Laser-optimized Pt-Y alloy nanoparticles embedded in Pt-Y oxide matrix for high stability and ORR electrocatalytic activity

The development of active yet stable catalysts for oxygen reduction reaction(ORR)is still a major issue for the extensive permeation of fuel cells into everyday technology.While nanostructured Pt catalysts are to date the best available systems in terms of activity,the same is not true for stability,particularly under operating conditions.In this work,Pt_(Х)Y alloy nanoparticles are proposed as active and durable electrocatalysts for ORR.Pt_(Х)Y nanoalloys are synthesized and further optimized by laser ablation in liquid followed by laser fragmentation in liquid.The novel integrated laser-assisted methodology succeeded in producing Pt_(Х)Y nanoparticles with the ideal size(<10 nm)of commercial Pt catalysts,yet resulting remarkably more active with E_(1/2)=0.943 V vs.RHE,specific activity=1095μA cm^(-2) and mass activity>1000 A g^(-1).At the same time,the nanoalloys are embedded in a fine Pt oxide matrix,which allows a greater stability of the catalyst than the commercial Pt reference,as directly verified on a gas diffusion electrode.

Molybdenum-doped titanium dioxide supported low-Pt electrocatalyst for highly efficient and stable hydrogen evolution reaction

The Platinum(Pt)-based catalysts exhibit excellent catalytic performance for the hydrogen evolution reaction(HER) while suffering from poor stability due to the weak interaction between the carbon support and Pt.Herein,a molybdenum-doped titanium dioxide(Ti_(0.9)Mo_(0.1)O_(2)) supported low-Pt electrocatalyst with stronger interaction between catalyst and support is applied to tune the electrocatalytic performance of Pt.The Ti_(0.9)Mo_(0.1)O_(2) support can not only tolerate the corrosion environment in the catalytic system,but also generate strong metal-support inte raction(SMSI) between the oxide and catalyst.A facile solvothermal method is used to prepareTi_(0.9)Mo_(0.1)O_(2) as support to anchor Pt nanoparticles.The 5% Pt supported on Ti_(0.9)Mo_(0.1)O_(2) catalyst exhibits 4.4-fold mass activity(MA) at an overpotential of 50 mV and higher stability than 20% Pt/C with only 1/4 Pt loading.The SMSI between the Ti_(0.9)Mo_(0.1)O_(2) and Pt prevents the Pt aggregation to achieve excellent stability,and hydrogen spillover effect in the interface between Pt and support benefits the hydrogen production process.This work presents a novel sight for the fabrication and design of oxide supported catalysts in various catalytic system by reasonably employing support effect.

Engineering titanium oxide-based support for electrocatalysis

The corrosion and weaker interaction with metal catalysts of common carbon supports during electrocatalysis push the development of alternative supports materials. Titanium oxide-based materials have been widely explored as electrocatalysts supports in consideration of their chemical stability, strong interactions with metal catalyst and wider applications in electrocatalytic reactions as well as the improved electronic conductivity. This review summarizes recent research advances in engineering titanium oxide-based supports for the catalysts in electrocatalysis field to provide guidance for designing high performance non-carbon supported electrocatalysts. Typically, the titanium oxide-based supports are classified into shaped TiO_(2), doped TiO_(2), titanium suboxide and TiO_(2)-carbon composites according to the modification methods and corresponding preparation methods. Then the engineering strategies and electrocatalytic applications are discussed in detail. Finally, the challenges, future research directions and perspectives of titanium oxide-based supports for electrocatalysis are presented for practical applications.

A NEW PROBE FOR IDENTIFYING PROPERTIES OF SUPPORTED METAL AND METAL OXIDE CATALYSTS

A novel molecular probe for identifying properties of supported transition metals and metal oxides catalysts was established.The catalytic mechanism of transition metals was proposed.

