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Six types of insoluble bead-shaped stable heterogeneous nanoparticle catalysts were prepared using two categories of poly(N-vinylimidazole) microbeads grafted with D(G2) and D(G3) matrices derived from 2% (LC) and 10% (HC) cross-linking monomer load, viz., divinylbenzene, followed by individual stabilization/immobilization of AuNPs/AuPdNPs. All these catalysts were characterized using FT-IR, UV-Vis, SEM, EDAX, XRD and TGA analyses. These catalysts were individually employed for the degradation of malachite green as a model reaction under pseudo first-order condition. Among the bimetallic catalysts, LC-PVIm-D(G3)–AuPdNP (36.61 × 10−3 min−1) was shown to be superior; specifically, it was three times more active than the monometallic catalyst, LC-PVIm-D(G2)–AuNP (11.35 × 10−3 min−1). Hence, the superior catalyst was employed for detailed kinetic studies by varying the [substrate], [NaBH4] and [catalyst], and each experimental parameter was found to influence the reaction. The recycling efficiency of this superior catalyst was studied five times, and the activity was found to remain unaltered even at the fifth cycle, and hence, the catalyst was stable and suitable to carry out the reduction reaction in the logistic mode. [ABSTRACT FROM AUTHOR]

Two sets of silica-supported nickel phosphide catalysts with a nickel content of about 2.5 and 10 wt % and Ni/P molar ratio 2/1, 1/1 and 1/2 in each set, were prepared by way of a temperature-programmed reduction method using (Ni(CH3COO)2) and ((NH4)2HPO4) as a precursor. The NixPy/SiO2 catalysts were characterized using chemical analysis N2 physisorption, XRD, TEM, 31P MAS NMR. Methyl palmitate hydrodeoxygenation (HDO) was performed in a trickle-bed reactor at 3 MPa and 290 °C with LHSV ranging from 0.3 to 16 h-1. The Ni/P ratio was found to affect the nickel phosphide phase composition, POx groups content and catalytic properties in methyl palmitate HDO with the TOF increased along with a decline of Ni/P ratio and a growth of POx groups' content. Taking into account the possible routes of methyl palmitate conversion (metal-catalyzed hydrogenolysis or acid-catalyzed hydrolysis), we proposed that the enhancement of acid POx groups' content with the Ni/P ratio decrease provides an enhancement of the rate of methyl palmitate conversion through the acceleration of acid-catalyzed hydrolysis. [ABSTRACT FROM AUTHOR]

A strategy for tuning the surface property of Single Walled Carbon Nanotubes (SWNTs) for enhanced methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR) along with methanol tolerance is presented. The surface functionality is tailored using controlled acid and base treatment. Acid treatment leads to the attachment of carboxylic carbon (CC) fragments to SWNT making it hydrophilic (P3-SWNT). Base treatment of P3-SWNT with 0.05 M NaOH reduces the CCs and makes it hydrophobic (P33-SWNT). Pt catalyst supported on the P3-SWNT possesses enhanced MOR whereas that supported on P33-SWNT not only enhances ORR kinetics but also possess good tolerance towards methanol oxidation as verified by the electrochemical technique. [ABSTRACT FROM AUTHOR]

Low working temperature and high sensitivity of gas sensors are critical in their practical applications; however, these properties are usually contradictory and cannot be realized simultaneously. Here, ZnO porous nanowires (PNWs) are prepared by a modified electrospinning method, and Pt nanoparticles (NPs) are doped on their surface by chemical reduction. The effects on morphology, specific surface area, and oxygen vacancy are discussed for the acetone gas-sensing performance. Results showed that Pt-ZnO PNWs responded optimally to acetone gas at 160 °C at 16.7–1.8 ppm, which was three-fold greater than that of pristine ZnO PNWs. In addition, the lowest detection limit is 50 ppb, a ten-fold lower level than pristine ZnO PNWs. The sensor exhibits superior acetone selectivity, humidity resistance, repeatability, long-time stability, noble metals, and a porous design with a large surface area, providing synergistic effects that increase the number of surface adsorption sites. Thus, the approach provided a new comprehension for loading a high-dispersibility catalyst onto the porous structure surface as a potential breath analyzer. [Display omitted] • Pt-ZnO with porous 1D nanowires morphology prepared by modified electrospinning. • The novel porous structure provided abundant active sites and diffusion channels. • Pt NPs doping induced more oxygen vacancy due to the catalytic action. • The Pt-ZnO PNWs sensor exhibited superior acetone sensing at low temperature. • The gas-sensing mechanism was expounded in detail. [ABSTRACT FROM AUTHOR]

The rapidly rising concentration of carbon dioxide (CO 2) in the atmosphere as a result of human activity poses serious threats and alarming situations not only to humans but also to our environment. Within the context of this agenda, electrochemical CO 2 reduction to value-added chemicals is one of the most effective approaches to lowering environmental CO 2 concentrations. However, this approach requires highly robust electrocatalysts; therefore, in the last few years, there has been a dramatic increase in the demand for the synthesis and development of efficient electrocatalysts. Recently, metal-organic framework (MOF)-based materials, having high porosity, large surface area, stability, and chemical tunability, have been extensively studied as an emerging class of electrocatalysts for CO 2 reduction reaction (CO 2 RR). In this article, we reviewed the fundamentals of CO 2 RR, including its mechanism and activity descriptors, and current developments in MOF-based electrocatalysts for CO 2 RR are described along with their underlying chemistry. Finally, we explore the current difficulties and potential future developments of MOFs for CO 2 RR. It is intended that this review will aid in the development of ever-more effective MOF-based materials for CO 2 abatement and raise awareness of the need for additional work to be done in order to explore MOFs' potential for tackling important environmental sustainability challenges. Particularly, ligand engineering in MOFs remains an important topic for developing a highly efficient CO 2 RR catalyst. [Display omitted] • Concepts of CO 2 RR, mechanisms, and MOFs fabrication strategies are highlighted. • Recent developments in MOFs-based materials as CO 2 RR electrocatalysts are reviewed. • The challenges and prospects with MOF-based materials for CO 2 RR are provided. [ABSTRACT FROM AUTHOR]

By using in situ X-ray diffraction, we were able to demonstrate the effect of H 2 O on the reduction of cobalt oxide particles for Fischer-Tropsch Synthesis. Reduction of Co 3 O 4 to Co via CoO in H 2 produces large quantities of water, which was thought to have an impact upon the reduction of the catalyst down a reactor bed. Bed profiles are produced from saturation of the bottom of the catalyst bed from the H 2 O produced from the top of the bed. This contribution clearly shows the impact of H 2 O on the cobalt crystallites to hinder reduction and facilitate sintering of the cobalt particles. In situ X-ray diffraction was used to follow the reduction of the cobalt phase throughout the evolution of the reduction process, while controlled water production and cofeed was used to study the effect across different water levels (from 0 up to 1% H 2 O). Each study in turn produced clear transitions to CoO and Co metal, while H 2 O shifted the peaks to higher transition temperatures and slowed the reduction process to cobalt metal. [ABSTRACT FROM AUTHOR]

