Alloy Nanocatalysts Research Articles

Selective formation of acetate intermediate prolongs robust ethylene removal at 0 °C for 15 days

Efficient ethylene (C2H4) removal below room temperatures, especially near 0 °C, is of great importance to suppress that the vegetables and fruits spoil during cold-chain transportation and storage. However, no catalysts have been developed to fulfill the longer-than-2-h C2H4 removal at this low temperature effectively. Here we prepare gold-platinum (Au-Pt) nanoalloy catalysts that show robust C2H4 (of 50 ppm) removal capacity at 0 °C for 15 days (360 h). We find, by virtue of operando Fourier transformed infrared spectroscopy and online temperature-programmed desorption equipped mass spectrometry, that the Au-Pt nanoalloys favor the formation of acetate from selective C2H4 oxidation. And this on-site-formed acetate intermediate would partially cover the catalyst surface at 0 °C, thus exposing active sites to prolong the continuous and effective C2H4 removal. We also demonstrate, by heat treatment, that the performance of the used catalysts will be fully recovered for at least two times.

Frustrating Surface Segregation by Nanoconfinement: Boosting Electrochemical Ozone Production over a B13C2-Encapsulated PtNi Alloy Electrocatalyst

A major challenge that limits the applications of nanostructured electrocatalysts is precise surface structure regulation. The critical performance-impeding factors for the important electrochemical ozone production (EOP) lie in the leaching-induced poor stability as well as the competing oxygen evolution and ozone production reactions over the most promising platinum-based electrocatalysts. Although composition diversification by alloying appears to be a prevailing strategy to optimize platinum-based electrocatalysts, a practical restriction turns out to be the inevitable surface segregation and termination of platinum-enriched structures due to their lower surface energies. In this work, we introduce the nanoconfinement of intermetallic platinum–nickel nanostructures encapsulated by boron carbide, which effectively frustrates the surface segregation of alloy nanostructures and well maintains the pristine termination of the alloy. Precise atomic-level structural elucidation and model construction of the encapsulated alloy nanostructures are achieved by quantitative electron microscopy. The composite nanoalloy with a unique surface termination evokes synergetic catalytic effects that promote the charge transfer between the surface and adsorbed oxygen intermediates, which entails outstanding EOP performance with a high Faraday efficiency of 14.8% in neutral media and long-term stability of up to 120 h as a qualified electrocatalyst for the EOP electrolyzer devices. More importantly, the current work paves a new route to overwhelm the thermodynamically limited surface structures of bare nanoalloy catalysts through diverse nanoconfinement strategies.

Space Confinement to Regulate Ultrafine CoPt Nanoalloy for Reliable Oxygen Reduction Reaction Catalyst in PEMFC.

A Co-based zeolitic imidazolate framework (ZIF-67) derived catalyst with ultrafine CoPt nanoalloy particles is designed via a two-step space confinement method, to achieve a robust oxygen reduction reaction (ORR) performance for proton exchange membrane fuel cell (PEMFC). The core-shell structure of ZIF-67 (core) and SiO2 (shell) is carefully adjusted to inhibit the agglomeration of Co nanoparticles. In the subsequent adsorption-annealing process, the in situ formed graphene shell on the surface of Co nanoparticles further protects metal particles from coalescence, leading to the ultrafine CoPt nanoalloy (average diameter is 2.61nm). Benefitting from the high utilization of Pt metal, the mass activity of CoPt nanoalloy catalyst reaches 681.8mA mgPt -1 at 0.9V versus RHE according to the rotating disk electrode test in 0.1m HClO4 solution. The CoPt nanoalloy-based PEMFC provides a high maximum power density of 2.22W cm-2 (H2 /O2 ) and 0.923W cm-2 (H2 /air). Simultaneously, itshows good stability in the long-time dynamic test at low humidity, due to the robust CoPt@graphene core-shell nanostructure. This work provides a viable strategy for designing Pt-based nanoalloy catalysts with ultrafine metal particles and high stability.

