Photocatalytic Oxidation Of Benzyl Alcohol Research Articles

Synthesis and characterization of Zn-In-S composites for photocatalytic benzyl alcohol oxidation and nitrobenzene reduction

Photocatalytic transformation of organics is a promising alternative to conventional synthetic methodologies. ZnIn2S4 is active in photocatalytic redox reactions, but its performance is hindered by fast charge carrier recombination, and optimizing its properties through synthesis or modification is complicated. Herein, Zn-In-S based composites were prepared via a facile solvothermal method by varying the ratio of sulfide precursor (TAA) with a fixed Zn/ In molar ratio of 1: 2. The phase composition of the obtained materials depends on the amount of TAA. At lower ratios, composites consisting of crystalline In(OH)3 and unknown ZnxInySz phase were formed. Pure-phase ZnIn2S4 was obtained when the feed molar ratio of zinc and TAA was 1: 6 or higher. The photocatalytic oxidation of benzyl alcohol (BA) and reduction of nitrobenzene (NB) in a coupled system were applied to evaluate the activity of Zn-In-S-based composites. Under visible light irradiation, the ZnxInySz/ In(OH)3 composite (ZIS14) synthesized with a molar ratio of Zn to TAA of 1: 4 exhibited boosted and optimal performance compared to the bare ZnIn2S4 and other samples. After 5 hours of irradiation, the BA conversion and benzaldehyde (BAD) yield were 57 % and 55 %, respectively, and the NB conversion and aniline (AN) yield were 70 % and 35 %, individually, outperforming previous studies under similar experimental conditions. This work not only elucidates the photoredox process of BA and NB in one system, but also has significant implications for understanding the complex hydro/solvothermal processes involved in the fabrication of multicomponent sulfides.

High-Efficiency Photocatalytic Oxidation of Benzyl Alcohol by NH2-UiO-66-(Indole-2,3-Dione)-Fe.

The photocatalytic oxidation of biomass-derived benzyl alcohol provides a promising way for the synthesis of benzoic acid, which is an important intermediate with wide applications. To improve the efficiency of photocatalytic benzyl alcohol oxidation to benzoic acid is of great interest. In this work, we propose the utilization of NH2-UiO-66-ID-Fe catalyst for photocatalytic oxidation of benzyl alcohol to benzoic acid, where NH2-UiO-66 is a typically used metal-organic framework, ID is indole-2,3-dione (ID) that has biocompatibility, light absorption property and can be covalently combined with amino-functionalized substances. The NH2-UiO-66-ID-Fe catalyst exhibits improved light absorption and photo-generated electron-hole separation ability compared with NH2-UiO-66. The photocatalytic performance of NH2-UiO-66-ID-Fe was examined for the oxidation of bio-based benzyl alcohol under mild conditions of air atmosphere, room temperature and no additive or additional oxidant involved. The results show that the conversion of benzyl alcohol and the selectivity to benzoic acid could both reach over 99 % in 6 h, and the generation rate of benzoic acid per gram of catalyst is 3.36 mmol g-1 h-1. The reaction mechanism was detected by radical trapping method and in situ electron paramagnetic resonance. This study presents an efficient and environmentally benign avenue for the synthesis of carboxylic acid compounds.

Facile interfacial synthesis of thin AuPd alloy nanowires for plasmon-enhanced selective photocatalytic oxidation of benzyl alcohol

Bimetallic AuPd plasmonic photocatalyst is a promising candidate for catalyzing selective oxidation of aromatic alcohol. However, developing a simple one-step method for the preparation of free-standing AuPd nanostructures with excellent photocatalytic performance remains a huge challenge. Here, a facile liquid–liquid interface route was exploited to one-pot prepare free-standing AuPd alloy nanowires (NWs) under mild conditions. Specifically, Au1Pd1 NWs are grown via oriented attachment at chloroform-water interface and 40 °C with Na2PdCl4 and HAuCl4 as precursors and 1-naphthol as reductant. Au1Pd1 NWs possess many advantages, such as thin diameter (4.0 nm), large aspect ratio, abundant defects and strong Au-Pd electronic interaction. During benzyl alcohol oxidation to benzaldehyde, Au1Pd1 NWs exhibit excellent photocatalytic activity and durability. At 40 min of visible light illumination, 98 % conversion of benzyl alcohol and 100 % selectivity to benzaldehyde are finished. After five cycles, Au1Pd1 NWs still maintain high photocatalytic activity. Compared to pure Au NWs, alloying Pd with Au in Au1Pd1 NWs dramatically enhances photocatalytic activity. The results indicate that the generated abundant •O2– under illumination play an important role in significantly improving benzyl alcohol oxidation to benzaldehyde.

