Number Of Pt Atoms Research Articles

Microwave heating-assisted synthesis of ultrathin platinum-based trimetallic nanosheets as highly stable catalysts towards oxygen reduction reaction in acidic medium

There are currently almost no ternary platinum-based nanosheets used for acidic oxygen reduction reactions (ORR) due to the difficulty in synthesizing ternary nanosheets with high Pt content. In this work, several ultrathin platinum-palladium-copper nanosheets (PtPdCu NSs) with a thickness of around 1.90 nm were prepared via a microwave heating-assisted method. Microwave heating allows a large number of Pt atoms to deposit into PdCu nanosheets, forming Pt-based ternary nanosheets with high Pt content. Among them, Pt38Pd50Cu12 NSs catalyst displays the highest mass activity (MA) measured in 0.1 M HClO4 of 0.932 A/mgPt+Pd which is 8.6 times of that Pt/C. Besides, Pt38Pd50Cu12 NSs catalyst also exhibits excellent stability with an extremely low MA attenuation after 80,000 cycles accelerated durability testing (ADT) tests. In the single cell tests, the Pt38Pd50Cu12 NSs catalyst manifests higher maximum power density of 796 mW cm−2 than Pt/C of 606 mW cm−2. Density functional theory (DFT) calculations indicate the weaker adsorption between Pt and O-species in Pt38Pd50Cu12 NSs leads to a significant enhancement of ORR activity. This study provides a new strategy to design and prepare ultrathin Pt-based trimetallic nanosheets as efficient and durable ORR catalysts.

Surface-Enriched Single-Bi-Atoms Tailoring of Pt Nanorings for Direct Methanol Fuel Cells with Ultralow-Pt-Loading.

Single-atom decorating of Pt emerges as a highly effective strategy to boost catalytic properties, which can trigger the most Pt active sites while blocking the smallest number of Pt atoms. However, the rational design and creation of high-density single-atoms on Pt surface remain as a huge challenge. Herein, a customized synthesis of surface-enriched single-Bi-atoms tailored Pt nanorings (SE-Bi1/Pt NRs) toward methanol oxidation is reported, which is guided by the density functional theory (DFT) calculations suggesting that a relatively higher density of Bi species on Pt surface can ensure a CO-free pathway and accelerate the kinetics of *HCOOH formation. Decorating Pt NRs with dense single-Bi-atoms is achieved by starting from PtBi intermetallic nanoplates (NPs) with intrinsically isolated Bi atoms and subsequent etching and annealing treatments. The SE-Bi1/Pt NRs exhibit a mass activity of 23.77 A mg-1 Pt toward methanol oxidation in alkaline electrolyte, which is 2.2 and 12.8 times higher than those of Pt-Bi NRs and Pt/C, respectively. This excellent activity endows the SE-Bi1/Pt NRs with a high likelihood to be used as a practical anodic electrocatalyst for direct methanol fuel cells （DMFCs） with high power density of 85.3mW cm-2 and ultralow Pt loading of 0.39 mg cm-2.

Formation of pyramidal structures through mixing gold and platinum atoms: the AuxPty2+ clusters with x + y = 10.

The geometric and electronic structures of a small series of mixed gold and platinum AuxPty2+ clusters, with x + y = 10, were investigated using quantum chemical methods. A consistent tetrahedral pyramid structure emerges, displaying two patterns of structural growth by a notable critical point at y = 5. This affects the clusters' electron population, chemical bonding, and stability. For the Pt-doped Au clusters with y values from 2 to 5, the bonds enable Pt atoms to assemble into symmetric line, triangle, quadrangle, and tetragonal pyramidal Pty blocks, respectively. For the Au-doped Pt clusters, with larger values of y > 5, the structures are more relaxed and the d electrons of Pt atoms become delocalized over more centers, leading to lower symmetry structures. A certain aromaticity arising from delocalization of d electrons over the multi-center framework in the doped Pt clusters contributes to their stability, with Pt102+ at y = 10 exhibiting the highest stability. While the ground electronic state of the neutral platinum atom [Xe]. 4f145d96s1 leads to a triplet state (3D3), the total magnetic moments of AuxPty2+ are large increasing steadily from 0 to 10 μB and primarily located on Pt atoms, corresponding to the increase of the number of Pt atoms from 0 to 10 and significantly enhancing the magnetic moments. An admixture of both Au and Pt atoms thus emerges as an elegant way of keeping a small pyramidal structure but bringing in a high and controllable magnetic moment.