This publication highlights the effect of CO treatments on both calcined and reduced catalysts by using novel in situ techniques to track particle transformations, which are so vital to catalyst performance and activity. Cobalt carbide formation has been shown to occur readily with CO treatments on metallic cobalt particles, and in this study we have used in situ XRD and temperature-programmed reduction (TPR) techniques to track the evolution of the carbide. We were able to show a dependence on CO partial pressures and the formation of a single hexagonal phase of cobalt as a result of the carbide step. The stability of cobalt carbide was studied and its reduction in hydrogen to cobalt metal was observed. CO was also used as the reducing gas and by using TPR and in situ XRD we were able to demonstrate the reduction of cobalt oxide (Co3O4) to cobalt carbide (Co2C) via both oxide (CoO) and metal (Co) intermediates. [ABSTRACT FROM AUTHOR]

New insights for the mechanism of nitro to amino groups conversion have been revealed on both N-doped graphene and Ag nanoparticles catalysts, based on the paper assisted ultrasonic spray ionization mass spectrometry: (1) water molecules not NaBH 4 are the hydrogen source for the reduced amino groups, (2) NaBH 4 could contribute to the ionization of H + from water, facilitating its adsorption on nitro groups, (3) six different intermediates have been detected to depict the whole catalytic process, and no condensed roots are involved in and (4) this reduction process is spontaneous to some extent, and even without catalysts it is not totally stopped as obtained from the spectral measurements. [ABSTRACT FROM AUTHOR]

In this work, the regeneration of rich CO 2 -loaded monoethanolamine (MEA) solvent with two catalysts (e.g. SAPO-34 and SO 4 2− /TiO 2 ) was investigated in order to reduce the energy requirement for solvent regeneration. The regeneration behavior with and without catalyst of a 5M MEA solution with an initial CO 2 loading of 0.5 mol CO 2 /mol amine at 96 °C was studied to compare their CO 2 desorption rate and heat duties. The results show that the two solid acid catalysts can reduce the heat duty for solvent regeneration and increase the CO 2 desorption rate in comparison with blank test. The mechanism of CO 2 desorption with catalyst in 5M MEA was proposed based on the result of catalyst characterization (e.g. N 2 absorption/desorption experiment, Py-IR, NH 3 -TPD, FT-IR and XRD) to better understand the desorption process. The results indicate that SAPO-34 with the higher joint value of Brϕnsted/Lewis acid sites ratio (B/L) and mesopore surface area (MSA) shows the faster CO 2 desorption rate and lower heat duty than SO 4 2− /TiO 2 . Based on the experimental results, the addition of solid acid catalysts into amine solution could be considered as one of choices to reduce the heat duty for CO 2 desorption from CO 2 -loaded amine solvent. [ABSTRACT FROM AUTHOR]

N-doped microporous carbon as an exceptional metal-free catalyst from waste biomass ( banana peel as representative ) was obtained via fast catalysis carbonization, followed by N-doping modification. The method achieves a relatively high C conversion efficiency of ∼41.9%. The final carbon materials are doped by N (∼3 at.%) and possess high surface area (∼1097 m 2 g −1 ) and abundant micropores. Compared to commercial Pt/C materials, the as-prepared carbon catalyst exhibits a comparable electrocatalytic activity and much better stability. Furthermore, the metal-free catalyst loaded Zn-air battery possesses higher discharge voltage and power density as compared with that of commercial Pt/C. This novel technique can also be readily applied to produce metal-free carbon catalysts from other typical waste biomass (e.g., orange peel, leaves) as the carbon sources. The method can be developed as a potentially general and effective industrial route to transform waste biomass into high value-added microporous carbon with superior functionalities. [ABSTRACT FROM AUTHOR]

A strategy for the rational design and synthesis of nitrogen doped carbon as an efficient cathode catalyst for the oxygen reduction reaction (ORR) is developed. A high performance catalyst is obtained directly by carbonization of a bicomponent mixture containing Gentiana scabra Bunge (nature provided biomass) and ammonium chloride (NH4Cl), which are easily available and inexpensive. Gentiana scabra Bunge functions as a carbon source, while ammonium chloride acts as both a nitrogen dopant and a porogen. Furthermore, synergistically tailoring the NH4Cl/Gentiana scabra Bunge feed ratio and the carbonization temperature makes the chemical and physical properties of the as-prepared carbon controllable and thus helps in realising ORR-performance-oriented design and synthesis of nitrogen doped carbon. The synthesized porous carbon (specific surface area of up to 1440 m2 g−1 and 14 wt% nitrogen content) is an ideal material in the ORR that requires high specific surface area, easy accessibility to the active sites through the hierarchical porous system and excellent electrical conductivity. Therefore, the synthesized porous carbon shows high ORR activity with comparable performance to a Pt/C catalyst in both acidic and alkaline solutions, allowing large scale production of carbon materials for practical application in fuel cells. [ABSTRACT FROM AUTHOR]

A novel polymeric nanocomposites (TiO 2 /poly(acrylamide-co-methylenbisacrylamide)) decorated with silver nanoparticles (Ag NPs) denoted as (Ag–TiO 2 /poly(AM-co-MBAM)) was prepared and fully characterized. Initially, the surface of TiO 2 nanoparticles was modified using methacryloxypropyltrimethoxysilan (MAPTMS), thus a C C bond for polymerization was generated, which polymerized wih acrylamide and methylenbisacrylamide monomers. Ag NPs then were immoblized on the surface of this obtained polymeric nanocomposites via reduction in the presence of AgNO 3 . The catalytic efficiency of Ag–TiO 2 /poly(AM-co-MBAM) nanocomposites was investigated for the reduction of nitroarenes and some carbonyl compounds in the presence of sodium borohydride (NaBH 4 ) as reducing agent in aqueous media to give the corresponding anilines and alcohols with excellent yields and short reaction times, respectively. The nanocatalyst was easily recovered and reused for at least seven cycles without appreciable loss of its catalytic activity. [ABSTRACT FROM AUTHOR]