Construction of a Dual-Function Mo-ZIS@Ti for Photocatalytic Benzyl Alcohol Oxidation and Hydrogen Evolution Performance.

The photocatalytic oxidation of benzyl alcohol and the simultaneous evolution of hydrogen from water are efficient dual-optimal routes. It is important to develop composite catalysts that combine redox properties and facilitate electron-hole separation and transport. Herein, the bimetallic-doped Mo-ZIS@Ti photocatalyst was designed and synthesized, and the selective oxidation of benzyl alcohol and hydrogen evolution by water splitting was realized at the same time. Under visible light irradiation, benzyl alcohol was completely converted with more than 99% selectivity for benzaldehyde, and the H2 production rate was 5.6 times higher than the initial ZIS. The exceptional catalytic performance was ascribed to utilizing Ti-MIL-125 as a precursor, wherein slowly releasing-doped Ti formed robust Ti-S bonds that quickly transfer electrons and reduce sites. Meanwhile, doping Mo effectively captures photogenerated holes and acts as active sites for oxidation reactions. Both experimental characterization and work function calculations demonstrate that the bimetallic synergism effectively modulates the electronic structure of ZIS, promotes the directional separation of electrons and holes, and significantly improves the photoactivity and stability of ZIS. This work contributes a route to obtain benzaldehyde and green hydrogen at the same time and also gives new insights for the construction and mechanism study of bimetallic-doping catalysts.

Fabricating a Structured Single‐Atom Catalyst via High‐Resolution Photopolymerization 3D Printing

AbstractThis study introduces a novel solution to the design of structured catalysts, integrating single‐piece 3D printing with single‐atom catalysis. Structured catalysts are widely employed in industrial processes, as they provide optimal mass and heat transfer, leading to a more efficient use of catalytic materials. They are conventionally prepared using ceramic or metallic bodies, which are then washcoated and impregnated with catalytically active layers. However, this approach may lead to adhesion issues of the latter. By employing photopolymerization printing, a stable and active single‐atom catalyst is directly shaped into a stand‐alone, single‐piece structured material. The battery of characterization methods employed in the present study confirms the uniform distribution of catalytically active species and the structural integrity of the material. Computational fluid dynamics simulations are applied to demonstrate enhanced momentum transfer and light distribution within the structured body. The materials are finally evaluated in the continuous‐flow photocatalytic oxidation of benzyl alcohol to benzaldehyde, a relevant reaction to prepare biomass‐derived building blocks. The innovative approach reported herein to manufacture a structured single‐atom catalyst circumvents the complexities of traditional synthetic methods, offering scalability and efficiency improvements, and highlights the transformative role of 3D printing in catalysis engineering to revolutionize catalysts’ design.

Kinetic Analysis of Solvent Effect in the Photocatalytic, Aerobic Oxidation of Benzyl Alcohol over P25

