Desulfurization through Photocatalytic Oxidation: A Critical Review

Highly efficient photocatalytic degradation of ciprofloxacin under simulated sunlight using g-C3N4/CeO2/Fe3O4 heterogeneous composite

The presence of antibiotic residues in water bodies has become a serious environmental concern due to their persistence and ability to cause bacterial resistance. Traditional water treatment methods are often ineffective at completely degrading these pollutants, highlighting the need to investigate more effective remediation methods. In this study, the photocatalytic degradation of ciprofloxacin, a widely used fluoroquinolone antibiotic, was investigated using a novel heterogeneous composite of g-C3N4, CeO2, and Fe3O4 under simulated sunlight irradiation. The composite was synthesized and thoroughly characterized using SEM, EDX, TEM, XRD, BET, PL, RIS, and FT-IR analysis to validate its structural and morphological properties. The effects of key operational parameters, including composite concentration, CeO2 weight percentage, pH, and H2O2 concentration, on photocatalytic performance were investigated. Among all the synthesized composites, the sample with a 0.75:0.75:1 wt ratio (designated as F0.75C0.75 G) displayed the highest photocatalytic activity, achieving a ciprofloxacin removal efficiency of 97.5 % within 180 min. The ternary composite outperformed individual components (g-C3N4, CeO2) and binary composites (g-C3N4/CeO2) due to enhanced charge separation and extended light absorption. In addition, recyclability tests confirmed that the composite maintained high degradation efficiency even after five cycles, highlighting its stability. The treated solution demonstrated excellent biocompatibility, as evidenced by improved lentil seed germination. These findings presents a cost-effective and sustainable approach for the degradation of pharmaceutical pollutants in water resources, offering a promising solution for environmental remediation.

Long-term exposure to low-concentration sulfur dioxide and mental disorders in middle-aged and older urban adults

The World Health Organization loosened the air quality guideline for daily sulfur dioxide (SO2) concentrations from 20 μg/m3 to 40 μg/m3. However, the guideline for SO2 concentrations in 2021 raised public concerns since there was no sufficient evidence that low-concentration SO2 exposure is harmless to the population's health, including mental health. We analyzed the associations between low-concentration SO2 exposure and incidence risks of total and cause-specific mental disorders, including depressive disorder, anxiety disorder, bipolar disorder, and schizophrenia spectrum disorder. 245,820 urban participants with low-concentration SO2 exposure (<8 μg/m3) at baseline were involved in the analyses from the UK Biobank. SO2 exposure (2006-2022) was estimated using high-resolution annual mean concentration maps from the Department for Environment, Food and Rural Affairs. Mental disorders and corresponding symptoms were identified using healthcare records and an online questionnaire, respectively. Associations were examined using both time-independent (2006-2010) and time-dependent (from 2006 to 2022) Cox regression models and logistic regression models with full adjustments for potential confounders. Stratification analyses were further conducted to identify vulnerable populations. Long-term exposure to low-concentration SO2 (per 1.36 μg/m3) was associated with increased risks of mental disorders, depressive disorder, and anxiety disorder with hazard ratios of 1.02 (95% confidence interval [CI]: 1.00, 1.03), 1.11 (95% CI: 1.07, 1.16), and 1.10 (95% CI: 1.06, 1.14) in the time-independent model, respectively. Associations were stronger for younger individuals. Additionally, the low-concentration SO2 exposure was linked to several psychiatric symptoms, such as trouble concentrating and restlessness, with odds ratios of 1.07 (95% CI: 1.04, 1.10) and 1.11 (95% CI: 1.07, 1.14), respectively. This study demonstrated significant associations of long-term exposure to low-concentration SO2 with mental disorders, highlighting the need for stricter regulations for SO2 to better protect public health and improve air quality in urban areas, in support of the Sustainable Development Goals.

