Reusable Catalyst Research Articles

Synthesis of CeO2/SO4/Ni nanoparticle with a greener perspective for the selective oxidation of propylene glycol in continuous reactor

The selective oxidation of 2,3-propanediol was performed with acidic nickel supported sulphated ceria catalyst. The ceria nanoparticles were synthesized through greener techniques by utilizing environmental resources. In this work, Coleus Amboinicus leaf extract was used to prepare ecofriendly non-hazardous ceria nanoparticles through sol gel methods. Adopting the nano and green chemistry techniques, cerium oxide nanoparticles are obtained which were further sulphated to increase the acidity of the catalyst. The synthesis was carried out by impregnating the nickel in sulphated ceria nanoparticles. Nickel ceria catalyst in O2 atmosphere enhances the selectivity of the value-based hydroxy acetone. The structure and properties of this catalyst were analyzed through X-Ray diffraction, FTIR spectroscopy, Brunauer-Emmett-Teller surface area analysis, Scanning electron microscopy, Transmission electron microscopy andNH3-Temperature-Programmed Desorption Analysis. The oxidative potential of the catalyst was investigated under different reaction parameters to obtain (hydroxy acetone) HA. Nickel Cerium oxide nanoparticles in O2 atmosphere at 90 °C show the highest selectivity towards the oxidation of (propylene glycol) PG. Tert‑butyl hydro peroxide was used as both solvent and an oxidant. Amongst the variants, CeO2/SO4/Ni (6%) delivered the highest selectivity and conversion. This study provides an economical, ecofriendly, thermally stable, reusable and active catalyst for obtaining hydroxy acetone.

Three-dimensional rGO/CNT/g-C3N4 macro discs as an efficient peroxymonosulfate activator for catalytic degradation of sulfamethoxazole

Over the past few years, advanced oxidation processes (AOPs) have shown promising efficiencies for wastewater remediation. Carbocatalysis, in particular, has been exploited widely thanks to its sustainable and economical properties but has an issue of recovery and reusability of the catalysts. To address this, three-dimensional (3D) binary and ternary graphene-based composites in the form of macro discs were created to activate peroxymonosulfate (PMS) for catalytic oxidation of sulfamethoxazole (SMX). Graphene oxide served as the base, while graphitic carbon nitride (g-C3N4) and/or single-walled carbon nanotubes (SWCNTs) were added. Among the various discs synthesized, rGNTCN discs (ternary composite) were proven to be the most efficient by completely degrading SMX in 60 min owing to their large surface area and nitrogen loading. The catalytic system was further optimized by varying the reaction parameters, and selective radical quenching and electron paramagnetic resonance tests were performed to identify the active radical, revealing the synergistic role of both radical and non-radical pathways. This led to the development of possible SMX degradation pathways. This research not only provides insights into ternary carbocatalysis but also gives a novel breakthrough in catalyst recovery and reusability by transforming nanocatalysts into macro catalysts.

Hydroxyapatite nanoparticles decorated with metal–organic framework, Co‐Cu/ZIF@HAp, and evaluation of photocatalytic performance of the prepared nanocomposite in the degradation of organic pollutants

