Heterogeneous Oxidation Research Articles

Oxygen activation-boosted manganese oxide with unique interface for chlorobenzene oxidation: Unveiling the roles and dynamic variation of active oxygen species in heterogeneous catalytic oxidation process

In-depth study of active oxygen species (AOS) is essential to heterogeneous catalytic oxidation techniques. Herein, a facile strategy of constructing dual-phase MnOx with unique Mn2O3Mn3O4 interface is reported for chlorobenzene (CB) catalytic oxidation. The interface induces lattice distortion and generates oxygen vacancies, promoting the formation and mobility of surface adsorbed oxygen (Oads) and surface lattice oxygen (Olatt), while the surface acidity and CB adsorption capacity are also enhanced. Thereby, MnOx catalyst exhibits superior activity and lower activation energy (41.7 kJ/mol), with the CB total degradation temperature decreasing by ca. 40 °C. Noteworthily, the dynamic variation of AOS in CB oxidation is unveiled by in situ techniques combined with isotope labelling, where Oads and Olatt are determined to function as AOS at low and high temperatures (over 300 °C), respectively. Furthermore, the reaction pathway and the rate-determining step (cleavage of aromatic ring) are revealed by systematic mechanism study.

Efficient activation of persulfate by Ti3C2 MXene QDs modified ZnFe2O4 for the rapid degradation of tetracycline

Mxene-based catalysts with specific interfacial characteristics are beneficial for photocatalytic applications. Herein, Ti3C2 MXene modified ZnFe2O4 nanocomposite materials were prepared for photocatalysis. The morphology and structure of the nanocmposites were characterized by scanning electron microscopy (SEM), High-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), which revealed that Ti3C2 MXene as quantum dots (QDs) was uniformly distributed on the ZnFe2O4 surface. The Ti3C2 QDs modified ZnFe2O4 catalyst (ZnFe2O4/MXene-15%) under visible light achieved 87% degradation efficiency of tetracycline within 60 min when coupled with persulfate (PS) system. The initial solution pH, PS dosage and co-existing ions were found to be the main factors affecting the heterogeneous oxidation process, while quenching experiments showed that O2•- is the main oxidizing species in the removal of tetracycline in ZnFe2O4/MXene-PS system. In addition, the cyclic experiments suggested that ZnFe2O4/MXene had good stability and thus it may have practical applications in industry.

Biostarch-assisted synthesis of microscopic heterogeneous manganese-cobalt oxides for efficient catalytic combustion of toluene

A nanoparticles-stacking MnCox oxide with multifarious active phases was successfully synthesized by a starch-paste assisted method, which achieved complete combustion of 1,000 ppm toluene at 226 °C. The characterization results showed that by using this method, it resulted in not only the construction of the porous structure but also successful enrichment of active species such as trivalent manganese, trivalent cobalt and electrophilic oxygen species, thanks to the intensive interaction of Mn and Co species with the assistance of starch-paste. The special metal dispersibility and valence adjustment functions of starch contributed to the production of multifarious active phases with amazing reducibility as well as oxygen mobility at lower temperature. In situ DRIFTS experiments and DFT calculation results showed that the synergistic complementary regions provided vibrant lattice oxygen and the reproducible electrophilic oxygen species for toluene combustion, guaranteeing the continuous and efficient catalytic performance. This study provides a new viewpoint and idea for creating of novel catalysts with multiple active regions.

Se and P dual doped carbon for highly selective oxidation of benzyl alcohol

Metal-free heterogeneous oxidation of alcohols to corresponding aldehydes is a typical green selective oxidation reaction. Rational designing of the metal-free catalyst is highly desired. In the present work, P and Se dual doped carbon catalyst was prepared to achieve a high catalytic efficiency for the selective oxidation of benzyl alcohols to benzaldehyde. The doped P and Se exhibited a synergistic effect for enhancing the titled catalytic performance. The doped P can donate electrons to the adjacent atoms while the doped Se can accept electrons from the adjacent atoms. These interactions accelerated the electron transfer on the carbon surface and consequently enhanced the catalytic activity. Kinetic study revealed that the selectivity was kinetically improved by the doped heteroatoms. The oxidation mechanism investigation indicated that both radical and nonradical routes were involved in the titled reaction. In addition, the dual doped carbon catalyst also showed a good catalytic performance for the various benzyl alcohol derivatives. These finding suggest that the dual doped atoms are promising strategy to improve the catalytic activity and selectivity of the carbon-based metal-free catalysts for the aerobic selective oxidation reactions.

