Activity For Oxidation Of Alcohols Research Articles

Green Synthesis of Au‐Ag@TiO2 Nanocomposite for Photocatalytic Oxidation of Substituted Benzyl Alcohols

AbstractThe scaling‐up of methodologies in the oxidation of alcohols to carbonyl compounds faced widespread hindrance in industries due to large‐scale use of toxic and expensive metal oxidants. Novel, cost‐effective and eco‐friendly approaches need to be developed to address these problems. Bimetallic nanoparticles (BMNPs) show synergistic effects at atomic level, which makes them excellent catalysts for organic transformations. Transition metal nanocomposite with unique physicochemical properties and high surface area offers a promising alternative to traditional catalysts. Herein, an environment‐friendly methodology was adopted for the synthesis of Au−Ag BMNPs using phenolic‐rich Ocimum basilicum (L.) leaf extract, which was then incorporated into TiO2 matrix for the synthesis of plasmonic Au−Ag@TiO2 nanocomposite. The formation of the nanocomposite was confirmed through analytical characterizations, such as UV–Vis. DRS, FT‐IR, PL, SEM, TEM and XRD. The nanocomposite exhibited excellent catalytic activity in the selective oxidation of primary and secondary alcohols in aqueous media using H2O2 as an oxidant under visible light irradiation at room temperature. The nanocomposite also demonstrated good reusability of 84 % in the fifth cycle, which established its promising candidature for wide‐scale applications. This work holds significant relevance for industries dealing with pharmaceuticals and personal care products, and thus, offers sustainable solution for organic transformations.

Effects of the ligand linkers on stability of mixed-valence Cu(I)Cu(II) and catalytic aerobic alcohol oxidation activity

We synthesized a class of ligands that feature single (L1) and dual amine-bis(triazole) chelates (L2 with a 1,3-phenylene linker and L3 with a 1,5-naphthalene linker). Our findings which were derived from UV–Vis titrations, crystal structure analysis of relevant copper complexes, and DFT calculations indicate the formation of both mononuclear CuBr(L1) and dinuclear (μ-Ln)(CuBr)2 (Ln = L2 and L3) complexes. The catalytic activities of CuBr/Ln, in combination with TEMPO (2,2,6,6-tetramethylpiperidin-1-yl)oxyl) co-catalyst and NMI (N-methylimidazole) for aerobic alcohol oxidation, reveal the following activity trend: CuBr/L3 > CuBr/L2 > CuBr/L1. Furthermore, electrochemical data from in-situ generated CuBr complexes suggest that the higher catalytic performance of CuBr/L3 is attributed to the presence of less stable mixed-valence and more reducible Cu(I)-L3-Cu(II) species compared to Cu(I)-L2-Cu(II). This difference is a result of weaker σ interactions between Cu–Namine, larger bridging π systems, and a longer Cu···Cu distance in the presence of L3. Additionally, the catalyst system, CuBr/L3/TEMPO/NMI, efficiently promotes the aerobic oxidation of benzyl alcohol to benzaldehyde at room temperature in CH3CN with a high turnover frequency (TOF) of 38 h−1 at 1 h.

N/Se co-doped porous carbon catalyst derived from a deep eutectic solvent and chitosan as green precursors: Investigation of catalytic activity for metal-free oxidation of alcohols

Heteroatom-doped porous carbon-based materials with high surface area compared to their metal-based homologs are considered environmentally friendly and ideal catalysts for organic reactions. In this paper, a new method for the convenient fabrication, cost-effective, and high efficiency of nitrogen/selenium co-doped porous carbon-based catalysis (marked as N/SePC-T) was designed. The N/SePC-T catalysts were created from the direct pyrolysis of a eutectic solvent containing choline chloride/urea as the nitrogen-rich carbon source, selenium dioxide as a source of heteroatom and chitosan as a secondary carbon source in different temperatures (T). The efficacy of the carbonization temperature on the pore structure, morphology, and catalytic activity of the N/SePC-T materials was investigated and displayed, the N/SePC-900 (having a surface area of 562.01 m2/g and total pore volume of 0.2351 cm3 g−1) has the best performance. The morphology, structure, and physicochemical properties of N/SePC-900 were characterized using various analyses including XRD, TEM, TGA, FE-SEM, EDX, FT-IR, XPS, and Raman. The optimized N/SePC-900 catalyst indicated excellent catalytic performance in the oxidation of benzylalcohols to corresponding aldehydes in very mild conditions.