Enhanced catalytic performance of Pd-Pt bimetallic alloy nanocatalyst for hydrogenation of nitrile butadiene rubber

Nowadays, the rational design of high-performance catalysts with desirable resistance to metal leaching has become the principal challenge in the hydrogenation of nitrile butadiene rubber. In the present work, the Pd-Pt bimetallic alloy nanocatalyst exhibits an outstanding hydrogenation degree of 99.0%, obviously higher than that of the conventional monometallic Pd/SiO2 catalyst with the same Pd content (92.9%), accompanied by approximately 100% selectivity to C=C bonds. The results reveal that electron transfer from Pt to Pd confirms that the Pd species are in a rich-electron state, which boosts hydrogen activation and improves catalytic activity. Additionally, the incorporation of inactive Pt species promotes the formation of uniformly dispersed Pd-Pt alloy nanoparticles. The incorporation of inactive Pt species can enhance the metal-support interaction, reducing the residual metal content in hydrogenated nitrile butadiene rubber. The current research demonstrates a simple procedure for designing efficient bimetallic catalysts for the hydrogenation of unsaturated elastomer.

Inducing Covalent Atomic Interaction in Intermetallic Pt Alloy Nanocatalysts for High-Performance Fuel Cells.

The harsh working environments of proton exchange membrane fuel cells (PEMFCs) pose huge challenges to the stability of Pt-based alloy catalysts. The widespread presence of metallic bonds with significantly delocalized electron distribution often lead to component segregation and rapid performance decay. Here we report L10 -Pt2 CuGa intermetallic nanoparticles with a unique covalent atomic interaction between Pt-Ga as high-performance PEMFC cathode catalysts. The L10 -Pt2 CuGa/C catalyst shows superb oxygen reduction reaction (ORR) activity and stability in fuel cell cathode (mass activity=0.57 A mgPt -1 at 0.9 V, peak power density=2.60/1.24 W cm-2 in H2 -O2 /air, 28 mV voltage loss at 0.8 A cm-2 after 30 000 cycles). Theoretical calculations reveal the optimized adsorption of oxygen intermediates via the formed biaxial strain on L10 -Pt2 CuGa surface, and the durability enhancement stems from the stronger Pt-M bonds than those in L11 -PtCu resulted from Pt-Ga covalent interactions.

Inducing Covalent Atomic Interaction in Intermetallic Pt Alloy Nanocatalysts for High‐Performance Fuel Cells

AbstractThe harsh working environments of proton exchange membrane fuel cells (PEMFCs) pose huge challenges to the stability of Pt‐based alloy catalysts. The widespread presence of metallic bonds with significantly delocalized electron distribution often lead to component segregation and rapid performance decay. Here we report L10−Pt2CuGa intermetallic nanoparticles with a unique covalent atomic interaction between Pt−Ga as high‐performance PEMFC cathode catalysts. The L10−Pt2CuGa/C catalyst shows superb oxygen reduction reaction (ORR) activity and stability in fuel cell cathode (mass activity=0.57 A mgPt−1 at 0.9 V, peak power density=2.60/1.24 W cm−2 in H2‐O2/air, 28 mV voltage loss at 0.8 A cm−2 after 30 000 cycles). Theoretical calculations reveal the optimized adsorption of oxygen intermediates via the formed biaxial strain on L10−Pt2CuGa surface, and the durability enhancement stems from the stronger Pt−M bonds than those in L11−PtCu resulted from Pt−Ga covalent interactions.