Improvement mechanism of Ru species on Hg0 oxidation reactivity over V2O5/TiO2 Catalyst: A density functional theory study

With the increasing demand for Hg0 removal, the heterogeneous catalytic oxidation using modified V/Ti catalysts has attracted more attention, among which the VRu/Ti doped with RuO2 has higher activity and Cl2 yield than V/Ti. In this work, the surface performance, adsorption properties and Hg0 oxidation pathways of V/Ti and VRu/Ti catalysts were studied in DFT method and explain in mechanism level. The doping of Ru species in low oxidized state causes the oxygen vacancies and the further electronic structure change, which strengthens the nucleophilicity while weakening the electrophilicity. Therefore, the dissociation of HCl on VRu/Ti changed more active. In addition, the mixed reaction pathway on VRu/Ti shows a lower energy barrier than that on V/Ti catalyst, indicating that Ru species improves the oxidation activity through the special Semi-Deacon reaction, which is rarely reported in other research. The conclusions of this paper provide important support for the future modification research.

Adsorption-enhanced catalytic oxidation for long-lasting dynamic degradation of organic dyes by porous manganese-based biopolymeric catalyst

Improving the adsorption kinetics of metal-oxide catalysts is critical for the enhancement of catalytic performance in heterogeneous catalytic oxidation reactions. Herein, based on the biopolymer pomelo peels (PP) and metal-oxide catalyst manganese oxide (MnOx), an adsorption-enhanced catalyst (MnOx-PP) was constructed for catalytic organic dyes oxidative-degradation. MnOx-PP shows excellent methylene blue (MB) and total carbon content (TOC) removal efficiency of 99.5 % and 66.31 % respectively, and keeps the long-lasting stable dynamic degradation efficiency during 72 h based on the self-built continuous single-pass MB purification device. The chemical structure similarity and negative-charge polarity sites of the biopolymer PP improve the adsorption kinetics of organic macromolecule MB, and construct the adsorption-enhanced catalytic oxidation microenvironment. Meanwhile, the adsorption-enhanced catalyst MnOx-PP obtains lower ionization potential and O2 adsorption energy to promote the continuous generation of active substance (O2*, OH*) for the further catalytic oxidation of adsorbed MB molecules. This work explored the adsorption-enhanced catalytic oxidation mechanism for the degradation of organic pollutants, and provided a feasible technical idea for designing adsorption-enhanced catalysts for the long-lasting efficient removal of organic dyes.

Heterogeneous catalytic oxidation regeneration of desulfurization-rich liquor with Fe3+ modified chitosan

To solve the problem of pipeline blockage caused by sulfur deposition in industrial gas wet oxidative desulfurization operations, this study developed an iron-modified chitosan catalyst for the catalytic oxidation regeneration of conventional wet oxidative desulfurization-rich liquids. Detailed characterization results show that Fe3+ species are successfully coordinated with the chitosan substrate. The results of desulfurization and regeneration experiments showed that the Fe3+-modified chitosan could effectively regenerate the desulfurization waste stream and remain stable in the acidic desulfurization stream. The powdered iron-based modified chitosan catalyst prepared with a mass ratio of chitosan to FeCl3 of 1:5 and glutaraldehyde of 12.5% by mass has better catalytic performance than the microbead counterpart. The regeneration performance of the catalyst was evaluated by the desulfurization performance of the regenerated desulfurization solution. The iron-based modified chitosan shows a good regeneration performance, and the loss of Fe content is less than 1.5% after five runs. This study provides an efficient way to develop cost-effective catalysts for the regeneration of wet oxidative desulfurization-rich liquids.

