Finned Zn-MFI zeolite encapsulated noble metal nanoparticle catalysts for the oxidative dehydrogenation of propane with carbon dioxide

Oxidative dehydrogenation of propane with carbon dioxide(CO_(2)-ODP)characterizes the tandem dehydrogenation of propane to propylene with the reduction of the greenhouse gas of CO_(2)to valuable CO.However,the existing catalyst is limited due to the poor activity and stability,which hinders its industrialization.Herein,we design the finned Zn-MFI zeolite encapsulated noble metal nanoparticles(NPs)as bifunctional catalysts(NPs@Zn-MFI)for CO_(2)-ODP.Characterization results reveal that the Zn2+species are coordinated with the MFI zeolite matrix as isolated cations and the NPs of Pt,Rh,or Rh Pt are highly dispersed in the zeolite crystals.The isolated Zn2+cations are very effective for activating the propane and the small NPs are favorable for activating the CO_(2),which synergistically promote the selective transformation of propane and CO_(2)to propylene and CO.As a result,the optimal 0.25%Rh0.50%Pt@Zn-MFI catalyst shows the best propylene yield,satisfactory CO_(2)conversion,and long-term stability.Moreover,considering the tunable synergetic effects between the isolated cations and NPs,the developed approach offers a general guideline to design more efficient CO_(2)-ODP catalysts,which is validated by the improved performance of the bifunctional catalysts via simply substituting Sn4+cations for Zn2+cations in the MFI zeolite matrix.

State of arts on the bio-synthesis of noble metal nanoparticles and their biological application

Nanomaterials are materials in which at least one of the dimensions of the particles is 100 nm and below.There are many types of nanomaterials,but noble metal nanoparticles are of interest due to their uniquely large surface-to-volume ratio,high surface area,optical and electronic properties,high stability,easy synthesis,and tunable surface functionalization.More importantly,noble metal nanoparticles are known to have excellent compatibility with bio-materials,which is why they are widely used in biological applications.The synthesis method of noble metal nanoparticles conventionally involves the reduction of the noble metal salt precursor by toxic reaction agents such as NaBH4,hydrazine,and formaldehyde.This is a major drawback for researchers involved in biological application researches.Hence,the bio-synthesis of noble metal nanoparticles(NPs)by bio-materials via bio-reduction provides an alternative method to synthesize noble metal nanoparticles which are potentially non-toxic and safer for biological application.In this review,the bio-synthesis of noble metal nanoparticle including gold nanoparticle(AuNPs),silver nanoparticle(AgNPs),platinum nanoparticle(PtNPs),and palladium nanoparticle(PdNPs)are first discussed.This is followed by a discussion of these biosynthesized noble metal in biological applications including antimicrobial,wound healing,anticancer drug,and bioimaging.Based on these,it can be concluded that the study on bio-synthesized noble metal nanoparticles will expand further involving bio-reduction by unexplored bio-materials.However,many questions remain on the feasibility of bio-synthesized noble metal nanoparticles to replace existing methods on various biological applications.Nevertheless,the current development of the biological application by bio-synthesized noble metal NPs is still intensively ongoing,and will eventually reach the goal of full commercialization.

Effect of noble metal nanoparticle size on C–N bond cleavage performance in hydrodenitrogenation: a study of active sites

Breakage of the C-N bond is a structure sensitive process,and the catalyst size significantly affects its activity.On the active metal nanoparticle scale,the role of catalyst size in C-N bond cleavage has not been clearly elucidated.So,Ru catalysts with variable nanoparticle sizes were obtained by modulating the reduction temperature,and the catalytic activity was evaluated using 1,2,3,4-tetrahydroquinoline and o-propylaniline with different C-N bond hybridization patterns as reactants.Results showed a 13 times higher reaction rate for sp3-hybridized C-N bond cleavage than sp2-hybridized C-N bond cleavage,while the reaction rate tended to increase first and then decrease as the catalyst nanoparticle size increased.Different concentrations of terrace,step,and corner sites were found in different sizes of Ru nanoparticles.The relationship between catalytic site variation and C-N bond cleavage activity was further investigated by calculating the turnover frequency values for each site.This analysis indicates that the variation of different sites on the catalyst is the intrinsic factor of the size dependence of C-N bond cleavage activity,and the step atoms are the active sites for the C-N bond cleavage.When Ru nanoparticles are smaller than 1.9 nm,they have a strong adsorption effect on the reactants,which will affect the catalytic performance of the Ru catalyst.Furthermore,these findings were also confirmed on other metallic Pd/Pt catalysts.The role of step sites in C-N bond cleavage was proposed using the density function theory calculations.The reactants have stronger adsorption energies on the step atoms,and step atoms have d-band center nearer to the Fermi level.In this case,the interaction with the reactant is stronger,which is beneficial for activating the C-N bond of the reactant.

