Exploration of electrodeposited platinum alloy catalysts for methanol electro-oxidation in 0.5�M H2SO4: Pt-Ni system

Synthesis of octahedral Pt-Ni-Ir yolk-shell nanoparticles and their catalysis in oxygen reduction and methanol oxidization under both acidic and alkaline conditions

Fuel cells are expected to be one of the most promising alternatives to the increasingly scarce fossil fuels, and Pt is the most commonly used catalyst for anodic and cathodic electrochemical reactions. To realize large-scale commercialization, it is most urgent to improve the efficiency of Pt and reduce the cost. Here, we synthesized an octahedral Pt-Ni-Ir yolk-shell catalyst through stepwise co-deposition (SCD), surface-limited Pt deposition (SLPD) and Ni-coordinating etching (NCE) processes. Experimental studies showed that the catalytic activities of the as-prepared trimetal yolk-shell catalyst were several times higher than that of the commercial Pt/C towards oxygen reduction and methanol oxidization under both acidic and alkaline conditions. This work may be extended to designing other multimetallic functional materials with complex hierarchical nanostructures, which is conducive to greatly enhancing the performance.

Constructing Patch-Ni-Shelled Pt@Ni Nanoparticles within Confined Nanoreactors for Catalytic Oxidation of Insoluble Polysulfides in Li-S Batteries

Reducing the deposit of discharge products and suppressing the polysulfide shuttle are critical to enhancing reaction kinetics in Li-S batteries. Herein, a Pt@Ni core-shell bimetallic catalyst with a patch-like or complete Ni shell based on a confined catalysis reaction in porous carbon spheres is reported. The Pt nanodots can effectively direct and catalyze in situ reduction of Ni²⁺ ions to form core-shell catalysts with a seamless interface that facilitates the charge transfer between the two metals. Thus, the bimetallic catalysts offer a synergic effect on catalyzing reactions, which shows dual functions for catalytic oxidation of insoluble polysulfides to soluble polysulfides by effectively reducing the energy barrier with simultaneous strong adsorption, ensuring a high reversible capacity and cycling stability. A novel process based on the Pt@Ni core-shell bimetallic catalyst with a patch-like Ni shell is proposed: electronic migration from Ni to Pt forces Ni to activate Li₂ S₂ /Li₂ S molecules by promoting the transformation of Li-S-Li to Ni-S-Li, consequently releasing Li⁺ and free electrons, simultaneously enhancing protonic/electronic conductivity. The presence of the intermediate state Ni-S-Li is more active to oxidize Li₂ S to polysulfides. The Li₂ S bound to adjacent Pt sites reacts with abundant -S-Li species and then releases the Pt sites for the next round of reactions.

CoPtx/γ-Al2O3 bimetallic nanoalloys as promising catalysts for hydrazine electrooxidation

Stable bimetallic catalysts composed of CoPtx/γ-Al2O3 (x = Pt/Co molar ratio) were synthesized by wet impregnation method followed by calcination and the H2 reduction. The powders were characterized using XRD, AAS, BET, SEM, EDX, TPR, and TPO techniques. The prepared catalysts were drop casted on the glassy carbon electrode (GCE) and catalytic performance was examined for hydrazine electrooxidation in alkaline medium via cyclic voltammetry (CV). All the compositions in CoPtx/γ-Al2O3 series showed high responses towards hydrazine electrooxidation, however; high activity of CoPt0.034/γ-Al2O3 catalyst inferred it as a best material with an anodic peak current (iP) response of 200 μA at 0.86 V. The prominent electrochemical (EC) responses for this composition are attributed to better accessible surface area resulting in a fast electron transfer. The CoPtx/γ-Al2O3 catalysts are reported as the robust and superior prospective materials for extensive electroanalytical and catalytic studies.

Pt Nanoparticles Loaded on W18O49 Nanocables-rGO Nanocomposite as a Highly Active and Durable Catalyst for Methanol Electro-Oxidation

Highly active and durable electrocatalysts are vital for commercialization of direct methanol fuel cells. In this work, a three-dimensional nanocomposite consisting of platinum nanoparticles, W₁₈O₄₉ nanocables, and reduced graphene oxide composite (Pt/W₁₈O₄₉ NCs-rGO) has been prepared as an electrocatalyst for methanol oxidation reaction (MOR). The catalyst is prepared through a two-step method. The W₁₈O₄₉ nanocables and the reduced graphene oxide composite are prepared by a solvothermal process. Then, Pt nanoparticles are loaded on the W₁₈O₄₉ nanocables and the reduced graphene oxide composite by a hydrogen reduction at ambient condition. The obtained catalyst has a special three-dimensional architecture consisting of two-dimensional nanosheets, assembled one-dimensional nanocables, and the loaded nanoparticles on their surface. The Pt/W₁₈O₄₉ NCs-rGO catalyst shows 1.56 time mass activities than the Pt/C, with the current density of the forward anodic peak reaching 1624 mA/mg_Pt at 0.854 V versus reversible hydrogen electrode potential in 0.1 M HClO₄ and 0.5 M CH₃OH mixed electrolyte. It also shows a strong antipoisoning property toward CO. For the durability testing, the current density of Pt/W₁₈O₄₉ NCs-rGO shows a 37% decay, whereas the current of Pt/C catalyst shows a 41% degradation from 600 to 3600 s at 0.7 V. The high activity toward MOR, good antipoisoning for intermediate products, and excellent stability are ascribed to strong metal-support interaction effects between the Pt nanoparticles and the W₁₈O₄₉ NCs.