Hydroxyl radical induced Cr flocculation via redox reaction: The extending application of heterogeneous advanced oxidation processes on Cr removal

Flocculation is a traditional and effective method to remove Cr from wastewater, but the addition of flocculants inevitably leads to secondary pollution. In this study, Cr flocculation was induced using hydroxyl radical (•OH) (•OH flocculation) generated in an electro-Fenton-like system, achieving total Cr removal of 98.68% at initial pH = 8 within 40 min. The obtained Cr flocs showed significantly higher Cr content, lower sludge yield, and good settling properties compared to alkali precipitation and polyaluminum chloride flocculation. •OH flocculation behaved like a typical flocculant, introducing electrostatic neutralization and bridging. The mechanism proposed that •OH could overcome the steric hindrance of Cr(H2O)63+ and combine with it as an additional ligand. Then Cr(III) was proved to undergo multi-step oxidation to form Cr(IV) and Cr(V). After these oxidation reactions, •OH flocculation took precedence over Cr(VI) generation. As a result, Cr(VI) didn’t accumulate in solution until •OH flocculation was completed. This work provided a clean and eco-friendly strategy for Cr flocculation instead of flocculants and extended the application of advanced oxidation processes (AOPs), which is expected to enrich existing strategies of AOPs towards Cr removal.

The combined effects of heterogeneous chemistry and aerosol-radiation interaction on severe haze simulation by atmospheric chemistry model in Middle-Eastern China

Heterogeneous chemistry and aerosol-radiation interaction (ARI) are considered two of the key mechanisms affecting haze formation and their reasonable parameterizations in atmospherically chemical models play an important role in accurate haze or air quality prediction. However, until the present, their relative contributions to severe haze have rarely been evaluated. Using the double-way atmospherically chemical model GRAPES_Meso5.1/CUACE CW, the relative contributions of heterogeneous chemistry and ARI to PM2.5 are investigated under different pollution levels in Middle-Eastern China (MEC) during December 2016. Study results show that the combined effects of heterogeneous chemistry and ARI generate 29.7% of total PM2.5 mass in MEC of December 2016, of which ARI contributes 19.7%, much higher than heterogeneous chemistry (6.1%). However, heterogeneous chemistry is important for reasonable reproduction of the proportion of secondary inorganic aerosols (SIA) of PM2.5, especially during heavy haze. Both the contributions of heterogeneous chemistry and ARI to PM2.5 increase with the haze pollution aggravation but to different degrees. The contribution of heterogeneous chemistry to modeled PM2.5 concentration rises from 4.0% on clean days to 6.6% under moderate pollution and 7.8% under heavy haze. And that of ARI increases rapidly from 9.1% on clean days to 21.0% under moderate pollution and 29.1% during heavy pollution. It is worth noticing that there is an additional contribution to PM2.5 caused by the combination of heterogeneous chemistry and ARI except for their respective contributions, which reaches up to 7.3% of PM2.5 mass and 18.5% of SIA generation under heavily polluted conditions. This is because ARI further promotes heterogeneous oxidation of SO2 and NOx by increasing the aerosol surface area concentration (SAC), causing additional SIA production via heterogeneous pathways. This work indicates the contribution of ARI to severe haze formation not only by altering meteorological conditions but also by reforming the chemical processes in the model.

Porous graphitized carbon-supported FeOCl as a bifunctional adsorbent-catalyst for the wet peroxide oxidation of chlorinated volatile organic compounds: Effect of mesopores and mechanistic study

Wet scrubbing coupled with adsorption-enhanced heterogeneous advanced oxidation processes (AOPs) are promising approaches to the treatment of chlorinated volatile organic compounds (CVOCs). However, microporous activated carbon-based adsorbents and catalyst supports have the disadvantage of difficult molecule diffusion. Herein, we have demonstrated that porous graphitized carbon (PGC) allowed faster intra-particle diffusion of organic molecules due to its well-developed mesoporous structure. Therefore, a wet scrubbing system containing H2O2 and a PGC-supported FeOCl catalyst has been developed to effectively remove gaseous dichloroethane, trichloroethylene, dichloromethane and chlorobenzene. The scrubber performed well at pH 3.0 using a FeOCl/PGC dosage of 0.2 g/L and initial H2O2 concentration of 40 mM. Its good long-term performance was achieved by replenishing H2O2 to maintain a suitable concentration. The degradation pathways of dichloroethane have been proposed using a combination of intermediate analysis and density functional theory calculations. PGC-supported catalysts may be desirable bifunctional adsorbent-catalyst materials for wet scrubbing of CVOCs.