Background: Photocatalysis is of particular importance in the oxidation of alcohols to aldehydes to increase the conversion of benzyl alcohol oxidation to benzaldehyde at high selectivity, which could be useful for the pharmaceutical and perfumery industries. Objective: The oxidation of benzyl alcohol over P25 was investigated in various solvents (water, benzotrifluoride, toluene and acetonitrile) Methods: The reaction was performed in an isothermal slurry batch reactor in the presence and absence of UV-light. The products were analysed using GC-FID; the deposits formed on the catalyst was analysed using TGA and FTIR. Results: In the presence of light, the reaction was very selective for the formation of benzaldehyde (e.g., 99% selectivity at 53% conversion using acetonitrile as a solvent), whereas, in the absence of light, the formation of higher molecular weight products was observed (e.g., 22% selectivity at 1.7% conversion using acetonitrile as a solvent). It was observed that the activity in the absence of oxygen was initially high, but it dropped rapidly from initially 0.4 to 0 mmol g-1 h-1 after 2-4 h (using acetonitrile as a solvent). This was attributed to the activity of the few oxidized sites present on P25. Conclusion: Acetonitrile appears to be the most effective solvent, as it seems to interact least with the catalytically active sites. The photocatalytic oxidation of benzyl alcohol over P25 does not only yield products in the solution, but also deposits on the surface. The deposits can be removed in an oxidative environment or an inert environment.

Guest-Regulated Generation of Reactive Oxygen Species from Porphyrin-Based Multicomponent Metallacages for Selective Photocatalysis.

The development of novel materials for highly efficient and selective photocatalysis is crucial for their practical applications. Herein, we employ the host-guest chemistry of porphyrin-based metallacages to regulate the generation of reactive oxygen species and further use them for the selective photocatalytic oxidation of benzyl alcohols. Upon irradiation, the sole metallacage (6) can generate singlet oxygen (1O2) effectively via excited energy transfer, while its complex with C70 (6⊃C70) opens a pathway for electron transfer to promote the formation of superoxide anion (O2⋅-), producing both 1O2 and O2⋅-. The addition of 4,4'-bipyridine (BPY) to complex 6⊃C70 forms a more stable complex (6⊃BPY) via the coordination of the Zn-porphyrin faces of 6 and BPY, which drives fullerenes out of the cavities and restores the ability of 1O2 generation. Therefore, benzyl alcohols are oxidized into benzyl aldehydes upon irradiation in the presence of 6 or 6⊃BPY, while they are oxidized into benzoic acids when 6⊃C70 is employed as the photosensitizing agent. This study demonstrates a highly efficient strategy that utilizes the host-guest chemistry of metallacages to regulate the generation of reactive oxygen species for selective photooxidation reactions, which could promote the utilization of metallacages and their related host-guest complexes for photocatalytic applications.

Guest‐Regulated Generation of Reactive Oxygen Species from Porphyrin‐Based Multicomponent Metallacages for Selective Photocatalysis

AbstractThe development of novel materials for highly efficient and selective photocatalysis is crucial for their practical applications. Herein, we employ the host‐guest chemistry of porphyrin‐based metallacages to regulate the generation of reactive oxygen species and further use them for the selective photocatalytic oxidation of benzyl alcohols. Upon irradiation, the sole metallacage (6) can generate singlet oxygen (1O2) effectively via excited energy transfer, while its complex with C70 (6⊃C70) opens a pathway for electron transfer to promote the formation of superoxide anion (O2⋅−), producing both 1O2 and O2⋅−. The addition of 4,4′‐bipyridine (BPY) to complex 6⊃C70 forms a more stable complex (6⊃BPY) via the coordination of the Zn‐porphyrin faces of 6 and BPY, which drives fullerenes out of the cavities and restores the ability of 1O2 generation. Therefore, benzyl alcohols are oxidized into benzyl aldehydes upon irradiation in the presence of 6 or 6⊃BPY, while they are oxidized into benzoic acids when 6⊃C70 is employed as the photosensitizing agent. This study demonstrates a highly efficient strategy that utilizes the host‐guest chemistry of metallacages to regulate the generation of reactive oxygen species for selective photooxidation reactions, which could promote the utilization of metallacages and their related host‐guest complexes for photocatalytic applications.

{Ru(C6 H6 )}-Decorating Heteropolymolybdate for Highly Activity Photocatalytic Oxidation of Benzyl Alcohol to Benzaldehyde.