H-ZSM-5 was modified with transition metals (including Fe, Cu, Mn, and Co) by homogeneous deposition precipitation (HDP) method and tested as catalyst for the selective reduction of NO with ammonia (NH3-SCR). The selectivity to N2 was higher than 95% in all the nanocatalysts and the NO conversion over nanocatalysts decreased in the following sequence Cu-ZSM-5 > Mn-ZSM-5 > Co-ZSM-5 > Fe-ZSM-5 at 200-300°C. The Cu-ZSM-5 catalyst showed the highest catalytic activity, 95% of NO conversion at 300°C, among the catalysts investigated. The nature of the active sites was characterized by BET, TEM, H2-TPR, and NH3-TPD. Characterization results revealed that acidity and the redox properties of the catalysts play an important role in achieving high activity for NH3-SCR reaction. The highest catalytic activity of Cu/ZSM-5 can be correlated to easy reducibility of Cu species and strong acidic sites created by the Cu species. © 2017 American Institute of Chemical Engineers Environ Prog, 36: 1049-1055, 2017 [ABSTRACT FROM AUTHOR]

CuO-CeO 2 -ZrO 2 /cordierite catalysts have been successfully prepared by the impregnation reduction method. The effects of processing parameters such as the condition of reduction process, calcination temperature, the addition of surfactant on the size and shape of catalyst particles were studied by X-ray diffraction (XRD), BET surface area measurements, and scanning electron microscopy (SEM). The catalytic performance of the as-prepared catalysts for CO oxidation were evaluated by using a microreactor-GC system. The results indicate that the processing parameters influence greatly the size and shape of catalyst particles. Fragmental shape catalysts were formed when the impregnated samples were reduced in the thermostat water bath. However, spherical-like particles were obtained by ultrasonic-assisted in the reduction process. Tiny flower-like catalyst particles were found when the surfactant were used. When the calcination temperature decreased, the grain size of catalysts has reduced, and the catalytic activity for CO oxidation has been improved. The introduction of ultrasonic and surfactant resulted in larger specific surface area and better catalytic performance. [ABSTRACT FROM AUTHOR]

The present work introduces spinel oxide nanocrystals self-assembled into mesoporous spheres that are bifunctionally active towards catalyzing both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). The electrochemical evaluation reveals that (Ni,Co)3O4 demonstrates a significantly positive-shifted ORR onset and half-wave potentials [−0.127 and −0.292 V vs. saturated calomel electrode (SCE), respectively], whereas Co3O4 results in a negative-shifted OER potential (0.65 V vs. SCE) measured at 10 mA cm−2. Based on the DFT analysis, the potential at which all oxygen intermediate reactions proceed spontaneously is the highest for (Ni,Co)3O4 ( U=0.66 eV) during ORR, whereas it is the lowest for Co3O4 ( U=2.09 eV) during OER. The high ORR activity of (Ni,Co)3O4 is attributed to the enhanced electrical conductivity of the spinel lattice, and the high OER activity of Co3O4 is attributed to relatively weak adsorption energy promoting rapid release of evolved oxygen. [ABSTRACT FROM AUTHOR]

The development of efficient heterogeneous catalysts for degrading organic pollutants or converting them into harmless and even useful products is of vital significance for environmental remediation. Herein, we reported the facile synthesis of a highly active and stable nanocatalyst (AuNPs/uTiO 2 ) via a simple photoreduction deposition of Au nanoparticles (AuNPs) on urchin-like TiO 2 nanosphere (uTiO 2 ), and demonstrated its excellent performances as a catalyst for oxidative degradation of organic dyes and reductive conversion of 4-nitrophenol (4-NP). The AuNPs/uTiO 2 nanocomposite showed high surface area (147.5 m 2 ·g − 1 ), large pore volume (0.52 cm 3 ·g − 1 ), and high dispersity of AuNPs. In particular, the uTiO 2 support could combine AuNPs strongly and serve as a shield to prevent leaching or aggregation of AuNPs, while allowing guest organic molecules to diffuse in and out easily. Benefiting from the excellent characteristics, the AuNPs/uTiO 2 exhibited superior catalytic properties for dyes degradation and 4-NP reduction with significantly higher catalytic efficiencies than many previously reported heterogeneous catalysts. Moreover, the catalytic activity of AuNPs/uTiO 2 could remain almost unchanged after being recycled for several times, demonstrating its long-term stability. The AuNPs/uTiO 2 , combining the advantages of high activity, favorable kinetics, and excellent durability for dye degradation and 4-NP reduction, should be very promising for wastewater treatment. [ABSTRACT FROM AUTHOR]

Treatment of a secondary amine (piperidine or N -benzylmethylamine) with sequentially trimethylaluminum and carbodiimide CyN C NCy in a molar ratio of 1:1:1 afforded two mononuclear guanidinatoaluminum complexes, [{(C 5 H 10 N)C(NCy) 2 }AlMe 2 ] ( 1 ) and. [{(Bz(Me)N)C(NCy) 2 }AlMe 2 ] ( 2 ). Introducing dry oxygen slowly into the solution of 1 or 2 , [{(C 5 H 10 N)C(NCy) 2 }AlMe( μ -OMe)] 2 ( 3 ) and [{(Bz(Me)N)C(NCy) 2 }AlMe( μ -OMe)] 2 ( 4 ) were obtained, respectively. Both of 3 and 4 were also prepared by treatment of piperidine or N-benzylmethylamine with trimethylaluminum and carbodiimide CyN C NCy in the presence of O 2 . The complexes 1 – 4 were characterized by 1 H, 13 C NMR spectra and single crystal X-ray diffraction analysis. 1 – 4 were also used to catalyze the Meerwein–Ponndorf–Verley (MPV) reaction. [ABSTRACT FROM AUTHOR]

Low-valent TiII species have typically been synthesized by the reaction of TiIV h alides with strong metal reductants. Herein we report that TiII species can be generated simply by reacting TiIV imido complexes with 2 equiv of alkyne, yielding a metallacycle that can reductively eliminate pyrrole while liberating TiII. In order to probe the generality of this process, TiII-catalyzed alkyne trimerization reactions were carried out with a diverse range of TiIV precatalysts. [ABSTRACT FROM AUTHOR]

Attaching the phosphonated molecular catalyst [ReIBr(bpy)(CO)3]0 to the wide-bandgap semiconductor TiO2 strongly enhances the rate of visible-light-driven reduction of CO2 to CO in dimethylformamide with triethanolamine (TEOA) as sacrificial electron donor. Herein, we show by transient mid-IR spectroscopy that the mechanism of catalyst photoreduction is initiated by ultrafast electron injection into TiO2, followed by rapid (ps-ns) and sequential two-electron oxidation of TEOA that is coordinated to the Re center. The injected electrons can be stored in the conduction band of TiO2 on an ms-s time scale, and we propose that they lead to further reduction of the Re catalyst and completion of the catalytic cycle. Thus, the excited Re catalyst gives away one electron and would eventually get three electrons back. The function of an electron reservoir would represent a role for TiO2 in photocatalytic CO2 reduction that has previously not been considered. We propose that the increase in photocatalytic activity upon heterogenization of the catalyst to TiO2 is due to the slow charge recombination and the high oxidative power of the ReII species after electron injection as compared to the excited MLCT state of the unbound Re catalyst or when immobilized on ZrO2, which results in a more efficient reaction with TEOA. [ABSTRACT FROM AUTHOR]