Performance and mechanisms of iron/copper-doped zirconium-based catalyst containing hydroxyl radicals for enhanced removal of gaseous benzene.

In the present study, novel copper-doped zirconium-based MOF (UIO-66) and copper-doped iron-based UIO-66 catalysts were prepared by hydrothermal synthesis method to improve the removal performance of gaseous benzene. The characteristics of the catalysts were analyzed by means of XRD, SEM, XPS, BET, and EPR. The copper loading catalyst had high crystallinity and irregular globular. The three kinds of catalysts with different Cu/Fe ratios had regular cubic shape. Compared with the catalyst supported with single copper, the bimetal Cu/Fe modification had a certain adjustment effect on the morphology, which specifically reflected in the uniform size and shape of catalyst particles with better dispersibility. The factors of different metal loading, dose of H2O2, and reaction temperature on benzene removal have been studied. It has been observed that in heterogeneous advanced oxidation removal of benzene, 3-Cu@UIO-66 and Cu1.5/Fe1.5@UIO-66 achieved the highest benzene removal efficiency of 81.2% and 94.6%, respectively. EPR results showed that the increase of Cu loading and different Cu/Fe ratios promoted the yield of hydroxyl radicals, thus promoted the benzene removal efficiency. The efficiency of heterogeneous oxidation removal of benzene first increased and then decreased with the increase of temperature due to H2O2 instability. DFT calculations exhibited that the Feoct-Cu-O site was a more effective activation site than the single Feoct-O site. Dissociative adsorption occurred with the O-O bond of H2O2 cracked, and the formed hydroxyls parallel adsorbed on the benzene surface. The combination of benzene and hydroxyls was strong chemisorption with the torsion angle of benzene ring obviously turned. The work was of great importance for identifying the roles of the novel catalyst for the removal of benzene pollutant from waste gases.

Insight into the Mechanism and Kinetics of the Heterogeneous Reaction between SO2 and NO2 on Diesel Black Carbon under Light Irradiation.

The heterogeneous oxidation of SO2 by NO2 has been extensively proposed as an important pathway of sulfate production during haze events in China. However, the kinetics and mechanism of oxidation of SO2 by NO2 on the surface of complex particles remain poorly understood. Here, we systematically explore the mechanism and kinetics of the reaction between SO2 and NO2 on diesel black carbon (DBC) under light irradiation. The experimental results prove that DBC photochemistry can not only significantly promote the heterogeneous reduction of NO2 to produce HONO via transferring photoinduced electrons but also indirectly promote OH radical formation. These reduction products of NO2 as well as NO2 itself greatly promote the heterogeneous oxidation of SO2 on DBC. NO2 oxidation, HONO oxidation, and the surface photo-oxidation process are proven to be three major surface oxidation pathways of SO2. The kinetics results indicate that the surface photooxidation pathway accounts for the majority of the total SO2 uptake (∼63%), followed by the HONO oxidation pathway (∼27%) and direct oxidation by NO2 (∼10%). This work highlights the significant synergistic roles of DBC, NO2, and light irradiation in enhancing the atmospheric oxidation capacity and promoting the heterogeneous formation of sulfate.

Temperature of photoanode for photoelectrochemical water oxidation

Solar-light-driven photoelectrochemical that can utilise water for high-performance artificial photosynthesis for low-cost green hydrogen fuel production. However, the interaction of photoanode with water is crucial to its heterogeneous water oxidation for sustainable fuel production for the replacement of fossil fuels. Here, we report experiment investigations of photoelectrode with temperature for solar energy conversion. These measurements revealed that a rise in temperature affects the catalytic generation of hydrogen in three routes, viz., minimising the required energy for water splitting, reducing bandgap energy and mitigating the resistance at the interface.

