Photocatalytic Kinetics Research Articles

Enhancement of photocatalytic activity of CeO2 nanorods through lanthanum doping (La–CeO2) for the degradation of Congo red dyes

The discharge of synthetic dyes into water bodies poses severe environmental risks due to their toxic and recalcitrant nature. This study explores the enhancement of photocatalytic properties of cerium dioxide (CeO2) nanorods by doping with lanthanum (La) to improve their efficacy in degrading aqueous solutions of Congo red dye. The CeO2 nanorods were synthesized via a hydrothermal method and subsequently doped with varying concentrations of La. The scanning electron microscopy (SEM) images confirmed the rod-like structures (nanorods) were observed for all samples, while the energy-dispersive X-ray spectroscopy (EDX) confirmed the homogeneous incorporation of La into the CeO2 matrix. The X-ray diffraction (XRD) spectra demonstrate lattice distortion due to substitutional defect. Photocatalytic experiments revealed that La-doped CeO2 nanorods exhibited significantly enhanced degradation capabilities compared to undoped counterparts, achieving up to a 3-fold photocatalytic kinetics ((30 ± 2) × 10−3 min−1) compared to the undoped counterparts ((11.5 ± 0.4) × 10−3 min−1). Influence of various parameters that affect the photocatalysis performance (i.e., contact time, initial dye concentration, catalyst dosage, and dye solution pH value) were also investigated. Radical scavenger experiments reveal that superoxide radicals play a dominant role in the photocatalytic process. Collectively, these findings confirm that the strategic incorporation of lanthanum into CeO2 nanorods not only enhances their overall photocatalytic efficiency but also tailors their activity towards specific pollutants through radical-mediated pathways.

Fabrication of Ag2MoO4/CuWO4 Nanocomposite Photocatalyst for the Degradation of Rhodamine‐B

AbstractHerein, we investigate the photocatalytic properties of a new Ag2MoO4/CuWO4 composite. Three different composites with 5, 10, and 15 weight percent of fine Ag2MoO4 nanostructures were precipitated on CuWO4 nanoparticles. Given the staggered valence and conduction band positions of the two components, the composite with the 10 % weight percent Ag2MoO4 loading on CuWO4 demonstrated the slowest recombination kinetics. The same composite also exhibited the best photocatalytic degradation of RhB under UV light irradiation. The photocatalytic turnover frequency of this composite was also among the best reported for RhB degradation reported in the literature. Photocatalytic kinetics, active species trapping, and various control experiments were carried out to get an insight into the photocatalytic mechanism. The optimum photocatalyst exhibited its highest activity at pH 3 and a RhB degradation turnover frequency (photocatalytic activity) comparable to the best values reported in the literature.

Three CoS/CoO microspheres and their mixed matrix membranes for the highly efficient photocatalytic degradation of methyl blue.

Photocatalytic degradation technology, as one of the most important advanced oxidation technologies for environmental remediation, has attracted great attention in recent years, but designing photocatalysts with excellent photocatalytic activity and good reusability remains a challenge. Herein, three CoS/CoO microspheres (CoS/CoO-M-1 (1), CoS/CoO-M-2 (2), and CoS/CoO-M-3 (3)) were prepared via a hydrothermal method using cobalt chloride hexahydrate, thiourea, deionized water and polyethylene glycol (PEG) with different polymerization degrees as raw materials, which have a uniform size distribution in the range of 5-24 μm and specific surface areas of 6.1924 m2 g-1 (1), 6.2870 m2 g-1 (2) and 6.6663 m2 g-1 (3). It is worth noting that all the three CoS/CoO microspheres showed a wide optical absorption range from the ultraviolet to the near-infrared (NIR) region and a high photocatalytic activity for degrading methyl blue under visible light (500 W metal halide lamp) irradiation. In order to improve the portability and recyclability of 3, a mixed matrix membrane (MMM) of 3 (3-MMM) was manufactured by coating a mixture dispersion of 3 and polyvinylidene fluoride (PVDF) on a glass substrate, which not only displayed excellent photocatalytic degradation performance, but also showed good portability and reusability (cycles > 12 times). Furthermore, adsorption and photocatalytic kinetics and possible mechanisms were studied.