Constructing efficient ternary PtTeCu nano-catalysts with 2D ultrathin-sheet structures for oxidation reaction of alcohols

Ternary Pt-based nanomaterials have arisen much interest due to their outstanding electro-catalytic performance to reactions in fuel cells as well as the decrease of the utilization of Pt atoms. The construction of two-dimensional (2D) ternary Pt-based nanocatalysts by combining the advantages of alloy and geometric structure were appealing. In this work, we prepared free-standing ultrathin and highly flexible PtTeCu nanosheets (NSs) by a one-pot polyol method. The ultrathin feature and nanopore structure at the edges allowed the exposure of a large number of Pt atoms, supplying sufficient active sites for the catalytic reaction. The obtained PtTeCu NSs exhibited significantly higher ethylene glycol oxidation reaction (EGOR) and methanol oxidation reaction (MOR) performance reaching mass activities of 7.1 A/mg and 4.9 A/mg, compared to 6.5 and 6.1 times that of commercial Pt/C, respectively. The freestanding PtTeCu NS were subjected to long-term stability tests (200 cycles) where activity decay and structural changes were negligible. DFT calculations showed that the introduction of Cu and Te into Pt resulted in a significant downward shift of the d-band center of Pt. This weakened the adsorption energy of the products on PtTeCu NSs and accelerated the desorption of the products to the catalyst surface, enhancing the catalyst activity and stability. The unique ultrathin nano-sheet structures could provide sufficient active sites for the catalytic reaction, which also contributed to the excellent catalytic performance.

Synthesis of Pt Nanoparticles Encapsulated inside Dendrimers As Tunable Oxidase Mimics for Turn-on Fluorescent Sensing of Oxygen

Here, we present the controllable synthesis of dendrimer-encapsulated Pt nanoparticles (Pt DENs) utilizing repetitively coupled chemical reduction and galvanic exchange reactions. This facile method allowed controllable synthesis of the Pt DENs with fair homogeneity in size and composition. In particular, in contrast to the conventional dendrimer-templating methods, the proposed synthesis method allowed substantial increase in the applicable number of Pt atoms up to 1320 in Pt DENs without being limited by the fixed number of complexation sites for the Pt2+ precursor ions in dendrimers. We also present a detailed investigation on the oxidase-mimetic activity of the Pt DENs for catalytic oxidation of Amplex Red to resorufin with O2. Importantly, after clarifying intrinsic oxidase-mimetic activity of the Pt DENs, we disclosed that the Pt DENs’ oxidase-mimetic activity was tailorable for the oxidation of Amplex Red to resorufin especially with fine-tuning of the Pt2+/dendrimer ratios by using the proposed synthesis method.

Combining quantitative ADF STEM with SiNx membrane-based MEMS devices: A simulation study with Pt nanoparticles

Computer simulations are used to assess the influence of a 20-nm-thick SiNx membrane on the quantification of atomic-resolution annular dark-field (ADF) scanning transmission electron microscopy images of Pt nanoparticles. The discussions include the effect of different nanoparticle/membrane arrangements, accelerating voltage, nanoparticle thickness and the presence of adjacent atomic columns on the accuracy with which the number of Pt atoms in each atom column can be counted. The results, which are based on the use of ADF scattering cross-sections, show that an accuracy of better than a single atom is attainable at 200 and 300 kV. At 80kV, the scattering in a typical SiNx membrane is sufficiently strong that the best possible atom counting accuracy is reduced to +/- 2 atoms. The implications of the work for quantitative studies of Pt nanoparticles imaged through SiNx membranes are discussed.

Formation of Cu–Pt nanocontacts in STM breaking junction simulations: MD simulations and one-dimensional diffusion model

In this paper, we propose a new theoretical approach that combines classical MD method and a one-dimensional diffusion model. We have shown that our approach allows to extrapolate the results of MD simulations to the experimental timescale. As an example, the formation of Cu–Pt nanocontacts in the STM-BJ experiments was investigated. STM-BJ simulations with copper STM tips and Cu–Pt surface alloys were performed in a wide range of temperatures (300–900 K), number of Pt atoms in the substrate (1–7) and for different orientations ((100), (110) and (111)) of the STM tip. Using our approach, we predicted that it is possible to use the STM-BJ technique to prepare Cu–Pt nanocontacts. The presented approach should work well in all cases when the diffusion of atoms occurs via interlayer jumps.

Geometric and electronic properties of AulPtm (l + m ≤ 10) clusters: a first-principles study.