An unclassical structure of {Ru(C6 H6 )}-based polyoxometalate, Cs6 H4 [Te2 Mo12 O46 {Ru(C6 H6 )}] ⋅ 16.5H2 O (1), has been successfully constructed from {Te2 Mo12 O46 }-type heteropolymolybdate and {Ru(C6 H6 )} group, which structure type was discovered for the first time. Compound 1 not only possesses strong light-harvesting ability, but also exhibits high carrier separation efficiency and lower charge transfer resistance. Under visible light irradiation, compound 1 displayed excellent catalytic activity and circularity in the conversion of benzyl alcohol to benzaldehyde (yield=94 %; turnover number=500; turnover frequency=20.8 h-1 ). Finally, the electron paramagnetic resonance measurement and energy level matching analysis provide theoretical basis for the derivation of the reaction mechanism.

Atomistic understanding of enhanced selectivity in photocatalytic oxidation of benzyl alcohol to benzaldehyde using graphitic carbon nitride loaded with single copper atoms.

The loading of graphitic carbon nitride (gCN) with transition metals has received significant attention for efficient light-driven catalysis. However, the contribution of the loaded metals to enhanced performance remains unclear. In this study, Cu is loaded onto gCN to understand how photocatalytic activity is regulated by the loaded metals. Loading gCN with 3 wt% of Cu increases the electron population by 8.1 and 4.6 times under UV (λ < 370 nm) and visible light (390 < λ < 740 nm), respectively. This sample shows nearly 100% selectivity for oxidizing benzyl alcohol to benzaldehyde and a high yield-to-power ratio, reaching 0.35 mmol g-1 h-1 W-1. The loaded Cu species exist as single atoms with a +1-oxidation state. Each Cu+ cation is coordinated to two (at 3 wt% Cu) or four (at 6 wt% Cu) N atoms within the cavity of the gCN framework. Doubling the Cu loading results in a smaller electron population and coordinatively more saturated Cu+ cations, making it catalytically less reactive. Ab initio molecular dynamics simulations show that Cu+ cations produce filled mid-gap states above the valence band, which function as hole traps and hence oxidation centers. The Cu+ cation and the neighboring N atoms are electron-depletion and electron-accumulation sites due to Cu → N electron transfer, making it highly reactive for oxidative transformations via the hole transfer pathway. The role of Cu as a hole-transfer site updates the received understanding that surface-loaded Cu serves as an electron-accumulation site. A strong correlation is observed between the electron population at steady-state and the product yield, indicating that it could serve as a promising performance indicator for the design of future photocatalysts.

Bimetallic synergy significantly enhances the photocatalytic performance of lanthanide porphyrin-based MOFs: Efficient photocatalytic oxidation of benzyl alcohol and benzylamine under mild conditions in air

Metal-organic frameworks as photocatalysts for the conversion of light energy into chemical energy applied to organic conversion is an efficient and sustainable strategy. Lanthanide organometallic frameworks perform poorly in photocatalytic organic reactions owing to their high electron and hole complexation rates. Inspired by the synergistic effect of biomacromolecule porphyrin as a photosensitizer with bimetallic pairs that can boost electron transport efficiency. We synthesized a series of lanthanide porphyrin mechanism MOFs (Nd PMOFs, Co–Nd PMOFs, Ni–Nd PMOFs). These PMOFs are endowed with a novel three-dimensional structure. It is noteworthy that Ni in the middle of the porphyrin ring enhances the photocatalytic performance of Ni–Nd PMOFs. The reasons can be attributed to the introduced Ni and the coordinated Nd elements, which interact synergistically with the porphyrin skeleton. This interaction results in a good photoresponse and promotes an efficient separation of photogenerated electrons and holes. The photocatalytic performance of Ni–Nd PMOFs was tested under mild conditions (12 W visible light, air) using the photocatalytic oxidation of benzyl alcohol and the oxidative coupling of benzylamine as model reactions. The conversion rate for benzyl alcohol was 90 % with a selectivity 94 %, and the conversion rate for benzylamine was 85 % with a selectivity 83 %. The photocatalytic oxidation performance of Ni–Nd PMOFs has been found to be excellent for a wide range of reactions and substrates, indicating that it is a promising photocatalyst. To some extent, the presentation of this work expands the possibilities of lanthanide metal frameworks for photocatalytic organic transformations and sheds new light on the multidirectional applications of lanthanide metal–organic frameworks.