High electrocatalytic performance inspired by crystalline/amorphous interface in PtPb nanoplate

Nanoscale PtPb catalysts with core-shell structure have been actively explored in recent years owing to their outstanding catalytic activity. We report on a new class of PtPb nanoplate (NP) catalyst with a novel structure realized by ion irradiation modification, which contains an interface formed by a crystalline phase and an amorphous phase simultaneously in an annular state. Significantly, the PtPb NP with the new structure shows superior catalytic activity towards the methanol oxidation reaction (MOR). The specific activity of PtPb NPs with the new structure reaches 4.32 mA cm-2 towards the MOR and the mass activity reaches 1.31 A mg-1, which is 1.9-fold and 1.4-fold greater than those for the original crystalline PtPb NPs, respectively. The outstanding catalytic activity could be attributed to the presence of the interface between a crystalline phase and an amorphous phase with a special electronic structure created by ion irradiation. Density functional theory calculations reveal that the novel interface activates the C-H and O-H bonds, leading to high electrocatalytic activity, and optimizes the adsorption of hydroxyl and intermediates on the surface to facilitate the oxidation reaction. The novel structure with an interface formed by a crystalline phase and an amorphous phase opens up a new approach to improve electrocatalytic activity.

Design of ultrathin Pt-Mo-Ni nanowire catalysts for ethanol electrooxidation

Developing cost-effective, active, and durable electrocatalysts is one of the most important issues for the commercialization of fuel cells. Ultrathin Pt-Mo-Ni nanowires (NWs) with a diameter of ~2.5 nm and lengths of up to several micrometers were synthesized via a H2-assisted solution route (HASR). This catalyst was designed on the basis of the following three points: (i) ultrathin NWs with high numbers of surface atoms can increase the atomic efficiency of Pt and thus decrease the catalyst cost; (ii) the incorporation of Ni can isolate Pt atoms on the surface and produce surface defects, leading to high catalytic activity (the unique structure and superior activity were confirmed by spherical aberration-corrected electron microscopy measurements and ethanol oxidation tests, respectively); and (iii) the incorporation of Mo can stabilize both Ni and Pt atoms, leading to high catalytic stability, which was confirmed by experiments and density functional theory calculations. Furthermore, the developed HASR strategy can be extended to synthesize a series of Pt-Mo-M (M = Fe, Co, Mn, Ru, etc.) NWs. These multimetallic NWs would open up new opportunities for practical fuel cell applications.

Hydrazine assisted catalytic hydrogenation of PNP to PAP by NixPd100−x nanocatalyst

NiPd nanocatalyst assisted catalytic hydrogenation of PNP to PAP by hydrazine.

Electrodeposition of multilayered bimetallic nanoclusters of ruthenium and platinum via surface-limited redox-replacement reactions for electrocatalytic applications

An electrochemical synthesis of multilayered bimetallic Ru|Pt nanoclusters, supported on glassy carbon, is reported for the first time. The novel nanoclusters were synthesized via surface-limited redox-replacement reactions involving sacrificial Cu, deposited prior to the formation of each individual noble metal layer, in a sequential fashion. It has been shown that the Cu adlayers control the morphology and electrochemical properties of the resultant nanostructures. Sequentially deposited Ru|Pt nanoclusters exhibited superior electrocatalytic activity (when compared to equivalent monometallic Pt and an alloy-type codeposited Pt-Ru nanostructures) with respect to methanol electrooxidation in an acidic medium. Moreover, it has been established that the electrochemical process taking place at the Ru|Pt nanoclusters followed the bifunctional mechanism. Electrokinetic studies of the oxygen reduction reaction (ORR) were also performed. Analysis of hydrodynamic linear sweep voltammetric experiments, performed at various flow rates on oxygen-saturated acidic medium, revealed that the Pt and Ru|Pt nanoclusters exhibited direct four- and two-electron ORR pathways, respectively. A specially designed electrochemical flow-cell was used for automated sequential electrodeposition of the multilayered nanoclusters of predefined composition and electrochemical and electrocatalytic investigations.