Enhanced desulfurization performance of model fuel by Cu-ZnO/TiO2 heterostructure

A facile hydrothermal approach was employed to synthesize a novel Cu-ZnO/TiO2 Z-heterojunction with a high density of defects, which was then utilized for the oxidative desulfurization process, demonstrating excellent photodegradation performance. The results showed that by adjusting components such as Cu, ZnO, and TiO2, the removal efficiency of DBT reached 88.12% within a duration of 240 min. In the 5 repeated experiments, 7.5%Cu-ZnO/TiO2 still exhibited high stability and could be reused. The improved photocatalytic performance of the 7.5%Cu-ZnO/TiO2 composite can be attributed to its high light absorption capability and well-matched energy levels, which are due to the abundant presence of imperfections. The adoption of a Z-heterojunction has enabled efficient separation and transfer of photo-generated electrons and holes (e-/h+), thereby reducing the probability of charge carrier recombination.

Summary of sulfur hazards in high‑sulfur bauxite and desulfurization methods

With the gradual depletion of high-grade bauxite, the development of the alumina industry has been seriously constrained. High‑sulfur bauxite reserves are abundant and can be used as an effective supplement to bauxite resources. Therefore, the development of desulfurization and comprehensive utilization methods for high sulfur bauxite has been widely studied. Excessive sulfur content in bauxite and complex valence changes in the Bayer process have serious impacts on products and equipment. This paper will introduce pre-treatment desulfurization and post-treatment desulfurization methods such as roasting, flotation, electrochemical and biological methods. Roasting methods use oxidative roasting to convert sulfur to sulfur dioxide-containing flue gas; flotation methods enrich pyrite through flotation chemicals; biological methods use complex chemical reactions of microorganisms to remove sulfur; and electrolysis methods convert sulfur to sulfate through oxidants produced by electrolysis. Post-treatment methods add precipitants such as zinc oxide to treat small amounts of sulfur entering the Bayer process. The reaction mechanism and development of various desulfurization methods are summarized, and the problems of these desulfurization methods are analyzed. The aim is to combine their advantages to develop economical and environmentally friendly desulfurization methods, and propose suggestions for the future resource utilization of high‑sulfur bauxite.

Ag/Mo Doping for Enhanced Photocatalytic Activity of Titanium (IV) Dioxide during Fuel Desulphurization

Regarding photocatalytic oxidative desulphurization (PODS), titanium oxide (TiO2) is a promising contender as a catalyst due to its photocatalytic prowess and long-term performance in desulphurization applications. This work demonstrates the effectiveness of double-doping TiO2 in silver (Ag) and molybdenum (Mo) for use as a novel catalyst in the desulphurization of light-cut hydrocarbons. FESEM, EDS, and AFM were used to characterize the morphology, doping concentration, surface features, grain size, and grain surface area of the Ag/Mo powder. On the other hand, XRD, FTIR spectroscopy, UV-Vis, and PL were used for structure and functional group detection and light absorption analysis based on TiO2's illumination properties. The microscopic images revealed nanoparticles with irregular shapes, and a 3D-AFM image was used to determine the catalyst's physiognomies: 0.612 nm roughness and a surface area of 811.79 m2/g. The average sizes of the grains and particles were calculated to be 32.15 and 344.4 nm, respectively. The XRD analysis revealed an anatase structure for the doped TiO2, and the FTIR analysis exposed localized functional groups, while the absorption spectra of the catalyst, obtained via UV-Vis, revealed a broad spectrum, including visible and near-infrared regions up to 1053.34 nm. The PL analysis showed luminescence with a lower emission intensity, indicating that the charge carriers were not thoroughly combined. This study's findings indicate a desulphurization efficiency of 97%. Additionally, the promise of a nano-homogeneous particle distribution bodes well for catalytic reactions. The catalyst retains its efficiency when it is dried and reused, demonstrating its sustainable use while maintaining the desulphurization efficacy. This study highlights the potential of the double doping approach in enhancing the catalytic properties of TiO2, opening up new possibilities for improving the performance of photo-oxidative processes.