A New Type of Strong Metal-Support Interaction Caused by Antimony Species

Interactions between metals and supports are of fundamental interest in heterogeneous catalysis, Noble metal particles supported on transition metal oxides (TMO) may undergo a so-called strong metal-support interaction via encapsulation. This perspective addresses catalytic properties of the metal catalysts in the SMSI state which can be explained on the basis of complementary studies. The electronic geometric and bifunctional effects originating from strong metal-support interactions (SMSI) that are responsible for the catalyst’s activity, selectivity, and stability are key factors that determine performance. A series of Pd-Sb supported on different metal oxide (i.e. SiO2, γ-Al2O3, TiO2, and ZrO2) were prepared by the impregnation method. The catalysts were characterized by N2 adsorption (BET-SA and pore size distribution), TEM (transmission electron microscope), TPR (temperature-programmed reduction), CO-chemisorption, the structural characterization of Pd (dispersity, surface area), interaction between Pd and Sb2O3 and also the influence of the nature of the support were investigated. SiO2 supported Pd catalyst exhibited the highest surface area (192.6 m2/g) and pore volume (0.542 cm3/g) compared to the other supported oxides catalysts. The electron micrographs of these catalysts showed a narrow size particle distribution of Pd, but with varying sizes which in the range from 1 to 10 nm, depending on the type of support used. The results show almost completely suppressed of CO chemisorption when the catalysts were subjected to high temperature reduction (HTR), this suppression was overcome by oxidation of a reduced Pd/MeOx catalysts followed by re-reduction in hydrogen at 453 K low temperature reduction (LTR), almost completely restored the normal chemisorptive properties of the catalysts, this suppression was attributed by SbOx species by a typical SMSI effect as known for other reducible supports such as TiO2, ZrO2, CeO2, and Nb2O5.

Selective oxidation of ethane to aldehydes over SBA-15 supported molybdenum catalyst

SBA-15 supported Mo catalysts （Moy/SBA-15） were prepared by an ultrasonic assisted incipient-wetness impregnation method. The physical and chemical properties of the catalysts were characterized by means of N2-adsorption-desorption, XRD, TEM, UV-Vis, Raman, XANES and H2-TPR. The results showed that a trace amount of MoO3 was produced on high Mo content samples. Tum-over frequency （TOF） and product selectivity are dependent on the molybdenum content. Both Mo0.75/SBA-15 and Mo1.75/SBA-15 catalysts give the higher catalytic activity and the selectivity to the total aldehydes for the selective oxidation of C2H6. At the reaction temperature of 625℃, the maximum yield of aldehydes reached 4.2% over Mo0.75/SBA-15 catalyst. The improvement of the activity and selectivity was related with the state of MoOx species.

Pt/FeSnO(OH)_5： A Novel Supported Pt Catalyst for Catalytic Oxidation of Benzene

Pt/FeSnO（OH）_5 was synthesized as a novel catalyst for VOCs oxidation. Compared with Pt/γ-Al_2O_3 during catalytic oxidation of benzene, Pt/Fe Sn O（OH）5 showed better catalytic activity. After characterization of the catalysts by XRD, SEM, TEM, EDS, XPS, BET, TGA and DTA, we found most Pt could be reduced to metallic state when the hydroxyl catalyst was used as supporter, and the metallic Pt in Pt/Fe Sn O（OH）5 was more active than the oxidized Pt in Pt/γ-Al_2O_3 in catalytic oxidation of VOCs. Pt/FeSnO（OH）_5 shows both good catalytic activity and high stability, which may be a promising catalyst. This study may also be helpful for the design and fabrication of new catalysts.

Effects of preparation conditions of Au/FeO_x /Al_2O_3 catalysts prepared by a modified two-step method on the stability for CO oxidation

Composite oxide FeO x /Al 2 O 3 -supported gold catalysts were prepared by a modified two-step method. The effects of preparation conditions on the initial catalytic activity and long-time stability were studied for CO oxidation. XRD, XPS and in situ FTIR were employed to investigate the state of FeO x and the species on the catalyst surface. The results showed that Au/FeO x /Al 2 O 3 catalysts prepared by this method exhibited high activity and high stability in a wide pH value range. Calcination pretreatment was proved to be beneficial to improving the activity and stability. The beneficial effects of FeO x acting as a structural promoter could be ascribed to the ability to supply active oxygen species. As the precursor of FeO x , Fe（NO 3 ） 3 is superior to FeCl 3 for obtaining higher stability.

