Preparation and Characterization of PtRu Nanoparticles Supported on Nitrogen-Doped Porous Carbon for Electrooxidation of Methanol

N-doped porous carbon nanospheres (PCNs) were prepared by chemical activation of nonporous carbon nanospheres (CNs), which were obtained via carbonization of polypyrrole nanospheres (PNs). The catalysts, PtRu and Pt nanoparticles supported on PCNs and Vulcan XC-72 carbon black, were prepared by ethylene glycol chemical reduction. Transmission electron microscopy, X-ray diffraction, and energy-dispersive X-ray spectroscopy were employed to characterize samples. It was found that PCNs containing N function groups possess a large number of micropores. Uniform and well-dispersed Pt and PtRu particles with narrow particle size distribution were observed. The electrooxidation of liquid methanol on these catalysts was investigated at room temperature by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy (EIS). The results showed that alloy catalyst (Pt1Ru1/PCN) possessed the highest catalytic activity and better CO tolerance than the other PtRu and Pt-only catalysts; PtRu nanoparticles supported on PCN showed a higher catalytic activity and more stable sustained current than on carbon black XC-72. Compared to commercial Alfa Aesar PtRu catalyst, Pt1Ru1/PCN reveals an enhanced and durable catalytic activity in methanol oxidation because of the high dispersion of small PtRu nanoparticles and the presence of N species of support PCNs

Synthesis of PtRu Nanoparticles from the Hydrosilylation Reaction and Application as Catalyst for Direct Methanol Fuel Cell

Nanosized Pt, PtRu, and Ru particles were prepared by a novel process, the hydrosilylation reaction. The hydrosilylation reaction is an effective method of preparation not only for Pt particles but also for other metal colloids, such as Ru. Vulcan XC-72 was selected as catalyst support for Pt, PtRu, and Ru colloids, and TEM investigations showed nanoscale particles and narrow size distribution for both supported and unsupported metals. All Pt and Pt-rich catalysts showed the X-ray diffraction pattern of a face-centered cubic (fcc) crystal structure, whereas the Ru and Ru-rich alloys were more typical of a hexagonal close-packed (hcp) structure. As evidenced by XPS, most Pt and Ru atoms in the nanoparticles were zerovalent, except a trace of oxidation-state metals. The electrooxidation of liquid methanol on these catalysts was investigated at room temperature by cyclic voltammetry and chronoamperometry. The results concluded that some alloy catalysts showed higher catalytic activities and better CO tolerance than the Pt-only catalyst; Pt56Ru44/C have displayed the best electrocatalytic performance among all carbon-supported catalysts

Pt-Decorated PdFe Nanoparticles as Methanol-Tolerant Oxygen Reduction Electrocatalyst

The activity and selectivity of carbon-supported Pt-decorated PdFe nanoparticles in the oxygen reduction reaction (ORR) were investigated in the presence and absence of methanol. The Pt-decorated PdFe nanoparticles, which consist of a PdPt surface and a PdFe interior, were prepared by the galvanic reaction between PdFe/C alloy nanoparticles and PtCl42− in aqueous solution. The presence of a Pt-enriched surface after the replacement reaction was independently confirmed by several microstructural characterization techniques and cyclic voltammetry. The catalyst with such heterogeneous architecture is catalytically more active than a bulk PdFePt alloy catalyst with the same overall composition. The observed enhancements in catalyst performance can be attributed to the lattice strain effect between the shell and core components. The Pt-decorated PdFe (PdFe@PdPt/C) catalyst also compares favorably with a commercial Pt/C catalyst with four times as much Pt in terms of ORR activity, cost, and methanol tolerance

Physical and Electrochemical Characterizations of Microwave-Assisted Polyol Preparation of Carbon-Supported PtRu Nanoparticles

PtRu nanoparticles supported on Vulcan XC-72 carbon and carbon nanotubes were prepared by a microwave-assisted polyol process. The catalysts were characterized by transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy (XPS). The PtRu nanoparticles, which were uniformly dispersed on carbon, were 2−6 nm in diameter. All PtRu/C catalysts prepared as such displayed the characteristic diffraction peaks of a Pt face-centered cubic structure, excepting that the 2θ values were shifted to slightly higher values. XPS analysis revealed that the catalysts contained mostly Pt(0) and Ru(0), with traces of Pt(II), Pt(IV), and Ru(IV). The electro-oxidation of methanol was studied by cyclic voltammetry, linear sweep voltammetry, and chronoamperometry. It was found that both PtRu/C catalysts had high and more durable electrocatalytic activities for methanol oxidation than a comparative Pt/C catalyst. Preliminary data from a direct methanol fuel cell single stack test cell using the Vulcan-carbon-supported PtRu alloy as the anode catalyst showed high power density

Platinum Nanoparticles from the Hydrosilylation Reaction: Capping Agents, Physical Characterizations, and Electrochemical Properties