A magnetically separable core-shell-like catalyst Ni-Pd/CB is designed and synthesized via a facile sequential reduction strategy. It is found that the Pd nanocrystals with a thickness of ∼1.67 nm and a length of ∼7.92 nm are intimately coupled with the Ni cores and the formed core-shell-like Ni-Pd nanoparticles are well dispersed on the CB surface with much smaller particle size and narrower size distribution as compared with that of unsupported ones. The ligand-free Ni-Pd/CB nanocatalyst is evaluated for Suzuki-Miyaura coupling reaction and exhibits excellent catalytic activity under mild aerobic conditions without using toxic solvents and inert protective atmosphere, achieving green catalysis. The high catalytic performance of Ni-Pd/CB catalyst can be attributed to its unique core-shell-like nanostructure and the concerted effects between the individual components. The introduction of Ni not only makes the catalyst magnetically separable in a suspension system, but also significantly lowers the cost. [ABSTRACT FROM AUTHOR]

A concept of surface/interface construction in-situ to design Cu 2 O/Cu catalysts on Cu 2 O nanostructures with highly active facets as highly efficient CO 2 RR catalysts have been demonstrated. [Display omitted] • Cu 2 O catalysts with active facets and morphologies are synthesized via the wet chemical reduction method. • The surface of Cu 2 O catalysts is reconstructed in situ to form Cu 2 O/Cu catalysts with highly active interface during converting CO 2 to C 2+ products. • Cu 2 O/Cu catalyst shows the maximum FE C2+ values of 70.0 % for CO 2 RR at −1.2 V vs RHE in 0.1 M KCl. • The Cu 2 O/Cu interface enhances the *CO adsorption and decrease the activation energy of C C coupling. Converting CO 2 to value-added chemicals and fuels by the electrocatalytic reduction reaction (CO 2 RR) is a promising strategy for reducing CO 2 emissions and achieving clean energy storage. Herein, Cu 2 O catalysts with various morphologies (hexapod concave rhombic dodecahedrons microcrystals enclosed with (3 3 1), (1 1 1) and (1 0 0) facets (D-Cu 2 O), cubic microcrystals enclosed with (1 0 0) facet (C-Cu 2 O) and octahedron microcrystals with (1 1 1) and (1 0 0) facets (O-Cu 2 O)) are prepared via the wet chemical reduction method. The in-situ formation of D-Cu 2 O/Cu, C-Cu 2 O/Cu and O-Cu 2 O/Cu surface/interface and the conversion mechanism of CO 2 to C 2+ products have been systematically studied. The electrocatalytic performance of D-Cu 2 O/Cu for CO 2 to form C 2+ products is superior to that of C-Cu 2 O/Cu and O-Cu 2 O/Cu, which the Faraday efficiencies (FE) of C 2+ products (ethylene and ethanol) reaches 70 %. The experimental results combined in-situ Raman spectroscopy and density function theory (DFT) calculations demonstrate that the good electrochemical performance is relate to the surface reconstruction and facet interface, which provides a positive local electronic environment to enhance the adsorption of *CO intermediates and reduces the energy barrier for the activation the C C coupling. This study will provide a new approach to improve the selectivity of CO 2 RR by interface engineering and surface. [ABSTRACT FROM AUTHOR]

Two new copper complexes with anions derived from 3-furancarboxylic/ 5-nitro-2-furancarboxylic acid and 4-phenylpyridine were obtained. These catalysts are the first example of copper catalysts for the selective hydrogenation of dicyclopentadiene in flow type reactors. [Display omitted] The reaction of copper(II) acetate with 3-furancarboxylic acid (Hfur) and 5-nitro-2-furancarboxylic acid (Hnfur) with participation of 4-phenylpyridine (phpy) in acetonitrile resulted in mononuclear complexes [Cu(L) 2 (phpy) 2 (H 2 O)]·solv (L = fur (1), nfur (2); solv = phpy (1)) whose structures were determined by direct single crystal X-ray analysis. According to X-ray data, the complexing component in 1 and 2 is in a distorted square-pyramidal environment (CuN 2 O 3); the pyramid base is formed by monodentate-bound oxygen atoms of fur-/nfur- anions and a pair of nitrogen atoms of the phpy moieties, while the water molecule occupies an axial position. It was found for the first time that copper nanoparticles immobilized on the surface of γ-Al 2 O 3 obtained by chemical reduction of 1 and 2 (pre-deposited on the surface from solution) with sodium tetrahydroborate show high selectivity of monohydrogenation of tricyclo[5.2.1.02,6]deca-3,8-diene (dicyclopentadiene, DCPD) to give tricyclo[5.2.1.02,6]dec-4-ene (5,6-dihydrocyclopentadiene, DHDCPD). The catalytic activity tests show high selectivity (up to 100 %) of the catalysts studied in the reaction of partial hydrogenation to DHDCPD under continuous process conditions even at high conversion values (up to 96 %) and with hydrogen present in excess. Thermal behavior of 1 and 2 was studied by simultaneous thermal analysis (STA). [ABSTRACT FROM AUTHOR]

Efficient and low cost reduced graphene oxide (rGOV) is prepared by chemical reduction of graphene oxide (GO) using vitamin C. Detailed characterization by XRD, SEM and Raman techniques confirm the successful reduction of GO. Thin films of rGOV with various thickness are deposited by spin coating on FTO glass substrates and are used as counter electrodes (CEs) in dye-sensitized solar cells (DSCs) incorporating the organic sensitizer D35 dye and the Co(bpy) 3 3+ /Co(bpy) 3 2+ redox couple. These devices present high photocurrent density ( j sc ) and open-circuit voltage ( V oc ) values resulting in enhanced photovoltaic performance in comparison with the Pt catalyst. The novel rGOV electrodes constitute an excellent, low-cost and environmentally friendly alternative solution to the costly platinum-based cathodes. [ABSTRACT FROM AUTHOR]

Similarities are established between well-known reactivity descriptors of metal electrodes for their activity in the oxygen reduction reaction (ORR) and the reactivity of molecular catalysts, in particular macrocyclic MN4 metal complexes confined to electrode surfaces. We show that there is a correlation between the MIII/MII redox potential of MN4 chelates and the M-O2 binding energies. Specifically, the binding energy of O2 (and other O species) follows the MIII-OH/MII redox transition for MnN4 and FeN4 chelates. The ORR volcano plot for MN4 catalysts is similar to that for metal catalysts: catalysts on the weak binding side (mostly CoN4 chelates) yield mainly H2O2 as the product, with an ORR onset potential independent of the pH value on the NHE scale (and therefore pH-dependent on the RHE scale); catalysts on the stronger binding side yield H2O as the product with the expected pH-dependence on the NHE scale. The suggested descriptors also apply to heat-treated pyrolyzed MN4 catalysts. [ABSTRACT FROM AUTHOR]