The aomogeneous and heterogeneous oxidation of organophosphate esters (OPEs) in the atmosphere: Take diphenyl phosphate (DPhP) as an example

Organophosphate esters (OPEs) are widely detected in the atmosphere. However, the atmospheric oxidative degradation mechanism of OPEs has not been closely examined. This work took density functional theory (DFT) to investigate the tropospheric ozonolysis of organophosphates, represented by diphenyl phosphate (DPhP), including adsorption mechanisms on the surface of titanium dioxide (TiO2) mineral aerosols and oxidation reaction of hydroxyl groups (·OH) after photolysis. Besides, the reaction mechanism, reaction kinetics, adsorption mechanism, and ecotoxicity evaluation of the transformation products were also studied. At 298 K, the total reaction rate constants kO3, kOH, kTiO2-O3, and kTiO2-OH are 5.72 × 10−15 cm3 molecule−1 s−1, 1.68 × 10−13 cm3 molecule−1 s−1, 1.91 × 10−23 cm3 molecule−1 s−1, and 2.30 × 10−10 cm3 molecule−1 s−1. The atmospheric lifetime of DPhP ozonolysis in the near-surface troposphere is 4 min, much lower than that of hydroxyl radicals (·OH). Besides, the lower the altitude is, the stronger the oxidation is. The TiO2 clusters carry DPhP promoting ·OH oxidation but inhibiting ozonolysis of DPhP. Finally, the main transformation products of this process are glyoxal, malealdehyde, aromatic aldehydes, etc., which are still ecotoxic. The findings shed new light on the atmospheric governance of OPEs.

Cytotoxicity and performance of Pectin/ Ferric vanadate oxide/ Cetyltrimethylammonium Bromide foaming nano-system for drilling sustainable geothermal wells

The geothermal energy industry is exploring environmental friendly alternatives for the current foaming systems used in geothermal well drilling. In this study, Pectin/ Ferric vanadate/ Cetyltrimethylammonium Bromide nanocomposites (P-FV-C) were fabricated through two stages. The structure analysis and thermal stability of the nanomaterials in both stages were confirmed by Fourier Transfer Infra-Red (FT-IR), Dynamic Light Scattering (DLS), Scanning Electron Microscope (SEM), and Differential Scanning Calorimetry (DSC).The main objective is to decrease the cytotoxicity of CTAB without losing its foaming properties by incorporating the pectin heterogeneous vanadate oxide nanocomposite (P-FV) into the CTAB foaming system structure. The best results, in terms of foaming properties and cell viability, were exhibited for P-FV-C5 when the weight ratio of P-FV to CTAB was 1:1. The cytotoxicity results revealed that the cell viability increased from 4.47 to 79.58% for 1 µg/ml of pure CTAB and P-FV-C5 respectively. The temperature and period of aging didn't obviously affect the foaming properties (foam volume and drainage half time) for the P-FV-C nanocomposites unlike the pure CTAB, of which foaming properties were drastically decreased. For CTAB (1.0 wt.%), the foam volume decreased from 700 to 300 ml and the drainage half time decreased from 30 to 16 min when the temperature increased from 150 to 200 °C after dynamic aging for 16 h. At the same previous conditions and concentration, P-FV-C5 showed stable foaming properties (foam volume = 700 ml and drainage half time= 45 min). The foam volume was decreased from 761 to 695 ml and drainage half time was stable by increasing the aging period from 8 to 24 h at 200 °C for P-FV-C5 (1.0 wt.%) while the foam volume decreased from 789 to 253 ml and the drainage half time decreased from 30 to 14 min for pure CTAB at the same conditions and concentration. Also, the drainage half time was decreased from 40 to 15 min by increasing the calcium chloride content from 1 to 5 wt.% while it was stable for P-FV-C5 nanocomposite. These results were explained based on the surface and rheological properties of the nanocomposites. The above findings indicate that the P-FV-C5 nanocomposite could attain environmental and operational success while drilling high temperature and salinity geothermal wells.

