Efficient and stable PtFe alloy catalyst for electrocatalytic methanol oxidation with high resistance to CO

Direct methanol fuel cells(DMFC) are widely considered to be an ideal green energy conversion device but their widespread applications are limited by the high price of the Pt-based catalysts and the instability in terms of surface CO toxicity in long-term operation.Herein,the PtFe alloy nanoparticles(NPs) with small particle size(~4.12 nm) supported on carbon black catalysts with different Pt/Fe atomic ratios(Pt_(1)Fe_(2)/C,Pt_(3)Fe_(4)/C,Pt_(1)Fe_(1)/C,and Pt_(2)Fe_(1)/C) are successfully prepared for enhanced anti-CO poisoning during methanol oxidation reaction(MOR).The optimal atomic ratio of Pt/Fe for the MOR is 1:2,and the mass activity of Pt_(1)Fe_(2)/C(5.40 A mg_(Pt)^(-1)) is 13.5 times higher than that of conventional commercial Pt/C(Pt/C-JM)(0.40 A mg_(Pt)^(-1)).The introduction of Fe into the Pt lattice forms the PtFe alloy phase,and the electron density of Pt is reduced after forming the PtFe alloy.In-situ Fourier transform infrared results indicate that the addition of oxyphilic metal Fe has reduced the adsorption of reactant molecules on Pt during the MOR.The doping of Fe atoms helps to desorb toxic intermediates and regenerate Pt active sites,promoting the cleavage of C-O bonds with good selectivity of CO_(2)(58.1%).Moreover,the Pt_(1)Fe_(2)/C catalyst exhibits higher CO tolerance,methanol electrooxidation activity,and long-term stability than other Pt_(x)Fe_(y)/C catalysts.

Selective Hydrodeoxygenation of Lignin-Derived Vanillin via Hetero-Structured High-Entropy Alloy/Oxide Catalysts

The chemoselective hydrodeoxygenation of natural lignocellulosic materials plays a crucial role in converting biomass into value-added chemicals.Yet their complex molecular structures often require multiple active sites synergy for effective activation and achieving high chemoselectivity.Herein,it is reported that a high-entropy alloy(HEA)on high-entropy oxide(HEO)hetero-structured catalyst for highly active,chemoselective,and robust vanillin hydrodeoxygenation.The heterogenous HEA/HEO catalysts were prepared by thermal reduction of senary HEOs(NiZnCuFeAlZrO_(x)),where exsolvable metals(e.g.,Ni,Zn,Cu)in situ emerged and formed randomly dispersed HEA nanoparticles anchoring on the HEO matrix.This catalyst exhibits excellent catalytic performance:100%conversion of vanillin and 95%selectivity toward high-value 2-methyl-4 methoxy phenol at low temperature of 120℃,which were attributed to the synergistic effect among HEO matrix(with abundant oxygen vacancies),anchored HEA nanoparticles(having excellent hydrogenolysis capability),and their intimate hetero-interfaces(showing strong electron transferring effect).Therefore,our work reported the successful construction of HEA/HEO heterogeneous catalysts and their superior multifunctionality in biomass conversion,which could shed light on catalyst design for many important reactions that are complex and require multifunctional active sites.

Micro-aluminum powder with bi-or tri-component alloy coating as a promising catalyst:Boosting pyrolysis and combustion of ammonium perchlorate