In-situ Hf/Zr co-doped Fe2O3 nanorod decorated with CuOx/CoOx: Enhanced photocatalytic performance for antibacterial and organic pollutants

Herein, we successfully synthesized Hf/Zr co-doping on Fe2O3 nanorod photocatalyst by a hydrothermal process and quenching methods. The synergistic roles of Hf and Zr double-doping on the bacteria inactivation test and decomposition of organic pollutants were investigated in detail for the 1 wt% CoOx loaded Hf/Zr–Fe2O3 NRs and CuOx/CoOx loaded Hf/Zr–Fe2O3 NRs photocatalyst. Initially, the rod-like porous morphology of the Hf/Zr-doped Fe2O3 NRs was produced via a hydrothermal method at various Hf co-doping (0, 2, 4, 7 and 10)%. Further, CoOx and CuOx loaded by a wet impregnation approach on the Hf/Zr–Fe2O3 NRs and a highly photoactive Hf(4)/Zr–Fe2O3 [CoOx/CuOx] NRs photocatalyst were developed. After the Hf(4)/Zr–Fe2O3 [CoOx/CuOx] NRs photocatalyst treatment, the Bio–TEM imagery of bacterial cells showed extensive morphological deviations in cell membranes. Hf(4)/Zr–Fe2O3 NR achieved 84.1% orange II degradation upon 3 h illumination, which is higher than that of Hf–Fe2O3 and Zr–Fe2O3 (68.7 and 73.5%, respectively). Additionally, the optimum sample, Hf(4)/Zr–Fe2O3 [CoOx/CuOx] photocatalyst, exhibited 95.5% orange II dye degradation after light radiation for 3 h. Optimized Hf(4)/Zr–Fe2O3 [CoOx/CuOx] catalysts exhibited 99.9% and 99.7% inactivation of E. coli and S. aureus with 120 min, respectively. Further, scavenger experiments revealed that the electrons are the primary responsible species for photocatalytic kinetics. This work will provide a rapid method for the development of high photocatalytic performance materials for bacterial disinfection and organic degradation.

Enhancing photocatalytic efficiency and durability: Ag-modified CNS–TiO2 thin films for sustainable industrial wastewater treatment

This study explores a novel approach to address the persistent challenges encountered in recovering powder catalysts and achieving superior photocatalytic performance tailored for environmental remediation and industrial wastewater (IE) treatment. Isopropyl alcohol (IPA), chosen as the solvent through Liyanage classical equations and zeta potential measurements (−33.6 mV), sets the stage for investigating the critical role of the surfactant (PVP) and binder (SiO2) in optimizing colloidal stability, thin-film coating, and photocatalytic activity. Meticulous experimentation reveals a synergistic 10:1 g/L ratio of PVP and SiO2 solutions as the key to achieving a delicate balance in enhancing colloidal stability, facilitating thin-film coating, and optimizing photocatalytic kinetics (84 ± 3%, k = 0.0303 ± 0.002 min−1). Additionally, the study emphasizes the need for a holistic optimization approach, highlighting colloidal stability and film adhesion to unlock the full potential of these advanced photocatalytic materials in engineering applications.

Separation of TiO2 and Fe2O3 from Indonesia Ilmenite Minerals and their Application as Photocatalysts for Eriochrome Black‐T Dye Degradation

AbstractAnatase‐TiO2 and α‐Fe2O3 were successfully separated from Indonesia ilmenite minerals using a modification of the hydrometallurgy process. Sodium salt was used as an initiated roasting before hydrochloric leaching. The study investigated parameters that affect separation such as mass ratios of sodium salt to ilmenite and leaching temperature. The results revealed that Ti composition in residue‐TiO2 increased to 76 % while Fe‐composition in filtrate‐Fe2O3 was 87 %. The XRD diffractogram analysis confirmed that main phase formed in residue of separation was anatase‐TiO2 whereas in hydrolysed of filtrate from separation was hematite. Both residue‐TiO2 and filtrate Fe2O3 had high thermal stability. The photocatalytic activity of anatase‐TiO2 and α‐Fe2O3 showed about 97 % and 85 % of Eriochrome Black‐T dye solution was degraded, respectively, when conducted to 4 hours of UV light irradiation. Photocatalytic kinetics study of anatase‐TiO2 and α‐Fe2O3 in degradation process followed pseudo‐first order with reaction rate at 0.0144 and 0.0070 min−1, respectively.