New insight into highly efficient CSA@g-C3 N4 for photocatalytic oxidation of benzyl alcohol and thioanisole: NAEDS as a promoter of photoactivity under blue LED irradiation.

An open new perspective has been established toward synthesizing eco-friendly CSA@g-C3 N4 employing surface engineering. The carbon nitride modified through camphorsulfonic acid was designed and developed in a category of the new generation of photocatalysts for the oxidation of benzyl alcohol and thioanisole in the existence of a natural deep eutectic solvent (NADES). In comparison with pure g-C3 N4 , not only does CSA@g-C3 N4 exhibit an extraordinarily higher ability for harvesting visible light stemming from declining the recombination rate of electrons/holes dependent on PL results but it also reveals notable photocatalytic oxidation capability in the transformation of alcohols as well as thiols into relevant compounds. In addition, non-metal compound (CSA) incorporation would result in considerably diminishing the energy band gap value from 2.8 to 2.28 eV to escalate the visible-light absorption of g-C3 N4 . While the conventional consensus implies that inherent properties of photocatalysts bring on high photoactivity, this study indicates that deploying choline chloride-urea deep eutectic solvent as an external factor plays the role of photoactivity accelerator. Furthermore, readily recycling and reusability can be achieved for the photocatalytic setup of CSA@g-C3 N4 ascribed to its heterogeneous nature with no drop in the photoactivity.

Microwave-assisted construction of 2D/2D direct Z-scheme g-C3N4/Bi4O5Br2 heterojunctions with enhanced molecular oxygen activation for boosting selective photocatalytic conversion of benzyl alcohol

Novel 2D/2D g-C3N4/Bi4O5Br2 heterojunctions were constructed via a facile microwave-assisted tactic, which exhibited excellent selective photocatalytic oxidation of benzyl alcohol under blue LED light. The reaction rate of the optimized sample was approximately 9.2 and 5.3 times higher than those of g-C3N4 or Bi4O5Br2 alone, respectively, with more than 99% selectivity for benzaldehyde. DFT calculations and experimental studies showed that there was no chemical bonding between Bi4O5Br2 and g-C3N4, but a direct Z-scheme system was created through weak van der Waals interactions. Electron spin resonance and radical quenching experiments revealed that the primary reactive species in the photoreaction system were superoxide radicals (•O2–) and holes (h+). Accordingly, the boosted photocatalytic activity of g-C3N4/Bi4O5Br2 heterojunctions arose from its optimized energy band configuration and van der Waals Z-scheme system, which effectively activated molecular oxygen to generate •O2– and triggered the first step in the photoconversion of benzyl alcohol. This work demonstrates the crucial role of semiconductor band regulation in selective photocatalytic organic conversion and the effective activation of molecular oxygen by rational design of heterogeneous interfaces.

Photocatalytic oxidation of benzyl alcohol coupled with p-dinitrobenzene reduction over poly(o-phenylenediamine) nanowires-decorated Gd-TiO2 nanorods

Simultaneous oxidation of benzyl alcohol (BA) and reduction of p-dinitrobenzene (p-DNB) over Gd-doped TiO2nanorods decorated with poly(o-phenylenediamine, PoPD) nanowires was reported in this work. The doping of TiO2 with Gd induced surface defects, i.e., oxygen vacancy (OV) and the Ti3+–on-Ti4+site, while incorporating PoPD highly enhanced the light absorption capability and electron conductivity of TiO2nanorods,as confirmed by UV–vis diffuse reflectance spectroscopy (DRS) and electrochemical measurements, respectively. BA was selectively oxidized by photogenerated h+to form benzaldehyde with a yield of 70.5% in water and 90.6% in acetonitrile solvent. Conversely, p-DNB was selectively reduced to p-nitroaniline (p-NA) with a yield of 89.1% in acetonitrile and to p-phenylenediamine (p-PDA) of 85.0% yield in water. This work demonstrates a vital strategy to utilize the full economic potential of photogenerated charge carriers and the decisive role of solvent for product selectivity in the course of selective organic transformations.