A novel design of micro-aluminum(μAl)powder coated with bi-/tri-component alloy layer,such as:Ni-P and Ni-P-Cu(namely,Al@Ni-P,Al@Ni-P-Cu,respectively),as combustion catalysts,were introduced to release its huge energy inside Al-core and promote rapid pyrolysis of ammonium perchlorate(AP)at a lower temperature in aluminized propellants.The microstructure of Al@Ni-P-Cu demonstrates that a three-layer Ni-P-Cu shell,with the thickness of~100 nm,is uniformly supported byμAl carrier(fuel unit),which has an amorphous surface with a thickness of~2.3 nm(catalytic unit).The peak temperature of AP with the addition of Al@Ni-P-Cu(3.5%)could significantly drop to 316.2℃ at high-temperature thermal decomposition,reduced by 124.3℃,in comparison to that of pure AP with 440.5℃.It illustrated that the introduction of Al@Ni-P-Cu could weaken or even eliminate the obstacle of AP pyrolysis due to its reduction of activation energy with 118.28 kJ/mol.The laser ignition results showed that the ignition delay time of Al@Ni-P-Cu/AP mixture with 78 ms in air is shorter than that of Al@Ni-P/AP(118 ms),decreased by 33.90%.Those astonishing breakthroughs were attributed to the synergistic effects of adequate active sites on amorphous surface and oxidation exothermic reactions(7597.7 J/g)of Al@Ni-P-Cu,resulting in accelerated mass and/or heat transfer rate to catalyze AP pyrolysis and combustion.Moreover,it is believed to provide an alternative Al-based combustion catalyst for propellant designer,to promote the development the propellants toward a higher energy.

Manipulating oxygenate adsorption on N-doped carbon by coupling with CoSn alloy for bifunctional oxygen electrocatalyst

Highly active bifunctional oxygen electrocatalysts accelerate the development of high-performance Zn-air battery,but suffer from the mismatched activities of oxygen evolution reaction(OER)and oxygen reduced reaction(ORR).Herein,highly integrated bifunctional oxygen electrocatalysts,cobalt-tin alloys coated by nitrogen doped carbon(CoSn@NC)are prepared by MOFs-derived method.In this hybrid catalyst,the binary CoSn nanoalloys mainly contribute to highly active OER process while the Co(or Sn)-N-C serves as ORR active sites.Rational interaction between CoSn and NC donates more rapid reaction kinetics than Pt/C(ORR)and IrO_(2)(OER).Such CoSn@NC holds a promise as air-cathode electrocatalyst in Zn-air battery,superior to Pt/C+IrO_(2)catalyst.First-principles calculations predict that CoSn alloys can upgrade charge redistribution on NC and promote the transfer to reactants,thus optimizing the adsorption strength of oxygen-containing intermediates to boost the overall reactivity.The tuning of oxygenate adsorption by interactions between alloy and heteroatom-doped carbon can guide the design of bifunctional oxygen electrocatalysts.

The effect of the support on the surface composition of PtCu alloy nanocatalysts: In situ XPS and HS-LEIS studies

Supported PtCu alloys have been broadly applied in heterogeneous catalysis and electrocatalysis owing to their excellent catalytic performance and high CO tolerance. It is important to analyze the outermost surface composition of the supported alloy nanoparticles to understand the nature of the catalytically active sites. In this paper, homogeneous face-centered cubic PtCu nanoparticles with a narrow particle size distribution were successfully fabricated and dispersed on a high-surface-area Ti〇2 powder support. The samples were oxidized and reduced in situ and then introduced into the ultrahigh vacuum chamber to measure the topmost surface composition by high-sensitivity low-energy ion scattering spectroscopy, and to determine the oxidation states of the elements by X-ray photoelectron spectroscopy. The surface composition and morphology, elemental distribu-tion, and oxidation states of the components were found to be significantly affected by the support and treatment conditions. The PtCu is de-alloyed upon oxidation with CuO wetting on the TiO2 sur-face and re-alloyed upon reduction. Phase diagrams of the surface composition and the bulk com-position were plotted and compared for the supported and unsupported materials.

Effect of Lanthanum on Performance of RuB Amorphous Alloy Catalyst for Benzene Selective Hydrogenation

The effect of La on the performance of a supported RuB amorphous alloy catalyst for benzene selective hydrogenation was studied by means of activity and selectivity tests, such as HRTEM, SAED, XPS, and XRD. The results show that the addition of La to RuB amorphous alloy catalyst can evidently increase the activity and improve the thermal stability of RuB amorphous alloy to refrain its crystallization. The promoting effect of La on the activity of RuB amorphous alloy catalyst is because of the high dispersion of the active components.