Study on the Enhancement of Efficiency, Photocatalytic Kinetics, and Mechanism of Trace GO on TiO2 for Cr(VI) Removal Under Visible Light Conditions

Study on the Enhancement of Efficiency, Photocatalytic Kinetics, and Mechanism of Trace GO on TiO2 for Cr(VI) Removal Under Visible Light Conditions

Second phase Cu2O boosted photocatalytic activity of fluorine doped CuO nanoparticles.

The photocatalytic activity of fluorine (F) doped CuO nanoparticles (NPs) prepared employing modified sol-gel process was investigated here in this study. Structural and elemental characterization using XRD and XPS data confirmed successful incorporation of F as dopant. F doping led to lattice distortion and reduced crystallinity with smaller crystallite size while promoting the emergence of Cu2O as the second phase. Morphological analysis showed irregularly shaped, fused particles with a decreasing particle size trend upon doping. Addition of hydrogen peroxide generated hydroxyl radicals (OH˙) under ultra-violet (UV) light, which effectively degrades pollutants by facilitating the photocatalytic kinetics. Photocatalytic activity of all the nanoparticles was examined against Rhodamine B (Rh B) dye and most efficient degradation (97.78%) was observed for 3 mol% F dopant concentration. The emergence of Cu2O phase for doping beyond 1 mol% F doped CuO might be the prime reason to enhance its degradation performance. Conversely, 5 mol% doping caused notable phase changes and decreased degradation rate (88.05%) due to increased recombination rate in presence of metallic copper. The ability of F doped CuO nanoparticles to disintegrate organic contaminants by producing reactive oxygen species when exposed to UV light suggests their potential effectiveness in applications such as dye degradation, water purification, and environmental sustainability.

Hollow Nanoreactors for Controlled Photocatalytic Behaviors: Fundamental Theory, Structure-Performance Relationship, and Catalytic Advantages.

Hollow nanoreactors (HoNRs) have regarded as an attractive catalytic material for photocatalysis due to their exceptional capabilities in enhancing light harvesting, facilitating charge separation and transfer, and optimizing surface reactions. Developing novel HoNRs offers new options to realize controllable catalytic behavior. However, the catalytic mechanism of photocatalysis occurring in HoNRs has not yet been fully revealed. Against this backdrop, this review elaborates on three aspects: 1) the fundamental theoretical insights of HoNRs-driven photocatalytic kinetics; 2) structure-performance relationship of HoNRs to photocatalysis; 3) catalytic advantages of HoNRs in photocatalytic applications. Specifically, the review focuses on the fundamental theories of HoNRs for photocatalysis and their structural advantages for strengthening light scattering, promoting charge separation and transfer, and facilitating surface reaction kinetics, and the relationship between key structural parameters of HoNRs and their photocatalytic performance is in-depth discussed. Also, future prospects and challenges are proposed. It is anticipated that this review paper will pave the way for forthcoming investigations in the realm of HoNRs for photocatalysis.

Compact device for in situ ultraviolet–visible spectrophotometric measurement of photocatalytic kinetics

In this work, we have designed a compact device that can be easily integrated with Ultraviolet–Visible spectrophotometers, utilizing Light Emitting Diode technology for in situ spectrophotometric measurements of photocatalytic reactions. Using our device, we present the test results for the breakdown of amaranth dye with Degussa P25 powder and compare them with those obtained from a conventional arc discharge reactor. The results show that the reaction constants obtained using our device are practically equivalent to those acquired with a conventional reactor. However, our device significantly simplifies the experimental task by requiring less test solution volume and fewer user interventions while enabling in situ monitoring of the reaction kinetics. Overall, the proposed approach offers a convenient and efficient means of studying photocatalytic materials for dye degradation.