CuInSe2 nanoplatelets decorated CdS nanosheets as 2D-2D S-scheme photocatalyst for photocatalytic H2 generation coupled with benzyl alcohol oxidation and microplastic degradation

In this work, a novel 2D layered heterojunction for various photocatalytic reactions is constructed by hybridizing CdS nanosheets and CuInSe2 nanoplatelets. By adjusting CuInSe2 content, the CdS-16% CuInSe2 sample displays a visible-light-induced H2 production rate of 4382 μmol g−1 h−1, approximately 7.5 times higher than pristine CdS. Furthermore, CdS-16% CuInSe2 demonstrates exceptional photocatalytic activity in H2 evolution simultaneous benzyl alcohol (BA) oxidation and polyethylene terephthalate (PET) degradation. The superior photocatalytic activity is ascribed to the unique S-scheme heterojunction and 2D-2D CdS–CuInSe2 layered heterostructures that effectively separate photoinduced charge carriers and provide appropriate interfacial band structures. The photocatalytic mechanism is thoroughly examined through experiments and density functional theory calculations. This work offers a valuable platform to develop innovative layered photocatalysts that are highly effective for a wide range of photocatalytic reactions.

Copper(II) complexes with BIAN-type ligands: Synthesis and catalytic activity in oxidation of hydrocarbons and alcohols

A series of copper(II) complexes of general formula [Cu(R-bian)X2] (X = Cl, Br) (1–5) containing rare and/or hard-to-get BIAN ligands with Ph, 4-OH-Ph, 3-NH2-Py and 3-Py functional groups, have been obtained by a template method. The composition of complexes 1–5 was confirmed by elemental analysis and IR spectroscopy. Complexes 1–5 exhibited high catalytic activity in the oxidation of alkanes and alcohols with peroxides. It has been established that alkyl hydroperoxides are intermediate products in reactions with alkanes. Maximum yield of the oxidation products of cyclohexane attained 31–32 % (complexes 2, 3 and 5). Based on the studies of kinetics and regio- and bond selectivity, it was concluded that hydroxyl radicals play a decisive role in the reaction.

Effect of different preparation technologies of CuCo2O4 on electrocatalytic activity for oxidation of alcohols

CuCo2O4 for electrocatalytic oxidation of alcohols (methanol, ethanol, ethylene glycol, glycerol) were successfully prepared by coprecipitation method (Cx-CuCo2O4), solvothermal method (Sxy-CuCo2O4) and bimetallic MOF template method (Bxy-CuCo2O4), respectively. The effect of different preparation technologies on the structure, morphology of CuCo2O4 were studied by X-ray diffraction (XRD), scanning electron microscope (SEM). The results show that C4–CuCo2O4 and S44–CuCo2O4 present spherical structure, while B64–CuCo2O4 displays cauliflower strip structure. X-ray photoelectron spectroscopy (XPS) results indicate that the molar ratios of Co3+/Co2+ in C4–CuCo2O4, S44–CuCo2O4 and B64–CuCo2O4 are 1.1, 0.94 and 0.93, respectively, and the area ratio of oxygen vacancy (Ov) to lattice oxygen (Olatt) in C4–CuCo2O4 reaches 0.99 while they are only 0.81 and 0.84 in S44–CuCo2O4 and B64–CuCo2O4 respectively, and more abundant Ov was also detected in C4– CuCo2O4 relative to the spinel oxides obtained by the other two preparation methods via electron paramagnetic resonance (EPR). Furthermore, C4–CuCo2O4 exhibits larger electrochemical active surface area (ECSA), smaller overpotential, lower electrochemical impedance, and smaller Tafel slope, its best catalytic activity may be attributed to its abundant oxygen vacancies and more content of Co3+ on the surface.