In-situ regeneration of a novel Fe3O4/GAC adsorbent for micropollutants removal in a continuous fixed-bed

Adsorption onto activated carbon is one of the most feasible techniques for micropollutants removal from water. Nevertheless, the sustainability and economy of this process is strongly limited by the difficult regeneration of the saturated adsorbents, which, in practice, are commonly disposed. This work aims to tackle this challenge by the development of a granular activated carbon (GAC) decorated with magnetite nanoparticles (Fe3O4/GAC), that allows the in-situ regeneration of the saturated solid by H2O2 addition (through heterogeneous Fenton oxidation). Its performance was tested in a fixed-bed column in continuous operation using the pharmaceutical diclofenac (DCF) as target pollutant. The adsorbent was synthesized by the incorporation of 5% wt. iron to commercial granular activated carbon (GAC) by incipient wetness impregnation, followed by calcination and reduction. The immobilization of magnetite nanoparticles did not significantly alter neither the specific surface area (∼1000 m2 g−1) nor the main properties of the solid, which was fully characterized. Accordingly, its adsorption capacity remained practically unchanged (∼400 mg g−1). Remarkably, the addition of H2O2 allowed to restore the adsorption capacity of the adsorbent at 25 ºC using a H2O2 dose of 3 - 6 g L−1 during 20 h. In-situ regeneration was demonstrated in three consecutive adsorption-regeneration runs for the treatment of 100 mg L−1 DCF, obtaining similar breakthrough curves. Notably, iron leaching was practically negligible during operation and was below 2% wt. of the solid along the regeneration treatment. As a proof of concept, the feasibility of the system was finally proved in the treatment of a representative concentration of DCF (500 µg L−1). The adsorbent led to the complete removal of the pollutant along 10 days and was effectively regenerated after saturation in just 3 h.

Size- and temperature-dependent oxidative pyrolysis and auto-ignition of spherical beech and spruce wood

Abstract Opposed to piloted ignition, where a substance is ignited by an external flame or spark, the term auto-ignition describes the onset of combustion by spontaneous ignition without an external source. In this study, the influence of the size of spherical wood samples and the temperature surrounding the samples was investigated by performing ignition experiments in a muffle furnace with beech and spruce wood. On a specially constructed rig, spheres with four different diameters (8 mm, 12 mm, 18 mm, and 25 mm) were put into a preheated furnace at five isothermal temperatures (240 °C, 270 °C, 300 °C, 330 °C, and 360 °C). For every temperature, diameter, and wood species, the experiments were repeated eight times, and positions of the spheres on the rig were changed for every measurement. Temperatures inside the samples were recorded with thermocouples (TC) positioned in holes drilled to the middle of the spheres. With rising size and temperature, samples were more prone to auto-ignition in a glowing mode, due to a larger, highly reactive pyrolyzed surface and internal overheating. During heating and oxidative pyrolysis, isothermal phases were present at approximately 360 °C in the recorded temperature curves. The comparison to simultaneous thermal analysis (STA) measurements shows decomposition of hemicelluloses, and cellulose is highest around 360 °C. It is concluded that pyrolysis and disintegration of the main wood constituents use up all arising energy. Due to differences in the composition of the wood polymers, beech wood samples already ignite at lower temperatures compared to spruce wood samples with the same diameter. It can be concluded that the size is a critical factor for auto-ignition at the used temperatures. Larger samples will produce more volatile compounds during pyrolysis and have a larger pyrolyzed, porous surface area where heterogenous oxidation reactions can happen. The influence of the size is already critical at differences on the millimetre scale.