Recent progress and new insights on semiconductor heterojunctions powered photocatalytic desulphurization: A review

Desulphurization of fossil fuels is a critical process in reducing the sulphur content from environment, which is a major contributor to atmospheric pollution. Traditional desulphurization techniques, while effective, often involve high energy consumption and the use of harsh chemicals. Recently, photocatalytic desulphurization has emerged as a promising, eco-friendly alternative, leveraging the potential of photocatalysts especially semiconductor heterojunctions to enhance photocatalytic efficiency. This review comprehensively discusses the significance and mechanism of photocatalytic desulphurization reactions, designing of various heterojunctions such as conventional, p-n, Z-scheme and S-scheme, their charge transfer mechanism and properties and their contribution to the photocatalytic desulphurization activity. Heterojunctions, formed by combining different semiconductor materials, facilitate efficient charge separation and broaden the light absorption range, thereby improving the photocatalytic performance under visible light. Furthermore, the recent advancements in the heterojunction systems in the field of photocatalytic desulphurization activity have been discussed in detail and summarized. The current limitations and challenges in this particular field are also explored. The paper concludes with an outlook on future research directions and the potential industrial applications of heterojunction-powered photocatalytic desulphurization, emphasizing its role in achieving cleaner energy production and environmental sustainability.

The powerful combination of 2D/2D Ni-MOF/carbon nitride for deep desulfurization of thiophene in fuel: Conversion route, DFT calculation, mechanism

2D/2D Ni-MOF/g-C3N4 nanocomposite was utilized for desulfurization. The multilayer pore structure and high specific surface area of Ni-MOF/g-C3N4 promote the adsorption and conversion of thiophene. In addition, the two-dimensional structure exposes more active centers and shortens photogenerated carrier migration to the material surface distance, it enhances photogenerated charge transfer. The Ni-MOF and g-C3N4 construct a Z-scheme heterojunction structure with tight contact, it effectively enhances the material's photocatalytic redox ability. In the light, the material generates more photocarriers for the production of free radicals including hydroxyl radicals, holes, and superoxide radicals. The higher carrier concentration of Ni-MOF/g-C3N4 promotes the activation and oxidation of thiophene, consequently enhancing the photocatalytic desulfurization capability. The results showed that the conversion of thiophene was 98.82 % in 3 h under visible light irradiation. Radical capture experiments and analysis using electron paramagnetic resonance spectroscopy demonstrated that superoxide radicals, holes, and hydroxyl radicals played crucial roles in PODS (photocatalytic oxidative desulfurization). In addition, DFT (density functional theory) calculations were conducted to determine the paths of electron migration and TH (thiophene) adsorption energy. Finally, a mechanism for photocatalytic desulfurization was proposed based on the comprehensive analysis of theoretical calculations and experimental studies.

In Situ Generation of H2O2 over MoOx Decorated on Cu2O@CuO Core-Shell Particle Nanoarchitectonics for Boosting Photocatalytic Oxidative Desulfurization

Photocatalytic oxidation desulfurization (PODS) has emerged as a promising, ecofriendly alternative to traditional, energy-intensive fuel desulfurization methods. Nevertheless, its progress is still hindered due to the slow sulfide oxidation kinetics in the current catalytic systems. Herein, we present a MoOx decorated on a Cu2O@CuO core-shell catalyst, which enables a new, efficient PODS pathway by in situ generation of hydrogen peroxide (H2O2) with saturated moist air as the oxidant source. The photocatalyst delivers remarkable specific activity in oxidizing dibenzothiophene (DBT), achieving a superior rate of 7.8 mmol g-1 h-1, while maintaining a consistent performance across consecutive reuses. Experimental investigations reveal that H2O2 is produced through the two-electron oxygen reduction reaction (ORR), and both H2O2 and the hydroxyl radicals (•OH) generated from it act as the primary reactive species responsible for sulfide oxidation. Importantly, our catalyst accomplishes complete PODS of real diesel fuel, underscoring an appealing industrial prospect for our photocatalyst.

