•Natural serpentine is used as an adsorbent material for MB dye, CR dye, and Cr(VI)ions.•The removal% is optimized versus contact time, dosage, concentration, temperature, and pH value.•Thermal and ...acidic treatment of serpentine enhanced the removal% of the contemplated pollutants.•The maximum removal% of the studied pollutants is reached via 15% HCl and 200 °C thermal treatment.•The best results are got at 3 cm bed thickness, 5 mL/min flow rate, and 25 mg/L initial concentration.
Natural layered magnesium silicate mineral (serpentine) was investigated as an adsorbent material for three common water pollutants (methylene blue dye, Congo red dye, and Cr(VI) metal ions). The adsorption properties of serpentine were explored as a function of contact time, serpentine dosage, initial concentrations and the initial pH value. The kinetic studies uncovered that the equilibrium time for the adsorption of Congo dye, methylene blue dye, and Cr(VI) ions was acquired after 180 min, 240 min, and 480 min, respectively. The uptake process of all the examined pollutants is chemical adsorption and represented by pseudo-second-order kinetic model instead of by Intra-particle diffusion and Elovich kinetic models. The adsorption equilibrium modeling of methylene blue and Cr(VI) was described as a monolayer adsorption and fitted well with Langmuir model rather than with Freundlich or Temkin isotherm models. The adsorption of Congo red dye occurred in a multilayer form and fitted well with Freundlich isotherm than the other studied models. The adsorption of the three pollutants controlled for the most part by the pH value. The basic media is promising for the removal of methylene blue, while the acidic conditions are favored for the adsorption of Congo red dye and Cr(VI) metal ions. The thermodynamic parameters revealed that the adsorption of methylene blue dye is endothermic reaction while the adsorption of Congo red dye and Cr(VI) metal ions is an exothermic reaction. Modifying the serpentine surface through acid and thermal activation improve the removal of the contemplated pollutants to a high degree. Acid leached serpentine utilizing HCl acid of 15%concentration and thermally activated serpentine at 200 °C are the best- modified products for maximum removal of Congo red dye, methylene blue dye, and Cr(VI) metal ions. Fixed bed Colum study gives the best results at bed thickness 3 cm, flow rate 5 mL/min and initial concentration 25 mg/L
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Hydrogen production from water splitting by a photocatalytic process is one way that can be used to solve global problems related to energy depletion and environmental pollution. This work aims to ...design and characterize a novel photocatalyst nanohybrid carbon nanotubes@TiO2 nanoribbons (CNTs@TNRs) for enhanced photoelectrochemical (PEC) water splitting in different electrolytes under visible light irradiance. Here, hydrothermal and chemical vapor deposition (HT-CVD) were combined to grow CNTs @ the nanopits of TNRs producing network of nanohybrid CNTs@TNRs. The structural, morphological, optical, and photocatylatic properties of the TNRs and CNTs@TNRs nanohybrid were characterized by different techniques. The crystallite size is increased from 14.86 nm for TNRs to 21.61 nm for CNTs@TNRs nanohybrid. The CNTs@TNRs nanohybrid has well-resolved nanopits on the surface of the TNRs with an average diameter of 10 nm. The absorption edge of CNTs@TNRs relative to TNRs was strongly shifted to the visible light region. The band gap values are 3.78 and 2.07 eV for TNRs and CNTs@TNRs, respectively. The TNRs and CNTs@TNRs were used for the photocatalytic water splitting under visible light irradiance in Na2S2O3, HCl and KOH electrolytes of different concentrations. The calculated incident photon-to-current conversion efficiency (IPCE) was 97% at 510 nm. These values are higher than those previously reported for different photoelectrodes. The number of hydrogen moles was calculated to be 300 μmol h−1 cm−2. Therefore, our work demonstrates a feasible route for efficient PEC water splitting under sunlight irradiation utilizing the novel CNTs@TNRs photocatalyst.
•A novel photocatalyst nanohybrid carbon nanotubes@TiO2 nanoribbons (CNTs@TNRs) is designed and characterized.•The hydrothermal and chemical vapor deposition (HT-CVD) are combined to grow CNTs @ the nanopits of TNRs.•The band gap values are 3.78 and 2.07 eV for TNRs and CNTs@TNRs, respectively.•TNRs and CNTs@TNRs are used for the photocatalytic water splitting under visible light in different electrolytes.•The conversion efficiency reached 97% at 510 nm with H2 evolution rate up to 300 μmol h−1 cm−2.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•The challenges in single metal atom catalysts (SACs) are highlighted.•COFs with tailored functionality serve as promising substrates for SACs.•Pore space and organic linkers of COFs ...provide a support to SACs.•Catalytic applications of COFs modified SACs are explored.•Foreseeable challenges and perspectives for COFs modified SACs are proposed.