Comparative study on the effects of {2 0 1} TiO2 and {2 0 1}TiO2−ZrO2 on arsenite photocatalysis

Escalated levels of arsenic (As) in drinking water is an urgent environmental problem that has attracted increasing public concern. The need for effective removal of As has motivated great research efforts. Herein, {2 0 1} TiO2 and its Zr doped composite were compared in reducing As toxicity via photocatalysis. Macroscopic photocatalytic kinetics show that the oxidization process of As(III) catalyzed by {2 0 1} TiO2, {2 0 1} TiO2 − ZrO2, and ZrO2 followed first-order kinetics with a rate constant of {2 0 1} TiO2 >{2 0 1}TiO2 − ZrO2 > ZrO2. UV–vis DRS and photoluminescence results suggested that the photooxidizing activity of {2 0 1} TiO2 outdone {2 0 1}TiO2 − ZrO2 due to its narrower band gap and higher electron-hole separation efficiency. After 190 min of UV irradiation, the quantum yields of •OH during {2 0 1} TiO2 and {2 0 1}TiO2 − ZrO2 photocatalysis were 146.1 and 112.6 μM, respectively. As evidenced by the radical-scavenging test, photocatalytically generated h+ and O2•- were the predominant participants in As(III) photooxidation for {2 0 1} TiO2 and {2 0 1}TiO2 − ZrO2, respectively. The photocatalytic mechanism gained from the investigation would be helpful for developing high-index TiO2-based environmental techniques.

Photocatalytic water splitting kinetics of CMV model

The photocatalytic water splitting kinetics has been analyzed in this paper. The experimental data are taken from the published works and fitted with different theoretical models. From the results, we find that the photocatalytic kinetics of water splitting can be described by Capelas-Mainardi–Vaz (CMV) model very well. This suggests that the water splitting kinetics can be regarded as a fractional first-order kinetics of the chemical reaction. Also, we notice that photocatalytic water splitting is not always completely a monotone kinetics process.

Modelling and experimental validation of reaction chamber simulating indoor air decontamination by photocatalytic paint

A photocatalytic paint for the air decontamination was tested under different operating conditions in a reaction chamber that simulates an indoor room. An experimental design was applied to cover a wide range of indoor air conditions (irradiation level, air flow rate, relative humidity and inlet pollutant concentration). It was proposed to develop a first principles model capable of predicting the outlet contaminant concentration from the continuous reaction chamber or the evolution of the reactant concentration operating the chamber in batch mode. The main inputs for the model were: i) optical properties of the paint, ii) characteristics and dimensions of the radiation source, iii) dimensions and operating conditions of the reaction chamber, and iv) intrinsic photocatalytic kinetics previously determined. The developed models showed a very good agreement with experimental measurements. The proposed methodology could be extended considering all indoor environmental conditions to simulate air decontamination in real applications of photocatalytic paints.

Insights into atomically dispersed reactive centers on g-C3N4 photocatalysts for water splitting

Co-catalysts decorations provide unique opportunities in promoting the photocatalytic water splitting performance of graphite carbon nitride (g-C 3 N 4 ) system, while mechanistic understanding of this complex catalytic network remains elusive. Here, taking the single-atom-based photocatalysts (M 1 -g-C 3 N 4 ) as an unprecedented simplified model system, we theoretically tracked the photocatalytic kinetics for a comprehensive understanding of the photocatalytic process and affords the descriptor α S1-T1/ α T1-S0 (ratio of the extent of S 1 -T 1 and T 1 -S 0 state mixing) and Δ G H* (hydrogen adsorption free energy) for rational screening of photocatalysts. The targeted Fe 1 -g-C 3 N 4 yielded an excellent H 2 evolution rate (ca. 3.2 mmol g cat −1 h −1 under full arc), two order of magnitude improvement relative to pristine g-C 3 N 4 counterpart and also outperforms other representative 3 d -transition-metal-based photocatalysts. This work presents a comprehensive understanding of the essential role of isolated atomic sites in the photocatalytic course and sheds light on the design of photocatalysts from both photophysical/photochemical aspects. This work presents a comprehensive understanding of the essential role of isolated atomic sites in the photocatalytic process based on a combination of theoretical with experimental studies. The photophysical, photochemical descriptors of α S1-T1/ α T1-S0 (ratio of the extent of S 1 -T 1 and T 1 -S 0 state mixing) and Δ G H* (hydrogen adsorption free energy) are proposed for rational screening of photocatalysts. • The photocatalytic courses of a prototype single-atom-based photocatalysts (M 1 -g-C 3 N 4 ) were tracked based on a combination of DFT calculations with experimental studies. • General descriptors α S1-T1/ α T1-S0 (ratio of the extent of S 1 -T 1 and T 1 -S 0 state mixing) and Δ G H* (hydrogen adsorption free energy) were proposed for rational screening of photocatalysts. • The targeted Fe 1 -g-C 3 N 4 yielded excellent H 2 evolution rate (ca. 3.2 mmol g cat −1 h −1 under full arc), two order of magnitude improvement relative to pristine g-C 3 N 4 and also outperforms other representative 3 d -transition-metal-based photocatalysts.