Regulating the Flexibility to Assemble Porous Single-Atom Fe-Coordinated Metallopolymers for Efficient Heterogeneous Catalytic Oxidations.

Metallopolymers as organic-inorganic hybrid materials formulated by metal embedding organic polymers show great potential for novel heterogeneous catalysis, in terms of the facile structural design and tunability. Herein, the disadvantage of nonporous stacking of one-dimensional (1D) structures has been suppressed by chain modulation of the 1D metallopolymers, allowing for the convenient construction of porous assemblies with single-atom dispersion and accessible active sites. By postmodification, the Fe/CM-1 catalyst readily synthesized by coordinating the Fe(II) to the twisted chain of 1D Schiff-base polymer possesses expedient flexibility, showing the highest porosity, remarkable heterogeneous recyclability, and thus prominent catalytic activity for the selective oxidation of benzylamine and alcohols. Moreover, control experiments supported by computational studies demonstrated that the unique pincer structure of Fe/CM-1 effectively maintains the valence state of the anchored single-atom iron, facilitating single-electron transfer and promoting efficient iron redox cycling during the catalytic process. Notably, these 1D metallopolymers have the advantage of cost-effectiveness, easy preparation in gram-scale, and utilization in continuous reaction, providing inspirations for facile synthesis of efficient heterogeneous catalysts from the well-developed 1D metallopolymers.

Isotype heterojunction: tuning the heptazine/triazine phase of crystalline nitrogen-rich C3N5 towards multifunctional photocatalytic applications.

Photocatalytic technology has been well studied as a means to achieve sustainable energy generation through water splitting or chemical synthesis. Recently, a low C/N atomic ratio carbon nitride allotrope, C3N5, has been found to be highly prospective due to its excellent electronic properties and ample N-active sites compared to g-C3N4. Tangentially, crystalline g-C3N4 has also been a prospective candidate due to its improved electron transport and extended π-conjugated system. For the first time, our group successfully employed a one-step molten salt calcination method to prepare novel N-rich crystalline C3N5 and elucidate the effect of calcination temperature on the heptazine/triazine phase. Calcination temperatures of 500 °C (CC3N5-500) and 550 °C (CC3N5-550) lead to crystalline carbon nitride with both heptazine and triazine phases, forming an intimate isotype heterojunction for robust interfacial charge separation. An excellent photocatalytic hydrogen evolution rate (359.97 μmol h-1; apparent quantum efficiency (AQE): 12.86% at 420 nm) was achieved using CC3N5-500, which was 15-fold higher than that of pristine C3N5. Furthermore, CC3N5-500 exhibited improved activity for simultaneous benzyl alcohol oxidation and hydrogen production, as well as H2O2 production (AQE: 9.49% at 420 nm), signifying its multitudinous photoredox capabilities. Moreover, the recyclability tests of the optimal CC3N5-500 on a 3D-printed substrate also showed a 92% performance retention after 4 cycles (16 h). This highlights that crystalline C3N5 significantly augmented the reaction performance for diverse multifunctional solar-driven applications. As such, these results serve as a guide toward the structural tuning of 2D metal-free carbon nanomaterials with tunable crystallinity toward achieving boosted photocatalysis.

