity for environmental remediation. The reduced graphene oxide (FRGO) is synthesized from edible sunflower oil via a simple flame synthesis method. Next, silver nanoparticles (Ag/AgO/Ag₂O) are produced by phytochemical reduction of AgNO₃ using a reducing agent based on flavonoids from Coleus aromaticus (Mexican mint), also used in food industry. Thus-obtained FRGO-Ag/AgO/Ag₂O composite is characterized using X-ray diffraction spectroscopy, scanning electron microscopy, fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. The degradation of anionic textile dye Methylene blue (MB) is used as a measure of photocatalytic activity of FRGO and FRGO/Ag/AgO/Ag₂O, with solution pH, initial dye concentration, and quantity of the catalyst considered as influencing factors. FRGO-Ag/AgO/Ag₂O composites show strong antioxidant activity, with improved radical inhibition as well as dye degradation properties when compared to pristine FRGO.

Noble-metal-free hexagonal wurtzite CdS nanoplates with exposed (110) and (112) crystal facets for efficient visible-light H2 production

Hexagonal wurtzite CdS has been regarded as one of the most promising semiconductors for photocatalysis.

Carbon-Graphitic Carbon Nitride Hybrids for Heterogeneous Photocatalysis

Polymeric graphitic carbon nitride (g-C₃ N₄ ) and various carbon materials have experienced a renaissance as viable alternates in photocatalysis due to their captivating metal-free features, favorable photoelectric properties, and economic adaptabilities. Although numerous efforts have focused on the integration of both materials with optimized photocatalytic performance in recent years, the direct parameters for this emerging enhancement are not fully summarized yet. Fully understanding the synergistic effects between g-C₃ N₄ and carbon materials on photocatalytic action is vital to further development of metal-free semiconductors in future studies. Here, recent advances of carbon/g-C₃ N₄ hybrids on various photocatalytic applications are reviewed. The dominant governing factors by inducing carbon into g-C₃ N₄ photocatalysts with involving photocatalytic mechanism are highlighted. Five typical carbon-induced enhancement effects are mainly discussed here, i.e., local electric modification, band structure tailoring, multiple charge carrier activation, chemical group functionalization, and abundant surface-modified engineering. Photocatalytic performance of carbon-induced g-C₃ N₄ photocatalysts for addressing directly both the renewable energy storage and environmental remediation is also summarized. Finally, perspectives and ongoing challenges encountered in the development of metal-free carbon-induced g-C₃ N₄ photocatalysts are presented.

Green synthesis of boron and nitrogen co-doped TiO2 with rich B-N motifs as Lewis acid-base couples for the effective artificial CO2 photoreduction under simulated sunlight

Boron and nitrogen co-doped Titanium dioxide (TiO₂) nanosheets (BNT) with high surface area of 136.5 m² g^-1 were synthesized using ammonia borane as the green and triple-functional regent, which avoids the harmful and explosive reducing regents commonly used to create surface defects on TiO₂. The decomposition of ammonia borane could incorporate reactive Lewis acid-base (B, N) pairs, together with the as-generated H₂ to create mesoporous structure and rich oxygen vacancies in pristine TiO₂. The BNTs prepared from various ammonia borane loading are evaluated in photoreduction of carbon dioxide (CO₂) with steam under simulated sunlight, achieving about 3.5 times higher carbon monoxide (CO) production than pristine TiO₂ under the same conditions. Steady state and transient optical measurements indicated BNT with reduced band gap, rich defect states and elevated conduction band position could enhance the light harvesting efficiency and promote the charge transfer at the catalyst/CO₂ interface. Density functional theory simulation and in situ FTIR suggest that the Lewis acid-base (B, N) pairs on BNT may very substantially increase the activation of inert CO₂ which facilitates their photoreduction with the hydrogen from the water splitting at the surface defects on TiO₂. Finally, a reaction mechanism of Lewis acid-base assisted CO₂ photoreduction leading to substantially improved performance is proposed.

Crystalline Carbon Nitride Supported Copper Single Atoms for Photocatalytic CO2 Reduction with Nearly 100% CO Selectivity

Single metal atom photocatalysts have received widespread attention due to the rational use of metal resources and maximum atom utilization efficiency. In particular, N-rich amorphous g-C₃N₄ is always used as a support to anchor single metal atoms. However, the enhancement of photocatalytic activity of g-C₃N₄ by introducing a single atom is limited due to the bulk morphology and the excess defects of amorphous g-C₃N₄. Here, we report crystalline g-C₃N₄ nanorod supported copper single atoms by molten salts and the reflux method. The prepared single Cu atoms/crystalline g-C₃N₄ photocatalyst (Cu-CCN) shows highly selective and efficient photocatalytic reduction of CO₂ under the absence of any cocatalyst or sacrificial agent. The introduction of single Cu atoms can be used as the CO₂ adsorption site, thus increasing the adsorption capacity of Cu-CCN samples to CO₂. Theoretical calculation results show that reducing CO₂ to CH₄ on Cu-CCN samples is an entropy-increasing process, whereas reducing CO₂ to CO is an entropy-decreasing process. As a result, the Cu-CCN samples exhibited enhanced photocatalytic CO₂ reduction with nearly 100% selective photocatalytic CO₂ to CO conversion. The mechanism of photocatalytic CO₂ reduction over Cu-CCN samples was proposed based on in situ Fourier transform infrared spectra, X-ray absorption spectroscopy, and density functional theory calculation. This work provides an in-depth understanding of the design of photocatalysts for enhancing active sites of the reactants.

Porous graphitic carbon nitride for solar photocatalytic applications

Photocatalysis is attracting increased attention in solving the energy crisis and environmental pollution. Graphitic carbon nitride (g-C3N4), a non-metal photocatalyst, has been regarded as an ideal photocatalyst to solve these problems because of its chemical stability and unique optical properties. However, traditional g-C3N4 exhibits moderate photocatalytic activity due to its low specific surface area and fast recombination rate of photogenerated electrons. Among the many modified g-C3N4 materials, porous carbon nitride (PCN) can solve the shortcomings of traditional g-C3N4 because of PCN's increased number of surface-active sites, specific surface area, light harvesting, diffusion and adsorption/activation. However, a frontier, comprehensive summary of the development of PCN is less reported. Thus, a review on recent developments in PCN research is urgently needed to further promote its advancement. In this review, the synthesis methods, structures and properties and photocatalytic applications of PCN photocatalysts are described in detail. The current challenges and future development of PCN/PCN-based photocatalysts are discussed. This review may present an up-to-date view of the PCN development to provide an in-depth understanding of PCN-based photocatalysts.

Nanosheet-assembled hierarchical flower-like g-C3N4 for enhanced photocatalytic CO2 reduction activity

Nanosheet-assembled hierarchical flower-like g-C₃N₄ prepared by a molecular self-assembly and ethanol insertion strategy shows enhanced photocatalytic CO₂ reduction activity.

C-Dot TiO2 nanorod composite for enhanced quantum efficiency under direct sunlight

Watermelon rind-derived C-dots were prepared via a facile route and decorated on Ti nanorods for enhanced electron mobilisation and visible light utilisation.