Synthesis of Alumina-Supported RhSn Alloy Nanocatalysts by Using Rh@Sn Core–Shell Nanoparticle Precursors for Toluene Catalytic Hydrogenation

Synthesis of Alumina-Supported RhSn Alloy Nanocatalysts by Using Rh@Sn Core–Shell Nanoparticle Precursors for Toluene Catalytic Hydrogenation

A robust direct-propane solid oxide fuel cell with hierarchically oriented full ceramic anode consisting with in-situ exsolved metallic nano-catalysts

Perovskite oxide Sr2Fe1.3Mo0.5Ni0.2O6-σ (SFMNi) impregnated on the scaffold of hierarchically oriented yttria-stabilized zirconia (YSZ) with open, straight pores (SFMNi@YSZ), that could transformed into in-situ exsolved Ni–Fe alloy nanoparticles structured SFMNi@YSZ (NiFe@SFMNi@YSZ) electrode, have been prepared and utilized for robust direct propane-fueled solid oxide fuel cell (SOFC). The hierarchically oriented open, straight pores can not only significantly facilitate the introduction of uniformly distributed SFMNi nano-catalyst network via the ion-impregnation method, but also greatly enhance the gas diffusion process in the porous electrode, thus greatly minimizing even eliminating the concentration resistance. The impregnated SFMNi nano-catalysts, especially the in-situ exsolved Ni–Fe alloy nano-catalysts, could effectively activate the fuel gas oxidation reaction in the anode, thereby drastically decreasing the activation resistance and enhancing the cell performance. The full ceramic electrode can efficiently avoid electrode aggregation and carbon coking, leading to excellent stability towards propane oxidation. Our findings indicate that NiFe@SFMNi@YSZ full ceramic electrode with hierarchically oriented open, straight pores offers a great promise for direct hydrocarbon SOFC.

Electro-triggered Joule heating method to synthesize single-phase CuNi nano-alloy catalyst for efficient electrocatalytic nitrate reduction toward ammonia

Electro-triggered Joule heating method to synthesize single-phase CuNi nano-alloy catalyst for efficient electrocatalytic nitrate reduction toward ammonia

Preparation adjacent Ni-Co bimetallic nano catalyst for dry reforming of methane

Catalytic reforming for hydrogen production is a bridge to sustainable energy. Coking is a big challenge for the industrialization of DRM. The key is to maintain a balance between the formation rate of *C and that of *O. A novel preparation strategy of Ni-Co nano alloy catalysts was proposed with microemulsion coupling with antisolvent extraction strategy.The prepared nanoparticles were highly dispersed and Ni,Co were closely adjacent. Compared with the monometallic 10Ni0Co/SiO2 catalyst and 0Ni10Co/SiO2 catalyst, the as-prepared bimetallic 5Ni5Co/SiO2 nano alloy catalyst showed the best catalytic activity. On the monometallic 10Ni0Co/SiO2 catalyst, owing to the faster cracking of methane on Ni particles, the catalytic activity decreased 10% by coking during the 50 h test. However, 0Ni10Co/SiO2 catalyst was deactivated by the oxidation of Co. In the 100 h test of 5Ni5Co/SiO2 bimetallic catalyst, the catalytic activity remained stable. TPSR showed that the dissociation of methane and the generation of *C was slightly inhibited and the activation of CO2 was intensified. More activated *O enhanced the reaction of *C or *CHx and *O. The anti-coking performance was improved. The results provide implications for anti-coking catalysts for catalytic reforming.

Enhanced membraneless fuel cells by electrooxidation of ethylene glycol with a nanostructured cobalt metal catalyst

