Fe2O3 Catalyst Research Articles

Deep insights into the promotion role of Sm doping in the sulfur resistance of Fe2O3 catalyst for NH3-SCR: A combined experimental and DFT study

To investigate the inherent role of Sm doping in metal sulfation over the surface of Fe2O3 catalyst and reveal the reason for the SO2 tolerance enhancement of Sm/Fe2O3 catalyst at low temperatures (<320 °C), sulfated Fe2O3 and Sm/Fe2O3 catalysts were prepared by pretreating fresh catalysts in SO2+O2 atmosphere. Selective catalytic reduction (SCR) of NOx by NH3 activities and physicochemical characteristics of fresh and sulfated catalysts were studied, and the reaction mechanisms on sulfated catalysts analyzed. The minor shift of Fe signal to high value and larger shift of S signal to low value of sulfated Sm/Fe2O3 compared with sulfated Fe2O3 was observed with X-ray photoelectron spectroscopy (XPS), indicating that Sm modification could weaken the sulfation of active Fe sites. Consistent with the XPS results, density functional theory calculations showed that SO2 is more easily adsorbed on the Sm/Fe2O3 catalyst with the adsorption sites located at Sm atom and its neighboring Fe atoms. In-situ DRIFTS results showed that the SCR reaction over the sulfated Fe2O3 catalyst followed both L-H (the adsorbed NH3 species react with adsorbed nitrate species) and E-R (the adsorbed NH3 species react with gaseous NO) mechanisms at 250 °C, with the L-H route much faster, whereas only the L-H pathway occurred over sulfated Sm/Fe2O3 catalyst because of too strong affinity of NH3 on the sulfated sites to inhibit NH3 activation – this was also the reason for its enhanced Lewis and Brønsted acidity. More reactive nitrate species were formed on the sulfated Sm/Fe2O3 catalyst due to the existence of more un-sulfated Fe sites, making the Sm/Fe2O3 catalyst resistant to SO2 poisoning at relatively low temperatures.

Optimization of iron-based catalyst for partial upgrading of Athabasca Bitumen: The role of Fe oxidation state, particle size, and concentration

The present investigation examines the prospective application of Fe-based catalysts for catalyzing the partial upgrading of Athabasca oil sand bitumen, aiming for developing an economically viable and environmentally sustainable process. The primary focus is to analyze the impact of the oxidation state of iron, catalyst particle size, and catalyst concentration on partial upgrading efficiency to optimize bitumen resource utilization without the need of an external source/supply of hydrogen gas using an autoclave reactor. The experimental results demonstrate that Fe-based catalysts, particularly those with lower oxidation states such as FeS, FeO, and Fe3O4, significantly improve the oil quality and reduce bitumen’s viscosity through increasing saturates and substantially reducing the asphaltene fractions. Furthermore, it is also identified that those catalysts can promote hydrogenation and cracking reactions that transform heavier fractions into lighter ones while achieving up to 59% vacuum residue conversion. A comprehensive screening process using Minitab statistical software was made to identify the best catalyst based on the catalyst’s oxidation state, concentration, and particle size range. As a result, Fe3O4 nanoparticles at a 0.5 wt% loading have been identified as the optimal catalyst combination for achieving the maximum liquid yield, while simultaneously producing the minimum asphaltene content, and maximum viscosity reduction. An assessment of the fresh and spent Fe3O4 catalyst yielded valuable insights concerning the catalytic partial upgrading of bitumen, unveiling a reaction mechanism involving iron catalyst sulfidation, desulfurization reactions, CH scission, and hydrocarbon cracking, in addition to the formation of coke. The potential role of various alloy materials employed in the fabrication of reactors for bitumen partial upgrading has also been studied and compared, discussing their unique advantages and limitations in terms of product quality and liquid yield. The findings presented in this study contribute significantly to the development of more efficient and sustainable upgrading processes, paving the way for optimizing catalyst properties for bitumen upgrading applications and providing a valuable perspective on the role of catalysts in the upgrading of heavy oils.