Keywords: chemical synthesis; electrochemical reactions; electrocatalysis; CO2 reduction EN chemical synthesis electrochemical reactions electrocatalysis CO2 reduction 1 1 1 11/21/22 20221116 NES 221116 Carbon dioxide, the most widely distributed carbon source in Nature, has been widely investigated for its reduction and reuse. Herein, we report for the first time, the latest preparation methods of metal aerogels and the recent progress in electrocatalytic CO SB 2 sb reduction. After that, the properties of several typical metallic aerogels and their latest applications in electrocatalytic CO SB 2 sb reduction are described. [Extracted from the article]

[Display omitted] • PtIr/C 0.40 (SnO 2) 0.60 nanowires showed enhanced catalytic activity toward methanol oxidation. • The synergy between C and SnO 2 as support results in a high catalytic performance. • The PtIr/C 0.40 (SnO 2) 0.60 catalyst displayed the lowest resistance to charge transfer. • The composition PtIr/C 0.40 (SnO 2) 0.60 is more stable than the other catalysts. • Different affinity between PtIr NWs and carbon or tin oxide results in different agglomeration of the NWs. PtIr nanowires (NWs) with a fixed ratio of 90% Pt and 10% Ir were supported in mixtures of Vulcan XC-72 R carbon and tin oxide (SnO 2) in the proportions of 50:50, 40:60, 30:70, 20:80, and 10:90 of carbon and SnO 2. We successfully synthesized PtIr NWs by chemical reduction of the metallic precursors with formic acid and tested them toward methanol electro-oxidation in acidic media. Neither surfactants nor templates were used during the syntheses. The electrochemical study was conducted by CO-stripping, cyclic voltammetry, chronoamperometry, and steady-state polarization curves. The PtIr NWs have a higher affinity to be anchored onto the carbon support than on SnO 2 , resulting in different distribution and agglomeration of the NWs that thereby has substantial consequences on the catalytic activity of the composites. The PtIr/C 0.4 (SnO 2) 0.6 catalytic composite exhibited the highest activity toward methanol oxidation. The high catalytic performance displayed by the PtIr/C 0.4 (SnO 2) 0.6 composite results from the synergy between C and SnO 2 as supports (specifically in this proportion), Ir as the co-catalyst, and the morphology of the nanowires. Therefore, these combined effects result in greater mobility of OH ads and CO ads , facilitating the CO removal from the catalyst surface and allowing better methanol adsorption for further oxidation. The PtIr/C 0.4 (SnO 2) 0.6 catalyst also showed the lowest resistance to charge transfer compared with the other binary catalysts. Thus, the use of SnO 2 + C as supports and PtIr nanocatalysts with NW morphology results in highly active materials toward methanol oxidation, which are promising to compose anodes for direct methanol fuel cells. [ABSTRACT FROM AUTHOR]

CO 2 conversion/utilization is a promising approach for accomplishing two objectives: using the single strategy of CO 2 reduction to value-added chemicals and solar fuels to mitigate global warming and meeting the growing energy demands. CO 2 reduction is kinetically and thermodynamically sluggish process; therefore, catalysts are always required for accelerating the reduction process. In the recent decades, the booming research studies on heterogeneously catalyzed CO 2 reduction has sprung up. Therefore, a critical review on catalytic CO 2 reduction and the recent progress in catalysts design is highly needed. This review presents a panorama of the recent progress in electrocatalytic, and photo driven CO 2 conversion to value-added chemicals. Moreover, the recent research accomplishments in product selective catalysis are comprehensively reviewed. Lastly, a brief perspective on the challenges and future directions is presented, which could be of great interest for enhancing the activity and selectivity of CO 2 reduction reactions and commercialization of CO 2 conversion approaches. [Display omitted] • A critical review on heterogeneously catalyzed CO 2 reduction. • Electrocatalytic and photo-driven CO 2 reduction. • Panorama of the recent progress in catalytic CO 2 conversion to value-added chemicals. • Accomplishments in product selective catalyst designing. [ABSTRACT FROM AUTHOR]

The enantioselective reduction of prochiral ketones with borane in the presence of a chiral ligand has received considerable attention. Hydroxylamine-based chiral ligands with amide and hydroxyl functions in the presence of other co-ordinating groups are highly effective in these asymmetric reductions. The current work presents a simple one step synthesis of a series of β-hydroxyamide-based ligands from the reaction between 3-hydroxy-2-naphthoic acid and chiral amino alcohols and their applications as catalysts in asymmetric borane-mediated reductions of aromatic prochiral ketones in THF. The reductions provided the corresponding secondary alcohols with up to 96% ee and in good to excellent yields (89–99%). DFT calculations at B3LYP/6-31+g(d) level offered theoretical models to account for the enantioselectivity imposed by the chiral ligands in the reductions of the ketones. [ABSTRACT FROM AUTHOR]

The aim of non-precious metal catalysts (NPMCs) is to replace expensive Pt-based catalysts for fuel cells. NPMCs require not only high oxygen reduction reaction (ORR) catalytic activity but also cheap ingredients, and the facile synthetic method of the catalyst is amendable to mass production. We describe a potential catalyst for catalyzing the cathodic ORR, which is synthesized by a facile method: uses porous carbon-supported melamine-formaldehyde resin as a precursor to a carbon–nitrogen template for high-temperature synthesis of catalysts incorporating iron. In the synthesis process of porous carbon-supported melamine-formaldehyde resin, the uses of surfactant (Tween 80), making the activity of catalysts have been improved significantly. As a result, the catalyst demonstrates remarkable ORR activity in both acid and alkaline electrolytes, thus making it a promising alternative as an ORR catalyst for application in fuel cells. [ABSTRACT FROM AUTHOR]

The ever growing increase of CO2 concentration in the atmosphere is one of the main causes of global warming. Thus, CO2 activation and conversion toward valuable added compounds is a major scientific challenge. A new set of Au/δ-MoC and Cu/δ-MoC catalysts exhibits high activity, selectivity, and stability for the reduction of CO2 to CO with some subsequent selective hydrogenation toward methanol. Sophisticated experiments under controlled conditions and calculations based on density functional theory have been used to study the unique behavior of these systems. A detailed comparison of the behavior of Au/β-Mo2C and Au/δ-MoC catalysts provides evidence of the impact of the metal/carbon ratio in the carbide on the performance of the catalysts. The present results show that this ratio governs the chemical behavior of the carbide and the properties of the admetal, up to the point of being able to switch the rate and mechanism of the process for CO2 conversion. A control of the metal/carbon ratio paves the road for an efficient reutilization of this environmental harmful greenhouse gas. [ABSTRACT FROM AUTHOR]