In this study, a novel hydroxyapatite (HAp)‐based composite, Co‐Cu/ZIF@HAp, was constructed through in situ growth and simultaneous sonication followed by magnetic string. Herein, the HAp‐based nanocomposite was obtained in which HAp was coated with cobalt–copper bimetallic zeolitic imidazolate framework (ZIF) in one‐pot synthesis method. The as‐synthesized composite was characterized by PXRD, FTIR, FE‐SEM, EDS, HR‐TEM, TGA‐DTG, XPS, BET, and UV‐DRS techniques, which suggested that HAp was well coated with bimetallic ZIF. The prepared composite was utilized as a catalyst in degradation of organic pollutants. Removal of organic pollutants such as organic dyes has become indispensable due to their higher stability, toxicity, and mutagenic nature. Two commonly found organic dyes, namely, Eosin Yellow (EY) and Brilliant Green (BG), were chosen for the investigation of photocatalytic activity of the as‐prepared catalyst. The degradation process was carried out under solar radiation, and there was no utilization of any oxidizing and reducing agent. Several parameters such as amount of catalyst dose, initial concentration of the dye solution, and effect of different pH conditions were evaluated for better understanding of photocatalytic performance of Co‐Cu/ZIF@HAp composite. Both EY and BG dyes were almost degraded up to 98.3% and 99.5%, respectively, within 50 min by the as‐prepared nanocomposite. Also, quenching test was performed that confirmed the formation of superoxide radicals (O2−.) as reactive oxygen species (ROS) in the photodegradation process. The as‐synthesized catalyst was repeatedly used for five times to ascertain the stability and reusability of catalyst.

Controlling the Physical Properties of Fe3O4-Immobilized Palladium Complexes towards Reusable Catalysts in the Methoxycarbonylation of 1-Hexene

This paper describes the use of immobilized palladium catalysts on Fe3O4 magnetic nanoparticles (MNPs) to afford magnetically separable catalysts in the methoxycarbonylation of 1-hexene. Immobilization of homogeneous complex [Pd(L1)Cl2] (Pd1), where L1 = N,N′E,N,N′E)-N,N′-(3-(3-(triethoxysilyl)propyl)pentane-2,4-diylidene)dianiline, on Fe3O4 MNPs at 100 °C and Pd loading of 10% (based on wt% of Pd1) afforded the corresponding complex [Pd1@Fe3O4] (Pd2) in good yields. The use of calcination temperatures of 150 °C and 200 °C produced compounds Pd3 and Pd4, respectively, while Pd metal loadings (based on wt% of Pd1) of 5% and 15% provided complexes Pd5 and Pd6, respectively. The immobilized compounds were analyzed using FT-IR spectroscopy, SEM-EDX, TEM, ICP-OES, and PXRD techniques. The surface areas and porosity of the materials were determined using nitrogen physisorption measurements and confirmed the formation of mesoporous materials, while SQUID measurements established Ms values in the range of 60.69 to 69.93 emu/g. The immobilized Pd(II) complexes catalyzed the methoxycarbonylation of 1-hexene, yielding mainly linear esters. The immobilized compounds could be recycled up to five times via magnetic separation without significant loss in catalytic activities.

Supported gold nanoparticles prepared from NHC-Au complex precursors as reusable heterogeneous catalysts

Gold nanoparticles supported on SiO2, Al2O3, TiO2, and carbon (Maxsorb, Ketjen black and Shirasagi New Gold) were prepared by impregnation and solid grinding methods using N-heterocyclic carbene (NHC)-Au complexes as precursors. A total of nine NHC-Au complex precursors were tested by impregnation and solid grinding method, and [Au(OH)(IPr)] (IPr = 1,3-bis(2,6-diisopropylphenyl)1,3-dihydro-2H-imidazol-2-ylidene) complex led to (1–2 nm) particle sizes by both methods. The prepared catalysts were characterized by XRD (X-ray diffraction), HAADF-STEM (high-angle annular dark-field scanning transmission electron microscopy), in situ XAFS (X-ray absorption fine structure), etc. In addition, [Au(OH)(IPr)] and its impregnated [Au(OH)(IPr)]/SiO2 were subjected to TG-DTA (thermogravimetry analysis-differential thermal analysis) and in situ XAFS analysis under calcination conditions, respectively. Moreover, the obtained supported Au nanoparticles (NPs) were effective as catalysts for low-temperature CO oxidation, intramolecular cyclization of alkynyl carboxylic acids, and isomerization of allylic esters. Their results suggested that the reduction of [Au(OH)(IPr)] proceeds rapidly from around 300°C, and the residual ligands should be attached to the surface of the Au NPs and protect them from drastic agglutination. These results reveal that properly designed NHC-Au complexes can facilitate the preparation of supported Au NP catalysts with small particle sizes and high activities.