Heterogeneous electro-Fenton treatment of chemotherapeutic drug busulfan using magnetic nanocomposites as catalyst

The rapid and efficient mineralization of the chemotherapeutic drug busulfan (BSF) as the target pollutant has been investigated for the first time by three different heterogeneous EF systems that were constructed to ensure the continuous electro-generation of H2O2 and •OH consisting of: i) a multifunctional carbon felt (CF) based cathode composed of reduced graphene oxide (rGO), iron oxide nanoparticles and carbon black (CB) (rGO-Fe3O4/CB@CF), ii) rGO modified cathode (rGO/CB@CF) and rGO supported Fe3O4 (rGO-Fe3O4) catalyst and iii) rGO modified cathode (rGO/CB@CF) and multi walled carbon nanotube supported Fe3O4 (MWCNT-Fe3O4) catalyst. The effects of main variables, including the catalyst amount, applied current and initial pH were investigated. Based on the results, H2O2 was produced by oxygen reduction reaction (ORR) on the liquid-solid interface of both fabricated cathodes. •OH was generated by the reaction of H2O2 with the active site of ≡FeII on the surface of the multifunctional cathode and heterogeneous EF catalysts. Utilizing carbon materials with high conductivity, the redox cycling between ≡FeII and ≡FeIII was effectively facilitated and therefore promoted the performance of the process. The results demonstrated almost complete mineralization of BSF through the heterogeneous systems over a wide applicable pH range. According to the reusability and stability tests, multifunctional cathode exhibited outstanding performance after five consecutive cycles which is promising for the efficient mineralization of refractory organic pollutants. Moreover, intermediates products of BSF oxidation were identified and a plausible oxidation pathway was proposed. Therefore, this study demonstrates efficient and stable cathodes and catalysts for the efficient treatment of an anticancer active substance.

Constructing multiple active sites in iron oxide catalysts for improving carbonylation reactions

Surface engineering is a promising strategy to improve the catalytic activities of heterogeneous catalysts. Nevertheless, few studies have been devoted to investigate the catalytic behavior differences of the multiple metal active sites triggered by the surface imperfections on catalysis. Herein, oxygen vacancies induced Fe2O3 catalyst are demonstrated with different Fe sites around one oxygen vacancy and exhibited significant catalytic performance for the carbonylation of various aryl halides and amines/alcohols with CO. The developed catalytic system displays excellent activity, selectivity, and reusability for the synthesis of carbonylated chemicals, including drugs and chiral molecules, via aminocarbonylation and alkoxycarbonylation. Combined characterizations disclose the formation of oxygen vacancies. Control experiments and density functional theory calculations demonstrate the selective combination of the three Fe sites is vital to improve the catalytic performance by catalyzing the elemental steps of PhI activation, CO insertion and C-N/C-O coupling respectively, endowing combinatorial sites catalyst for multistep reactions.

Structural reconstruction of iron oxide induces stable catalytic performance in the oxidative dehydrogenation of n-butane to 1,3-butadiene

The CO2-assisted oxidative dehydrogenation of n-butane to 1,3-C4H6 offers a perspective process for producing valuable chemicals while simultaneously utilizing CO2. In this work, iron-based ZnFe2Ox and Fe2O3 catalysts with high 1,3-C4H6 selectivity were prepared and their corresponding structure–activity relationships were investigated in detail. On basis of the in situ spectroscopic characterization, hydrogen-assisted CO2 activation pathway was captured. Kinetic studies show that Fe2O3 catalyst displays a higher reaction order depending on CO2 concentration than that of ZnFe2Ox catalyst. Fe2O3 is evidenced to serve as an effective mediator for oxygen exchange between CO2 and n-butane based on temperature-programmed experiments and deactivation kinetics analysis. Rapid deactivation is observed over ZnFe2Ox due to its strong CO2 adsorption ability, which triggers the reforming reaction accompanied by severe coke deposition. Interestingly, self-healing phenomena for catalytic performance are found on Fe2O3 catalyst after several test cycles. The reaction/regeneration cycles are proved to drive the surface reconstruction which greatly enhance its resistance to over reduction and coking. This study provides a fundamental insight into Fe-based catalysts in the CO2-assisted oxidative dehydrogenation reactions.