The advancement of effective and long-lasting electrocatalysts for energy storage devices is crucial to reduce the impact of the energy crisis. In this study, a two-stage reduction process was used to synthesize carbon-supported cobalt alloy nanocatalysts with varying atomic ratios of cobalt, nickel and iron. The formed alloy nanocatalysts were investigated using energy-dispersive X-ray spectroscopy, X-ray diffraction, and transmission electron microscopy to determine their physicochemical characterization. According to XRD results, Cobalt-based alloy nanocatalysts form a face-centered cubic solid solution pattern, illustrating thoroughly mixed ternary metal solid solutions. Transmission electron micrographs also demonstrated that samples of carbon-based cobalt alloys displayed homogeneous dispersion at particle sizes ranging from 18 to 37 nm. Measurements of cyclic voltammetry, linear sweep voltammetry, and chronoamperometry revealed that iron alloy samples exhibited much greater electrochemical activity than non-iron alloy samples. The alloy nanocatalysts were evaluated as anodes for the electrooxidation of ethylene glycol in a single membraneless fuel cell to assess their robustness and efficiency at ambient temperature. Remarkably, in line with the results of cyclic voltammetry and chronoamperometry, the single-cell test showed that the ternary anode works better than its counterparts. The significantly higher electrochemical activity was observed for alloy nanocatalysts containing iron than for non-iron alloy catalysts. Iron stimulates nickel sites to oxidize cobalt to cobalt oxyhydroxides at lower over-potentials, which contributes to the improved performance of ternary alloy catalysts containing iron.

Regulating Hollow Carbon Cage Supported NiCo Alloy Nanoparticles for Efficient Electrocatalytic Hydrogen Evolution Reaction.

The NiCo alloy is one of the most promising alternatives to the noble-metal electrocatalysts for the hydrogen evolution reaction (HER); however, its performance is largely restricted by insufficient active sites and low surface area. Here, we fabricated a hierarchical hollow carbon cage supported NiCo alloy (denoted as HC NiCo/C) and a bulk NiCo alloy (denoted as NiCo) by reduction of a partially ZIF-67 etched ZIF-67@NiCo-LDH (LDH = layered double hydroxide) precursor and a fully ZIF-67 etched NiCo-LDH precursor, respectively. The as-prepared HC NiCo/C, in which the Ni29Co71 alloy nanocrystals with an average 6 nm size were encapsulated in graphitic carbon layers, provided a vastly increased electrochemically active surface area (ca. 13 times than the NiCo) and abundant catalytic active sites, which resulted in a higher HER performance with an overpotential of 99 mV than the 198 mV for NiCo at 10 mA cm-2. Detailed experimental results suggested that only the HC NiCo/C possessed the active alloy surface composed of unsaturated Ni0 and Co0 atoms, and both the metal-support interaction and alloying effect influenced the electronic structure of Co and Ni in HC NiCo/C, whereas the NiCo exhibited pure Ni surface. Theoretical calculations further revealed the Ni29Co71 alloy surface in HC NiCo/C possessed the appropriate adsorption energy of the intermediate state (adsorbed H*). This work provided new insight into the construction of the stable small-sized bimetallic alloy nanocatalysts by regulating the reduction precursors.

Computational and Experimental Design of the Octahedral PdFe Alloy Nanocatalyst for Hiyama Cross-Coupling and Environmental Pollutant Degradation

The research on various bimetallic nanoparticles (NPs) is rapidly expanding due to their widespread applications. However, the formation of bimetallic nanostructures in a facile way remains challenging. In the present study, an octahedral (Oh) PdFe alloy nanostructure was designed by following an aqueous medium synthesis strategy. Different metal precursor ratios were varied to observe the change in the shape and distribution of the Oh PdFe alloy nanostructure. Surprisingly, increasing the Fe content directed the finer growth of Oh morphology. However, increasing the Pd amount resulted in an uneven Oh PdFe alloy shape. The catalytic activity of the optimized Oh PdFe alloy was examined for Hiyama cross-coupling, and the degradation of dyes was scrutinized at different pH. The suggested alloy nanostructured catalyst exhibited improved catalytic behavior compared to other nanocatalysts, such as commercial catalyst Pd/C (95%), monometallic Pd Oh (98%), Fe NPs (15%), and PdFe NPs (85%), for the Hiyama cross-coupling reaction. The optimized alloy catalyst with less Pd and more Fe demonstrated 98% yield and excellent reusability up to the fifth consecutive cycle, conveying 80% yield. The stability of the Oh PdFe alloy nanocatalyst and the mechanistic aspects of Hiyama cross-coupling was supported by density functional theory. The degradation of both anionic dyes, Congo red, Eosin Y, and cationic rhodamine B, was performed under normal along with acidic and basic conditions. The degradation reaction was completed in an adequate time interval for all the dyes with no change in the morphology of the synthesized catalyst.