The structural evolutions and electronic properties of AulPtm (l + m ≤ 10) clusters are investigated by using the first-principles methods. We use the inverse design of materials using the multi-objective differential evolution (IM2ODE) package to globally search the equilibrium structures and investigate the evolving trend from a two-dimensional structure to a three-dimensional structure on horizontal extension and vertical extension for AulPtm (l + m ≤ 10) clusters. The three-dimensional stable geometry of Au8Pt and Au8Pt2 is discovered for the first time in our work. We also notice that the equilibrium structures of AulPtm (l + m = 10 and l ≤ 8) tend to form a tetrahedral geometry and can be obtained by replacing the Au atom in the most stable structure of Aul+1Ptm-1 with the Pt atom, where Pt atoms assemble together and occupy the center of clusters and Au atoms prefer to lie on the vertex or edge position. The average binding energy (Eb) is mostly decided by Pt-Pt bond numbers, namely the numbers of Pt atoms, followed by Au-Pt bond numbers. The second-order energy difference (Δ2Ev and Δ2Eh) and the nearest-neighbor energy difference (Δ4Enn) show that Au6Pt, Au4Pt2, Au3Pt3, Au2Pt4 and AuPt7 clusters exhibit high relative physical stability, so we suggest that these clusters could be defined as the magic number clusters for AulPtm (l + m ≤ 10) clusters. The HOMO-LUMO energy gap (Eg), adiabatic ionization potential (AIP) and the adiabatic electron affinity (AEA) are also investigated to elaborate the relative electronic stability of all the clusters.

Synthesis and Applications of Dendrimer-Encapsulated Pt Nanoparticles in Chemical Sensors

Synthesis of nanoparticles having well-defined small sizes especially less than ~3 nm has been in the forefront of research attention in diverse fields including biological and chemical sensors because of unique features of such very small particles. Synthesis and characterization of such tiny particles still remains challenging due to the extremely small dimension of the particles, too. Here, I present the synthesis of ultra-small Pt nanoparticles having different but uniform sizes using dendrimers as a molecular template, which is usually denominated as dendrimer-encapsulated nanoparticles (DENs). Specifically, I present a new synthesis strategy of Pt DENs to expand the applicable number of Pt atoms in Pt DENs by utilizing repetitively coupled chemical reduction and galvanic exchange reactions. The applications of Pt DENs is also discussed in chemical sensors. For example, I present the modification of indium tin oxide (ITO) with Pt DENs to provide enhanced stable electrochemiluminescence (ECL) of Ru(bpy)3 2+/tripropylamine while preserving optical transparency of ITO for sensitive ECL-based analyses.

Interatomic potentials for Pt-C and Pd-C systems and a study of structure-adsorption relationship in large Pt/graphene system

Graphene-supported platinum (Pt) and palladium (Pd) nanoclusters have attracted attention as electrocatalysts for proton exchange membrane fuel cell (PEMFC) because of their high activity and resistance to CO poisoning. However, metal nanoparticles are weakly adsorbed to the graphene and easily migrate on the surface, causing sintering and loss of chemical activity. A thorough understanding of structure-adsorption relationship is important to design robust catalysts with high adsorption ability to stabilize metal nanoparticles, but this relationship is still not well understood, particularly in large scale systems (2–5 nm). Therefore, to investigate the structural evolution at atomic scale with atomistic simulations, we have developed interatomic potentials for the Pt-C and Pd-C binary systems, based on the second nearest-neighbor modified embedded-atom method (2NN MEAM) formalism. These potentials reproduce various fundamental properties of the alloy systems in reasonable agreement with the experimental data and first-principles calculations. Molecular dynamics simulations employing the 2NN MEAM potential were carried out to analyse structural factors that have decisive effect on the adsorption energy, by changing the symmetry of the nanoparticles and the configuration of the nanoparticles adsorbed to graphene. These factors were characterized via coordination numbers, number of Pt atoms in contact with the graphene and adsorption site. The results of our study suggest avenues for stabilizing and immobilizing metal clusters on graphene in large systems.

Surface mobility and impact of precursor dosing during atomic layer deposition of platinum: in situ monitoring of nucleation and island growth.