Supported noble metal nanoparticles as photo/sono-catalysts for synthesis of chemicals and degradation of pollutants

This review summarizes the utilization of supported noble metal nanoparticles (such as Au/TiO2, Au/ZrO2, Ag/AgCl) as efficient photo/sono-catalysts for the selective synthesis of chemicals and degradation of environmental pollutants. Supported noble metal nanoparticles could efficiently catalyze the conversion of solar energy into chemical energy. Under UV/visible light irradiation, important chemical transformations such as the oxidation of alcohols to carbonyl compounds, the oxidation of thiol to disulfide, the oxidation of benzene to phenol, and the reduction of nitroaromatic compounds to form aromatic azo compounds, are effectively achieved by supported noble metal nanoparticles. Under ultrasound irradiation, supported noble metal nanoparticles could efficiently catalyze the production of hydrogen from water. Moreover, various pollutants, including aldehydes, alcohols, acids, phenolic compounds, and dyes, can be effectively decomposed over supported noble metal nanoparticles under UV/visible light irradiation. Under ultrasound irradiation, pollutant molecules can also be completely degraded with supported noble metal nanoparticles as catalysts.

Recent Advances on Confining Noble Metal Nanoparticles Inside Metal-Organic Frameworks for Hydrogenation Reactions

Hydrogenation reaction is one of the pillars of the chemical industry for the synthesis of drugs and fine chemicals.To achieve high catalytic performance,it is still highly desirable for constructing novel supported metal catalysts.Different from conventional supports like metal oxides,zeolites and carbon materials,metal-organic frameworks(MOFs)as the emerging porous materials have exhibited great potential to host metal nanoparticles(NPs)for achieving hydrogenation reactions with high catalytic efficiency,due to their unique porous structures.Recently,many progresses have been made,and thus,it is necessary to summarize the recent progresses on confining metal NPs inside MOFs for hydrogenation reactions.In this review,we first introduced the general synthesis methods for confining noble metal NPs inside MOFs.Then,the applications of noble metal NPs/MOFs catalysts in hydrogenation reactions were summarized,and the synergistic catalytic performances among noble metal NPs,metal nodes,functional groups,and pore channels in MOFs were illustrated.Subsequently,the hydrogen spillover effect involved in the hydrogenation reactions was discussed.Finally,we provide an outlook on the future research directions and challenges of confining noble metal NPs inside MOFs for hydrogenation reactions.

Straightforward synthesis of beta zeolite encapsulated Pt nanoparticles for the transformation of 5-hydroxymethyl furfural into 2,5-furandicarboxylic acid

Encapsulating noble metal nanoparticles(NPs)within the zeolite framework enhances the stability and accessibility of active sites;however,direct synthesis remains a challenge because of the easy precipitation of noble metal species under strong alkali crystallization conditions.Herein,beta zeolite-encapsulated Pt NPs(Pt@Beta)were synthesized via a hydrothermal approach involving an unusual acid hydrolysis preaging step.The ligand—(3-mercaptopropyl)trimethoxysilane—and Pt precursor were cohydrolyzed and cocondensed with a silica source in an initially weak acidic environment to prevent colloidal precipitation by enhancing the interaction between the Pt and silica species.Thus,the resultant 0.2%Pt@Beta was highly active in the transformation of 5-hydroxymethylfurfural into 2,5-furandicarboxylic acid(FDCA)under atmospheric O2 conditions by using water as the solvent while stably evincing a high yield(90%)associated with a large turnover number of 176.The excellent catalysis behavior is attributable to the enhanced stability that inhibits Pt leaching and strengthens the intermediates that accelerate the rate-determining step for the oxidation of 5-formyl-2-furan carboxylic acid into FDCA.

Dielectric barrier discharge plasma synthesis of Ag/γ-Al_(2)O_(3) catalysts for catalytic oxidation of CO

In this study,Ag/γ-Al_(2)O_(3)catalysts were synthesized by an Ar dielectric barrier discharge plasma using silver nitrate as the Ag source andγ-alumina(γ-Al_(2)O_(3))as the support.It is revealed that plasma can reduce silver ions to generate crystalline silver nanoparticles(Ag NPs)of good dispersion and uniformity on the alumina surface,leading to the formation of Ag/γ-Al_(2)O_(3)catalysts in a green manner without traditional chemical reductants.Ag/γ-Al_(2)O_(3)exhibited good catalytic activity and stability in CO oxidation reactions,and the activity increased with increase in the Ag content.For catalysts with more than 2 wt%Ag,100%CO conversion can be achieved at 300°C.The catalytic activity of the Ag/γ-Al_(2)O_(3)catalysts is also closely related to the size of theγ-alumina,where Ag/nano-γ-Al_(2)O_(3)catalysts demonstrate better performance than Ag/micro-γ-Al_(2)O_(3)catalysts with the same Ag content.In addition,the catalytic properties of plasma-generated Ag/nano-γ-Al_(2)O_(3)(Ag/γ-Al_(2)O_(3)-P)catalysts were compared with those of Ag/nano-γ-Al_(2)O_(3)catalysts prepared by the traditional calcination approach(Ag/γ-Al_(2)O_(3)-C),with the plasma-generated samples demonstrating better overall performance.This simple,rapid and green plasma process is considered to be applicable for the synthesis of diverse noble metal-based catalysts.