Streamlining the biodesulfurization process: development of an integrated continuous system prototype using Gordonia alkanivorans strain 1B

Biodesulfurization is a biotechnological process that uses microorganisms as biocatalysts to actively remove sulfur from fuels. It has the potential to be cleaner and more efficient than the current industrial process, however several bottlenecks have prevented its implementation. Additionally, most works propose models based on direct cultivation on fuel, or batch production of biocatalysts followed by a processing step before application to batch biodesulfurization, which are difficult to replicate at a larger scale. Thus, there is a need for a model that can be adapted to a refining process, where fuel is being continuously produced to meet consumer needs. The main goal of this work was to develop the first bench-scale continuous biodesulfurization system that integrates biocatalyst production, biodesulfurization and fuel separation, into a single continuous process, taking advantage of the method for the continuous production of the biodesulfurization biocatalysts previously established. This system eliminates the need to process the biocatalysts and facilitates fuel separation, while mitigating some of the process bottlenecks. First, using the bacterium Gordonia alkanivorans strain 1B, continuous culture conditions were optimized to double biocatalyst production, and the produced biocatalysts were applied in batch biphasic biodesulfurization assays for a better understanding of the influence of different factors. Then, the novel integrated system was developed and evaluated using a model fuel (n-heptane + dibenzothiophene) in continuous biodesulfurization assays. With this system strain 1B surpassed its highest biodesulfurization rate, reaching 21 μmol h-1 g-1. Furthermore, by testing a recalcitrant model fuel, composed of n-heptane with dibenzothiophene and three alkylated derivatives (with 109 ppm of sulfur), 72% biodesulfurization was achieved by repeatedly passing the same fuel through the system, maintaining a constant response throughout sequential biodesulfurization cycles. Lastly, the system was also tested with real fuels (used tire/plastic pyrolysis oil; sweet and sour crude oils), revealing increased desulfurization activity. These results highlight the potential of the continuous biodesulfurization system to accelerate the transition from bench to commercial scale, contributing to the development of biodesulfurization biorefineries, centered on the valorization of sulfur-rich residues/biomasses for energy production.

Studying the mechanism and kinetics of fuel desulfurization using CexOy/NiOx piezo-catalysts as a new low-temperature method

In order to advance desulfurization technology, a new method for excellent oxidative desulfurization of fuel at room temperature will be of paramount importance. As a novel desulfurization method, we developed piezo-catalysts that do not require adding any oxidants and can be performed at room temperature. A microwave method was used to prepare CeO₂/Ce₂O₃/NiO_x nanocomposites. Model and real fuel desulfurization rates were examined as a function of synthesis parameters, such as microwave power and time, and operation conditions, such as pH and ultrasonic power. The results showed that CeO₂/Ce₂O₃/NiO_x nanocomposites demonstrated outstanding piezo-desulfurization at room temperature for both model and real fuels. Furthermore, CeO₂/Ce₂O₃/NiO_x nanocomposites exhibited remarkable reusability, maintaining 79% of their piezo-catalytic activity even after 17 repetitions for desulfurization of real fuel. An investigation of the mechanism of sulfur oxidation revealed that superoxide radicals and holes played a major role. Additionally, the kinetic study revealed that sulfur removal by piezo-catalyst follows a second-order reaction kinetic model.