Improved combustion of NH3/C2H4 with Ni modified Fe-based catalyst

An attempt to fabricate the catalyst with good reactivity and stability for catalytic premixed combustion of NH3/C2H4 is present and the catalytic performances of the catalyst were conducted with a designed catalytic combustor, where the catalyst was loaded in the jet. Results showed that a Ni lattice-doped Fe2O3 catalyst was found to be a cost-effective and environmentally friendly catalyst. The CO emissions, CO2 emissions, and combustion temperatures varied from 20 to 300 ppm, 3.5%–6%, and 760–880 °C with equivalent ratio (0.8–2.0) and NH3 volume ratio (50%–70%), which indicated that the combustion efficiency was higher than the conventional premixed combustion of NH3/C2H4. Besides, the NOX emission was significantly reduced by 39.6%–72.5% because the catalyst is full of oxygen vacancies and acid site, which contributed to the reduction of N2 formation energy barrier according to DFT calculation. Furthermore, XRD, SEM results indicated that the catalyst was stable and thus is suitable for catalytic combustion of NH3/C2H4.

Comparative study of TiO2–Fe3O4 photocatalysts synthesized by conventional and microwave methods for metronidazole removal

This study focused on a direct comparison of conventional hydrothermal and microwave treatment during the synthesis of TiO2–Fe3O4 photocatalyst, which is an effective catalyst for decomposing metronidazole. The photocatalyst underwent various characterization analyses, including X-ray diffraction, Raman spectroscopy, transmission electron microscopy, energy dispersive X-ray, and diffuse reflectance spectroscopy. The Raman spectroscopy analysis revealed that the materials obtained through the conventional hydrothermal treatment consisted of separate phases of anatase and magnetite. On the other hand, the materials synthesized using the microwave process showed a noticeable shift in the Eg band (143 cm−1) and its half-width towards higher wavenumbers. This shift is likely due to the introduction of Fe ions into the TiO2 lattice. Additionally, both conventional hydrothermal and microwave synthesis routes produced TiO2–Fe3O4 systems with superparamagnetic properties, as demonstrated by SQUID magnetic measurements. The TEM analysis revealed that the materials synthesized using the microwave process exhibited higher homogeneity, with no noticeable large aggregates observed. Finally, this work proposed a convenient LED photoreactor that effectively utilized the photo-oxidative properties of TiO2–Fe3O4 photocatalysts to remove metronidazole. Combining photoactive TiO2–Fe3O4 catalysts with an energy-efficient LED reactor resulted in a low electrical energy per order (EEO).

Thermochemical behavior and kinetics study of algae pyrolysis using iron oxide catalyst

AbstractThe shift in emphasis from fossil fuel‐derived energy to waste‐to‐energy technologies has widened the possibility for environmentally sustainable methods such as pyrolysis. Algae collected from local sources that grow in wastewater using atmospheric CO2 is a potential feedstock for pyrolysis. Thus, the work focuses on studying the pyrolysis reaction of macroalgae sourced from regional sources in the presence of Fe2O3 catalyst using the thermogravimetric analysis, followed by kinetic analysis using iso‐conversional methods of Flynn–Wall–Ozawa (FWO), Kissinger–Akahira–Sunose (KAS), and Starink methods, and model free Kissinger method. The kinetic model was developed using master plot method. XRD analysis of the Fe2O3 catalyst confirms the presence of the maghemite and hematite phases in the sample. Based on the conversion profile, DTG trend, and kinetic parameter variation, the overall pyrolysis process can be divided into three different stages of dissociation reactions. The apparent activation energy calculated from different models varies in the range: stage I (∼268 kJ/mol), stage II (∼261 kJ/mol), and stage III (∼328 kJ/mol), respectively. Master plot analysis of the kinetic data confirms the best fit of the nucleation model (A2) to experimental data in stage II. Further, the thermodynamic properties of the reaction, such as change in enthalpy (ΔH), change in Gibbs free energy (ΔG), and change in entropy (ΔS) range between 206 and 405 kJ/mol, 189 and 651 kJ/mol, −450 and 27 J/mol/K, respectively, corroborates the complexity of the reaction. Kinetics and thermodynamic property analysis of complex reactions like pyrolysis is essential for pilot plant design.