Progress on metal-support interactions in Pd-based catalysts for automobile emission control

The interactions between metals and oxide supports,so-called metal-support interactions(MSI),are of great importance in heterogeneous catalysis.Pd-based automotive exhaust control catalysts,especially Pd-based three-way catalysts (TWCs),have received considerable research attention owing to its prominent oxidation activity of HCs/CO,as well as excellent thermal stability.For Pd-based TWCs,the dispersion,chemical state and thermal stability of Pd species,which are crucial to the catalytic performance,are closely associated with interactions between metal nanoparticles and their supporting matrix.Progress on the research about MSI and utilization of MSI in advanced Pd-based three-way catalysts are reviewed here.Along with the development of advanced synthesis approaches and engine control technology,the study on MSI would play a notable role in further development of catalysts for automobile exhaust control.

Strong preciousmetal–metal oxide interaction for oxygen reduction reaction:A strategy for efficient catalyst design

Oxygen reduction reaction(ORR)is an electrochemical reaction in which dissolved oxygen in an electrolyte is reduced toOH−/H2Owhen receiving electrons.This reaction plays a crucial role in shaping the efficiency of both metal-air batteries and fuel cells,and precious metals are the dominant catalysts carrying out the ORR in their cathodes.However,how to manipulate the electronic structure of precious metals as active sites to further promote ORR performance and maximize the utilization rate is still under development.Metal oxide serves as suitable and promising support that can strongly interact with precious metals for both activity and durability enhancement.Herein,we present recent research updates on strong precious metal-metal oxide interaction(SPMMOI)utilized in ORR.We start by introducing the background of ORR,the issues to be solved,and its practical applications followed by a thorough discussion of the reaction mechanism and comprehensive evaluation protocols of performance.We then provide a complete understanding of theworking principle of SPMMOI and highlight the related advances.Finally,we summarize the merits of the precious metal-metal oxide systemand propose the research direction aswell as some urgent problems to be addressed in the future.

Probing crystalline phase effect of rare earth metal oxides(REO)on Cu/REO(RE=Gd,Eu,Sm)catalysts for methanol steam reforming(MSR)to produce H_(2)

In this work,to study the phase structure effect,three groups of Cu/REO catalysts were prepared with cubic and monoclinic Gd_(2)O_(3),Eu_(2)O_(3)and Sm_(2)O_(3) supports for MSR reaction to produce H_(2).Based on CH3OH conversion and H_(2)yield,the reaction perfo rmance of the catalysts ranks as Cu/Sm_(2)O_(3)-M>Cu/Sm_(2)O_(3)-C>Cu/Gd_(2)O_(3)-M>Cu/Gd_(2)O_(3)-C>Cu/Eu_(2)O_(3)-M>Cu/Eu_(2)O_(3)-C.For the same kind of REO,Cu supported on the monoclinic support shows better performance than on the cubic one.Despite the phase structure difference,Sm_(2)O_(3) is the best support among all the three kinds of REOs.Compared with Cu/REO catalysts prepared with cubic supports,the corresponding catalysts prepared with monoclinic supports generally possess mo re surface oxygen vacancies,which can generate mo re surface active oxygen(O_(2)^(-)) and moderate basic sites.Moreover,the contents of Cu^(+) on the catalysts follow the same sequence.The reaction performance is positively related to the amount of these three types of surface sites.But metallic Cuo species is necessary to maintain the Cu^(+)■Cu^(0) redox cycle.Furthe rmore,on a catalyst with good perfo rmance,those vital surface reaction intermediates can be stabilized during the reaction.Cu/Sm_(2)O_(3)-M possesses the largest quantities of these surface sites,and has the appropriate amount of Cu^(+) and Cu^(0) after reduction,thereby displaying the optimal performance in all the catalysts.In conclusion,evident support crystal structure effect is observed for Cu/REO catalysts,and a monoclinic phase REO is a better support than the respective cubic phase one.