Bimetallic Synergy in Single-Atom Alloy Nanocatalysts for CO2 Reduction to Ethylene

Carbon dioxide reduction has been regarded as a promising strategy for the generation of value-added multi-carbon compounds. Taking advantage of the synergy of the distinct chemical characters of adsorption sites, the single-atom Sc-doped Cu(111) surface exhibits excellent performance for C2H4 selectivity. O is more strongly bound to Sc than C to Cu, leading to the facilitation of CO2 activation and C2H4 desorption. The Sc dopant promotes C–C dimerization through the CO dimer into COCO, which is difficult to occur on the pristine Cu(111), and the COCO─involved reaction pathway is favorable both in thermodynamics and kinetics. This study sheds light on nanocatalyst design for reaction products with different chemical characters from reactants. Typically, the control of the electron-deficient and electron-sufficient sites on catalyst surfaces is beneficial for chemical reactions with oxygenated reactants and hydrocarbon products.

PdCu alloy prepared by ultrasonic method catalyzes the degradation of p-nitrophenol.

PdCu alloy nanocatalysts supported on NiFe layered double hydroxide (PdCu-LDHs) were prepared by a green ultrasound-assisted reduction method. The cavitation effect of ultrasound made part of CO32- decompose to CO2, and NO3- and Cl- replace intercalation, which anchor the PdCu between layers. The action of ultrasound dissociated hydroxyl groups (-OH) on surface of LDHs to H· to reduce Cu2+ and Pd2+ to Cu0 and Pd0 and Cu promote the synergy between Pd alloy and LDHs. The electronic effects between Cu and Pd improved the catalytic performance for the reduction reaction of 4-NP and the stability of PdCu-LDHs. The PdCu-LDHs prepared at 400 W, 25kHz, 1h, can completely degrade p-nitrophenol (4-NP) within 5min with n(4-NP)/n(Pd) = 50 and n(4-NP)/n(NaBH4) = 0.15. The TOF value is 988.20h-1, which is 27.7 times that of Pd/C catalyst (commercial).

Facile Synthesis of PtCuNi Nanohexapods as Active Electrocatalysts for Methanol Oxidation and Ethanol Oxidation

The design of Pt-based alloy nanocatalysts with sufficient accessible surface areas and abundant active sites is important for their application in direct methanol fuel cells (DMFCs) and direct ethanol fuel cells (DEFCs). Here, we report a simple one-pot method for the preparation of PtCuNi hexapod nanocrystals. The conversion mechanism of the nanoparticles from rhombic dodecahedra to hexapods was investigated by time evolution experiments. Electrochemical tests demonstrated that the PtCuNi nanohexapods exhibited greatly elevated catalytic performance for methanol oxidation reaction (MOR) and ethanol oxidation reaction (EOR) under acidic conditions. Specifically, the PtCuNi nanohexapods have mass activities of 1.73 and 2.31 A mgPt–1 for MOR and EOR, which are 2.9 and 2.3 times higher than those of the commercial Pt/C catalyst, respectively. Moreover, the PtCuNi nanohexapods also exhibit enhanced electrocatalytic stability compared to Pt/C. This work provides an effective strategy for the rational construction of nanocrystals with desired morphologies and structures in the application of catalysis, energy, sensors, and other fields.