Fe@FeO core-shell nanowires were synthesized via the reduction of Fe ions by sodium borohydride in an aqueous solution with a subsequent heat treatment to form FeO shell and employed as a cathode catalyst for non aqueous Li-air batteries. The synthesized core-shell nanowires with an average diameter of 50-100 nm manifest superior catalytic activity for oxygen evolution reaction (OER) in Li-O batteries with the charge voltage plateau reduced to ∼3.8 V. An outstanding performance of cycling stability was also achieved with a cutoff specific capacity of 1000 milliampere hour per gram over 40 cycles at a current density of 100 mA g. The excellent electrochemical properties of Fe@FeO as an O electrode are ascribed to the high surface area of the nanowires' structure and high electron conductivity. This study indicates that the resulting iron-containing nanostructures are promising catalyst in Li-O batteries. [ABSTRACT FROM AUTHOR]

Hollow porous gold nanoparticles (HPGNPs) were synthesized via a one-step solution phase method at ambient temperature. The particle size, ranging from 80 nm to 350 nm, was easily controlled by changing the concentration of HAuCl 4 . The morphology and the structure of the as-prepared HPGNPs were investigated by SEM, TEM, HRTEM and XPS. Langmuir isotherm analysis yielded values of 8973 m 2 /g for the outer surface area and 58724 m 2 /g for the inner surface area for the 80 nm HPGNPs. Due to a special hollow porous nanostructure, the HPGNPs exhibited superior catalytic activity and stability for the reduction of 4-nitrophenol (4-NP). No significant inactivation of the 80 nm HPGNPs was observed, even after recycling for six cycles or storing for more than 1 month. Due to these excellent properties, it is expected that HPGNPs can be used in such applications as water pollutant removal and environmental remediation. [ABSTRACT FROM AUTHOR]

Cobalt nanoparticles have been prepared by reduction of cobalt chloride by sodium borohydride. They are very active catalysts for ethanol steam reforming at moderate temperature. The best catalytic materials show full ethanol conversion and hydrogen yields of the order of 83% and stable activity for 8 h when tested at 773 K, GHSV 324,000 h −1 with diluted 1:6 ethanol:water feed in He 41.6%. The amount of coproduced methane is very low (yield <0.05%). Experiments performed at different space velocities provide evidence of the intermediate formation of acetaldehyde in the ethanol steam reforming path. The fresh Co nanopowders are amorphous and are actually contaminated mainly by Boron species and traces of Na, Cl and C. During reaction, Cobalt nanoparticles are transformed into cubic metallic Co crystallites. The surface properties of these materials are very sensitive to: (I) the separation procedure from the reaction medium at the end of the preparation step, and (II) the conditions of ageing and storage in the laboratory. An increasing time of ageing seems to favor the formation of borates species and the observed oxidation of metallic cobalt to cobalt oxides. These phenomena could be associated to the loss in the catalytic activity that results in a lower ethanol conversion, lower hydrogen yield and sometimes, higher selectivity to acetaldehyde. [ABSTRACT FROM AUTHOR]

B-doped, B–N co-doped and B–N–F tri-doped TiO 2 catalysts were prepared via a sol–gel method using H 3 BO 3 , NH 4 Cl and NH 4 F as B, N and N–F dopant precursors, respectively. N-doped, N–F co-doped and a pure TiO 2 (undoped) samples were also prepared by the same method as blank samples, for comparison. The catalysts were evaluated for the simultaneous photocatalytic reduction of Cr(VI) and oxidation of benzoic acid (BA). XRD analysis shows the formation of pure TiO 2 anatase phase in all cases, with crystallite size varying from 10.1 nm to 14.6 nm for all doped samples. UV–vis DRS spectra show narrowing of the band gap ( E g ) for all doped samples, compared to the undoped TiO 2 . Concomitant presence of N and F ions i.e. in N–F co-doped and B–N–F tri-doped TiO 2 catalysts, causes the most pronounced decrease of E g while B–N co-doped and B–N–F tri-doped TiO 2 have lower E g values than mono B-doped but higher than N-doped and N–F co-doped TiO 2 . B and N doping also causes an increase of specific surface area and a decrease in mean pore diameter. Electron Paramagnetic Resonance (EPR) spectroscopy was employed for a detailed investigation of the structure and photoexcited species formed in these catalysts. The EPR data show that N-doping forms N b photoexcited species which react as holes, Ti 4+ –O − oxygen vacancies (OVs) and Ti 3+ lattice and surface defects. B-doping enhances the formation of Ti 4+ –O − oxygen vacancies and the quantities of O 2 H and OH radicals. In B-doped and B–N co-doped samples, boron causes the most prominent induction of Ti 3+ lattice centers. Boron in interstitial sites, with oxygen atoms [BO 3 ] behaves as a three-electron donor leading to the formation of B 3+ and reduction of Ti 4+ to Ti 3+ . Under UV–vis irradiation, Cr(VI) reduction followed the trend: TB1 > TBN1 > TBNF1 > TNF1 > TN1 > undoped TiO 2 ; while benzoic acid (BA) oxidation trend was: TB1 > TBNF1 > TBN1 > TNF1 > TN1 > undoped TiO 2 . Cr(VI) reduction and BA oxidation rates are in agreement with EPR-detected Ti 4+ –O − oxygen vacancies and O 2 H, OH photoexcited radicals, respectively. [ABSTRACT FROM AUTHOR]

Bimetallic nanoparticle catalysts of PtRh supported on carbon were synthesized using an electron beam irradiation reduction method. The PtRh nanoparticle catalysts were composed of particles 2–3 nm in size, which were well dispersed on the surface of the carbon support nanoparticles. Analyses of X-ray diffraction and scanning transmission electron microscopy–energy-dispersive X-ray spectroscopy revealed that the PtRh nanoparticles have a randomly alloyed structure. The lattice constant of the PtRh nanoparticles showed good correlation with Vegard's law. These results are explained by the radiochemical formation process of the PtRh nanoparticles. Catalytic activities of PtRh/C nanoparticles for ethanol oxidation reaction were found to be higher than those obtained with Pt/C. [ABSTRACT FROM AUTHOR]