High-entropy alloy catalysts:From bulk to nano toward highly efficient carbon and nitrogen catalysis

High-entropy alloys(HEAs)have attracted widespread attention as both structural and functional materials owing to their huge multielement composition space and unique high-entropy mixing structure.Recently,emerging HEAs,either in nano or highly porous bulk forms,are developed and utilized for various catalytic and clean energy applications with superior activity and remarkable durability.Being catalysts,HEAs possess some unique advantages,including(1)a multielement composition space for the discovery of new catalysts and fine-tuning of surface adsorption(i.e.,activity and selectivity),(2)diverse active sites derived from the random multielement mixing that are especially suitable for multistep catalysis,and(3)a high-entropy stabilized structure that improves the structural durability in harsh catalytic environments.Benefited from these inherent advantages,HEA catalysts have demonstrated superior catalytic performances and are promising for complex carbon(C)and nitrogen(N)cycle reactions featuring multistep reaction pathways and many different intermediates.However,the design,synthesis,characterization,and understanding of HEA catalysts for C-and N-involved reactions are extremely challenging because of both complex high-entropy materials and complex reactions.In this review,we present the recent development of HEA catalysts,particularly on their innovative and extensive syntheses,advanced(in situ)characterizations,and applications in complex C and N looping reactions,aiming to provide a focused view on how to utilize intrinsically complex catalysts for these important and complex reactions.In the end,remaining challenges and future directions are proposed to guide the development and application of HEA catalysts for highly efficient energy storage and chemical conversion toward carbon neutrality.

Effects of Cerium Dopant on Ni-B Amorphous Alloy Catalysts Used in 2-Ethylanthraquinone Hydrogenation

A series of Ce-doped Ni-B amorphous alloy catalysts were prepared by a KBH_4 reduction method, characterized by ICP, BET, XRD, H_2-chemisorption, H_2-TPD, etc., and tested in the hydrogenation of 2-ethylanthraquinone. The results of characterization show that with the addition of Ce the amount of H_2-chemisorption and H_2-TPD areas first increases markedly and then decreases with the maximum appears at the atomic ratio of Ce to Ni of 0.036. The hydrogenation activity also shows the same trend. The effects of Ce are attributed to its dispersion of Ni particles, resulting in the formation of more surface Ni centers. However, much higher Ce contents may result in the decrease of the surface Ni contents. After heat treatment at higher temperatures, the amorphous structure of Ni-B is destroyed.

FeCo alloy catalysts promoting polysulfide conversion for advanced lithium-sulfur batteries

Lithium sulfur batteries(LSBs)draw extensive interest because of the ultra-high capacity and low material cost.However,the sluggish lithium polysulfides(LIPSs)conversion processes are detrimental to cycle stability and rate capability,inhibiting the commercial application of LSBs.Here we present the well-designed Fe Co alloy catalysts anchored on porous carbon(FeCo-C)as sulfur host to improve the electrochemical performance by accelerating the conversion reactions.The FeCo alloy demonstrates high catalytic effect and strong adsorption capability of LIPSs,in which potential polarization can be greatly decreased and"shuttle effects"can be largely avoided.As a result,the obtained S/Fe Co-C composites show an initial specific capacity of 791.9 m Ah g^-1 at a large current density of 2 C and maintain 502.5 mAh g^-1 even after 500 cycles.Moreover,720 m Ah g^-1(corresponding to 70%retention)can be achieved after 100 cycles at 0.2 C with a high sulfur content of 80 wt%,enabling high sulfur utilization.This work not only provides a new insight to investigate the conversion kinetics of Li PSs,but also opens up a new avenue for advanced lithium sulfur batteries.