Catalytic Activity of Atomic Metals Clusters Decorated Polyaniline Electrodes in Electrochemical Oxidation of 1-Propanol

Electrochemical sensors are capable to fast-detect chemicals with a high sensitivity at a low cost. Thanks to these advantages, electrochemical sensors are promising for detections of biomolecules, such as glucose, dopamine, uric acid, etc. The catalytic electrode in a electrochemical sensor is composed of noble noble metals, such as Au and Pd,and a suppoorting material. Polyaniline (PANI)[ 1]is an ideal supporting material for noble metal clusters because of its good electrical conductivity, high stability, large active surface area, and simple preparation process. Recently, PANI decorated with atomic level noble metal clusters is report to show distinct catalytic activity for the electrochemical oxidation of alcohols.[1] However, the effects of the number of the metal atoms in such clusters and the sequence of the atomic level deposition step on their electrocatalytic activity for electrochemical alcohol oxidation remain unexplored.In this presentation, the effects of the number of the metal atoms and the sequence of the atomic level deposition step in the atomic level noble metal clusters on the catalytic activity in electrochemical oxidation of 1-propanol (1-PrOH) are reported. The PANI was deposited on a Pt disk electrode (ϕ = 3 mm) by electrochemical polymerization in a 2 M HBF4 aqueous solution containing 0.1 M of aniline. Then, the PANI deposited electrode was decorated with mono-atomic noble metal clusters, bi-atomic, tri-atomic, or tetra-atomic noble metal clusters. The atomic noble metal clusters are denoted as PdxAuy, where x represents the number of Pd atoms in a cluster and y is the number of the Au atoms. The sources of the Pd and Au were K2PdCl4 and KAuCl4, respectively.. Fig. 1 shows the schematic procedures for fabricating a bi-atomic pure Pd (Pd2) decorated PANI electrode and a PdAu decorated PANI electrode. The catalytic activity for the electrochemical oxidation of 1-PrOH was evaluated by performing cyclic voltammetry measurements with an aqueous solution containing 0.5 M 1-PrOH and 1 M KOH.The catalytic activtiy was found be higher for the Pd2 and Pd4 decorated PANI electrodes than those of the Pd1 and Pd3 decorated PANI electrodes, which revealed odd-even pattern effects as reported in a previous study.[ 1] Furthermore, the catalytic activity was found to be affected by the sequence in deposition of the atomic level noble metal clusters. Reference [1] A. P. Jonke, J. L. Steeb, M. Josowicz, J. Janata, Catal Lett 2013, 143, 531–538. Figure 1

MnO2 shape dependent catalytic activity in vapour phase benzyl alcohol (BnOH) oxidation in presence of air

Understanding the relationship between the structure and the activity of the catalyst relies on the shape–controlled synthesis of nanostructures is crucial importance. The vapor phase oxidation of benzyl alcohol (BnOH) process over morphologically designed shape–selective manganese oxide nanorods (MnO2NR) and nanospheres (MnO2NS) catalysts are studied. The key catalytic properties are determined and demonstrated by various characterisation techniques such as P–XRD, BET, H2–TPR, O2–TPD, and Raman analysis. In addition, EDX and STEM–HRTEM microscopic analysis were carried out in better understanding the surface morphology, shape, and structure of the nanocatalysts. The prepared nanoporous MnO2NS catalyst enabled to generate more crystal defects, high surface area, strong reducing capacity, enhanced oxygen vacancies (Ov), and increased reactive surface oxygen species compared to nanorod shaped–MnO2NR catalyst. Significantly the rate of benzaldehyde (BnZA) formation in BnOH oxidation reaction over MnO2NS catalyst is ∼ 1.55 times higher than that of MnO2NR. Over MnO2NS creation of abundant O vacancies considerably improved the capacity of oxygen activation and redox ability.Thus, as a result, there are more active oxygen species which are mobile and reactive in accelerating the BnOH oxidation process.

Cooperation of ultrathin bowl-shaped scaffolds and oxygen vacancies promoting selective photo-oxidation of aromatic alcohols on layered oxyhalide PbBiO2Cl

Photocatalytic selective oxidation of aromatic alcohols into value-added chemicals has attracted increasing attention. Yet most processes suffer from sluggish charge kinetics, weak O2 affinity, low conversion efficiency and selectivity, which restrict their practical development. Herein, PbBiO2Cl ultrathin bowls (UBs) with rich oxygen vacancies (ROV) were initially fabricated via a combined microemulsion method and in-situ reduction process. The ultrathin bowl-shaped geometry and rich OVs effectively boost light absorption and charge separation. Theoretical results indicate the OVs on PbBiO2Cl not only generate abundant localized electrons, but also afford strong interfacial covalent bonds between O2 and OVs, which can act as atomic-level electron transfer highway and effectively promote the O2 adsorption and activation. As a result, ROV-PbBiO2Cl UBs show a 5.2-fold enhanced activity for aerobic oxidation of alcohols to aldehydes relative to PbBiO2Cl nanoplates (NPs). This work may inspire the design of more open hollow scaffolds with defect engineering for artificial photosynthesis.