Oxyethylated Fluoresceine-(thia)calix[4]arene Conjugates: Synthesis and Visible-Light Photoredox Catalysis in Water-Organic Media

Fluorescent derivatives attract the attention of researchers for their use as sensors, photocatalysts and for the creation of functional materials. In order to create amphiphilic fluorescent derivatives of calixarenes, a fluorescein derivative containing oligoethylene glycol and propargyl groups was obtained. The resulting fluorescein derivative was introduced into three different (thia)calix[4]arene azide derivatives. For all synthesized compounds, the luminescence quantum yields have been established in different solvents. Using UV-visible spectroscopy, dynamic light scattering, as well as transmission and confocal microscopy, aggregation of macrocycles was studied. It was evaluated that calixarene derivatives with alkyl substituents form spherical aggregates, while symmetrical tetrafluorescein-containing thiacalix[4]arene forms extended worm-like aggregates. The macrocycle containing tetradecyl fragments was found to be the most efficient in photoredox ipso-oxidation of phenylboronic acid. In addition, it was shown that in a number of different electron donors (NEt₃, DABCO and iPr₂EtN), the photoredox ipso-oxidation proceeds best with triethylamine. It has been shown that a low molecular weight surfactant Triton-X100 can also improve the photocatalytic abilities of an oligoethylene glycol fluorescein derivative, thus showing the importance of a combination of micellar and photoredox catalysis.

CdS Nanoparticles Decorated 1D CeO2 Nanorods for Enhanced Photocatalytic Desulfurization Performance

CdS nanoparticles were constructed onto one-dimensional (1D) CeO2 nanorods by a two-step hydrothermal method. The X-ray diffraction (XRD), transmission election microscopy (TEM), Raman spectra, X-ray photoelectron spectra (XPS) and UV-Vis diffuse reflection spectroscopy (DRS) techniques were used to characterize these CdS/CeO2 nanocomposites. It was concluded that when the molar ratio of CdS and CeO2 was 1:1, the nanocomposites exhibited the best photocatalytic desulfurization activity, reaching 92% in 3 h. Meanwhile, transient photocurrent (PT) measurement, photoluminescence (PL) spectra and electrochemical impedance spectroscopy (EIS) measurement indicated that the modification of CeO2 nanorods by CdS nanoparticles could significantly inhibit the recombination of photogenerated electrons and holes. In addition, the possible mechanism of photocatalytic oxidation desulfurization of the nanocomposites was proposed. This study may provide an effective CeO2-based photocatalyst for photocatalytic desulfurization applications.

Towards the Sustainable Production of Ultra-Low-Sulfur Fuels through Photocatalytic Oxidation

Nowadays, the sulfur-containing compounds are removed from motor fuels through the traditional hydrodesulfurization technology, which takes place under harsh reaction conditions (temperature of 350–450 °C and pressure of 30–60 atm) in the presence of catalysts based on alumina with impregnated cobalt and molybdenum. According to the principles of green chemistry, energy requirements should be recognized for their environmental and economic impacts and should be minimized, i.e., the chemical processes should be carried out at ambient temperature and atmospheric pressure. This approach could be implemented using photocatalysts that are sensitive to visible light. The creation of highly active photocatalytic systems for the deep purification of fuels from sulfur compounds becomes an important task of modern catalysis science. The present critical review reports recent progress over the last 5 years in heterogeneous photocatalytic desulfurization under visible light irradiation. Specific attention is paid to the methods for boosting the photocatalytic activity of materials, with a focus on the creation of heterojunctions as the most promising approach. This review also discusses the influence of operating parameters (nature of oxidant, molar ratio of oxidant/sulfur-containing compounds, photocatalyst loading, etc.) on the reaction efficiency. Some perspectives and future research directions on photocatalytic desulfurization are also provided.

Recent Advances in Application of Graphitic Carbon Nitride-Based Catalysts for Photocatalytic Nitrogen Fixation