The increasing interest in atomic layer deposition (ALD) of Pt for the controlled synthesis of supported nanoparticles for catalysis demands an in-depth understanding of the nucleation controlled growth behaviour. We present an in situ investigation of Pt ALD on planar Si substrates, with native SiO2, by means of X-ray fluorescence (XRF) and grazing incidence small-angle X-ray scattering (GISAXS), using a custom-built synchrotron-compatible high-vacuum ALD setup and focusing on the thermal Pt ALD process, comprising (methylcyclopentadienyl)trimethylplatinum (MeCpPtMe3) and O2 gas at 300 °C. The evolution in key scattering features provides insights into the growth kinetics of Pt deposits from small nuclei to isolated islands and coalesced worm-like structures. An analysis approach is introduced to extract dynamic information on the average real space parameters, such as Pt cluster shape, size, and spacing. The results indicate a nucleation stage, followed by a diffusion-mediated particle growth regime that is marked by a decrease in average areal density and the formation of laterally elongated Pt clusters. Growth of the Pt nanoparticles is thus not only governed by the adsorption of Pt precursor molecules from the gas-phase and subsequent combustion of the ligands, but is largely determined by adsorption of migrating Pt species on the surface and diffusion-driven particle coalescence. Moreover, the influence of the Pt precursor dose on the particle nucleation and growth is investigated. It is found that the precursor dose influences the deposition rate (number of Pt atoms per cycle), while the particle morphology for a specific Pt loading is independent of the precursor dose used in the ALD process. Our results prove that combining in situ GISAXS and XRF provides an excellent experimental strategy to obtain new fundamental insights about the role of deposition parameters on the morphology of Pt ALD depositions. This knowledge is vital to improve control over the Pt nucleation stage and enable efficient synthesis of supported nanocatalysts.

Structure, stability and electronic properties of bimetallic atomic chains of Au–Ag and Au–Pt

Quantum confinement of electrons in atomic chains provides the most powerful and versatile means to control electronic, optical, magnetic and thermoelectric properties of materials needed to make diodes, spin valves and optical labels. Furthermore, the alloying of metallic atoms in different compositions produces novel mechanical, electronic and chemical behaviours in bimetallic chains as well as in other structures. This motivated us to perform theoretical investigations on the structure, stability, magnetic and electronic properties of bimetallic atomic chains of Au–Ag and Au–Pt, by using Vienna ab-initio simulation package (VASP), which is based on the density functional theory (DFT) within generalised gradient approximation. We have used tension and cohesive energy criteria to assess the stability of the Au–Ag and Au–Pt atomic chains. A comparison between the computed cohesive energies of various possible structures are made to suggest the most probable chain structures that can occur in break junction experiments. Our computed results suggest that the ground state of the Au–Ag and Au–Pt atomic chains should have zig-zag geometry. Furthermore, the most favoured chain structures that can be formed at the last stage of nanowires stretching are: (i) an atomic chain with alternate arrangement of equal number of Au and Ag / Pt atoms and (ii) an atomic chain where two Ag / Pt atoms are separated by one Au atom. Our results on the electronic band structure and optical properties suggest that the Au–Ag atomic chain could be of semiconducting nature, while the most stable Au–Pt chain is metallic in nature. A spin-polarised calculation with the inclusion of spin–orbit coupling shows that the Au–Pt atomic chains are magnetic, if the number of Au atoms is not more than the number of Pt atoms.

Effect of number and properties of specific sites on alumina surfaces for Pt-Al2O3 catalysts

In this work, how the number and properties of specific sites on alumina surfaces affect the specific interaction between Pt and alumina was investigated by using X-ray diffraction, ethanol temperature programmed desorption, diffuse reflectance infrared Fourier transform spectroscopy, H2 chemisorption, scanning transmission electron microscopy and benzene hydrogenation reaction. Here, we chose two sets of model aluminas having different number of sites with the identical properties and different properties of sites with the same number based on ethanol TPD. The H2 chemisorption results for the model aluminas show that H/Pt are all similar for low Pt loadings, but significantly different for high Pt loadings. For 1 wt% Pt/Al2O3, the number of specific sites on all the aluminas was sufficient to disperse all the Pt, leading to only highly dispersed Pt clusters (∼1 nm). However, at 10 wt% Pt/Al2O3, the number of Pt atoms is greater than that of the specific sites on the alumina surface, resulting in a bimodal distribution of large agglomerated Pt (>10 nm) and highly dispersed Pt clusters (<3 nm) revealed by XRD and TEM. Overall, the results clearly demonstrated that Pt shows higher dispersion with increasing number of sites and interaction strength, because the Pt atoms can interact with specific sites on alumina in greater numbers and more strongly. However, these Pt dispersion changes do not represent the gradual change in Pt cluster sizes, but the relative population change of small (<3 nm) and large agglomerated Pt clusters (>10 nm) under bimodal distribution. The number of large agglomerated Pt clusters decreased with increasing number of sites and interaction strength. This fundamental understanding provides an important perspective for designing Al2O3-based supported catalysts.