Polyhedral Coordination Determined Co‐O Activity for Electrochemical Oxidation of Biomass Alcohols

AbstractEarth‐abundant transition metal oxides are promising electrocatalysts for oxidation of biomass alcohols. Here, CoO and Co3O4 are selected as representative cobalt oxide catalysts and grown on carbon fiber paper (CFP) electrodes to reveal the interplay between electronic structure and catalytic activity of catalysts for oxidation of glycerol, diols, and monohydric alcohols. In situ electrochemical tests elucidate that the CoO/CFP electrode has lower interfacial impedance, higher charge transfer, faster oxidation rate, and thereby the higher catalytic activity for alcohol oxidation than the Co3O4/CFP electrode. Especially for glycerol oxidation, the CoO/CFP electrode only requires 1.32 V to reach 10 mA cm−2, the potential is 120 mV lower than that for the Co3O4/CFP electrode. The CoO/CFP electrode can also produce value‐added products such as formate, acetate, and glycolate with high selectivity and efficiency at low energy consumptions from oxidation of biomass alcohols. Theoretical calculations further confirm the dominant role of octahedrally coordinated Co‐O sites in adsorption, activation, and oxidation of C3‐C1 alcohols. This work sheds light on the design of highly efficient transition metal oxide catalysts for oxidation of alcohols by populating octahedral sites in the crystal structure.

Defective Au nanoparticles manipulated by Au-MgxAl-LDH interplay for alkali-free oxidation of benzyl alcohol

Supported gold catalyst, especially in terms of nanosized particles with defective surface and low-coordinated structure, plays a vital role in the heterogeneous catalysis. However, such defective Au nanoparticles are hardly acquired when supporting on non-reducible metal oxides/hydroxides due to insufficient Au-support interaction. In this work, we found that the defective Au NPs could be fabricated via the strong interplay between Au and crystal lattices of layered double hydroxides-MgxAl-LDH. Experimental and theoretical evidences revealed that the formation of a preferential-oriented LDH(015) plane enabled the surface configuration for defective Au centers with the maximized number of step sites at Mg/Al ratio of 3.0–3.5. The optimized Au/Mg3.5Al-LDH catalyst shows a boosting catalytic activity for benzyl alcohol oxidation (TOF, 1008 h−1) at only 80 °C with the lowest activation energy in the absence of alkali. The work provides a new insight for manipulating the defective-enriched Au particles via the fine-tuning Au-LDH interplay for alkali-free selective oxidations.

Metal-Support Interaction in Gold Zeolitic Octahedral Metal Oxide and the Catalytic Activity for Low-Temperature Alcohol Oxidation.

Au nanoparticles are efficient catalysts for selective oxidations. The interaction between Au nanoparticles and supports is critical for achieving high catalytic activity. Herein, Au nanoparticles are supported on a zeolitic octahedral metal oxide based on Mo and V. The charge of Au is controlled by the surface oxygen vacancies of the supports, and the redox property of the zeolitic vanadomolybdate is highly dependent on Au loading. The Au-supported zeolitic vanadomolybdate is used as a heterogeneous catalyst for alcohol oxidation under mild conditions with molecular oxygen as an oxidant. The supported Au catalyst can be recovered and reused without the loss of activity.

Generation of Site-Selective Structural Vacancies in a Multinary Metal-Organic Framework for Enhanced Catalysis.