Brønsted-acidic ionic liquid supported nanomagnetic: a novel and reusable catalyst for synthesis of oxygen-containing heterocyclic compounds

Brønsted-acidic ionic liquid supported nanomagnetic: a novel and reusable catalyst for synthesis of oxygen-containing heterocyclic compounds

Cordierite@MOFs with Easy Recovery in CO2 Cycloaddition.

The objective of this research is to create monolithic heterogeneous catalysts (cordierite@MOFs) through the application of metal-organic framework (MOF) materials onto honeycomb cordierite for CO2 cycloaddition. By employing monolithic catalysts instead of powdered catalysts, the recycling and reusability of catalysts during postreaction treatment can be significantly improved.

Continuous Flow Photocatalytic Degradation of Phenol Using Palladium@Mesoporous TiO2 Core@Shell Nanoparticles

Palladium@mesoporous titania core@shell nanoparticles with uniform and narrow particle size distribution were synthesised using a four component ‘‘water in oil’’ microemulsion system. The prepared materials were well characterised using N2 adsorption–desorption measurements, temperature program oxidation, X-ray diffraction, ICP-OES, DRS UV-Vis, PL, TGA and transmission electron microscopy techniques. The core@shell nanoparticles showed very good absorption in both the UV and visible regions and a low bandgap, indicating that the prepared materials are visible-light-active, unlike the pristine TiO2 P25. The activity of the prepared materials was evaluated in the photodegradation of phenol using both UV and visible light, in batch and continuous flow trickle-bed and Taylor flow photoreactors. The prepared 2%Pd@mTiO2 core@shell nanoparticles showed better photocatalytic performance for phenol degradation in visible light in comparison to pristine TiO2 P25 and conventional 0.5%Pd/TiO2 P25 catalysts. The TiO2 P25 and conventional 0.5%Pd/TiO2 P25 catalysts showed gradual catalyst deactivation due to photocorrosion, the deposition of intermediates and Pd metal leaching. In comparison, the 2%Pd@mTiO2 catalyst showed higher catalyst stability and reusability. The 2%Pd@mTiO2 catalysts showed very high and stable phenol degradation (97% conversion) in continuous flow over 52 h. The results showed the feasibility of utilising the developed continuous Taylor flow photoreactor for phenol degradation or as a wastewater treatment plant.

Waste bull bone based reusable and biodegradable heterogeneous catalyst for alternate fuel production from WCO, and investigation of its usability as fuel substitute

Fast-growing fuel demand by an increase in diesel vehicles and diesel engine applications for various sectors motivates researchers to develop alternate fuels. Though many approaches have been proposed, this investigation is unique by producing alternate fuels from the waste cooking oil (WCO) using a biodegradable, reusable, easy-to-handle, eco-friendly, and heterogeneous catalyst developed to form the waste bull bone and characterized for alternate fuel production from WCO. The zero-waste approach, eco-friendly fuel blends, and low-cost production factors were considered. The preprocessing of WCO was carried out by the bubble washes method, followed by transesterification processing for producing biofuel. The fuel blends were tested with different ratios like 20% to 80% with diesel and short out B20 grade. Further, the blends were prepared with Diethyl ether (DEE) and Ethanol. Total eight fuels (Diesel, B20, B20 + 5 wt% DEE, B20 + 10 wt% DEE, B20 + 5 wt% Ethanol, B20 + 10 wt% Ethanol, B20 + 5 wt% Methanol, and B20 + 10 wt% Methanol) were tested including pure diesel from No load to full load engine condition at two different compression ratios (15:1 & 18:1). The results reveal that B20 + 5 wt% Methanol at 15:1 compression ratio outperformed in terms of brake power of 2.64 kW, indicated power of 6.35 kW, brake thermal efficiency of 33.21%, Indicated thermal efficiency of 67.18%, mechanical efficiency of 59.14%, low brake specific fuel consumption of 0.27 kg/kWh at full load. In conclusion, the heterogeneous catalyst obtained from the waste bull bone can be used in biodiesel production, which ensures the efficient usability of the waste bull bone in the fuel-processing sector.