Platinum nanoparticles synthesized by a unique synthetic approach, the hydrosilylation reaction, have been reported previously. However, the interaction between the underlying platinum nanosupport and the capping agents is poorly understood. Here we continue to investigate Pt nanoparticles from the hydrosilylation reaction to address this issue and present the characterization results of nuclear magnetic resonance, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. These characterization results conclude that two different modes of binding of the aliphatic capping agents with the platinum surface are attributed to the formation of Pt−C bonds under excess olefin concentration and Pt−Si bonds under excess hydrosilane concentration. Morphology and UV−vis spectra of the platinum nanoparticles were explored by transmission electron microscopy, X-ray diffraction, and UV−vis spectroscopy. Moreover, electrochemical properties of the platinum nanoparticles were also studied by cyclic voltammetry and chronoamperometry

Ultrathin MoS₂ Nanoplates with Rich Active Sites as Highly Efficient Catalyst for Hydrogen Evolution

Well-defined ultrathin MoS₂ nanoplates are developed by a facile solvent-dependent control route from single-source precursor for the first time. The obtained ultrathin nanoplate with a thickness of ∼5 nm features high density of basal edges and abundant unsaturated active S atoms. The multistage growth process is investigated and the formation mechanism is proposed. Ultrathin MoS₂ nanoplates exhibit an excellent activity for hydrogen evolution reaction (HER) with a small onset potential of 0.09 V, a low Tafel slope of 53 mV dec^–1, and remarkable stability. This work successfully demonstrates that the introduction of unsaturated active S atoms into ultrathin MoS₂ nanoplates for enhanced electrocatalytic properties is feasible through a facial one-step solvent control method, and that this may open up a potential way for designing more efficient MoS₂-based catalysts for HER

Ultrathin PtPdCu Nanowires Fused Porous Architecture with 3D Molecular Accessibility: An Active and Durable Platform for Methanol Oxidation

It is desirable but challenging to develop active and durable low-Pt catalysts for next-generation fuel cells. Herein, a three-dimensional porous PtPdCu architecture with ultrathin nanowires was obtained through a simple, rapid and aqueous method. This PtPdCu catalyst showed the remarkable performance for methanol oxidation reaction with a 6.5 times enhancement in precious-metal-based mass activity, a 7.2 times enhancement in specific activity and a better durability in comparison with a standard Pt/C catalyst. According to the structure–activity analysis, these enhancements were due to the beneficial structural feature and the multicomponent synergy effect

Pd Nanoparticles on Carbon Nitride–Graphene for the Selective Electro-Oxidation of Glycerol in Alkaline Solution

A hybrid support consisting of carbon nitride and graphene (CN_<i>x</i>/G) is prepared by annealing polypyrrole/GO at 800 °C. Pd nanoparticles (NPs) are then loaded onto the support by a microwave–polyol method. Pd-CN_<i>x</i>/G is used as a catalyst for glycerol electro-oxidation in 0.5 M NaOH aqueous solution. Electrochemical characterization and product analysis by high-performance liquid chromatography show that, in comparison to Pd NPs supported on carbon black, Pd NPs on a support containing nitrogen atoms has the ability to promote selectivity toward C3 products as well as increase activity. The main factors influencing the selectivity and activity are also discussed

Heterogeneous Electrocatalyst with Molecular Cobalt Ions Serving as the Center of Active Sites

Molecular Co²⁺ ions were grafted onto doped graphene in a coordination environment, resulting in the formation of molecularly well-defined, highly active electrocatalytic sites at a heterogeneous interface for the oxygen evolution reaction (OER). The S dopants of graphene are suggested to be one of the binding sites and to be responsible for improving the intrinsic activity of the Co sites. The turnover frequency of such Co sites is greater than that of many Co-based nanostructures and IrO₂ catalysts. Through a series of carefully designed experiments, the pathway for the evolution of the Co cation-based molecular catalyst for the OER was further demonstrated on such a single Co-ion site for the first time. The Co²⁺ ions were successively oxidized to Co³⁺ and Co⁴⁺ states prior to the OER. The sequential oxidation was coupled with the transfer of different numbers of protons/hydroxides and generated an active Co⁴⁺O fragment. A side-on hydroperoxo ligand of the Co⁴⁺ site is proposed as a key intermediate for the formation of dioxygen

Development of Cobalt Hydroxide as a Bifunctional Catalyst for Oxygen Electrocatalysis in Alkaline Solution

Co­(OH)₂ in the form of hexagonal nanoplates synthesized by a simple hydrothermal reaction has shown even greater activity than cobalt oxides (CoO and Co₃O₄) in oxygen reduction and oxygen evolution reactions (ORR and OER) under alkaline conditions. The bifunctionality for oxygen electrocatalysis as shown by the OER–ORR potential difference (Δ<i>E</i>) could be reduced to as low as 0.87 V, comparable to the state-of-the-art non-noble bifunctional catalysts, when the Co­(OH)₂ nanoplates were compounded with nitrogen-doped reduced graphene oxide (N-rGO). The good performance was attributed to the nanosizing of Co­(OH)₂ and the synergistic interaction between Co­(OH)₂ and N-rGO. A zinc–air cell assembled with a Co­(OH)₂–air electrode also showed a performance comparable to that of the state-of-the-art zinc–air cells. The combination of bifunctional activity and operational stability establishes Co­(OH)₂ as an effective low-cost alternative to the platinum group metal catalysts