Generating structural vacancies in metal-organic frameworks (MOFs) by partially removing the inorganic and organic units from the scaffolds is an effective strategy to modulate the pore parameters of the extended structures. However, pore enlargement is accomplished at the cost of loss in the number of active sites in typical MOFs, since dissociations of coordination linkages to create vacancies are not site-selective. Here, we performed site-specific vacancy generation in a multinary MOF (FDM-6) by selectively hydrolyzing the weak Zn─carboxylate linkages and keeping the strong Cu─pyrazolate linkages untouched. Surface area and pore size range of the materials could be systematically tuned by adjusting the water content and hydrolysis time. More than 56% of the Zn(II) sites in FDM-6 could be vacant, as evidenced by the atom occupancy analysis using powder X-ray diffraction, while most of the redox-active Cu sites are held in the backbone. The vacancies create highly connected mesopores, thus guaranteeing facile transportation of the guest molecules toward the active sites. Compared with the pristine MOF, FDM-6 with site-selective vacancies shows enhanced catalytic activity in bulky aromatic alcohol oxidation. Overall, the multinary MOF provides a platform in which both pore size enhancement and full retainment of active sites could be delivered in one framework by simple vacancy engineering.

Effect of loading of Pt-decorated TiO2 on the enhancement of aerobic photo-oxidation of benzyl alcohol

Using Pt loaded on semiconductor supports have created new opportunities for improving catalytic performance when exposed to light. This study used the photo-deposition method to create platinum loaded on TiO2, which was then examined using TEM, ICP, X-ray diffraction, BET analysis, and CO chemisorption. The effect of loading of Pt on P25 under UV light based on photocatalytic activity was assessed and compared, resulting facilitate the electron transfer from Pt to titanium element, which in turn facilitates the aerobic oxidation of C7H8O. Benzotrifluoride (BTF) was used as a solvent in the benzyl alcohol photooxidation. Different loading of Pt on P25 was investigated and the range between 1 wt.% to 3 wt.% Pt–TiO2 through photo-deposition method gave the highest photocatalytic activity (⁓5.8 gcat−1 h−1) than others because of the size of platinum, the surface area of sample and dispersion. The platinum particle size over 1 nm (less than 1nm not enough energy for electron transfer) to and less than 4 nm (over 4 nm cover semiconductor's active sites) were given the highest activity for benzyl alcohol oxidation. The surface area of the sample is increasing with increasing platinum loading before agglomeration is happening. Higher surface area caused more active sites and active species for adsorption and desorption, resulting in better activity.

From AuPd Nanoparticle Alloys towards Core‐Shell Motifs with Enhanced Alcohol Oxidation Activity

AbstractThe best activity of bimetallic AuPd nanoparticles for alcohol oxidation reaction is usually achieved by adjusting the Au/Pd molar ratio. Herein, alloy AuPd nanoparticles of ∼2.5–3.5 nm, ranging from Au‐rich to Pd‐rich compositions, were synthesized through a sol‐immobilization method. A calcination step under air conditions caused an increase in size up to 5.5 nm, but also driven the segregation of Pd to the surface, which generated an Au rich core with Pd on the shell. At high Pd content, the shell structure is formed by PdO. The catalytic activity of Pd‐rich samples (1 : 1, 1 : 2 and 1 : 4 Au : Pd) for benzyl alcohol oxidation increased ∼4‐fold after calcination. Upon reduction with H2, surface PdO motifs are reduced to Pd that did not dissolve back into the AuPd alloy core, maintaining the metallic Pd shell. The catalytic activity decreased. Therefore, restructuring alloyed AuPd nanoparticles into core‐shell like structures with PdO in the shell is beneficial to the catalytic activity, but reduction of PdO layer was detrimental. These results provide new insights on the optimization of AuPd catalysts, considering not only the Au/Pd molar ratio, but also the importance of PdO, which was not anticipated in the previous literature.