Ultrasound assisted photocatalytic degradation of isoproturon and triasulfuron herbicides using visible light driven impregnated zinc oxide catalysts

Herbicides in wastewater are considered as a serious issue to environmental pollution. Different impregnated metal zinc oxide (Cu/ZnO and Ni/ZnO) as catalysts were prepared through wet impregnation method for the degradation of herbicides Isoproturon and triasulfuron. The prepared impregnated catalysts were characterized using scanning electron microscopy (SEM) and x-ray diffraction (XRD), energy dispersive x-ray (EDX) analysis, Fourier-transform infrared spectroscopyand surface area. The degradation of selected herbicides were investigated using combined effect of photocatalysis and sonication. The experimental parameters such as pH, irradiation time, photocatalyst dose, effect of oxidants, diverse ion effect, herbicide concentration and catalyst reusability have been optimized. The percent removal of isoproturon was found to be 99 and 98% at pH 7 and triasulfuron was 98% at pH 6 using Cu/ZnO and 99% at pH 7 using Ni/ZnO photocatalysts respectively.Graphical Graphical abstract of Ultrasound Assisted Photocatalytic Degradation of Isoproturon and Triasulfuron Herbicides

Molybdenum (VI) complex of resorcinol‐based ligand immobilized on silica‐coated magnetic nanoparticles for biodiesel production

Reusability and durability of catalysts are main factors in biodiesel production. Fe3O4@SiO2‐APTES‐MoO2L2DHAPh catalyst was prepared in five steps. At first, Fe3O4 was synthesized and coated with silica (Fe3O4@SiO2). After that, the nanoparticles were functionalized by APTES (Fe3O4@SiO2‐APTES). In following, DHAPh ligand was anchored covalently onto the surface of aminated magnetic nanoparticles (Fe3O4@SiO2‐APTES‐LDHAPh), and at the end, DHAPh ligand was metalled by MoO2(acac)2 salt (Fe3O4@SiO2‐APTES‐MoO2L2DHAPh). The catalyst was characterized with analytical techniques such as FT‐IR, SEM, TEM, XRD, XPS, VSM, ICP, EDX, NH3‐TPD, and TGA. This novel catalyst with acidic and basic sites was used in (trans)esterification reaction for biodiesel production of rapeseed and other oils. The biodiesel yield of rapeseed, soybean, sunflower, and used frying oils was attained 97%, 98%, 96%, and 87%, respectively, under optimized reaction conditions, such as 0.1 mol% amount of catalyst, 0.05 mmol KOH as methanol activator, a short reaction time of 2 h, and methanol to oil ratio of 3:1 at room temperature. The conversion of oil to methyl ester biodiesel was confirmed by FT‐IR, 1H NMR, and GC‐MS analysis. The leaching and reusability tests of the prepared catalyst were checked, which displayed the biodiesel production proceeded via a heterogeneous pathway. Also, this catalyst can be reused for 11 cycles without tangible loss in its catalytic activity. The mentioned heterogeneously homogenized nanocatalyst has the main benefits such as easy reusability, high activity, and selectivity with acidic and basic sites that makes it a potential candidate for both esterification and (trans)esterification of low quality feedstock for low cost biodiesel production.