Modeling different structures in perturbed Poiseuille flow in a nanochannel by using of molecular dynamics simulation: Study the equilibrium

In this study modeling different structures in perturbed Poiseuille flow in a nanochannel by using of molecular dynamics simulation was performed. Nanochannel limited by parallel Platinum plates containing an Argon fluid. We found that the wall roughness increases the velocity in the nanochannel by shrinking the cross-section. Also, the rectangular roughness and hemispherical roughness have the maximum and minimum effects on the flow properties, respectively. The other result is that the nanochannel roughness reduces the range of fluctuations near the walls. This is due to the fact that less fluid particles reside in the vicinity of the rough nanochannel walls compared the ideal nanochannel. Finally, changing the configuration of the nanochannel roughness from ellipsoid to hemi-spherical increases the number of Pt atoms in the structure and the simulated system; therefore, the total energy is also expected to increase.

Repetitively Coupled Chemical Reduction and Galvanic Exchange as a Synthesis Strategy for Expanding Applicable Number of Pt Atoms in Dendrimer-Encapsulated Pt Nanoparticles.

In this study, we report the controllable synthesis of dendrimer-encapsulated Pt nanoparticles (Pt DENs) utilizing repetitively coupled chemical reduction and galvanic exchange reactions. The synthesis strategy allows the expansion of the applicable number of Pt atoms encapsulated inside dendrimers to more than 1000 without being limited by the fixed number of complexation sites for Pt2+ precursor ions in the dendrimers. The synthesis of Pt DENs is achieved in a short period of time (i.e., ∼10 min) simply by the coaddition of appropriate amounts of Cu2+ and Pt2+ precursors into aqueous dendrimer solution and subsequent addition of reducing agents such as BH4-, resulting in fast and selective complexation of Cu2+ with the dendrimers and subsequent chemical reduction of the complexed Cu2+ while uncomplexed Pt2+ precursors remain oxidized. Interestingly, the chemical reduction of Cu2+, leading to the formation of Cu nanoparticles encapsulated inside the dendrimers, is coupled with the galvanic exchange of the Cu nanoparticles with the nearby Pt2+. This coupling repetitively proceeds until all of the added Pt2+ ions form into Pt nanoparticles encapsulated inside the dendrimers. In contrast to the conventional method utilizing direct chemical reduction, this repetitively coupled chemical reduction and galvanic exchange enables a substantial increase in the applicable number of Pt atoms up to 1320 in Pt DENs while maintaining the unique features of DENs.

Empirical-potential global minima and DFT local minima of trimetallic AglAumPtn (l + m + n = 13, 19, 33, 38) clusters

Using a basin-hopping global optimization method, an exhaustive global search of the potential energy surface (PES) of trimetallic Ag-Au-Pt clusters is performed at the empirical potential (Gupta) level. The clusters contain a total of N=13, 19, 33, 38 atoms while the Ag, Au, Pt content range from 0% to 100%. A broad region of the PES of these systems is sampled, finding a menagerie of geometries, which are catalogued into structural families according to geometrical considerations. The structural families so defined contain a fixed number of Pt atoms while the loading of Ag and Au atoms varies, and indicate that selective Pt doping can stabilize Ag-Au subnanometer clusters. Structural stability trends are identified thus obtaining the optimal composition for each cluster size. Segregation is analyzed through a chemical order parameter, and found to exhibit a size-dependent behavior, with a transition from mixed to segregated structures clearly evidenced at 38-atom cluster size. Optimal composition structures of the Gupta global minima and a few isomers are subjected to DFT reoptimization, which is found to predict qualitatively similar atomic arrangements with a certain degree of deformation, especially for 38-atom clusters, and to introduce changes in the energy ordering among structures with respect to the Gupta potential predictions, although the stabilizing effect of Pt and a cross-over character of 38-atom size seem confirmed.