Iron and Copper Catalysts Derived from Inorganic Waste for Dye Degradation

AbstractDyes like methyl violet (MV) and methyl orange (MO) released from textile industries are considered to be water pollutants. Likewise metal waste from electronic devices and from metallurgical industries are causing harmful effects. Therefore, looking into the negative impact of such waste materials herein copper oxide (CuO) and iron oxide (Fe3O4) photocatalysts were prepared from electronic and candle waste, respectively materials. The metal oxides were supported on a graphitic carbon matrix obtained from waste tea leaves. The synthesized materials were well characterized using different analytical techniques. The carbon‐supported CuO and Fe3O4 catalysts exhibited good photocatalytic activity under UV‐light irradiation in the photo‐degradation of coloured dyes like methyl orange (MO) and methyl violet (MV). The copper (Cu)‐catalyst with band gap like that of titanium dioxide (TiO2) showed superior activity over the iron (Fe)‐catalyst under identical conditions. Cu‐catalyst was found to degrade the dyes within 10–15 min while it took longer time with Fe‐catalyst up to 50 min. The measure of total organic content (TOC) after the dye‐degradation study implied that Cu‐catalyst can carbonize MV upto 89.6 % within 15 min while the same was found to be less (79.5 %) for MO. The ability of the synthesized photocatalysts from waste materials in dye degradation was monitored through FTIR analysis. The mechanistic study suggested the involvement of both the holes and free radicals in the photo‐oxidation of dye components.

Aquathermolysis of heavy oil using a mixed nickel-oxide/iron-oxide catalyst: Effects induced by crystal phase of iron oxide

Nickel and iron compounds have garnered attention as catalysts for upgrading heavy oil via aquathermolysis. However, research on the performance of bimetallic oxide catalysts in aquathermolysis remains limited. To that end, NiO–Fe2O3 catalysts were prepared in this study using a simple physical mixing method and employed in heavy-oil aquathermolysis to investigate the synergistic relationship between NiO and Fe2O3. The product distributions and quality were systematically analyzed, and an asphaltene upgrading index was introduced to evaluate the coke-inhibiting ability of the catalysts. Interestingly, the crystal structure of Fe2O3 in the NiO–Fe2O3 catalysts remarkably influenced the catalytic performance. Particularly, the NiO/α-Fe2O3 catalyst with highly crystalline α-Fe2O3 considerably prolonged the coke induction period up to ∼30% of residue conversion and induced a high deasphalted oil yield from asphaltenes. Moreover, NiO/α-Fe2O3 improved the product quality by removing impurities (S, N, and O) and increasing the H/C ratio. However, the liquid product distribution remained dependent on the thermal cracking effect, as the NiO–Fe2O3 catalysts did not participate in C–C cleavage. Deuterium tracing was performed to elucidate the hydrogen-transfer mechanism in catalytic aquathermolysis. The formation of deuterium–carbon single bonds from catalytic aquathermolysis was three times higher than that in the absence of the catalyst, confirming that NiO/α-Fe2O3 facilitated hydrogen transfer from water molecules to hydrocarbons during aquathermolysis.