Mansonia altisima residue ash (MARA): A precursor for a Nano catalytic (CaO- SiO2-K2O) base employed for the production of JS.22 green diesel

JS.22 seed oil was transesterified into green diesel in an effort to create a nontoxic and environmentally friendly fuel. Mansonia altisima residual ash (MARA) was used to create an alkaline base catalyst, which was then evaluated using SEM, FTIR, BET, XRF, and qualitative analysis. Three factors (EtOH/OMR, reaction duration, catalyst quantity, and reaction temperature) were taken into account during process optimization utilizing the Stat Ease 360 optimizer.The catalyst reusability test was used to gage the strength of the utilized catalyst. The physical and chemical characteristics of oil made it suitable for transesterification. CaO-K2O-SiO2 is recognized as a catalyst composition by catalyst analysis. At the following conditions: reaction duration of 50 min, catalyst quantity of 2.0 (%wt), and E-OH/OMR of 4.0 (vol/vol), process optimization predicted a green diesel yield of 98.99% (vol/vol). Process optimization predicted a 98.99% (vol./vol.) green diesel yield under the following conditions: reaction time of 50 min; catalyst amount of 2.0 (%wt); and E-OH/OMR of 4.0 (vol./vol.). However, statistical analysis was validated, and the average means of 98.78% (vol./vol.) were obtained with p-values of 0.0001. The catalyst reusability test was suspended after the eighth cycle since the yield had significantly dropped.The green diesel qualities complied with the suggested green diesel standard.

Pd Immobilization Phenanthroline-2,9-Dicarbaldehyde Modified Magnetic CuBDC MOF as a Reusable Heterogeneous Catalyst for Suzuki-Miyaura Cross-Coupling Reactions

A porous magnetic multifunctional copper-based metal-organic framework (MOF) was developed through combined covalent and dative post-synthetic modification (PSM) of the CuBDC. In this regard, a novel magnetic metal-organic framework (MMOF) consisting of supported 1,10-phenanthroline-2,9-dicarbaldehyde (Fe3O4@Cu(BDC)-NH2-PHD) has been fabricated by post-synthetic modifications of Fe3O4@Cu(BDC)-NH2. Subsequently, the prepared nanocomposites were modified using palladium chloride ions (Fe3O4@Cu(BDC)-NH2-PdPHD) to impart catalytic sites. As a result, the fabricated magnetic porous catalyst exhibited great catalytic activity in Suzuki-Miyaura cross-coupling reactions. Some of the essential advantages of the synthesized catalyst are; high catalytic activity, short reaction times, mild conditions, high thermal stability, and reusability. Moreover, his porous magnetic nanomaterial can be used as a new support to immobilize other metals in different catalytic reactions.

Efficient Degradation of Antibiotics by Activating Peroxymonosulfate (PMS) with Biochar (BC)-Modified FeOx under UVA-LED Irradiation

There are obvious drawbacks for the traditional treatment methods of antibiotics, such as low efficiency and high cost. In this paper, FeOx catalysts, modified with the biochar (BC) of maple leaf (FeOx@BC), were successfully prepared by the hydrothermal method. Then, the FeOx@BC was investigated to activate peroxymonosulfate (PMS) under UVA-LED irradiation for the degradation of tetracycline hydrochloride (TC). Subsequently, the changes in valence states before and after the reaction of ions were investigated by XPS spectra, and the process mechanism was presented. The results demonstrated that the TC degradation efficiency reached 96% in the FeOx@BC + PMS + UVA-LED system within 40 min, which was higher than 57% efficiency for the α-Fe2O3 + PMS + UVA-LED system. The electron transfer was promoted in the FeOx@BC + PMS + UVA-LED system due to the doping of BC. The Fe(III) was transformed into Fe(II) under UVA-LED irradiation, and Fe(II) activated continuously PMS to generate active oxygen species. Furthermore, it had excellent reusable performance and structural stability, and the degradation efficiency was still as high as 80% after five cycles. It was proved that SO4−•, •OH, O2•− and h+ participated in the degradation process of TC to different degrees by quenching experiments and EPR tests. In summary, FeOx@BC is an inexpensive, reusable and efficient catalyst.