Synthesis of Highly Tunable Alloy Nanocatalyst through Heterogeneous Doping Method (Adv. Sci. 5/2023)

Synthesis of Highly Tunable Alloy Nanocatalyst through Heterogeneous Doping Method (Adv. Sci. 5/2023)

Regulating Competitive Adsorption on Pt Nanoparticles by Introducing Pb to Expedite Hydrogen Production via Ammonia Oxidation

Ammonia with a high hydrogen content is an ideal hydrogen carrier due to its mature storage and transport system. Ammonia electrooxidation is one of the most promising technologies for green and economic H2 production. However, ammonia oxidation reaction (AOR) is limited to a narrow potential window due to the slow kinetics and the competitive adsorption between the reactant and Had/OHad on active sites. Herein, an ultra-small PtPb alloy nanocatalyst is synthesized for AOR by the facile one-step solvothermal method. Experimental results demonstrate that the electronic structure of Pt is regulated by the introduction of Pb, inhibiting the competitive adsorption on Pt sites. Therefore, it exhibits improved AOR activity with a peak current density of 191.2 mA mg–1Pt at 10 mV s–1, which is 1.97 times that of Pt/C. The good performance is attributed to the high hydrogen evolution overpotential property of Pb and the strong p–d electron interaction of PtPb, which effectively modulates the adsorption/desorption of intermediates at the Pt site. Hence, this work proposes a simple and effective strategy for designing efficient AOR catalysts, promoting the development of H2 production by AOR.

Multivariate Porphyrinic MOFs as Precursors of Nanoalloy Catalysts for Efficient Dehydrogenation of Hydrogen Molecular Carriers

The realization of the Hydrogen Economy involves the development of efficient, safe, and lightweight H storage and delivery systems. Hydrogen molecular carriers (HMCs) have been proposed for this application, as they release and store H2 after catalyzed hydrogenation/dehydrogenation cycles, but efficient catalysts are still needed. In this work, we present a methodology for the development of nanocatalysts, using porphyrinic multivariate metal–organic frameworks (MTV-MOFs) as a precursor of supported nanoalloys/nanocomposites (M/ZrO2). MTV-MOFs with PCN-222 structure, containing atomically distributed mixtures of Pd, Pt, and Ni, yield dispersed nanoalloys after calcination, with a high metal loading. Both support and catalytically active phases are produced simultaneously during thermal treatment. The obtained materials demonstrate synergistic effects in the catalytic dehydrogenation of hydrogen molecular carriers, namely, ammonia borane (AB), 2-methylpiperidine (2MP), and a liquid mixture of 2MP and DHC (dodecahydro-1H-carbazole).

In situ SERS reveals the route regulation mechanism mediated by bimetallic alloy nanocatalysts for the catalytic hydrogenation reaction.

Synthesizing arylamines with high selectivity via hydrogenation of nitroaromatics is a long-standing challenge because of the complex reaction pathways. Revealing the route regulation mechanism is the key to obtain high selectivity of arylamines. However, the underlying reaction mechanism of route regulation is uncertain owing to a lack of direct in situ spectral evidence of the dynamic transformation of intermediate species during the reaction process. In this work, by using in situ surface-enhanced Raman spectroscopy (SERS), we have employed 13 nm Au100-x Cu x nanoparticles (NPs) deposited on a SERS-active 120 nm Au core to detect and track the dynamic transformation of intermediate species of hydrogenation of para-nitrothiophenol (p-NTP) into para-aminthiophenol (p-ATP). Direct spectroscopic evidence demonstrates that Au100 NPs exhibited a coupling route with the in situ detection of the Raman signal assigned to coupling product p,p'-dimercaptoazobenzene (p,p'-DMAB). However, Au67Cu33 NPs displayed a direct route without the detection of p,p'-DMAB. The combination of X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations reveals that Cu doping can favor the formation of active Cu-H species owing to the electron transfer from Au to Cu, which can promote the formation of phenylhydroxylamine (PhNHOH*) and favor the occurrence of the direct route on Au67Cu33 NPs. Our study provides direct spectral evidence demonstrating the critical role of Cu in route regulation for the nitroaromatic hydrogenation reaction at a molecular level and clarifies the route regulation mechanism. The results have significant implications for revealing multimetallic alloy nanocatalyst mediated reaction mechanisms and help to guide the rational design of multimetallic alloy catalysts for catalytic hydrogenation reactions.