Nanostructure cerium–titanium catalysts including fluoride (F − ) doped ones were prepared by impregnation (Ce/TiO 2 and Ce/F–TiO 2 ) and co-precipitation (CeTi and CeTiF) method, and tested as ozonation catalysts for low-temperature NO X removal ranging from 40 to 180 °C. Interestingly, the doping of F − promotes the NO X removal for CeTi whereas inhibits the removal for Ce/TiO 2 . The NO X removal presents linear relationship with the concentration of hydroxyl radicals ( OH). The surface –OH linked to Ce atoms as well as the H 2 O adsorption over Ce atoms play the important role in the generation of ·OH radicals. The doping of F − into CeTi improves the activation of Ce–OH linkage bonds and the adsorption of H 2 O over Ce atoms, thus increasing the concentration of OH radicals and catalytic activities. Although the doping of F − into Ce/TiO 2 enhances the density of surface –OH, the ones linked to Ce atoms remain constant and the H 2 O adsorption over Ce atoms are declined, finally declining the catalytic activities. [ABSTRACT FROM AUTHOR]

The reduction of a Re promoted Co/γ-Al2O3 catalyst was monitored in situ by synchrotron X-ray powder diffraction (XRPD) under H2 environment. Whole powder pattern analysis revealed a non-linear expansion of the unit cell of γ-Al2O3 during the reduction process, suggesting the diffusion of Co cations into the structure of the support. The non-linear cell expansion coincided with the formation of a CoO phase. In addition, space resolved diffraction at the inlet and the outlet of the reactor evidenced a negative effect of the partial pressure of indigenous H2O(g) on the reduction process. [ABSTRACT FROM AUTHOR]

We report the first examples of straightforward trans-hydroboration of internal alkynes at room temperature with 9-BBN, producing five-membered BN-heterocycles. Contrary to conventional cis-hydroboration, we demonstrate that the introduction of a pyridyl group switches the stereoselectivity of the reaction. A hydride migration mechanism has been proposed and supported by DFT calculations for the trans-hydroboration. This new hydroboration approach allows facile construction of new blue fluorescent BN-heterocyclic compounds. [ABSTRACT FROM AUTHOR]

The conversion of biomass into valuable carbon composites as efficient non-precious metal oxygen-reduction electrocatalysts is attractive for the development of commercially viable polymer electrolyte membrane fuel-cell technology. Herein, a versatile iron-tannin-framework ink coating strategy is developed to fabricate cellulose-derived Fe3C/Fe-N-C catalysts using commercial filter paper, tissue, or cotton as a carbon source, an iron-tannin framework as an iron source, and dicyandiamide as a nitrogen source. The oxygen reduction performance of the resultant Fe3C/Fe-N-C catalysts shows a high onset potential (i.e. 0.98 V vs the reversible hydrogen electrode (RHE)), and large kinetic current density normalized to both geometric electrode area and mass of catalysts (6.4 mA cm−2 and 32 mA mg−1 at 0.80 V vs RHE) in alkaline condition. This method can even be used to prepare efficient catalysts using waste carbon sources, such as used polyurethane foam. [ABSTRACT FROM AUTHOR]

Chiral boronic esters are useful intermediates in asymmetric synthesis. We have previously shown that carbonyl-directed catalytic asymmetric hydroboration (CAHB) is an efficient approach to the synthesis of functionalized primary and secondary chiral boronic esters. We now report that the oxime-directed CAHB of alkyl-substituted methylidene and trisubstituted alkene substrates by pinacolborane (pinBH) affords oxime-containing chiral tertiary boronic esters with yields up to 87 % and enantiomeric ratios up to 96:4 e.r. The utility of the method is demonstrated by the formation of chiral diols and O-substituted hydroxylamines, the generation of quaternary carbon stereocenters through carbon-carbon coupling reactions, and the preparation of chiral 3,4,4-trisubstituted isoxazolines. [ABSTRACT FROM AUTHOR]

The effect of cellular structure in the flexible polyurethane foams on the sound absorption behavior is investigated for improved sound environment within vehicles. Two types of gelling catalyst and water are used for producing well-defined cavity and pore structure in the foams. The catalyst, having high activity in urethane reaction, produces a larger number of small cavities and pores in the foams compared to the catalyst having low activity. A high number of small cavities can also be obtained at high water content from the restraint of neighboring cavities due to actively formed urethane matrix. The foam density decreases with increasing water and catalyst contents. Sound absorption efficiency is usually low at low foam density, but the results show improved sound absorption efficiency even at the reduced foam density because of the high number of well dispersed small cells in the foams. [ABSTRACT FROM AUTHOR]

We describe herein the synthesis of solid Au@Pd and hollow AgPd nanoflowers displaying controlled sizes and compositions in order to investigate how their size, composition, and the presence of Au in the core of the nanoparticles influence their catalytic performance toward both liquid and gas-phase transformations. While the size and composition of Au@Pd and AgPd the nanoflowers could be controlled as function of growth time, their structure (solid or hollow) was dependent on the nature of the seeds employed for the synthesis, i.e., Au or Ag nanoparticles. Moreover, Au@Pd and AgPd nanoflowers were successfully supported onto commercial silica displaying truly uniform dispersion. The catalytic activities of Au@Pd and AgPd nanoflowers were investigated toward the 4-nitrophenol reduction and the benzene, toluene, and o-xylene (BTX) oxidation. The catalytic activities for the reduction of 4-nitrophenol decreased as follows: Au@Pd > Au@Pd > AgPd and AgPd > Au@Pd > AgPd, suggesting that the Au core enhanced the catalytic activity relative to the hollow material when for Pd at.% was up to 80. Regarding the BTX oxidation, supported Au@Pd displayed higher catalytic activities than AgPd nanoflowers, also illustrating the role of the Au cores in the nanoflowers for improving catalytic performance. We believe these results may serve as a platform for the synthesis of Pd-based bimetallic nanomaterials that enable the correlation between these physical/chemical parameters and properties and thus optimized catalytic activities. [ABSTRACT FROM AUTHOR]

A series of WO 3 -doped Mn–Zr mixed oxide catalysts were investigated for the selective catalytic reduction of NO x by NH 3 (NH 3 –SCR). It was found that the added WO 3 significantly enhanced the catalytic performance of Mn–Zr mixed oxide catalyst for NH 3 –SCR of NO x . In situ diffuse reflectance infrared transform spectroscopy (DRIFTS) studies revealed that the highly dispersed WO 3 not only resulted in more acid sites formed on the catalyst surface, but also inhibited the adsorption of the inactive nitrate specie, leaving more active sites available for the adsorption of NH 3 . In addition, the synergetic effect between W and Mn contributes to improving the redox property of the catalyst. Therefore, the high catalytic deNO x performance was obtained over WO 3 -promoted Mn–Zr mixed oxide catalyst. [ABSTRACT FROM AUTHOR]