A novel Cu-based catalyst supported in chitosan nanoparticles for the hydrogenation of carbon dioxide to methanol: From the optimization of the catalyst performance to the reaction mechanism

Chitosan nanoparticles were used as a support for the Cu-based catalyst to convert carbon dioxide to methanol under mild conditions. A statistically significant model for space-time yield (STY) and selectivity as a function of synthesis-related parameters was achieved, predicting optimal values of pH, Cu and chitosan concentrations to be 9.3, 0.088 M and 0.01 M, respectively. A STY of 92.44 mgmethanol gcatalyst−1 h−1 and a selectivity higher than 90% were obtained. A constant reaction yield was obtained for 140 min and the STY only decreased by 18%. Catalyst's reusability was demonstrated for three cycles with a 20% of STY loss.

Triple superphosphate modified by tin (II) chloride: As a reusable and efficient catalyst for the one-pot synthesis of xanthene and xanthenone derivatives under green conditions

A simple method was developed for preparing tin (II) chloride-triple superphosphate. The material was thoroughly characterized using various techniques, including transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), thermogravimetric analysis (TGA), and Brunauer–Emmett–Teller (BET) analysis. XRD analysis, BET, and SEM images indicated that the catalyst exhibited a crystalline structure and had particle sizes ranging from 21 to 23 nm. The catalytic performance was evaluated by conducting multicomponent one-pot condensation reactions. Specifically, the condensation of 2-naphthol with aldehydes and dimedone was conducted to produce 12-aryl(alkyl)-8,9,10,12 tetrahydrobenzo [a]xanthen-11-one derivatives, and the condensation of 2-naphthol with aldehydes was performed to synthesize 14-aryl(alkyl)-14H-dibenzo [a,j]xanthene derivatives. The acidic sites of the catalyst were determined using pyridine FTIR spectroscopy. The studies revealed that this catalyst system exhibited excellent performance, resulting in high product yields (88–96%) and reduced reaction times (12–20 min). The catalyst demonstrated high catalytic activity, good reusability, and a simple preparation method, thereby showing promise for potential industrial-scale applications.

Synthesis, Characterization, and Environmental Applications of Cu-Ni-Doped Bismuth Molybdate

Bismuthoxide-based catalysts gained attention for photocatalytic remediation of environmental pollutants owing to their low cost, feasibility, stability, small, and tunable band gap. In the present work, bismuth molybdate was modified via transition metal doping to achieve maximum catalytic efficiency. This aim was accomplished by synthesizing novel Cu2+ and Ni2+ codoped bismuth molybdate (CuNi/Bi2MoO6, Cu/Bi2MoO6, and Ni/Bi2MoO6) which were utilized for heavy metal reduction and dyes degradation. Pure bismuth molybdate was also fabricated for comparative studies. All the prepared samples were characterized by XRD, Raman spectroscopy, SEM, and EDX. Optical studies for band gap calculations were carried out by UV-Visible spectrophotometry and decrease in band gap was observed in doped materials. Pseudo-first-order kinetic studies were performed to find the rate constants and regression values for Cr(VI) reduction and degradation of rhodamine B and malachite green using CuNi/Bi2MoO6. Codoped bismuth molybdate exhibited more than 95% photocatalytic performance for Cr(VI) reduction and degradation of rhodamine B and malachite green dyes. Reusability of catalyst was confirmed up to six cycles. Considering its catalytic proficiency, CuNi/Bi2MoO6 is anticipated to be utilized for more environment friendly applications in future.