Sustainable biodiesel production via transesterification of vegetable oils and waste frying oil over reusable magnetic Ca2Fe2O5/CaO@MgFe2O4-Fe2O3 catalyst

ABSTRACT The leaching and reusability problem of the catalyst in the catalytic transesterification for biodiesel production led to the poor sustainability and high posttreatment cost. Herein, a reusable magnetic Ca2Fe2O5/CaO@MgFe2O4-Fe2O3 catalyst with high textural stability and good catalytic activity was prepared in this study, and its catalytic performance toward transesterification of five different oil feedstocks was evaluated. Catalyst preparation conditions were optimized and characterizations including scanning electron microscope (SEM), X-ray diffraction analysis (XRD), and so on, were also conducted to investigate the catalytic behaviors. The results demonstrated that the catalyst has good ferromagnetism for magnetic separation, and the presence of synergistic interaction enhanced catalytic activity with all of > 90% biodiesel yield and improved the reusability with > 75% biodiesel yields at the 10th cycle. In addition, the biodiesel yield reached the maximum under the transesterification reaction parameters were optimized, and at the 15/1 methanol/oil molar ratio, 2.5 wt% catalyst dosage, 70°C for 120 min. Further, for biodiesel from five different oil feedstocks, the same composition, all of > 90% yield and the quality that met the American Society of Testing Materials (ASTM) standards demonstrated the strong oil feedstocks applicability and application potential of catalysts.

High throughput biodiesel production from waste cooking oil over metal oxide binded with Fe2O3

This research investigated the effects of magnetic metal oxide catalysts and operating parameters on the transesterification of waste cooking oil to biodiesel in a continuous reaction setup. Ferric oxide (Fe2O3) was incorporated in alkaline oxide to provide magnetic characteristics, instead of using filters to capture catalysts within the heating zone. Biodiesel production was conducted in a packed glass tubular reactor under ultrasonication in a water bath. The reaction parameters included reaction temperature, amount of catalyst, residence time, and ultrasonic power. Three different catalysts were studied, including calcium oxide on Fe2O3, zinc oxide on Fe2O3, and magnesium oxide on Fe2O3. The results revealed that the biodiesel yield increased with increasing reaction temperature, amount of catalyst, residence time, and ultrasonic power. The optimized biodiesel yield of 94.3% was produced over calcium on Fe2O3 at 65 °C, the methanol-to-oil ratio of 11:1, the residence time of 6.2 min, and the ultrasonic power of 185 W. An increase of reaction temperature to 75 °C resulted in a decline in biodiesel yield to 91.3% due to methanol evaporation at higher temperatures. The catalytic stability was also tested at 60 °C, 6 wt% catalyst, and 185 W ultrasonic power. It was revealed that calcium oxide on Fe2O3 catalyst demonstrated superior catalytic stability with a biodiesel yield decrease of only 10% after 34 days on stream. This suggested the magnetic feature of the catalyst helped prevent leakage of the catalyst from the system. Moreover, the quality of biodiesel met the ASTM D6751 standard for transportation fuel.

Hydrogenation of CO2 to Valuable C2-C5 Hydrocarbons on Mn-Promoted High-Surface-Area Iron Catalysts

Mn-promoted bulk iron catalysts with a high specific surface area (82–211 m2·g−1) were synthesized by coprecipitation followed by drying under supercritical conditions. The catalysts were tested in the CO2 hydrogenation to valuable C2-C5 hydrocarbons. The Mn-promoted iron catalysts exhibited better textural properties than the bare Fe2O3 catalyst, allowing better dispersion of the active phase, easier reduction and carburization of iron oxides and, consequently, resulting in higher catalytic activity than the bare Fe2O3 catalyst. The best activity results were obtained by catalyst promotion with a very low amount of Mn (Mn/Fe atomic ratio of 0.05). Upon steady state conditions (T = 340 °C, total pressure of 20 bar and H2/CO2 = 3), this catalyst exhibited high CO2 conversion (44.2%) and selectivity to C2-C4 hydrocarbons (68%, olefin to paraffin ratio of 0.54), while the selectivity to C5+ hydrocarbons, CH4 and CO was about 3.2, 38.5 and 5%, respectively. A close correlation was found between catalyst textural properties and CO2 conversion. The most active MnFe-0.05 catalyst exhibited high stability during 72 h of reaction related to a low amount of soft coke formation and catalyst activation through the formation of the χ-Fe5C2 phase during the on-stream reaction.