New reaction pathway induced by N-deficient conjugated polymer-supported bimetallic oxide quantum dot S-scheme heterojunction for benzyl alcohol oxidation in water

The catalytic conversion of aromatic alcohols to their corresponding carbonyls under mild conditions is challenging because of their low selectivity and activity. A 0D/2D based S-scheme heterojunction material with bimetallic oxide quantum dots (NixFe1-xO QD) and nitrogen-deficient conjugated polymers, such as g-C3N4 (NvCN), was designed for the photocatalytic conversion of benzyl alcohols to benzaldehyde/benzoic acid using simulated solar light. The optimized Ni0.5Fe0.5O QD/NvCN (NFO/NvCN) hybrid catalyst exhibited excellent conversion (85%) and selectivity (98%) for photocatalytic oxidation of benzyl alcohol (BzOH) to benzaldehyde (BzH) in an aqueous medium (88%) and for benzoic acid (BzA) under dilute alkaline conditions (99%). The structure-activity relationship was established using catalytic activity data, surface physicochemical characteristics, optoelectronic characteristics, and scavenging studies. The band alignment of the heterojunction converts the type-I junction into a type-II junction and follows S-scheme charge dynamic pathways through the nitrogen vacancy pathways, which can accelerate the separation and transfer of photogenerated charge carriers. Mechanistic pathways have been proposed based on O–H bond cleavage by electrons and C–H bond cleavage by holes. Hybrid materials based on defect-rich supports and bimetallic oxide-quantum dot interactions are promising catalysts that can compete with the best photocatalysts.

Carbazole-involved conjugated microporous polymer hollow spheres for selective photocatalytic oxidation of benzyl alcohol under visible-light irradiation

Conjugated microporous polymers (CMPs) have been considered a type of promising visible-light-driven, organic photocatalysts. However, apart from designing high-performance CMPs from a molecular perspective, little attention is paid to improving the photocatalytic properties of these polymers through macrostructural regulation. Herein, we prepared a kind of hollow spherical CMPs involving carbazole monomers and studied their performance on the selective photocatalytic oxidation of benzyl alcohol under visible light irradiation. The results demonstrate that the introduction of a hollow spherical structure improves the physicochemical properties of the as-designed CMPs, including the specific surface areas, optoelectronic characteristics, as well as photocatalytic performance, etc. In particular, the hollow CMPs can more effectively oxidize benzyl alcohol compared to pristine ones under blue light illumination, and produce >1 mmol of benzaldehyde in 4.5 h with a yield of up to 9 mmol·g−1·h−1, which is almost 5 times higher than that of the pristine ones. Furthermore, such hollow architecture has a similar enhanced effect on the oxidation of some other aromatic alcohols. This work shows that the deliberate construction of specific macrostructures can better arouse the photocatalytic activity of the as-designed CMPs, which will contribute to the further use of these organic polymer semiconductors in photocatalysis areas.

Solvent-controlled selective photocatalytic oxidation of benzyl alcohol over Ni@C/TiO2

Selective photocatalysis offers an alternative green and economically competitive approach for valuable fine chemical synthesis. In this research, the Ni@C/TiO2-Z catalyst was prepared for the efficient photocatalytic oxidation of various aromatic alcohols. Interestingly, the selectivity of the reaction products is affected by the absorbance of the solvents used in the reaction. The oxidation ability of the reaction system is stronger when the absorption peaks of the solvents are closer to light source wavelengths. Therefore, the reaction tends to generate aldehyde in acetonitrile and acid in ethyl acetate, which allows for the manipulation of product selectivity by choosing the solvent.