Atom-stepped surface-regulated Pd nanowires for boosting alcohol oxidation activity

A highly active surface can endow the electrocatalysts with extraordinary catalytic performances. However, it remains challenging to tailor the atomic packing characteristics and thus the physical and chemical characteristics of the electrocatalysts. Herein, penta-twinned Pd nanowires (NWs) with abundant high-energy atomic steps (i.e., stepped Pd) are synthesized by seeded synthesis on Pd NWs enclosed by (100) facets. Benefiting from the catalytically active atomic steps, such as [n(100) × m(111)] on the surface, the resultant stepped Pd NWs can work as an effective electrocatalyst for the ethanol oxidation reaction (EOR) and ethylene glycol oxidation reaction (EGOR), which are essential anode reactions in direct alcohol fuel cells (DAFCs). Compared with commercial Pd/C, the Pd nanowires bound by (100) facets and atomic steps both display enhanced catalytic activity and stability towards the EOR and EGOR. Importantly, the mass activities of the stepped Pd NWs toward the EOR and EGOR are 6.38 and 7.98 A mgPd−1, which are 3.1 and 2.6 times those of Pd NWs enclosed by (100) facets, respectively. Besides, our synthetic strategy also enables the formation of bimetallic Pd-Cu nanowires with abundant atomic steps. This work not only demonstrates a simple yet effective strategy to obtain mono- or bi-metallic nanowires with abundant atomic steps, but also highlights the significant role of atomic steps for boosting the activity of electrocatalysts.

Facile synthesis of CoSi alloy catalysts with rich vacancies for base- and solvent-free aerobic oxidation of aromatic alcohols

The rational design and green synthesis of low-cost, robust, and efficient catalysts for the selective oxidation of various alcohols are highly challenging. Herein, we report a fast and solvent-free arc-melting (AM) method to controllably synthesize a semimetallic CoSi alloy catalyst (denoted as AM-CoSi) that is efficient in the base- and solvent-free oxidation of six types of aromatic alcohols. X-ray absorption fine structure analysis, electron paramagnetic resonance spectroscopy, and aberration-corrected high angle annular dark field scanning transmission electron microscopy confirmed the successful synthesis of AM-CoSi with abundant Si vacancies (Siv). The as-prepared CoSi alloy catalysts exhibit an order of magnitude greater activity in the oxidation of a model reactant, benzyl alcohol (BAL) to benzyl benzoate (BBE), compared with their mono-counterparts, and provide 70% yield of BBE, the highest yield reported to date. Experimental results and density functional theory calculations suggest that the CoSi alloy structure improves the BAL conversion and that Si vacancy is the main contributor to the generation of BBE, based on which a potential reaction pathway is rationally proposed. Furthermore, the CoSi alloy maintains high stability and also exhibits high activity in the selective oxidation of various alcohols with different functional groups. This work demonstrates for the first time that semimetallic CoSi alloys can be robust catalysts for the green oxidation of various alcohols and proviedes a vast opportunity for the rational design and application of other semimetal alloy catalysts.

Versatile synthesis of nano-icosapods via cation exchange for effective photocatalytic conversion of biomass-relevant alcohols.

Branched metal chalcogenide nanostructures with well-defined composition and configuration are appealing photocatalysts for solar-driven organic transformations. However, precise design and controlled synthesis of such nanostructures still remain a great challenge. Herein, we report the construction of a variety of highly symmetrical metal sulfides and heterostructured icosapods based on them, in which twenty branches were radially grown in spatially ordered arrangement, with a high degree of structure homogeneity. Impressively, the as-obtained CdS-PdxS icosapods manifest a significantly improved photocatalytic activity for the selective oxidation of biomass-relevant alcohols into corresponding aldehydes coupled with H2 evolution under visible-light irradiation (>420 nm), and the apparent quantum yield of the benzyl alcohol reforming can be achieved as high as 31.4% at 420 nm. The photoreforming process over the CdS-PdxS icosapods is found to be directly triggered by the photogenerated electrons and holes without participation of radicals. The enhanced photocatalytic performance is attributed to the fast charge separation and abundant active sites originating from the well-defined configuration and spatial organization of the components in the branched heterostructures.