Activity Of Bimetallic Nanoparticles Research Articles

Investigating Periodic Table Interpolation for the Rational Design of Nanoalloy Catalysts for Green Hydrogen Production from Ammonia Decomposition

Developing highly active catalysts for the decomposition of ammonia to produce hydrogen is an important goal in the context of renewable energy. Allied with this is a need for identification strategies to efficiently design novel catalysts integral to ensuring rapid progress in this research field. We investigated the efficacy of N–binding energy and periodic table interpolation to predict active bimetallic nanoparticle catalysts. Supported iron-platinum and iron-palladium were identified and experimentally shown to be more active than their monometallic analogues. Atomic resolution electron microscopy indicated that the most active catalyst (5 wt% Fe80Pt20/γ-Al2O3) was principally formed of alloyed nanoparticles. It restructured during testing, yet no activity loss was noted at 20 h time-on-line. While these findings show that periodic table interpolation may be a viable tool for identifying active combinations of metals, the activity of the catalysts in the current work were not able to outperform the Ru/Al2O3 benchmark. Further catalyst optimization or refinement of reaction descriptors may facilitate the development of catalysts with higher intrinsic activity than the current state-of-the-art catalysts.Graphical

Electrochemical Activation Applied to Perovskite Titanate Fibers to Yield Supported Alloy Nanoparticles for Electrocatalytic Application.

Active bi-metallic nanoparticles are of key importance in catalysis and renewable energy. Here, the in situ formation of bi-metallic nanoparticles is investigated by exsolution on 200nm diameter perovskite fibers. The B-site co-doped perovskite fibers display a high degree of exsolution, decorated with NiCo or Ni3 Fe bi-metallic nanoparticles with average diameter about 29 and 35nm, respectively. The perovskite fibers are utilized as cathode materials in pure CO2 electrolysis cells due to their redox stability in the CO/CO2 atmosphere. After in situ electrochemical switching, the nanoparticles exsolved from the perovskite fiber demonstrate an enhanced performance in pure CO2 electrolysis. At 900°C, the current density of solid oxide electrolysis cell (SOEC) with 200µm YSZ electrolyte supported NiFe doped perovskite fiber anode reaches 0.75Acm-2 at 1.6V superior to the NiCo doped perovskite fiber anode (about 1.5 times) in pure CO2 . According to DFT calculations (PBE-D3 level) the superior CO2 conversion on NiFe compared to NiCo bi-metallic species is related to an enhanced driving force for C-O cleavage under formation of CO chemisorbed on the nanoparticle and a reduced binding energy of CO required to release this product.

Bimetallic Nanoparticles Supported on Cr2O3 Microspheres As Heterogeneous Photocatalysts for Light-Induced Alcohol Oxidation

The development of environmentally benign photocatalytic processes with high reaction rate and high selectivity has always been a significant challenge. Plasmonic metal nanoparticles have been promising light-driven photocatalysts in chemical transformations due to their localized surface plasmon resonance (LSPR). In this study, bimetallic catalysts with various loadings and Ag/Au ratios supported on Cr2O3 microspheres were synthesized and evaluated as heterogeneous photocatalysts for benzyl alcohol oxidation under monochromatic 532 nm laser irradiation. Au and Ag nanoparticles were uniformly decorated on Cr2O3 microspheres by deposition precipitation and wet impregnation method respectively. The optical and physical properties of the as-prepared photocatalysts were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-Ray spectroscopy (EDX), diffuse reflectance spectroscopy (DRS), X-Ray diffraction (XRD) and RAMAN spectroscopy. The bimetallic Ag-Au-Cr2O3 catalysts presented an enhanced photocatalytic activity compared to monometallic catalysts. It should be noted that the enhanced photocatalytic activity was dependent on Ag-Au ratio. Specifically, 0.5 wt.% Ag - 3 wt.% Au /Cr2O3 photocatalyst showed the highest photocatalytic activity, achieving up to 91.2% conversion and 98.5 % selectivity of the targeted benzaldehyde. The remarkable photocatalytic performance over bimetallic nanoparticles can be ascribed to the synergistic effect of Ag-Au alloy nanoparticles under visible light irradiation. Phototelectrochemical tests were performed to further evaluate the role of plasmon mediated charge transfer in the activity of bimetallic nanoparticles.

Synthesis of catalytically active bimetallic nanoparticles within solution-processable metal–organic-framework scaffolds

Bimetallic alloy nanoparticles are synthesized by in situ reduction of mixed metal ions inside CD-MOFs.

Simple Route for the Synthesis of Highly Active Bimetallic Nanoparticle Catalysts with Immiscible Ru and Ni Combination by utilizing a TiO2 Support

AbstractTiO2 support was proven to be acted as an efficient platform for the synthesis of RuNi bimetallic alloy, which are essentially immiscible at most of equilibrium composition, by simple impregnation followed by H2 reduction at 300 °C. Characterization by means of HAADF‐STEM and EDX analysis confirmed the formation of RuNi bimetallic nanoparticles (NPs) with a mean diameter of 2.3 nm. H2‐TPR and in situ XAFS measurements suggested the intraparticle hydrogen spillover mechanism on the surface of TiO2, which originated from the improved reducibility of the Ni species and retarded reducibility of the Ru species in comparison with those for the monometallic samples. RuNi/TiO2 catalyst exhibits remarkably high catalytic activity for the dehydrogenation from ammonia borane (AB, NH3BH3) (TOF=914 min−1) compared with those prepared with other conventional supports. DFT calculation study also suggested the synergistic alloying effect due to the random distribution of Ru−Ni NPs plays a crucial role in the improvement of the adsorption energy of AB, which ultimately resulted in the exceptional catalytic performance.