Metal-Organic Frameworks for Photocatalytic Water Splitting and CO2 Reduction.

Photocatalytic water splitting and carbon dioxide (CO2 ) reduction provide promising solutions to global energy and environmental issues. In recent years, metal-organic frameworks (MOFs), a class of crystalline porous solids featuring well-defined and tailorable structures as well as high surface areas, have captured great interest toward photocatalytic water splitting and CO2 reduction. In this review, the semiconductor-like behavior of MOFs is first discussed. We then summarize the recent advances in photocatalytic water splitting and CO2 reduction over MOF-based materials and focus on the unique advantage of MOFs for clarifying the structure-property relationship in photocatalysis. In addition, some representative characterization techniques have been presented to unveil the photocatalytic kinetics and reaction intermediates in MOF-based systems. Finally, the challenges, and perspectives for future directions are proposed.

Metal‐Organic Frameworks for Photocatalytic Water Splitting and CO2Reduction

AbstractPhotocatalytic water splitting and carbon dioxide (CO2) reduction provide promising solutions to global energy and environmental issues. In recent years, metal‐organic frameworks (MOFs), a class of crystalline porous solids featuring well‐defined and tailorable structures as well as high surface areas, have captured great interest toward photocatalytic water splitting and CO2reduction. In this review, the semiconductor‐like behavior of MOFs is first discussed. We then summarize the recent advances in photocatalytic water splitting and CO2reduction over MOF‐based materials and focus on the unique advantage of MOFs for clarifying the structure‐property relationship in photocatalysis. In addition, some representative characterization techniques have been presented to unveil the photocatalytic kinetics and reaction intermediates in MOF‐based systems. Finally, the challenges, and perspectives for future directions are proposed.

Dynamics of VOCs degradation and bacterial inactivation at the interface of AgxO/Ag/TiO2 prepared by HiPIMS under indoor light

• Indoor/outdoor air pollution and bacteria were degraded on sputtered Ag x O/Ag/TiO 2 on textile. • Photocatalytic kinetics are carried out in the dark and under visible light. • Ag/AgxO nanoparticles show a significant effect on the activity of TiO 2 . • A possible mechanism of photocatalytic processes is suggested. Ag x O/Ag/TiO 2 photoactive thin films were produced by different modes of magnetron sputtering (namely, DCMS and HiPIMS). The spectral and microstructural properties of the Ag-Ag x O/TiO 2 thin films were studied by Diffuse Reflection Spectroscopy (DRS) and X-Ray Photoemission Spectroscopy (XPS). The atomic deposition of TiO2 and Ag in the thin sputtered film were studied by TEM. Ag x O/Ag/TiO 2 exhibited fast photocatalytic volatile organic compounds (VOCs) degradation and bacterial inactivation under low visible light intensity. The Langmuir Hinshelwood model was applied to highlight the photocatalytic performance of the Ag x O/Ag/TiO 2 catalyst. The oxidative states of Ag-Ag x O/TiO 2 were studied by XPS. Deconvolution of the Ag3d peak of the Ag x O/Ag/TiO 2 thin films showed the presence of AgO and metallic Ag. It is suggested that the mechanism involving the degradation of VOCs on AgO/Ag/TiO 2 catalysts is due to the transfer of holes from AgO to TiO 2 via the AgO/Ag/TiO 2 heterojunction. The electrostatic interaction between both semiconductors allows this charge transfer. In addition, the contribution of reactive oxygen species (ROS) in bacterial inactivation at the interface of AgO/Ag/TiO 2 thin film was also examined. Light-induced interfacial charge transfer (IFCT) between AgO and TiO 2 leading to pollutants oxidation appears to require low photons’ energy and can oxidize pollutants even at high concentrations. The sputtered coatings have also been studied for repetitive reuse, showing the sustainable activity of the prepared materials.

