Photocatalytic hydrogen production from dye contaminated water and electrochemical supercapacitors using carbon nanohorns and TiO2 nanoflower heterogeneous catalysts

Nanohybrid Composites Based on TiO2 and Single-Walled Carbon Nanohorns as Promising Catalysts for Photodegradation of Amoxicillin

In this work, applications of nanohybrid composites based on titanium dioxide (TiO2) with anatase crystallin phase and single-walled carbon nanohorns (SWCNHs) as promising catalysts for the photodegradation of amoxicillin (AMOX) are reported. In this order, TiO2/SWCNH composites were prepared by the solid-state interaction of the two chemical compounds. The increase in the SWCNH concentration in the TiO2/SWCNH composite mass, from 1 wt.% to 5 wt.% and 10 wt.% induces (i) a change in the relative intensity ratio of the Raman lines located at 145 and 1595 cm-1, which are attributed to the Eg(1) vibrational mode of TiO2 and the graphitic structure of SWCNHs; and (ii) a gradual increase in the IR band absorbance at 1735 cm-1 because of the formation of new carboxylic groups on the SWCNHs' surface. The best photocatalytic properties were obtained for the TiO2/SWCNH composite with a SWCNH concentration of 5 wt.%, when approx. 92.4% of AMOX removal was achieved after 90 min of UV irradiation. The TiO2/SWCNH composite is a more efficient catalyst in AMOX photodegradation than TiO2 as a consequence of the SWCNHs' presence, which acts as a capture agent for the photogenerated electrons of TiO2 hindering the electron-hole recombination. The high stability of the TiO2/SWCNH composite with a SWCNH concentration of 5 wt.% is proved by the reusing of the catalyst in six photodegradation cycles of the 98.5 μM AMOX solution, when the efficiency decreases from 92.4% up to 78%.

Progress on simultaneous photocatalytic degradation of pollutants and production of clean energy: A review

In the current era of severe energy and environmental crises, the need for efficient and sustainable methods to control pollution and promote resource recycling has become increasingly important. Photocatalytic degradation of pollutants and simultaneous production of clean energy is one such approach that has garnered significant attention in recent years. The principle of photocatalysis involves the development of efficient photocatalysts and the efficient utilization of solar energy. The use of organic contaminants can enhance the photocatalytic reactions, leading to the sustainable generation of clean energy. Herein, we provide a comprehensive review of the latest advances in the application of photocatalytic synergized clean energy production in the environmental field. This review highlights the latest developments and achievements in this field, highlighting the potential for this approach to revolutionize the way we approach environmental pollution control and resource recycling. The review focuses on (1) the mechanism of photocatalytic degradation and synergistic energy production, (2) photocatalysts and synthesis strategies, (3) photocatalytic carbon dioxide reduction, (4) pollutant degradation, and (5) hydrogen and electricity production. In addition, perspectives on key challenges and opportunities in photocatalysis and clean energy for future developments are proposed. This review provides a roadmap for future research directions and innovations of photocatalysis that could contribute to the development of more sustainable and cleaner energy solutions.

Sharp-edged pencil type ZnO flowers and BiOI flakes combined with carbon nanofibers as heterostructured hybrid photocatalysts for the removal of hazardous pollutants from contaminated water

The growth of advanced micro-and nanostructures with metal oxides has consistently generated extraordinary interest in energy and environmental applications. Cutting-edge nanostructures exhibit superior reactive sites and surface areas, thus improving the performance in crucial domains. In this study, sharp-edged pencil-type ZnO flowers and BiOI flakes as pristine materials, and their composition with carbon nanofibers (CNFs) (ZnO-BiOI@CNFs) as a hetero hybrid catalyst as well as binary compositions such as ZnO-BiOI, ZnO@CNFs, and BiOI@CNFs catalysts were fabricated using a simple and convenient hydrothermal synthesis process. The composition of newly produced innovative nanostructures was examined for azo dye degradation under solar simulator exposure. Dye degradation of ∼95% was achieved by the hybrid catalyst (ZnO-BiOI@CNFs) during 120 min of irradiation, which was ∼1.8 and 2.1-times higher than pristine ZnO and BiOI nanostructures, respectively. The improved hybrid catalysts were able to degrade methyl orange (MO) and rhodamine B (RhB) dyes. Importantly, mixed dyes RhB, MO, and azo dye demonstrated 47% dye degradation using a hybrid catalyst. These mixed dye-scalable hybrid catalyst performances offer additional insights into commercialization/industrialization. The outstanding performance of the hybrid catalyst is attributed to the unidirectional electron flow with pencil-like ZnO, a catalyst with a larger absorption zone, high surface area, and reactive sites, particularly ZnO and BiOI nanostructures, and decreased recombination rate with a heterojunction interface. In addition, CNFs can operate as electron traps and sinks, providing very quick redox reactions. To produce the sophisticated nanostructures with homogeneous morphologies, this work presents new insights into energy and environmental applications.