Ammonia, the second most-produced chemical, is widely used in agricultural and industrial applications. However, traditional industrial ammonia production dominated by the Haber-Bosch process presents huge resource and environment issues due to the massive energy consumption and CO₂ emission. The newly emerged nitrogen fixation technology, photocatalytic N₂ reduction reaction (p-NRR), uses clean solar energy with zero-emission, holding great prospect to achieve sustainable ammonia synthesis. Although great efforts are made, the p-NRR catalysts still suffer from poor N₂ adsorption and activation, inferior light absorption, and fast recombination of photocarriers. Due to the tunable electronic structure of the metal-free polymeric graphitic carbon nitride (g-C₃ N₄ ), the above-mentioned issues can be significantly alleviated, making it the most promising p-NRR photocatalyst. This review summarizes the recent development of g-C₃ N₄ -based catalysts for p-NRR, including the working principle of p-NRR catalysts, the challenges of developing p-NRR catalysts, and corresponding solutions. Particularly, the roles of defect engineering and heterojunction construction on g-C₃ N₄ to the enhancement of photocatalytic performances are emphasized. In addition, computational studies are introduced to deepen the understanding of reaction pathways. At last, perspectives are provided on the development of p-NRR catalysts.

Synthesis and Characterization of Bi2WxMo1−xO6 Solid Solutions and Their Application in Photocatalytic Desulfurization under Visible Light

Photocatalytic oxidative desulfurization has attracted much attention in recent years due to the continuous tightening of the sulfur content requirements in motor fuels and the disadvantages of the industrial hydrodesulfurization process. This work is devoted to the investigation of the photocatalytic activity of Bi2WxMo1−xO6 solid solutions (x = 1, 0.75, 0.5, 0.25, 0) in the oxidative desulfurization of hydrocarbons under visible light irradiation using hydrogen peroxide as an oxidant. The synthesized photocatalysts were characterized in detail using XRD, SEM, EDS, low-temperature nitrogen adsorption–desorption, and DRS. It was shown that the use of solid solutions Bi2WxMo1−xO6 with x = 0.5–0.75 leads to the complete oxidation of organosulfur compounds to CO2 and H2O within 120 min. The high photocatalytic activity of solid solutions (x = 0.5–0.75) is attributed to their ability to absorb more visible light, the presence of the corner-shared [Mo/WO6] octahedral layers, which may promote the generation and separation of photogenerated charges, and the hierarchical 3D flower-like structure. The reaction mechanism of the desulfurization was also analyzed in this work.

Construction of 2D layered phosphorus-doped graphitic carbon nitride/BiOBr heterojunction for highly efficient photocatalytic disinfection

Infectious diseases caused by bacteria intimidate the health of human beings all over the world. Although many avenues have been tried, various operating conditions limit their actual applications. Photocatalytic nanomaterials are becoming candidates to be competent for water purification. Here, a novel and more efficient S-scheme has been engineered between two dimensional (2D) layered phosphorus-doped graphitic carbon nitride (P-g-C 3 N 4 ) and BiOBr via hydrothermal polymerization to inhibit the recombination of charge and broaden light absorption. The as-prepared P-g-C 3 N 4 /BiOBr hybrids exhibits significantly improved photocatalytic disinfection contrast to g-C 3 N 4 /BiOBr in visible wavelengths, suggesting phosphorus doping which adjusts the band structure plays a significant role in the S-scheme system. And the sterilization rate of multidrug-resistant Acinetobacter baumannii 28 ( AB 28 ) was 99.9999% within 80 min and Staphylococcus aureus ( S. aureus ) was 99.9%.

Photocatalytic Air Purification Using Functional Polymeric Carbon Nitrides

The techniques for the production of the environment have received attention because of the increasing air pollution, which results in a negative impact on the living environment of mankind. Over the decades, burgeoning interest in polymeric carbon nitride (PCN) based photocatalysts for heterogeneous catalysis of air pollutants has been witnessed, which is improved by harvesting visible light, layered/defective structures, functional groups, suitable/adjustable band positions, and existing Lewis basic sites. PCN-based photocatalytic air purification can reduce the negative impacts of the emission of air pollutants and convert the undesirable and harmful materials into value-added or nontoxic, or low-toxic chemicals. However, based on previous reports, the systematic summary and analysis of PCN-based photocatalysts in the catalytic elimination of air pollutants have not been reported. The research progress of functional PCN-based composite materials as photocatalysts for the removal of air pollutants is reviewed here. The working mechanisms of each enhancement modification are elucidated and discussed on structures (nanostructure, molecular structue, and composite) regarding their effects on light-absorption/utilization, reactant adsorption, intermediate/product desorption, charge kinetics, and reactive oxygen species production. Perspectives related to further challenges and directions as well as design strategies of PCN-based photocatalysts in the heterogeneous catalysis of air pollutants are also provided.