Color as a tool for quantitative analysis of heterogeneous polymer degradation

Despite the fact that polymers are widely used in both our homes and industrial applications, critical insights into their degradation mechanisms when exposed to harsh environmental conditions, such as elevated temperature or radiation, are lacking quantifiable metrics. In oxygenated environments, polymer degradation is dominated by thermal-oxidation or photo-oxidation and in many cases occurs in a heterogeneous fashion throughout the thickness. While the heterogeneous oxidation of polymers is a common phenomenon, the effect on the functional lifetime of polymers is not well understood. Methods to evaluate such oxidation phenomena are time consuming and a challenge to implement. Here we show a novel approach for a quantitative evaluation of heterogeneous oxidation in polymers, using a fast and accurate color measurement technique. The proposed color analysis approach was observed to improve the efficiency of obtaining heterogenous oxidation profiles in half the time of common approaches, such as indention or Fourier transform infrared spectroscopy. Furthermore, the method was verified by mapping oxygen concentration through sample thickness using energy dispersive X-ray spectroscopy. The utility of the proposed method is demonstrated through the generation of an oxidation framework, aimed at an intelligent design of experiments for polymer lifetime prediction. We anticipate this work to be a starting point for further evaluation of heterogeneous oxidation in polymers using optical properties.

MoS2 Nanostructures for Solar Hydrogen Generation via Membraneless Electrochemical Water Splitting

Storing and delivering green hydrogen generated by solar energy have the potential to significantly supplement and disburse the share of promising but intermittent renewable energy. In this scenario, robust materials capable of delivering solar-driven electrochemical water splitting for hydrogen generation provide an interesting protocol that is applicable to all sectors of energy. Electrochemical water splitting is the conventional and most prevalent technique for hydrogen generation, which utilizes platinum-based materials for the hydrogen evolution reaction (HER). However, these platinum-based noble metal catalysts possess poor cyclic stability, limiting their commercial application for economical hydrogen generation. Therefore, the development of efficient non-noble metal-based electrocatalysts is urgently needed to produce cost-competitive hydrogen energy. Several kinds of non-noble metal-based heterogeneous electrocatalysts, including carbides, sulfides, selenides, oxides, and phosphides, have been developed and studied. The unique physicochemical properties of carbonaceous materials make them promising candidates to support catalysts. In this paper, molybdenum disulfide (MoS2) nanomaterial catalysts have been synthesized, deposited on carbon fiber (CF)-based materials, and then used for solar hydrogen generation by membraneless electrochemical water splitting. At 430 W/m2 irradiation and 35 °C working temperature, the solar-to-hydrogen conversion efficiency is found to be 2.46%.

Mesoporous carbon framework supported Fe-Cu-Mn oxides as an efficient peroxymonosulfate catalyst for the control of harmful algal blooms: Synergism of Fe-Cu-Mn and role of mesoporous carbon

Few studies have focused on the advanced oxidation processes (AOPs) based on heterogeneous catalysis to control harmful algal blooms (HABs). Herein, a mesoporous carbon framework supported Fe-Cu-Mn oxides (MnFe2O4/CuO; FCMT) was synthesized via calcination of cost-effective metal-polyphenol coordination polymers for peroxymonosulfate (PMS) activation to eliminating Microcystis aeruginosa and algal organic matters (AOMs). >99% of algae were removed at low FCMT and PMS dosages in the FCMT/PMS within 120 min. The FCMT/PMS system removed algae effectively over extensive pH (3.0–9.0) and algal density (OD680 = 0.05–0.4) ranges. Although FCMT/PMS-induced oxidative stress damaged cell membranes, over 50% of the dissolved organic carbon and 54% of microcystins were eliminated, avoiding serious secondary pollution caused by cell lysis. Algal removal by the FCMT/PMS system involved pathways associated with both free radicals and non-free radicals, with the dominant reactive oxygen species being O2− and 1O2. Synergy between Fe, Mn, and Cu promoted the elimination of algae and AOMs. Mn found to be the primary active site on the FCMT surface, while Fe(III) was cooperated with Mn by acting as the main adsorption site. The mesoporous carbon allowed uniform spatial distribution of the nanosized Fe-Cu-Mn oxides as well as modulating the direction of reactive oxygen species generation by the metals. In conclusion, the proposed heterogeneous advanced oxidation process using the FCMT/PMS system is highly potential in the control of HABs.