Reaction mechanism of selective catalytic reduction of NO with NH3 on Fe3O4 (1 1 1) surface: Experimental and DFT studies

Iron-based catalysts have vast potential for application prospect in selective catalytic reduction of NOx with NH3 (NH3-SCR). These catalysts offer excellent SCR activity at medium and high temperatures, N2 selectivity and environmental performance. Among these catalysts, Fe3O4 catalyst is highly active and significant in the denitration reaction due to the presence of both ferrous and ferric ions. This study utilized density functional theory (DFT) in combination with experimental measurements to investigate the reaction pathway of NH3-SCR on the Fe3O4(111) surface. The research found that the surface was favorable for the adsorption of NO molecules and followed the NO activation mechanism. Upon activation of NO at the Feoct site, it reacted with NH3 to form NH2NO, This compound then underwent decomposition into N2 and H2O. The presence of O2 on the catalyst facilitated the surface dehydrogenation reaction and completed the SCR cycle reaction. Based on the DFT results, the formation of NH2NO intermediate was the rate-determining step of SCR reaction. The Fe3O4(111) surface followed the L-H mechanism, which was in line with the experimental results. This study provided novel insights into the SCR reaction process and can be useful in developing new iron-based SCR catalysts.

Facet-dependent electrochemical uranium extraction in seawater over Fe3O4 catalysts

Electrochemical uranium extraction from seawater represents an efficient strategy for the sustainable supplement of nuclear fuel, whereas the rational design of highly active electrocatalysts remains challenging due to the lack of study on structure–activity relationship. In this work, we demonstrated that the facet-dependent electrochemical uranium extraction from seawater by comparing Fe3O4 nanooctahedra with exposed {222} facet and Fe3O4 nanocubes with exposed {200} facet. In uranium-spiked electrolyte, the Fe3O4 nanooctahedra possessed extraction efficiency of 93.7 % in 8 h, which was 1.45-time larger than Fe3O4 nanocubes. In 10 L of real seawater, the Fe3O4 nanooctahedra extracted 17.49 μg of uranium within 8 h, corresponding to 3.49 mg/g of extraction capacity. The theoretical model revealed that {222} facet of Fe3O4 possessed a proper atomic distance to form a pocket of four O atoms and two Fe atoms. Such pocket enabled the binding of UO22+ with four O atoms, together with the low valent Fe atoms binding with the original two O atoms of UO22+. This binding model accounted for the more negative adsorption energy for UO22+ on {222} facet than that on {200} facet and the enhanced uranium extraction of Fe3O4 nanooctahedra.

Effet of hematite (Fe2O3) from natural iron ore as a catalyst in MgH2 as hydrogen storage materials

The main obstacle that hinders the application of fuel cell fuels for vehicles today is the hydrogen storage tube. Therefore, this paper will report the results of a study on MgH2-based hydrogen storage materials with Fe2O3 catalyst inserted (5 wt%, 10 wt%, 15wt%) and prepared by mechanical alloying technique for 10 hours. Fe2O3 samples were obtained from the Lhoong Setia Mining site in Jantang Village, Lhoong, Aceh Besar. The initial sample separation process was carried out manually using a bar magnet. Furthermore, hematite extraction was carried out with the addition of 1M HCL and NaOH each. Then the milling process of MgH2-Fe2O3 samples was carried out using a planetary ball mill. The results of the X-ray diffraction test showed that the MgH2 phase was the most dominant/mainstream phase. Thermal testing with DSC showed that the H2 desorption process experienced a decrease in temperature from 194.56 °C with a milling time variation of 7 hours.