With the motive of bridging the gap between homocatalysis and heterocatalysis, atomically dispersed single metal atom catalysts (SACs) on different supports have rapidly progressed in the field of catalysis. In recent years, covalent organic frameworks (COFs) have been recognized as promising 2D and 3D crystalline polymers for producing SACs, featured with distinct benefits of porous structure, tailored functionality and high metal loading. The superior efficiency of catalytic reactions in COF modified SACs mainly depends upon the single atom catalytic active sites, ultrafine atomic dispersion of metal atoms, and coordination environment provided by COFs skeleton which collectively determines the electronic properties. This review explores the strategic synthesis routes, advanced characterisation, and catalytic applications of COF-based SACs. The versatile potentials provided by COFs for fulling the prerequisites of SACs formation are discussed. A critical discussion on the strategic synthesis of COF-based SACs is proposed, by exploiting the structural merits of COFs. We summarize the strengths of advanced characterization techniques in identifying the successful construction of SACs. A sketch of the reported work is presented for catalytic energy related applications including photocatalysis, electrocatalysis and carboxylation processes. Also, a suggestive overview on the existing challenges, foresighted ideas and future perspectives for COF-based SACs are mentioned.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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Nowadays, increasing extortions regarding environmental problems and energy scarcity have stuck the development and endurance of human society. The issue of inorganic and organic ...pollutants that exist in water from agricultural, domestic, and industrial activities has directed the development of advanced technologies to address the challenges of water scarcity efficiently. To solve this major issue, various scientists and researchers are looking for novel and effective technologies that can efficiently remove pollutants from wastewater. Nanoscale metal oxide materials have been proposed due to their distinctive size, physical and chemical properties along with promising applications. Cupric Oxide (CuO) is one of the most commonly used benchmark photocatalysts in photodegradation owing to the fact that they are cost-effective, non-toxic, and more efficient in absorption across a significant fraction of solar spectrum. In this review, we have summarized synthetic strategies of CuO fabrication, modification methods with applications for water treatment purposes. Moreover, an elaborative discussion on feasible strategies includes; binary and ternary heterojunction formation, Z-scheme based photocatalytic system, incorporation of rare earth/transition metal ions as dopants, and carbonaceous materials serving as a support system. The mechanistic insight inferring photo-induced charge separation and transfer, the functional reactive radical species involved in a photocatalytic reaction, have been successfully featured and examined. Finally, a conclusive remark regarding current studies and unresolved challenges related to CuO are put forth for future perspectives.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•Construction of Ag3VO4/ CNT / Fe doped C3N4 based dual Z-scheme photocatalyst.•Conversion of photocatalyst into photo-Fenton like catalyst via H2O2 coupling.•Hydroxyl radicals ...dominated degradation process.•The complete mineralization of phenol was attainted.•The proposed system exhibited high recyclability and stability.
Rational design strategy with a facile synthetic approach of environmental-friendly photocatalysts is a unique challenge in photocatalytic technology. The precedent work reports the successful synthesis of a Z-scheme Fe doped graphitic carbon nitride coupled Ag3VO4 compounded with carbon nanotubes (FeCN/AV/CNT) photocatalyst through facile precipitation-deposition technique. Characterization analysis including FESEM, XRD, FTIR, XPS and EDS was conducted to clarify the morphology and structure engineering properties of as-synthesized heterostructures (FeCN/AV/CNT). The efficient photocatalytic removal of 2,4 dimethyl phenol was attributed to multi electron transference route comprising of incorporation of Fe dopant in graphitic carbon nitride (g-C3N4), proceeded by coupling with Ag3VO4 (AV) simultaneously under solar light illumination. FeCN/AV/CNT photocatalyst was converted into a heterogeneous system with the addition of H2O2. The augmentation in catalytic activity was corroborated by photo-Fenton Fe3+ ions and H2O2 to generate more hydroxyl radicals. The positive synergistic effect between Fe-CN/AV/CNT Z-scheme approaches promoted enhancement in photodegradation performance by achieving maximum separation and rapid migration of photogenerated charge carriers, prolonged absorption in visible spectrum with augmented light absorption ability. The rate constant for FeCN/AV/CNT activated H2O2 is about 1.37 and 1.63 times high compared to FeCN/AV/CNT and FeCN/AV and exhibited outstanding catalytic efficiency and stability for five consecutive catalytic cycles. The plausible mechanism of FeCN/AV/CNT H2O2 based Z scheme system was also explored.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•Fundamentals and influential factors for photocatalytic CO2 conversion.•Alluring features of polymeric carbon nitride (g-C3N4) for CO2 reduction.•Strategies to enhance photocatalytic ...efficiency of g-C3N4 photocatalyst.•Extended optical response and charge carrier separation in modified g-C3N4.•Future research directions on g-C3N4 assisted CO2 conversion into chemicals.