Synthesis of Bi2O3 NPs with polyethylene glycol and investigation of photodegradation of phenazopyridine in aqueous solution

The synthesis of Bi2O3 by a simple chemical route in the presence of polyvinylpyrrolidone (PP) as surfactant was studied. The sample was characterized by XRD, FTIR, and DRS techniques. Its pHpzc was estimated about 9.5. Crystallite size of the as-synthesized sample was estimated about 45 and 14 nm by the Scherrer and Williamson-Hall models, respectively. Band gap energy was estimated about 2.98 eV using the adsorption edge wavelength, while by using the Kubelka-Munk theory Eg-values of 3.21, 3.13, 3.27, and 3.24 eV were obtained for n-values of 2, 1/2, 3/2, and 3, respectively. The photocatalytic performance of the Bi2O3 NPs was evaluated against phenazopyridine as a model pollutant. Experimental optimized parameters were as adsorbent dosage = 0.7 g/L, contact time = 60 min, pH 7, illumination time: 60 min, CPP: 20 ppm. The photocatalytic kinetics model obeyed the pseudo-first order kinetic model.

Unique kinetics feature and excellent photocatalytic performance of tetracycline photodegradation using yolk-shell TiO2@void@TiO2:Eu3+

The multifunctional yolk-shell TiO2 @void@TiO2:Eu3+ calcined at different temperatures were successfully fabricated by sacrificial template method for the photodegradation of tetracycline. The impacts of yolk-shell and calcination temperature on the photoluminescence and photocatalytic properties have been investigated in detail. The photoluminescence results show that sample calcined at 800 °C exhibits the strongest red emission. The photocatalytic efficiency for tetracycline reached 90.34 % in 50 min at 20 mg/L TC solution by sample calcined at 900 °C. The kinetics fitting curves is with different slopes, which is reported for the first time so far. Meanwhile, the photocatalytic mechanism and possible photodegradation pathway of tetracycline were proposed. Compared with the double-shell samples, the yolk-shell samples show a high photodegradation rate within 5 min and unique kinetics feature. The analysis of photocatalytic kinetics provides a new idea for studying the photocatalysis mechanism. The rapid tetracycline photodegradation by the yolk shell material also provides new strategies for practical water purification.

Simple Synthesis Pathway of Uniform Nanoparticle TiO2 from Hydrolysis of TiCl4 and Kinetic Study of Photocatalytic Decomposition of Azo Compounds

Contamination of clean water has been recognized as a serious environmental problem. Meanwhile, photocatalyst technology is seen as a promising alternative method to overcome environmental problems. However, several obstacles are currently faced. Hydrolysis of TiCl4 to form TiO2 usually produces ununiform phase of TiO2 which makes the kinetic study of TiO2 for photocatalyst reaction difficult to determine. A new synthesis pathway to produce a uniform phase with a simple method has not been established yet. This study has found a controllable and simple route to synthesize a single anatase phase of TiO2. For this experiment, TiCl4 is used as a precursor to TiO2 and calcined at 600°C, then tested for its photocatalytic ability with a solution of organic dyes. According to the X-ray diffraction and Scanning electron microscope characterizations, TiO2 anatase was successfully synthesized in a single phase without impurities. Furthermore, the synthesized TiO2 was able to degrade organic dyes with a maximum degradation of 60%, 93%, 97% and 87% for methyl orange, methyl violet, bromothymol blue as well as congo red respectively and is therefore an excellent catalyst to reduce water pollutants. Finally, the photocatalytic kinetics calculated using the Langmuir–Hinshelwood first order model showed that the efficiency for the degradation of bromothymol blue showed significant results, 212% more efficient activity compared to TiO2 P25.