Nepenthes-inspired hierarchical ZnIn2S4/Ru nanotubes with chemical bond-mediated interface enable efficient photocatalytic benzyl alcohol oxidation

In nature, Nepenthes has a unique tubular structure for harvesting and preserving goals. Herein, inspired by Nepenthes, we report the selective photocatalytic oxidation of benzyl alcohol by using the hierarchical ZnIn2S4/Ru nanotubes. The tubular chamber with abundant active sites not only facilitates enriching the target molecules but also shortening the bulk-to-surface distance, and the Zn-S-Ru interfacial bonds creates direct charge transfer channels for the activating O2 to generate •O2– species boosting the benzyl alcohol selective conversion to benzaldehyde. The photocatalytic benzyl alcohol oxidation reaction has a high conversion rate of 68.2 % as well as a benzaldehyde selectivity of 99 % under visible light irradiation. The effects of Zn-S-Ru interfacial bonds on modulating the carrier transfer dynamics for the selective catalytic oxidation reaction are investigated by electrochemical characterization and density functional theory simulation. This work offers an inspiration on regulating the interfacial charge transfer channel for the photo-driven selective oxidation reaction.

0D/2D CuFe2O4/MXene Z-scheme heterojunction for improved photocatalytic selective oxidation reaction

The high rate of recombination of photoinduced electrons and holes restricts their utilization in photocatalysis. In this study, an in-situ synthesis route for the fabrication of 0D/2D CuFe2O4/MXene heterojunctions was proposed. The developed heterojunction enhances the charge transfer during the photocatalytic reaction, and the enhanced mechanism is investigated based on the energy band structures of the heterojunction. The conduction band energies of CuFe2O4 and the MXene are 0.17 and − 0.04 eV, respectively, (vs NHE, pH = 7). Moreover, the valence band energies of CuFe2O4 and the MXene are 2.83 and 1.53 eV, respectively, (vs NHE, pH = 7). Therefore, the Z-scheme mechanism of the heterojunctions is proposed, clarifying how the charge separation efficiency of the material is improved through the transfer of the photoinduced holes from the MXene to CuFe2O4. The heterojunctions exhibit superior activity in the photocatalytic selective oxidation of benzyl alcohol to benzaldehyde showing a yield of 99 %, which is significantly higher than that of pure CuFe2O4 and MXene. The results indicate that the novel 0D/2D heterojunction significantly enhances the selective photocatalytic oxidation of benzyl alcohol, and also indicate that ·O2His themainactive species in the photocatalytic oxidation reaction.

TiO2 supported-reduced graphene oxide co-doped with gallium and sulfur as an efficient heterogeneous catalyst for the selective photochemical oxidation of alcohols; DFT and mechanism insights

Achieving organic transformation reactions using green synthesis methods under mild conditions is always an aspiration of scientists. In this study, Ga, S co-doped TiO2/reduced graphene oxide (GaxSy@TRG) nanocomposite was synthesized by an innovative surfactant-free ultrasonic-assisted solvothermal method and used to catalyze the selective photocatalytic oxidation of benzyl alcohol under visible light irradiation. The prepared photocatalyst was analyzed via XRD, FT-IR, Raman, N2 adsorption–desorption, SEM, TEM, EDX, ICP-MS, UV–Vis absorption, and electrochemical impedance spectroscopy (EIS) measurement. The characterization outcomes indicated the prepared co-doped TiO2 nanoparticles with anatase crystal structure possessed a mesoporous texture and were uniformly distributed on the RGO surface. The conversion of GO to RGO was confirmed through FT-IR and Raman spectra. The prepared nanocomposites were examined for their ability in artificial photocatalysis and displayed remarkable catalytic activity for the selective oxidation of alcohols into benzaldehyde. The co-doped catalysts showed significantly enhanced photocatalytic ability, due to improved photogenerated electrons transfer, enhanced charge carriers separation and extended optical absorption to the visible light range. Moreover, the synergistic effect of dopants that could act as electron trapping centers and RGO as a powerful acceptor material efficiently reduced photogenerated electron-hole recombination and promoted charge migration. A high conversion rate of 85% was obtained over the Ga5.0S10.0@TRG photocatalyst after 110 min under visible light irradiation. The results from density functional theory (DFT) calculations revealed that the hybridization of Ga 4s and S 3p orbitals with valance band can remarkably affect the decreasing of band gap energy. The mechanism of photocatalytic oxidation of benzyl alcohol under visible light irradiation was proposed using the combination of experimental and computational methods.