Inspired from artificial photosynthesis, photocatalytic CO2 conversion driven by visible light seems to be an effectual tactic to convert CO2 into hydrocarbon fuels like CO, CH4, CH3OH and HCOOH. Polymeric graphite like carbon nitride (PCN) is a metal-free and reductive type semiconductor photocatalyst with inherent features involving exceptionally well physicochemical firmness and optoelectronic properties. However, the complexity of photoreduction reactions and certain drawbacks associated with pristine PCN demands strategic modulations for its efficient use as sustainable photocatalytic material. The present review involves the comprehensive exploration of photocatalytic CO2 conversion into useful solar fuels starting from fundamentals and important factors influencing photocatalytic CO2 reduction. The review systematically highlights the useful approaches to modulate the major sequential steps of photocatalysis involving visible light absorption and isolation of photocarriers via doping, incorporation of co-catalyst, defect engineering and heterostructure formation. Finally, the review concluded various perspectives and challenges accompanying PCN based photocatalytic CO2 reduction.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•ZnIn2S4/BiOCl/FeVO4 ternary heterojunction synthesised by facile co-precipitation method.•The ternary heterojunction was meticulously characterised and studied.•Improved light ...absorption, redox capability, and easy magnetic separation.•Decolourised 98 % of 10 ppm solution of RhB in 30 min with excellent photostability.•Dual S-Scheme mechanism of charge transfer.
The dual S-scheme ZnIn2S4/BiOCl/FeVO4 heterojunction was synthesized as it can promote carrier separation while enhancing redox capability. The XRD results indicated the synthesis of pure ZnIn2S4, BiOCl, and FeVO4 and the presence of peaks corresponding to these semiconductors in the ternary nanocomposite. The FTIR and XPS investigations confirmed these findings and revealed a change in structural characteristics because of strong heterogeneous contact at the surface. The improved light absorption in the construction of binary and ternary composite was confirmed by UV–vis spectroscopy. Electrochemical impedance spectroscopy confirmed reduced resistance at the interface and better charge separation. The faster interfacial transport was found, and lower photogenerated charge recombination was found for ternary photocatalysts using the EIS Nyquist plot and the photoluminescence spectrum. The RhB degrading efficiency order was found to be ZnIn2S4/BiOCl/FeVO4 > BiOCl/FeVO4 > FeVO4 > BiOCl > ZnIn2S4. The ternary photocatalyst ZnIn2S4/BiOCl/FeVO4 decolorized RhB almost completely (98 %) in 30 min, and COD studies showed 71.2 % of RhB completely degraded under simulated solar radiations. GC–MS spectra for samples drawn from the reaction over time validated the results. The ternary composite has the highest rate constant value (0. 0.12415 min−1), which is 13.42, 10.70, 11.04, and 5.30 times more than ZnIn2S4, FeVO4, BiOCl, and BiOCl/FeVO4, respectively. Radical scavenging studies confirmed reactive oxidizing species, OH, O2−, and h+, and validated the proposed dual S-scheme charge transfer mechanism. Moreover, ternary photocatalyst can be reused four times with high photocatalytic stability.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this study graphitic carbon nitride (g-C3N4 or GCN) and phosphorus doped graphitic carbon nitride (p-g-C3N4 or PCN) were prepared using facile thermal polycondensation method. Phosphorus doping ...was employed to preserve the non-metallic nature of GCN. The AgCl/PCN/Fe3O4 heterojunction was synthesized using a simple in-situ route. The photocatalytic performance of the GCN, PCN, Fe3O4 and AgCl/PCN/Fe3O4 was tested towards 2, 4-dimethylphenol (DMP) pollutant. The work explored improvement in physiochemical properties and reduction of band gap of GCN after P doping (through Tauc's plot method). Coupling with AgCl (silver halide) also enhanced photoinduced charge carriers' separation and migration ability due to apt band alignment among both AgCl and PCN photocatalysts which resulted in formation of direct Z-scheme charge transfer mechanism. Similarly, the incorporation of ferrimagnetic material i.e. Fe3O4 enhanced the generation of hydroxyl (•OH) radicals via photo-Fenton process and facilitated photocatalysts easy separation from the aqueous medium. Through PL and EIS analysis the enhanced charge separation and migration ability in AgCl/PCN/Fe3O4 nanocomposite was validated. The attained DMP degradation efficiency of photo-Fenton assisted AgCl/PCN/Fe3O4/H2O2 Z-scheme nanocomposite was much higher i.e. 99% compared to other photocatalysts within 60 min of visible light irradiation following pseudo-first-order kinetics. Electron paramagnetic resonance (EPR) and scavenging tests confirmed the substantial role of •OH and •O2− radicals in the photo-Fenton reaction. Furthermore, liquid chromatography-mass spectrometry (LC-MS) analysis detected the generated oxidative products and mineralization pathways associated with DMP degradation. The proposed direct Z-scheme charge transfer route presented efficient charge separation and migration ability in AgCl/PCN/Fe3O4 nanocomposite. Recycle ability of the fabricated AgCl/PCN/Fe3O4 photocatalyst was tested up to 5 cycles with 90% removal efficacy, confirming the excellent reusability and stability of AgCl/PCN/Fe3O4 photocatalyst.