Boosting the water gas shift reaction on Pt/CeO_(2)-based nanocatalysts by compositional modification: Support doping versus bimetallic alloying

The water gas shift reaction is of vital significance for the generation and transition of energy due to the application in hydrogen production and industries such as ammonia synthesis and fuel cells.The influence of support doping and bimetallic alloying on the catalytic performance of Pt/Ce O_(2)-based nanocatalysts in water gas shift reaction was reported in this work.Various lanthanide ions and 3d transition metals were respectively introduced into the Ce O_(2)support or Pt to form Pt/Ce O_(2):Ln(Ln=La,Nd,Gd,Tb,Yb)and Pt M/Ce O_(2)(M=Fe,Co,Ni)nanocatalysts.The sample of Pt/Ce O_(2):Tb showed the highest activity(TOF at 200℃=0.051 s^(-1))among the Pt/Ce O_(2):Ln and the undoped Pt/Ce O_(2)catalysts.Besides,the sample of Pt Fe/Ce O_(2)exhibited the highest activity(TOF at 200℃=0.12 s^(-1))among Pt M/Ce O_(2)catalysts.The results of the multiple characterizations indicated that the catalytic activity of Pt/Ce O_(2):Ln catalysts was closely correlated with the amount of oxygen vacancies in doped ceria support.However,the different activity of Pt M/Ce O_(2)bimetallic catalysts was owing to the various Pt oxidation states of the bimetals dispersed on ceria.The study of the reaction pathway indicated that both the samples of Pt/Ce O_(2)and Pt/Ce O_(2):Tb catalyzed the reaction through the formate pathway,and the enhanced activity of the latter derived from the increased concentration of oxygen vacancies along with promoted water dissociation.As for the sample of Pt Fe/Ce O_(2),its catalytic mechanism was the carboxyl route with a higher reaction rate due to the moderate valence of Pt along with improved CO activation.

High-loading Pt-alloy catalysts for boosted oxygen reduction reaction performance

To improve performance of membrane electrode assembly(MEA)at large current density region,efficient mass transfer at the cathode is desired,for which a feasible strategy is to lower catalyst layer thickness by constructing high loading Pt-alloy catalysts on carbon.But the high loading may induce unwanted par-ticle aggregation.In this work,H-PtNi/C with 33%(mass)Pt loading on carbon and monodisperse distri-bution of 3.55 nm PtNi nanoparticles,was prepared by a bimodal-pore route.In electrocatalytic oxygen reduction reaction(ORR),H-PtNi/C displays an activity inferior to the low Pt loading catalyst L-PtNi/C(13.3%(mass))in the half-cell.While in H_(2)-0_(2) MEA,H-PtNi/C delivers the peak power density of 1.51 W·cm^(-2) and the mass transfer limiting current density of 4.4 A·cm^(-2),being 21%and 16%higher than those of L-PtNi/C(1.25 W·cm^(-2),3.8 A·cm^(-2))respectively,which can be ascribed to enhanced mass trans-fer brought by the thinner catalyst layer in the former.In addition,the same method can be used to pre-pare PtFe alloy catalyst with a high-Pt loading of 36%(mass).This work may lead to a range of catalyst materials for the large current density applications,such as fuel cell vehicles.

Scission of C–O and C–C linkages in lignin over RuRe alloy catalyst

The performance of lignin depolymerization is basically determined by the interunit C–O and C–C bonds.Numerous C–O bond cleavage strategies have been developed, while the cleavage of C–C bond between the primary aromatic units remains a challenging task due to the high dissociation energy of C–C bond.Herein, a multifunctional Ru Re alloy catalyst was designed, which exhibited exceptional catalytic activity for the cleavage of both C–O and C–C linkages in a broad range of lignin model compounds(β-1, a-5, 5–5,β-O-4, 4-O-5) and two stubborn lignins(kraft lignin and alkaline lignin), affording 97.5% overall yield of monocyclic compounds from model compounds and up to 129% of the maximum theoretical yield of monocyclic products based on C–O bonds cleavage from realistic lignin. Scanning transmission electron microscopy(STEM) characterization showed that Ru Re(1:1) alloy particles with hexagonal close-packed structure were homogeneously dispersed on the support. Quasi-in situ X-ray photoelectron spectroscopy(XPS), and X-ray absorption spectroscopy(XAS) indicate that Ru species were predominantly metallic state, whereas Re species were partially oxidized;meanwhile, there was a strong interaction between Ru and Re, where the electron transfer from Re to Ru was occurred, resulting in great improvement on the capability of C–O and C–C bonds cleavage in lignin conversion.