Total oxidation of toluene over a CuO–CeO 2 /Al 2 O 3 catalyst was studied by means of Temporal Analysis of Products (TAP) at temperatures of 723–873 K in the absence and presence of oxygen (molar toluene:oxygen ratio = 1:9) at degrees of reduction of the catalyst up to 0.42. A single set of kinetic parameters corresponding to the steps of the detailed mechanism can describe the experimental data. A detailed mechanism with oxidation occurring on Ce 3+ sites and reduction on Cu 2+ sites formed the basis of a microkinetic model. The interaction of reactants and products with the catalyst support was taken into account. A distinction was made between O atoms at the surface of the catalytically active phase and those in the bulk. Transport of the latter to the surface was explicitly accounted for in the model. The abstraction of hydrogen atoms leading to the formation of water is the fastest process. The formation of carbon dioxide occurs through three kinetically significant steps. The potentially slowest step in the whole process was found to be the destruction of the aromatic ring. A linear dependency of the activation energies of the processes which include transport of oxygen from the bulk to the catalyst surface, on the degree of reduction of the catalyst was found. Analysis of the dependency of the catalytic behavior on the catalyst descriptors provided information about the optimum catalyst composition and fraction of the active component exposed, which can be used for catalyst optimization. [ABSTRACT FROM AUTHOR]

Herein we propose a novel in situ N-doping method to develop a new type of mesoporous N-doped carbons constructed by direct pyrolysis of properly rigid strut N-rich metal-organic frameworks at 950 °C. This facile fabrication method creates doped N that is evenly dispersed on mesoporous carbons (≈4.0 nm) formed simultaneously without the need for a second carbon precursor, external nitrogen supplier, or pore-forming agent. The resulting mesoporous N-doped carbons bear a low N content but a high proportion of graphitic N species and exhibit superior catalytic performance toward the reduction of 4-nitrophenol relative to that shown by previously reported metal catalysts and N-doped graphene. The ensemble effect of the mesostructured framework and effective N doping is responsible for the excellent performance, as better diffusion, adsorption, and activation of 4-nitrophenol in wastewaters are achieved through the elaborately fabricated mesoporous N-doped carbons. [ABSTRACT FROM AUTHOR]

In this study, a series of PtSnK/Al 2 O 3 catalysts were prepared by an impregnation-reduction method and employed as a catalyst in an isobutane dehydrogenation reaction. In order to improve the dehydrogenation performance of isobutane, the preparation conditions of the PtSnK/Al 2 O 3 catalysts were optimized by the Taguchi method of experimental design. The effects of four variables, mass ratio of platinum to tin, concentration of H 2 PtCl 6 , calcination temperature, and K loading (mass fraction) at four levels were investigated. The results revealed that the order of the affecting factors was mass ratio of platinum to tin > K loading > calcination temperature > concentration of H 2 PtCl 6 . The optimum preparation conditions were as follows: mass ratio of platinum to tin 1:1, concentration of H 2 PtCl 6 7.72 × 10 −4 mol/L, calcination temperature 500 °C, and K loading 0.8%. The optimized PtSnK/Al 2 O 3 catalysts exhibited good catalytic performance for isobutane dehydrogenation. The average isobutane conversion, selectivity toward isobutene, and deactivation parameter were 46.59 ± 0.83%, 95.37 ± 0.49%, 1.45 ± 0.74%, respectively. [ABSTRACT FROM AUTHOR]

A photocatalytic system that consists of an Ir-based photosensitizer and a RuII bipyridine catalyst was developed for the selective reduction of CO2 to formic acid using triethanolamine as the electron donor. Catalyst turnover numbers up to 526 and a selectivity of 80 % towards formic acid were observed if the photocatalytic reaction was performed with [Ir(ppy)2(bpy)]PF6 (ppy=2-(pyridine-2-yl)benzene-1-ide, bpy=2,2′-bipyridine) as the photosensitizer and [Ru(bpy)2(Cl)(CO)]PF6 as the catalyst under visible-light irradiation ( λ=400-700 nm). Interestingly, this photocatalytic system showed activity for the photoreduction of Na2CO3 to formic acid as well. The investigation of different ruthenium(II) catalysts revealed the positive influence of carbonyl ligands coordinated to the metal center. The enhancement of the catalytic activity is explained by a more favorable electron transfer from the photosensitizer to the catalyst, which is supported by the redox potentials of the complexes. [ABSTRACT FROM AUTHOR]

This work summarizes the advanced materials developed by various research groups for improving the stability of platinum (Pt), and Pt-based catalysts center toward the oxygen reduction reaction (ORR) in acid medium. The ORR stability enhancement of Pt catalytic center can be classified according to the different nature of the supporting materials, namely, carbon-, oxide-based-, and oxide-carbon composites. The enhancement and stability of a catalytic center can be related to either its electronic modification induced by a strong interaction with the support, another metal (alloy), or to geometric effects. In addition, other parameters come into play, the size, the morphology of the catalytic center, the temperature, the dispersion, and mass loading, along with the measuring methods. This mini-review mainly focusses on the stability improvement, depending on the substrate nature. This latter can be further modified via functionalization or by the chemical interaction nature between the substrate and catalyst. [ABSTRACT FROM AUTHOR]

• An advanced eggshells-CaO supported Pd-Ru nanocatalysts is successfully constructed. • Pd and Ru NPs are uniformly-dispersed on CaO with small size leading to high ECSA. • Physical characterizations show that Ru enhanced the electronic structure of Pd NPs. • The Pd-Ru/CaO exhibits superior electrocatalytic activity and long term stability towards EOR process. • The excellent performance is attributed to the well-organized structure and bimetallic synergy effect. Herein, we developed a unique Pd-Ru nanocatalyst supported on CaO derived from waste eggshells via a direct sodium borohydride chemical reduction strategy for the electrooxidation of ethanol under mild conditions. The electronic state and size of the alloy nanoparticles can be effectively optimized by taking advantage of the strong electron interactions between Pd and Ru, alleviating the CO poisoning and aggregation issues of the catalytic species. The morphological characterization results demonstrate that the Pd-Ru/CaO has a well-defined morphology with uniform metal dispersion and a high surface area. XRD and XPS patterns revealed that Ru causes a shift in the electronic band of Pd, which leads to a desired structure with a high ECSA. Furthermore, the Pd-Ru/CaO electrocatalyst has significantly higher electrocatalytic activity (3581.1 mA mg Pd + Ru − 1), long-term stability, and improved CO ads antitoxic tolerance than the supportless Pd-Ru (2779.57 mA mg Pd + Ru − 1), Pd/CaO (1603.6 mA mg Pd + Ru − 1), and Pd/C (JM) (587.4 mA mg Pd + Ru − 1) nanocatalysts. The outstanding electrocatalytic performance was due to the usage of high surface area CaO NPs as the supports and the synergetic effect of Pd and Ru NPs in EOR process. The proposed rational designed Pd-Ru/CaO nanocatalysts with well-defined morphology and small particle sizes could contribute to enhancing the performance of Pd-based nanoocatalysts and favor the overall DEFC process. [Display omitted] [ABSTRACT FROM AUTHOR]