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•Doping of g-C3N4 with phosphorus atom to preserve the non-metallic nature.•99% DMP removal efficacy achieved by AgCl/PCN/Fe3O4/H2O2 nanocomposite.••O2− and •OH radicals are the major reactive species during photo-Fenton reaction.•Excellent recyclability of photocatalyst from solution due to magnetic property.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•Fabrication of Ag3PO4/CdS/Fe doped C3N4 based dual Z-scheme photocatalyst.•Conversion of photocatalyst into photo-Fenton catalyst via H2O2 coupling.•Enhanced production of hydroxyl ...radicals during degradation process.•The complete mineralization of phenol was attainted.•The proposed system exhibited negligible iron leaching and high recyclability.
In this work, a dual Z-scheme Ag3PO4/CdS/Fe-g-C3N4 (AP/CdS/FeCN) photocatalyst was prepared by precipitation- deposition method. AP/CdS/FeCN photocatalyst was converted into the heterogenous photo-Fenton system with the addition of H2O2. The synergistic coupling between AP/CdS/FeCN and H2O2 resulted in enhanced for phenol degradation, with a rate constant of constant 6.2×10−4s-1, which is 1.31 and 1.61 times than that of AP/CdS/FeCN and Fe2O3/H2O2. The enhancement in photodegradation was attributed to (i) more regeneration of Fe2+ ions, (ii) enhanced visible light absorption, (iii) elevated redox potential due to more hydroxyl radical’s formation, and (iv) low Fe leaching in the reaction solution. As indicated by EIS, PL, and trapping experiments, photoinduced CB electrons of g-C3N4 and CdS were transferred entirely to Fe3+ to regenerate Fe2+ ions to accelerate the Fenton cycle. In comparison to the conventional Fe2O3/H2O2 Fenton process, Fe ion leaching in AP/CdS/FeCN/H2O2 catalytic system was almost negligible. It confirmed strong chemical interaction of Fe3+ with g-C3N4. AP/CdS/FeCN/H2O2 displayed significant catalytic efficacy and firmness for five successive catalytic cycles. Moreover, the AP/CdS/FeCN/H2O2 nanocomposite exhibited substantial mineralization perfomance for other phenolic pollutants. The results demonstrate that AP/CdS/FeCN/H2O2 catalytic system has the potential for water purification.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Despite metal oxides offer excellent characteristics in the field of photocatalysis, they often suffer from charge carrier recombination as well as limited visible response, which indeed reduce the ...charge kinetics process and ultimately reduce the photocatalytic output. Defect engineering is a sophisticated technique to manufacture defects and alter the geometric structure and chemical environment of the host. The present study provides an all-inclusive outline of recent developments on the classification of metal oxide defects based on the dimensions of a host crystal lattice. Precisely, surface modification of metal oxides through 0D (point), 1D (line), 2D (planar), and 3D (volume) defects with their subsequent mechanism and impact on photocatalytic performance are presented. By wisely amending the morphology (cores along with the shells) and electronic structure of metal oxide photocatalysts (TiO2, ZnO, Bi2O3, Fe2O4 etc.) through different attuned and veritable approaches, their photocatalytic activity can be substantially improved. Optimal studies on defect engineering not only expose the altered physicochemical features but also modulate the electron-hole pair dynamics, stability, and active radical production for various photoredox reactions. Altered atomic, as well as electronic configuration, facilitated a photocatalyst material to have different optical features, adsorption properties along with improved carrier transfer as well as isolation rate. Thus, the systematic exploration of photocatalytic rudiments of defect rich metal oxide for various applications such as H2 evolution, CO2 reduction, pollutant degradation, and bacterial disinfection could bring significant research advancement in this field.
Representation of different dimensionality driven defects in MOs photocatalysts along with strategic modification in photocatalytic activity. Display omitted
•Distinctive surface step defects heighten the photoactivity of porous metal oxides.•Diverse strategies for controlled vacancies, metal defects in metal oxides nanostructure are highlighted.•Spectroscopic techniques were used to reveal the role of dislocations, boundaries, and voids on performance of metal oxides.•Dimensionality driven defects in metal oxide catalysts is explored with systematic modifications in lattice compositions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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