Hydrogen absorption/desorption cycling performance of Mg-based alloys with in-situ formed Mg_(2)Ni and LaH_(x)(x=2,3)nanocrystallines

Aiming to elucidate the hydrogen absorption/desorption cycling properties of Mg-based alloys with in-situ formed Mg_(2)Ni and LaH_(x)(x=2,3)nanocrystallines,the hydrogen storage cycle stability,hydriding/dehydriding cycling kinetics and thermodynamic stability of the experimental alloys have been investigated in detail.The results show that the Mg-Ni-La alloys exhibit improved hydrogen storage cycling properties and can remain storage hydrogen above 5.5 wt%after 200 cycles.With the increase of cycling numbers,the dehydrogenation rates of the experimental samples increase firstly and then gradually decrease,and eventually maintain relative stable state.Microstructure observation reveals that powders sintering and hydrogen decrepitation both exist during hydrogen absorption/desorption cycles due to repeated volume expansion and contraction.Meanwhile,the in-situ formed LaH_(x)(x=2,3)and Mg_(2)Ni nanocrystallines stabilize the microstructures of the particles and hinder the powders sintering.After 200 cycles,the average particle size of the experimental samples decreases and the specific surface area apparently increases,which leads to the decomposition temperatures of MgH_(2)and Mg_(2)NiH_(4)slightly shift to lower temperatures.Moreover,Mg_(2)Ni and LaH_(x)(x=2,3)have been proven to be stable catalysts during long-term cycling,which can still uniformly distribute within the powders after 200 cycles.

Are Ni/and Ni5Fe1/biochar catalysts suitable for synthetic natural gas production?A comparison with g-Al2O3 supported catalysts

Among challenges implicit in the transition to the post-fossil fuel energetic model,the finite amount of resources available for the technological implementation of CO_(2) revalorizing processes arises as a central issue.The development of fully renewable catalytic systems with easier metal recovery strategies would promote the viability and sustainability of synthetic natural gas production circular routes.Taking Ni and NiFe catalysts supported over g-Al_(2)O_(3) oxide as reference materials,this work evaluates the potentiality of Ni and NiFe supported biochar catalysts for CO_(2) methanation.The development of competitive biochar catalysts was found dependent on the creation of basic sites on the catalyst surface.Displaying lower Turn Over Frequencies than Ni/Al catalyst,the absence of basic sites achieved over Ni/C catalyst was related to the depleted catalyst performances.For NiFe catalysts,analogous Ni_(5)Fe_(1) alloys were constituted over both alumina and biochar supports.The highest specific activity of the catalyst series,exhibited by the NiFe/C catalyst,was related to the development of surface basic sites along with weaker NiFe-C interactions,which resulted in increased Ni0:NiO surface populations under reaction conditions.In summary,the present work establishes biochar supports as a competitive material to consider within the future low-carbon energetic panorama.

Preparation of Uniform Ni-B Amorphous Alloy Catalyst on CNTs and its Performance for Acetylene Selective Hydrogenation

Uniform Ni-B amorphous alloys about 14 nm have been prepared on CNTs-A support,named Ni-B/CNTs-A. In comparison with the Ni-B/CNTs amorphous catalyst, Ni-B/CNTs-A showed higher nickel loading, determined by ICP and better catalytic activity and ethylene selectivity in the acetylene hydrogenation reaction.

Characterizations of Skeletal Iron Catalysts Prepared from Rapidly and Naturally Quenched Fe-Al Alloys

Surface morphology, physical-chemical properties of skeletal iron catalysts prepared by leaching of the rapidly quenched(RQ) and naturally quenched(NQ) Fe-Al alloys with an aqueous solution of NaOH were characterized by using a series of techniques including XRD, BET, XPS, SEM, H_2 and CO-TPD. It was found that the RQ skeletal iron catalyst exhibits a smaller particle size, larger specific surface area and pore volume than the NQ one. The H_2 and CO-TPD experiments showed that the RQ skeletal iron exhibits stronger affinity for H_2 and milder affinity for CO compared with the NQ one. But the NQ skeletal catalyst shows a better thermal stability than the RQ catalyst.