低温CO氧化中担载Co_3O_4催化剂失活的影响因素(英文)

This study focused on the influences of a variety of reaction parameters and guest molecules such as H2O and C3H8 on the deactivation of supported Co3O4 catalysts for CO oxidation.Additionally,the physical features of and carbon deposition on some samples after the reaction under the chosen conditions were determined by BET and X-ray diffraction as well as by carbon analyses to deduce the precursors associated with catalyst deactivation.Activity maintenance profiles of the catalysts for CO oxidation at 100°C significantly depended on the support for Co3O4 nanoparticle dispersion,the loading,the preparation technique and the calcination temperature.The best on-stream performance was achieved using a 5%Co3O4/TiO2 catalyst prepared by the incipient wetness method followed by calcination at 350°C.All the reaction parameters chosen here such as the reaction temperature,the feed gas composition of CO,O2,H2O,and C3H8,and the gas space velocity strongly influenced the extent of catalyst deactivation during CO oxidation and also the rate of catalyst deactivation.However,the deactivation behavior is very complicated.No appreciable changes in the surface area,the porosity,and the phase of the Co3O4 nanoparticles and their size occurred even for the samples that were severely deactivated.Significant deposition of carbon on the catalysts after the reaction was visible and it depended on the reaction parameters chosen here.Consequently,this extensive parametric study on the deactivation of catalysts during oxidation and with the chosen reaction parameters and guest gases can lead to an understanding of the deactivation precursors that are associated with carbonaceous species including carbonates and surface free carbon.

Effects of tungsten oxide on the activity and thermal stability of a sulfate-derived titania supported platinum catalyst for propane oxidation

A Pt/WO3/TiO2 catalyst for propane oxidation was prepared by a stepwise wet impregnation method, and was aged at 800°C for 5 hr. Compared to the sulfate-derived titania supported catalyst, the introduction of tungsten oxide as stable Br nsted acid sites led to the formation of more metallic platinum active sites at the Pt/WO3 interface. The dissociation of surface intermediates for propane oxidation was promoted on the WO3-modified catalyst. This, as well as the inhibition effects of tungsten oxide on the sintering of anatase and the phase transformation to rutile, resulting in a high activity and thermal stability for the Pt/WO3/TiO2 catalyst.

Preparation and characterization of Ce(1-x)PrxO2 supports and their catalytic activities

In this work, the addition of praseodymium（Pr） into ceria as a mixed oxide support in a form of Ce（1-x）PrxO2（x = 0.01,0.025, 0.050, 0.075 and 0.10） was prepared using a co-precipitation method. The structural and textural properties of the synthesized supports were characterized by X-ray diffraction（XRD）, N2 adsorption-desorption, Raman spectroscopy, H2-temperature programmed reduction（H2-TPR） and H2-chemisorption. Upon addition of Pr, XRD patterns and Raman spectra indicated an enlargement of ceria unit cell and the characteristics Raman broad peak at 570 cm^（-1） which was attributed to the existence of oxygen vacancies in the ceria lattice. This indicated that some Ce^（4＋） ions in ceria were replaced by larger Pr^（3＋） cations. To evidence the incorporation of Pr^（3＋） cations into ceria lattice,X-ray absorption near edge structure（XANES） was employed. The results showed that the oxidation states of Ce in mixed oxide supports were slightly lower than 4＋ while those of Pr were still the same as a precursor salt. Therefore, the incorporation of Pr^（3＋） into ceria lattice would lead to strain and unbalanced charge and result in oxygen vacancies. The reducibility of Ce（1-x）PrxO2 mixed oxide supports was investigated by H2-TPR and temperature-resolved X-ray absorption spectroscopy experiment under reduction conditions. XANES spectra of Ce L3 edges showed a lower surface reduction temperature（Ce^（4＋）to Ce^（3＋）） of Ce（0.925）Pr（0.075）O2 than that of CeO2 which agreed with H2-TPR results. H2-chemisorption indicated that Pr promoted the dispersion of the metal catalyst on the mixed oxide support and increased the adsorption site for CO. For WGS reaction, 1% Pd/mixed oxide support had higher WGS activity than 1%Pd/ceria. The increase of WGS activity was due to the increase of Pd dispersion on the support and the existence of oxygen vacancies produced from incorporation of Pr into the ceria lattice.