Biorefining of platinum group metals from model waste solutions into catalytically active bimetallic nanoparticles.

SummaryBacteria can fabricate platinum group metal (PGM) catalysts cheaply, a key consideration of industrial processes and waste decontaminations. Biorecovery of PGMs from wastes is promising but PGM leachates made from metallic scraps are acidic. A two‐step biosynthesis ‘pre‐seeds’ metallic deposits onto bacterial cells benignly; chemical reduction of subsequent metal from acidic solution via the seeds makes bioscaffolded nanoparticles (NPs). Cells of Escherichia coli were seeded using Pd(II) or Pt(IV) and exposed to a mixed Pd(II)/Pt(IV) model solution under H2 to make bimetallic catalyst. Its catalytic activity was assessed in the reduction of Cr(VI), with 2 wt% or 5 wt% preloading of Pd giving the best catalytic activity, while 1 wt% seeds gave a poorer catalyst. Use of Pt seeds gave less effective catalyst in the final bimetallic catalyst, attributed to fewer and larger initial seeds as shown by electron microscopy, which also showed a different pattern of Pd and Pt deposition. Bimetallic catalyst (using cells preloaded with 2 wt% Pd) was used in the hydrogenation of soybean oil which was enhanced by ~fourfold using the bimetallic catalyst made from a model waste solution as compared to 2 wt% Pd preloaded cells alone, with a similar selectivity to cis C18:1 product as found using a Pd‐Al2O3 commercial catalyst.

Catalytically Active Bimetallic Nanoparticles Supported on Porous Carbon Capsules Derived From Metal-Organic Framework Composites.

We report a new methodology for producing monometallic or bimetallic nanoparticles confined within hollow nitrogen-doped porous carbon capsules. The capsules are derived from metal-organic framework (MOF) crystals that are coated with a shell of a secondary material comprising either a metal-tannic acid coordination polymer or a resorcinol-formaldehyde polymer. Platinum nanoparticles are optionally sandwiched between the MOF core and the shell. Pyrolysis of the MOF-shell composites produces hollow capsules of porous nitrogen-doped carbon that bear either monometallic (Pt, Co, and Ni) or alloyed (PtCo and PtNi) metal nanoparticles. The Co and Ni components of the bimetallic nanoparticles are derived from the shell surrounding the MOF crystals. The hollow capsules prevent sintering and detachment of the nanoparticles, and their porous walls allow for efficient mass transport. Alloyed PtCo nanoparticles embedded in the capsule walls are highly active, selective, and recyclable catalysts for the hydrogenation of nitroarenes to anilines.

Surface Composition Tuning of Au–Pt Bimetallic Nanoparticles for Enhanced Carbon Monoxide and Methanol Electro-oxidation

The ability to direct bimetallic nanoparticles to express desirable surface composition is a crucial step toward effective heterogeneous catalysis, sensing, and bionanotechnology applications. Here we report surface composition tuning of bimetallic Au-Pt electrocatalysts for carbon monoxide and methanol oxidation reactions. We establish a direct correlation between the surface composition of Au-Pt nanoparticles and their catalytic activities. We find that the intrinsic activities of Au-Pt nanoparticles with the same bulk composition of Au0.5Pt0.5 can be enhanced by orders of magnitude by simply controlling the surface composition. We attribute this enhancement to the weakened CO binding on Pt in discrete Pt or Pt-rich clusters surrounded by surface Au atoms. Our finding demonstrates the importance of surface composition control at the nanoscale in harnessing the true electrocatalytic potential of bimetallic nanoparticles and opens up strategies for the development of highly active bimetallic nanoparticles for electrochemical energy conversion.

In Situ Growth of Catalytic Active Au−Pt Bimetallic Nanorods in Thermoresponsive Core−Shell Microgels

Here, we demonstrate that bimetallic Au-Pt nanorods (NRs) can be grown in situ into thermosensitive core-shell microgel particles by a novel two-step approach. In the first step, Au NRs with an average width of 6.6 ± 0.3 nm and length of 34.5 ± 5.2 nm (aspect ratio 5.2 ± 0.6) were homogeneously embedded into the shell of PNIPA networks. The volume transition of the microgel network leads to a strong red shift of the longitudinal plasmon band of the Au NRs. In the second step, platinum was preferentially deposited onto the tips of Au NRs to form dumbbell-shaped bimetallic nanoparticles. The novel synthesis forms bimetallic Au-Pt NRs immobilized in microgels without impeding their colloidal stability. Quantitative analysis of the catalytic activity for the reduction of 4-nitrophenol indicates that bimetallic Au-Pt NRs show highly enhanced catalytic activity, which is due to the synergistic effect of bimetallic nanoparticles. The catalytic activity of immobilized Au-Pt NRs can be modulated by the volume transition of thermosensitive microgels. This demonstrates that core-shell microgels are capable of serving as "smart nanoreactors" for the catalytic active bimetallic nanoparticles with controlled morphology and high colloidal stability.

Internal/External use of dendrimer in catalysis

Dendrimers, well-defined hyper-branched macromolecules with characteristic globular structures, have inspired chemists and chemical engineers to develop new materials and several applications have been explored. The dendritic molecule has emerged as an attractive material in the field of catalysis and various dendrimer catalysts have been applied not only to catalytic reactions but also to non-catalytic ones such as nanoscale reactor systems. This article presents a review of research work on the dendrimer-based catalysis involving the rational design of homogeneous or heterogeneous chiral dendrimer catalysts for enantioselective reactions and the synthesis of catalytically active bimetallic nanoparticles in the presence of dendrimer as a template.