Heterostructure of vanadium pentoxide and mesoporous SBA-15 derived from natural halloysite for highly efficient photocatalytic oxidative desulphurisation

Integration between conventional semiconductors and porous materials can enhance electron–hole separation, improving photocatalytic activity. Here, we introduce a heterostructure that was successfully constructed between vanadium pentoxide (V₂O₅) and mesoporous SBA-15 using inexpensive halloysite clay as the silica–aluminium source. The composite material with 40% doped V₂O₅ shows excellent catalytic performance in the oxidative desulphurisation of dibenzothiophene (conversion of 99% with only a minor change after four-cycle tests). These results suggest the development of new catalysts made from widely available natural minerals that show high stability and can operate in natural light to produce fuel oils with ultra-low sulphur content.

New and robust catalysts made from natural minerals that can operate in sunlight to produce fuel oils with ultra-low-sulphur content.

Amorphous Fe(OH)3 Passivating CeO2 Nanorods: A Noble-Metal-Free Photocatalyst for Water Oxidation

Noble-metal-free composites with good photocatalytic property are of great interest. Here, CeO₂ nanorods composites loaded with amorphous Fe(OH)₃ cocatalyst were designed and prepared via a secondary water bath at 100 °C. The as-synthesized CeO₂ /amorphous Fe(OH)₃ composites exhibited superior light photocatalytic activities compared to pure CeO₂ , especially the sample with a loading time of 60 min. The photocatalytic oxygen generation rate could reach to 357.2 μmol h^-1  g^-1 , and the average apparent quantum yield (AQY) was 24.67 %, which was a 5.5-fold increase compared to the CeO₂ sample. The improvement of photocatalytic performance could be ascribed to three main reasons: First, loading the amorphous Fe(OH)₃ enlarged the specific surface area and passivated the surface of the pristine CeO₂ . Second, the amorphous Fe(OH)₃ ,which acted as a cocatalyst, provided many active sites, and reduced the reaction activation energy. Thirdly, the maximum interface with intimate contact between CeO₂ and amorphous Fe(OH)₃ cocatalyst accelerated the photogenerated charge separation efficiency and thus improved the photocatalytic performance of CeO₂ in photocatalytic water oxidation.

A current overview of the oxidative desulfurization of fuels utilizing heat and solar light: from materials design to catalysis for clean energy

The ceaseless increase of pollution cases due to the tremendous consumption of fossil fuels has steered the world towards an environmental crisis and necessitated urgency to curtail noxious sulfur oxide emissions. Since the world is moving toward green chemistry, a fuel desulfurization process driven by clean technology is of paramount significance in the field of environmental remediation. Among the novel desulfurization techniques, the oxidative desulfurization (ODS) process has been intensively studied and is highlighted as the rising star to effectuate sulfur-free fuels due to its mild reaction conditions and remarkable desulfurization performances in the past decade. This critical review emphasizes the latest advances in thermal catalytic ODS and photocatalytic ODS related to the design and synthesis routes of myriad materials. This encompasses the engineering of metal oxides, ionic liquids, deep eutectic solvents, polyoxometalates, metal-organic frameworks, metal-free materials and their hybrids in the customization of advantageous properties in terms of morphology, topography, composition and electronic states. The essential connection between catalyst characteristics and performances in ODS will be critically discussed along with corresponding reaction mechanisms to provide thorough insight for shaping future research directions. The impacts of oxidant type, solvent type, temperature and other pivotal factors on the effectiveness of ODS are outlined. Finally, a summary of confronted challenges and future outlooks in the journey to ODS application is presented.