Surface composition dominates the electrocatalytic reduction of CO2 on ultrafine CuPd nanoalloys

Preciously tuning the surface composition of noble metal nanoparticles with the particle size of only 2 nm or less by alloying with other metals represents a powerful strategy to boost their electrocatalytic selectivity.However,the synthesis of ultrafine nanoalloys and tuning their surface composition remain challenging.In this report,ultrafine CuPd nanoalloys with the particle size of ca.2 nm are synthesized based on the galvanic replacement reaction between presynthesized Cu nanoparticles and Pd2+precursors,and the tuning of their surface compositions is also achieved by changing the atom ratios of Cu/Pd.For the electrocatalytic reduction of CO2,Cu5Pd5 nanoalloys show the CO Faradaic efficiency(FE)of 88%at−0.87 V,and the corresponding mass activity reaches 56 A/g that is much higher than those of Cu8Pd2 nanoalloys,Cu3Pd7 nanoalloys and most of previously reported catalysts.Density functional theory uncovers that with the increase of Pd on the surface of the ultrafine CuPd nanoalloys,the adsorbed energy of both of intermediate COOH*and CO*to the Pd sites is strengthened.The Cu5Pd5 nanoalloys with the optimal surface composition better balance the adsorption of COOH*and desorption of CO*,achieving the highest selectivity and activity.The difficult liberation of absorbed CO*on the surface of Cu3Pd7 nanoalloys provides carbon source to favor the production of ethylene,endowing the Cu3Pd7 nanoalloys with the highest selectivity for ethylene among these ultrafine CuPd nanoalloys.

Photothermal nonlinear scattering of shell-isolated gold nanoparticles and applications in super-resolution imaging

In this Letter,we report on the investigations of nonlinear scattering of plasmonic nanoparticles by manipulating ambient environments.We create different local thermal hosts for gold nanospheres that are immersed in oil,encapsulated in silica glass and also coated with silica shells.In terms of regulable effective thermal conductivity,silica coatings are found to contribute significantly to scattering saturation.Benefitting from the enhanced thermal stability and the reduced plasmonic coupling provided by the shell-isolated nanoparticles,we achieve super-resolution imaging with a feature size of 52 nm(λ/10),and we can readily resolve pairs of nanoparticles with a gap-to-gap distance of 5 nm.

Graphene nanosheets decorated with Pd,Pt,Au,and Ag nanoparticles:Synthesis,characterization,and catalysis applications

We report that noble metal nanopartcles (Pd, Pt, Au, and Ag) decorated-graphene nanosheets can be synthesized with the template of graphene oxide by a one-pot solution-based method. The resulting hybrid materials are characterized by transmission electronic microscopy, energy dispersive X-ray spectroscopy, scanning electronic microscopy, atomic force microscopy, X-ray diffraction, and Raman spectroscopy, which demonstrate that the metal nanoparticles have been uniformly deposited on the surfaces of graphene nanosheets. Our results in turn verify that the carboxylic groups of graphene oxide are statistically distributed on its whole sheet surface rather than just at its edges. The graphene-metal nanohybrids can be used as catalysts in the reduction of potassium hexacyanoferrate(Ⅲ) with NaBH4 in aqueous solution. Our results suggest that graphene is a superior substrate to support metals for applications in the heterogeneous catalysis.

Characterization of the nanosized porous structure of black Si solar cells fabricated via a screen printing process

A silicon（Si） surface with a nanosized porous structure was formed via simple wet chemical etching catalyzed by gold（Au） nanoparticles on p-type Cz-Si（100）.The average reflectivity from 300 to 1200 nm was less than 1.5%.Black Si solar cells were then fabricated using a conventional production process.The results reflected the output characteristics of the cells fabricated using different etching depths and emitter dopant profiles.Heavier dopants and shallower etching depths should be adopted to optimize the black Si solar cell output characteristics. The efficiency at the optimized etching time and dopant profile was 12.17%.However,surface passivation and electrode contact due to the nanosized porous surface structure are still obstacles to obtaining high conversion efficiency for the black Si solar cells.