Structural Optimization of (Aum‐Agn‐Pdo‐Ptp) (m=10 and n+o+p=10) Tetrametallic Clusters Using a Combined Empirical Potential‐Density Functional (EP‐DF) Approach

AbstractThe putative global minimum structures of (Aum‐Agn‐Pdo‐Ptp) (m=10 and n+o+p=10) tetrametallic clusters with 20 atoms are obtained by basin hopping algorithm using Gupta potential parameters. A system‐comparison approach through combined empirical potential (EP)‐density functional (DF) method is adopted to investigate the energy competition and segregation effect for thirty six structural motifs. Vibrational analysis has been carried out to check the stability of these doped metal clusters. The thermal and chemical stability are measured by binding energy and HOMO‐LUMO gap. We have calculated the excess mixing energy, mixing energy and mixing coefficient, order parameter, average nearest neighbor distance (ANND) and shape deformation parameter for these doped metal clusters. Mixing/segregation effect is also discussed. Overall the calculated energy by EP parameters is lower for moderate number of (Pt, Pd) or higher number of Pt atoms and reasonably accurate for the other doped clusters. Results show that Au and Ag atoms occupy the surface sites while Pt and Pd atoms prefer mostly to the inner and middle shell.

Elucidating the Mechanisms Driving the Aging of Porous Hollow PtNi/C Nanoparticles by Means of COads Stripping.

The oxygen reduction reaction (ORR) activity of Pt-alloy electrocatalysts depends on (i) the strain/ligand effects induced by the non-noble metal (3d-transition metal or a rare-earth element) alloyed to Pt, (ii) the orientation of the catalytic surfaces, and (iii) the density of structural defects (SDs) (e.g., vacancies, voids, interconnections). These SDs influence the "generalized" coordination number of Pt atoms, the Pt-alloy lattice parameter, and thus the adsorption strength of the ORR intermediates (O*, OH*, OOH*). Here, we discuss a set of parameters derived from COads stripping measurements and the Rietveld refinement of X-ray diffraction (XRD) patterns, aiming to show how the leaching of the non-noble metal and the density of SDs influence the ORR activity of porous hollow PtNi/C nanoparticles (PH-PtNi/C NPs). PH-PtNi/C NPs were aged at T = 353 K in an Ar-saturated 0.1 M HClO4 electrolyte during 20 000 potential cycles between E = 0.6 and 1.0 V versus the reversible hydrogen electrode, with an intermediate characterization after 5000 cycles. The losses in the ORR specific activity were attributed to the dissolution of Ni atoms (modifying strain/ligand effects) and to the increase of the crystallite size (dXRD), resulting in a diminution of the density of grain boundaries. In agreement with the Gibbs-Thompson equation, the electrocatalysts that presented larger crystallites (dXRD > 3 nm) were far more stable than the ones with the smallest crystallites (dXRD < 2 nm). We also observed that performing intermediate characterizations (in an O2-saturated electrolyte) results in activity losses for the ORR.

The Key Gold: Enhanced Platinum Catalysis for the Selective Hydrogenation of α,β-Unsaturated Ketone

AuPt alloy nanoparticles (NPs) were facilely synthesized with oleylamine as the stabilizing ligand and characterized by high-resolution transmission electron microscopy, powder X-ray diffraction, inductively coupled plasma-atomic emission spectrometer analysis, and so on. In addition, the AuPt alloys supported by the nano CeO2 exhibit high selectivity and efficiency in hydrogenation of benzylidene acetone under ambient temperature and pressure. By analyzing the catalytic performance over the NPs with different Au:Pt compositions, we found that the TONPt values (based on the number of Pt atoms) vary in the same trend with the change of conversion. Despite that gold itself shows no catalytic activity, the improved conversion and TONPt with the alloy catalysts clearly show the promotion effect of gold on the catalytic activity of the platinum. The inactive metal significantly improves the catalytic activity of active metal, which shows that the AuPt alloy exhibits an interesting synergistic effect.

Manganese-tuned chemical etching of a platinum–copper nanocatalyst with platinum-rich surfaces

This work presents a modified chemical etching strategy to fabricate binary metal nanocatalysts with large active areas. The strategy employs PtCu alloy particles with Pt-rich outer layers as the precursor and manganese species to manipulate the acid leaching processes. X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy techniques are used to analyze the catalyst structures and the tuning mechanism of manganese species during etching. It is found that the introduction of manganese species allows more Pt active sites to be formed onto the catalyst surface after etching, possibly due to reduction in the number of Pt atoms enclosed inside particles. The electrochemically active surface area of the synthetic MnA-PtCu/C catalyst increases by 90% relative to commercial Pt/C catalyst. As a result of the increase in active areas and the additional promotion effects by Cu, the MnA-PtCu/C catalyst reveals a methanol oxidation activity 1.7 and 4.0 times higher than that of the synthetic PtCu/C and commercial Pt/C catalysts, respectively.