A sustainable avenue for the synthesis of propargylamines and benzofurans using a Cu-functionalized MIL-101(Cr) as a reusable heterogeneous catalyst

A heterogeneous copper-catalyzed A3 coupling reaction of aldehydes, amines, and alkynes for the synthesis of propargylamines and benzofurans has been developed. Here, the modified metal–organic framework MIL-101(Cr)-SB-Cu complex was chosen as the heterogeneous copper catalyst and prepared via post-synthetic modification of amino-functionalized MIL-101(Cr). The structure, morphology, thermal stability, and copper content of the catalyst were determined by FT-IR, PXRD, SEM, TEM, EDX, TGA, XPS, and ICP-OES. The catalyst shows high catalytic activity for the aforementioned reactions under solvent-free reaction conditions. High yields, low catalyst loading, easy catalyst recovery and reusability with not much shrink in catalytic activity, and a good yield of 82% in gram-scale synthesis are some of the benefits of this protocol that drove it towards sustainability.

Potato-on-rod like of Z-scheme plasmon Ag2CrO4-Ag2Mo2O7 heterojunction nanophotocatalyst with high stability and accelerated photo-degradation evolution of organic contaminants

The shocking increase of resistant dye pollutants in the environment and their harmful effects has become a potential threat to the ecosystem. In the current work, the novel and highly efficient potato-on-rod-like Z-scheme plasmon Ag2CrO4–Ag2Mo2O7 heterojunction nano-photocatalyst was synthesized by precipitation method to photodegrade different organic dyes under artificial sunlight. The required analysises were carried out to characterize nanophotocatalysts. FESEM and TEM results showed the placement way of potato-like Ag2CrO4 between/on rod-like Ag2Mo2O7 which was leading to suitable structure and surface morphology. Besides, the morphology observations released the meso-/macroporous potato-on-rod like architecture self-assembled by nanoparticles. DRS analysis also confirmed two band gap energies of 2.55 and 1.72 eV in Ag2CrO4–Ag2Mo2O7 (3:1) resulting from forming a heterojunction structure and the plasmon Ag. Ag2CrO4–Ag2Mo2O7 (3:1) nanophotocatalyst exhibited the most remarkable activity in the photodegradation of 10 mg/L 2-naphthol orange (97.8%), 10 mg/L rhodamine B (99.7%), 10 mg/L crystal violet (98.9%), and 10 mg/L methyl orange (56.1%) with a catalyst dosage of 0.1 gr for about 90 min. The appropriate energy band gap, the formation of the heterostructure, the presence of meso (0.0038 cm3/g) and macro (0.0044 cm3/g) holes, and pore diameter at about 17.2 nm based on BET-BJH analysis that facilitated the penetration of pollutant molecules, increased pollutant adsorption and demonstrated stunning capability of efficient light harvesting, the reason was electron-hole pairs recombination rate reduction. Moreover, the fabricated samples showed tremendous catalyst constancy and reusability even after the fourth run. Results have shown the remarkable photocatalytic activity under visible light and provide an environment-friendly and green strategy to overcome the challenges of organic pollutants present in aqueous solutions.

Catalyst Design through Grafting of Diazonium Salts-A Critical Review on Catalyst Stability.

In the pursuit of designing a reusable catalyst with enhanced catalytic activity, recent studies indicate that electrochemical grafting of diazonium salts is an efficient method of forming heterogeneous catalysts. The aim of this review is to assess the industrial applicability of diazonium-based catalysts with particular emphasis on their mechanical, chemical, and thermal stability. To this end, different approaches to catalyst production via diazonium salt chemistry have been compared, including the immobilization of catalysts by a chemical reaction with a diazonium moiety, the direct use of diazonium salts and nanoparticles as catalysts, the use of diazonium layers to modulate wettability of a carrier, as well as the possibility of transforming the catalyst into the corresponding diazonium salt. After providing descriptions of the most suitable carriers, the most common deactivation routes of catalysts have been discussed. Although diazonium-based catalysts are expected to exhibit good stability owing to the covalent bond created between a catalyst and a post-diazonium layer, this review indicates the paucity of studies that experimentally verify this hypothesis. Therefore, use of diazonium salts appears a promising approach in catalysts formation if more research efforts can focus on assessing their stability and long-term catalytic performance.