Synthesis and Characterization of ZnO Bicrystalline Nanosheets Grown via Ag-Au Alloy Catalyst

ZnO bicrystalline nanosheets have been synthesized by using Ax=AU1-x alloy catalyst via the vapor transport and condensation method at 650 ℃. High resolution transmission electron microscopy characterization reveals a twin boundary with {01-13} plane existing in the bicrystalline. A series of control experiments show that both AgxAu1-x alloy catalyst and high supersaturation of Zn vapor are prerequisites for the formation of ZnO bicrystalline nanosheet. Moreover, it is found that the density of ZnO bicrytalline nanosheets can be tuned through varying the ratio of Ag to Au in the alloy catalyst. The result demonstrates that new complicated nanostructures can be produced controllably with appropriate alloy catalyst.

ACTIVATION MECHANISM OF AMORPHOUS Ni_(63)Zr_(32)La_5 ALLOY HYDROGENATION CATALYST

The catalytic activity of amorphous Ni_63 Zr_32 La_5 ribbon for hydrogenation of ethyne to ethylene can be greatly enhanced when the alloy ribbon is pretreated with dilute acid solution,heated under negative atmosphere pressure and subjected to hydrogen reduction successively. The change of surface state of the ribbon during the activation has been analysed by AES and XPS. The surface of as-received ribbon is covered with a thin film of La_2 O_3. After pretreatment. the surface concentrations of both Ni and Zr increase obviously, whereas the surface concentration of La decreases markedly.Finally, on the surface of activated catalyst the Ni and NiO disperse finely on the matrix consisting of oxides of both Zr and La and a small amount of fluorides of Zr and La.

Kinetics Research on In-situ Rapid Dechlorination of 1,4-dichlorobenzene by Microwave-assisted Raney Ni-Al Alloy Catalyst

[Objective]The research aimed to study rapid dechlodnation kinetics of 1,4-dichlorobenzene （1,4-DCB） by microwave-assisted Raney Ni -AI alloy catalyst. [ Method] Microwave-assisted Raney Ni -AI alloy catalyst was used for dechlorination of chlorobenzene （CB） and 1,4-DCB to analyze dechlorination kinetics of 1,4-DCB. [ Result] Reductive dechlorination reaction of 1,4-DCB by microwave-assisted Raney Ni- AI alloy catalyst was in accordance of the two-order reaction kinetics. Reaction rate constants of 1,4-DCB dechlorination at 35 and 50 ℃ were 0.037 6 and 0.151 mol/（ L . min）, and the activation energy was 76.66 kJ/mol. By microwave-assisted Raney Ni - AI alloy catalyst, dechlorination rate of 1,4- DCB reached 90% at 10 rain and 35 ℃. Moreover, two chlorine atoms were removed simultaneously, reaching the target of efficient dechlorination. [ Condusion] Oechlodnation of polychlodnated organic compounds by microwave-assisted Raney Ni- AI alloy catalyst obtained good effect .

Possibility of Using Ni-Co Alloy As Catalyst for Oxygen Electrode of Fuel Cell

In recent years, the scale of use of fuel cells （FCs） has been increasing continuously. One of the essential elements that affect their work is a catalyst. Precious metals （mainly platinum） are known for their high efficiency as FC catalysts. However, their high cost holds back the FCs from application on a large scale. Therefore, catalysts that do not contain precious metals are sought. Studies are focused mainly on the search for fuel electrode catalysts, but for the efficiency of FCs also the oxygen electrode catalyst is of great significance. The paper presents an analysis of the possibilitiesof using Ni-Co alloy as a catalyst for the oxygen electrode of the FC.