TiO2 nanoflower photocatalysts: Synthesis, modifications and applications in wastewater treatment for removal of emerging organic pollutants

Titanium dioxide (TiO₂) has been considered as one of the most promising photocatalysts nanomaterials and is being used in a variety of fields of energy and environment under sunlight irradiation via photocatalysis. Highly efficient photocatalytic materials require the design of the proper structure with excellent morphology, interfacial structures, optical and surface properties, etc. Which are the key points to realize effective light-harvesting for photocatalytic applications. Hierarchical TiO₂ based nanoflower structures (i.e., 3D nanostructures) possess such characteristics and have attracted much attention in recent years. The uniqueness of TiO₂ nanoflowers (NFs) with a coarse texture and arranged structures demonstrates higher photocatalytic activity. This review deals with the hydrothermal synthesis of 3D TiO₂ NFs and effect of shape/size as well as various key synthesis parameters to improve their optoelectronic and photocatalytic properties. Furthermore, to improve their photocatalytic properties, various strategies such as doping engineering and heterojunction/nanocomposite formation with other functional nanomaterials have been discussed followed by their potential applications in photocatalytic degradation of various emerging pollutants discharged into the wastewater from various sources. Importance of such 3D nanoarchitecutres and future research in other fields of current interest in environments are discussed.

Characterization of hydrophilic carbon nanohorns prepared by the arc-in-water method

Hydrophilic single-wall carbon nanohorns (SWNHs) are produced by using the arc-in-water method. These hydrophilic SWNHs are easily formed in clusters with a diameter of ∼30–40 nm. The XRD pattern features a peak at around 26°, which is typical for SWCNHs. There are evidences of C–C, C=C, C–O, C=O and O=C–O– bonding units based on the XPS spectra of hydrophilic SWNHs. The Raman spectra show that the hydrophilic SWNHs have a high number of defects. Furthermore, stretching vibration bands of C–O, C=C, O=C–O–, C–H and O–H units have been observed by FTIR measurements. All these spectroscopic results are consistent with the structural concepts.

g-C3N4 nanosheets functionalized yttrium-doped ZrO2 nanoparticles for efficient photocatalytic Cr(VI) reduction and energy storage applications

Novel g-C₃N₄ functionalized yttrium-doped ZrO₂ hybrid heterostructured (g-YZr) nanoparticles have been synthesized to investigate photocatalytic Cr(VI) reduction as well as electrochemical energy storage applications. The nanoparticles have been characterized to examine their structural, optical, and photocatalytic properties. XRD confirmed the incorporation of dopant ions and heterostructure development between g-C₃N₄ and doped ZrO₂. When g-C₃N₄ was doped with ZrO_2, the ability of light adsorption was greatly enhanced due to the narrow band gap. The distinctive structure of g-YZr exhibited outstanding photocatalytic Cr(VI) reduction owing to its superior surface area, which greatly prevented the charge carriers' recombination rate and exhibited superior photocatalytic performance within 90 min of solar light irradiation. Furthermore, these catalysts demonstrated similar catalytic Cr(VI) reduction activity following four repeatability tests, indicating the exceptional structural stability of g-YZr catalysts. The electrochemical performance of the electrodes revealed that g-YZr exhibited superior specific capacitance over the other electrodes owing to extra energetic sites and robust synergic effect. Enhanced specific capacitance and long cyclic stability of the hybrid heterostructures displayed their usefulness for energy storage applications.

Investigation of electrochemical performance of an efficient Ti2O3-CeO2 nanocomposite for enhanced pollution-free energy conversion applications

The development of an economical, abundant, stable, and greatly active electrocatalyst for water oxidation is extremely important for future energy conversion system. Electrochemical water splitting is a new move toward H₂ and O₂ gas production. It can be used in sustainable and pollution-free energy conversion applications. In this work, Ti₂O₃-CeO₂ nanocomposites were successfully synthesized with different molar ratios by facile hydrothermal method for electrochemical water oxidation. Mixed phase structure of Ti₂O₃-CeO₂ nanocomposites was confirmed by X-ray diffraction spectra and well identified by highest peak of Ti₂O₃ in 2θ values of 33.0 and CeO₂ in 2θ values of 28.5. The characteristic peaks from Raman and photoluminescence spectroscopy further confirmed Ti₂O₃-CeO₂ nanocomposite formation. Existence of multidimensional nanostructures such as nanoparticles and small nanocubes of Ti₂O₃-CeO₂ nanocomposites were investigated by scanning electron microscope images. Mesoporous nature of Ti₂O₃-CeO₂ nanocomposites was further analyzed by Brunauer-Emmett-Teller analysis. The high surface area could benefit the Ti₂O₃-CeO₂ nanocomposites with greatly improved oxygen evolution reaction (OER) performance. In three molar ratios, 1:3 M ratios of Ti₂O₃-CeO₂ nanocomposites showed high catalytic action at overpotential of 244 mV. The best OER electrocatalyst was obtained by 1:3 M ratios of Ti₂O₃-CeO₂ nanocomposites, which exhibited high current density and high specific capacitance values of 238 mA/g and 517 F/g, respectively. Therefore, Ti/Ce molar ratio played a crucial role in enhancing the OER performance.