Effects of support property on the catalytic performance of CeO_2-ZrO_2-CrO_x for 1,2-dichloroethane oxidation

HZSM-5, Al_2O_3, TiO_2 and SiO_2 supported CeO_2-ZrO_2-CrO_x catalysts were prepared by deposition-precipitation method and tested for deep catalytic oxidation of 1,2-dichloroethane（DCE）, as one of the common chlorinated organic pollutants. All the catalysts were characterized by means of N_2 adsorption-desorption, X-ray photoelectron spectroscopy（XPS）, ammonia-temperatureprogrammed desorption（NH_3-TPD） and hydrogen temperature-programmed reduction（H2-TPR）. The characterization results revealed that there was strongly synergistic effect between the oxidizability of CZCr species and the acidity of supports, which obviously promoted the catalytic activity for DCE degradation. 20% CZCr/HZSM-5 showed the highest activity and good durability during the long-term continuous test. The catalytic activity decreased in the order： 20%CZCr/HZSM-5〉CZCr〉20%CZCr/TiO_2〉20%CZCr/Al_2O_3〉20%CZCr/SiO_2.

A silica gel supported cobalt(Ⅱ) Schiff base complex as efficient and recyclable heterogeneous catalyst for the selective aerobic oxidation of alkyl aromatics

A silica gel supported cobalt（lI） Schiff base complex was synthesized and used for the oxidation of alkyl aromatics using molecular oxygen as an oxidant under atmosphere pressure. The catalyst shows a high conversion of alkyl aromatics and selectivity to benzylic ketones, and could be reused at least 5 times without significant loss of catalytic activity.

Porous FeO_x/BiVO_(4-δ)S_(0.08): Highly efcient photocatalysts for the degradation of Methylene Blue under visible-light illumination

Porous S-doped bismuth vanadate with an olive-like morphology and its supported iron oxide （y wt.% FeOx/BiVO4-δS0.08, y = 0.06, 0.76, and 1.40） photocatalysts were fabricated using the dodecylamine-assisted alcohol-hydrothermal and incipient wetness impregnation methods, respectively. It is shown that the y wt.% FeOx/BiVO4-δS0.08 photocatalysts contained a monoclinic scheetlite BiVO4 phase with a porous olive-like morphology, a surface area of 8.8-9.2 m^2/g, and a bandgap energy of 2.38-2.42 eV. There was co-presence of surface Bi^5＋, Bi^3＋, V^5＋, V^3＋, Fe^3＋, and Fe^2＋ species in y wt.% FeOx/BiVO4-δS0.08. The 1.40 wt.% FeOx/BiVO4-δS0.08 sample performed the best for Methylene Blue degradation under visible-light illumination. The photocatalytic mechanism was also discussed. We believe that the sulfur and FeOx co-doping, higher oxygen adspecies concentration, and lower baudgap energy were responsible for the excellent visible-light-driven catalytic activity of 1.40 wt.% FeOx/BiVO4-δS0.08.

The contribution of mediated oxidation mechanisms in the electrolytic degradation of cyanuric acid using diamond anodes

In this work, the contribution of mediated oxidation mechanisms in the electrolytic degradation of cyanuric acid using boron-doped diamond（BDD） anodes was investigated in different electrolytes. A complete mineralization of cyanuric acid was obtained in Na Cl;however lower degrees of mineralization of 70% and 40% were obtained in Na2SO4 and Na Cl O4, respectively. This can be explained by the nature of the oxidants electrogenerated in each electrolyte. It is clear that the contribution of active chlorine（Cl2, HCl O, Cl O-）electrogenerated from oxidation of chlorides on BDD is much more important in the electrolytic degradation of cyanuric acid than the persulfate and hydroxyl radicals produced by electro-oxidation of sulfate and water on BDD anodes. This could be explained by the high affinity of active chlorine towards nitrogen compounds. No organic intermediates were detected during the electrolytic degradation of cyanuric acid in any the electrolytes, which can be explained by their immediate depletion by hydroxyl radicals produced on the BDD surface. Nitrates and ammonium were the final products of electrolytic degradation of cyanuric acid on BDD anodes in all electrolytes. In addition, small amounts of chloramines were formed in the chloride medium. Low current density（≤ 10 m A/cm2） and neutral medium（p H in the range 6–9） should be used for high efficiency electrolytic degradation and negligible formation of hazardous chlorate and perchlorate.