Enhanced heterogeneous Fenton degradation of p-nitrophenol by Fe3O4 nanoparticles decorated cellulose aerogel from banana stem

Fe3O4 nanoparticles decorated on cellulose aerogel (CA) from banana stems (Fe3O4@CA) were synthesized for application in the Fenton degradation of p-nitrophenol (PNP). Cellulose aerogel extracted from raw banana stems was synthesized with kymene as a crosslinking agent and freeze-dried method. The Fe3O4@CA samples were characterized by X-ray diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDS), Scanning Electron Microscope (SEM), Transmission Electron Microscopy (TEM), X-ray photoelectron spectroscopy (XPS). The samples with different contents of Fe3O4 on cellulose aerogel were investigated for the degradation yield of PNP in water. The affect of the loaded content of Fe3O4 and H2O2 concentration on the PNP treatment efficiency were also investigated to suggest suitable values including the Fe3O4 catalyst content loaded on CA of 0.40 g/g and the H2O2 concentration of 5.0 g/L. As the results, Fe3O4@CA reached the removal efficiency of 87.92% in 100 mins to obey the pseudo-first kinetic model with a reaction rate constant of 0.0301 min−1. This study’s finding provides a method for creating environmentally friendly catalytic material, which might be used in green chemical engineering.

Rapid removal of methylene blue by a heterogeneous photo-Fenton process using economical and simple-synthesized magnetite–zeolite composite

A hetero-Fenton zeolite-supported Fe3O4 catalyst was synthesized using a simple impregnation–precipitation method. The structure, morphology, and components of the catalyst were characterized using various analytical methods (XRD, SEM, and ICP-MS). Subsequently, the catalyst was used to degrade the azo dye methylene blue (MB), via a heterogeneous photo-Fenton process under UV irradiation in an aqueous solution. This study investigated the influence of different parameters on MB decolorization efficiency, such as the initial concentration of hydrogen peroxide, amount of catalyst, initial dye concentration, and reusability of the catalyst. The removal efficiency was nearly 100% within only 5 min with an initial concentration of methylene blue of 50 mg L−1 under the following experimental conditions: a pH solution of 3, a catalyst of 0.6 g L−1, an H2O2 concentration of 66 mg L−1, and a UV lamp power of 6 W. Moreover, the Fe3O4/zeolite A catalyst (Fe/ZA) showed good stability in the photo-Fenton degradation of methylene blue after four consecutive cycles, implying that the Fe/ZA catalyst could be a potential wastewater treatment option. Furthermore, the findings of the reaction kinetics study demonstrate that the kinetics of the dye removal reaction can be fitted using the Langmuir–Hinshelwood model for heterogeneous catalytic reactions.

Spin‐Enhanced O−H Cleavage in Electrochemical Water Oxidation

AbstractHerein we report the vital role of spin polarization in proton‐transfer‐mediated water oxidation over a magnetized catalyst. During the electrochemical oxygen evolution reaction (OER) over ferrimagnetic Fe3O4, the external magnetic field induced a remarkable increase in the OER current, however, this increment achieved in weakly alkaline pH (pH 9) was almost 20 times that under strongly alkaline conditions (pH 14). The results of the surface modification experiment and H/D kinetic isotope effect investigation confirm that, at weakly alkaline pH, during the nucleophilic attack of FeIV=O by molecular water, the magnetized Fe3O4 catalyst polarizes the spin states of the nucleophilic attacking intermediates. The spin‐enhanced singlet O−H cleavage and triplet O−O bonding occur synergistically, which promotes the O2 generation more significantly than the strongly alkaline case involving only spin‐enhanced O−O bonding.

Spin-Enhanced O-H Cleavage in Electrochemical Water Oxidation.

Herein we report the vital role of spin polarization in proton-transfer-mediated water oxidation over a magnetized catalyst. During the electrochemical oxygen evolution reaction (OER) over ferrimagnetic Fe3O4, the external magnetic field induced a remarkable increase in the OER current, however, this increment achieved in weakly alkaline pH (pH 9) was almost 20 times that under strongly alkaline conditions (pH 14). The results of the surface modification experiment and H/D kinetic isotope effect investigation confirm that, at weakly alkaline pH, during the nucleophilic attack of FeIV=O by molecular water, the magnetized Fe3O4 catalyst polarizes the spin states of the nucleophilic attacking intermediates. The spin-enhanced singlet O-H cleavage and triplet O-O bonding occur synergistically, which promotes the O2 generation more significantly than the strongly alkaline case involving only spin-enhanced O-O bonding.