Methanol oxidation reaction

The precise control over the composition and the structure is highly important for designing highly active nanostructured electrocatalysts. Herein, we report a one-step strategy to directly synthesize trimetallic Pt-Pd-Ru nanodendrites in an aqueous solution at room temperature. These newly designed nanodendrites exhibit superior catalytic activities for both methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR) in comparison with bimetallic Pt-Pd nanoflowers and commercially available Pt/C catalysts.

In this work, Cobalt molybdate nanoflakes were grown on nickel foam which is used as an electrode for the supercapacitor and electrocatalyst for the methanol oxidation reaction. XRD, Raman, and XPS analysis further confirm the formation of CoMoO 4. FESEM image shows that the CoMoO 4 nanoflakes with a thickness of ~91 nm and diameter of ~1 µm were formed. In a three-electrode system, CoMoO 4 /NF exhibited a capacitance (capacity) of 359.8 F g-1 (215.88 Cg-1). CoMoO 4 /NF retained 73.8 % of capacitance after 9500 cycles with 89.4 % of coulombic efficiency. After a long cycle, the electrode undergoes XPS and FESEM analysis. From XPS, its major oxidation state was changed from 2+ to 3+ and Mo was leached out from the electrode. FESEM analysis showed that nanoflake size decreased to 53.34 nm from 91 nm. The aqueous hybrid supercapacitor (HSC) exhibited a capacitance of 86 F g-1 at 1 A g-1. Aqueous HSC exhibited an energy density of 17.5 Wh Kg-1 and a power density of 2970 W Kg-1. CoMoO 4 /NF showed good oxidation properties towards methanol to carbon dioxide. After the 1000 cycles, the forward oxidation peak shifted to-0.052 V from-0.00884 V vs Hg/HgO. After the 1000 cycles, a 46 % decrease in methanol oxidation current is observed.

Ammonia borane is widely used in most areas including fuel cell applications. The present paper describes electrochemical behavior of ammonia borane in alkaline media on the poly(p-aminophenol) film modified with Au and Ag bimetallic nanoparticles. The glassy carbon electrode was firstly covered with polymeric film electrochemically and then, Au, Ag, and Au-Ag nanoparticles were deposited on the polymeric film, respectively. The surface morphology and chemical composition of these electrodes were examined by scanning electron microscopy, transmission electron microscopy, electrochemical impedance spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. It was found that alloyed Au-Ag bimetallic nanoparticles are formed. Electrochemical measurements indicate that the developed electrode modified by Au-Ag bimetallic nanoparticles exhibit the highest electrocatalytic activity for ammonia borane oxidation in alkaline media. The rotating disk electrode voltammetry demonstrates that the developed electrode can catalyze almost six-electron oxidation pathway of ammonia borane. Our results may be attractive for anode materials of ammonia borane fuel cells under alkaline conditions.

Selective reduction of various nitroarenes to amines was achieved up to 93% under autoclave condition in isopropanol using catalytic amount of palladium oxide/copper oxide (PdO/CuO) nanoparticles (NPs) supported on mesoporous zeolite-Y, PdO/CuO-Y. The catalyst was also found to be highly effective for one-pot cascade synthesis of the 3,3'-diaminobiphenyl from 3nitrophenylboronic acid (NPBA). The hybridization of PdO/CuO-Y with multi-walled carbon nanotubes (MWCNTs) resulted in a highly effective and durable electrocatalyst for the methanol oxidation reaction (MOR). The mass activity of the electrocatalyst was found to be 690 A/g and was stable for 4000 seconds. The catalytic activity of the PdO/CuO-Y catalyst was found to be superior in terms of productivity and recyclability in comparison to that of the bared PdO/CuO NPs separated by the ultracentrifugation (UC) method. On the other hand, the one modified with carbon matrix retained the same activity and reduced the reaction time in nitroarene reduction reaction (NAR) under identical conditions. Electrochemical studies and density functional theory (DFT) calculations were performed to understand the mechanism of the NAR process. Both the experimental and theoretical evidence explicitly demonstrated the individual role of both palladium (Pd) and copper (Cu). Pd was found to be the active site for nitroarene interaction while CuO NPs played an important role in isopropanol oxidation.

Direct methanol fuel cells (DMFCs) proved to be promising alternative for renewable energy resources. There are several factors involved for the hindrance of their commercialization. Herein, the alteration in catalyst's chemistry has been mainly focused to improve the performance of DMFCs. Mesoporous carbon supported bimetallic combinations of Pt with metallic oxides such as, Pt/CeO 2-MC, Pt/PrO 2-MC, Pt/NdO 2-MC, and Pt/SmO 2-MC were synthesized and tested as methanol electro-oxidation anode catalysts. These high-surface area anodes were synthesized by impregnation with Pt to form the desired methanol electro-oxidation catalysts. The as-prepared catalysts were characterized using XRD, BET surface area, and EDS. High surface areas of 684-778 m 2 /g were achieved for the CeO 2-MC, PrO 2-MC, NdO 2-MC, and SmO 2-MC, which enabled excellent dispersion of the Pt nanoparticles onto their surfaces. The Pt/CeO 2-MC catalyst showed the highest activity for methanol electro-oxidation, which is about 3.5% more than that of the commercial Pt-Ru/C (E-TEK) catalyst. In addition, the prepared catalysts showed significant stability and durability.

Graphene oxide supported clean Pd nanoparticles were synthesized by using CO as a reducing agent. Pt film was deposited on Pd NPs through electrochemical potential cycling method. The as-developed catalyst, which exhibits higher catalytic performance for electro oxidation of methanol and better tolerance to the CO poisoning effect suffered during methanol oxidation reaction (MOR). The higher performance of catalyst attribute towards the long chain organic capping agent free formation process of clean PdPt nanocomposite. This facile and effective route is of great significance for the synthesis of Pd-based catalysts on electrode surface directly with highest MOR activity. The synergistic electronic pull provided by graphene oxide supported Pd nanoparticles to Pt in the composite material highly enhanced the electro catalytic activity.

Direct methanol fuel cells (DMFCs) proved to be promising alternative for renewable energy resources. There are several factors involved for the hindrance of their commercialization. Herein, the alteration in catalyst's chemistry has been mainly focused to improve the performance of DMFCs. Mesoporous carbon supported bimetallic combinations of Pt with metallic oxides such as, Pt/CeO 2-MC, Pt/PrO 2-MC, Pt/NdO 2-MC, and Pt/SmO 2-MC were synthesized and tested as methanol electro-oxidation anode catalysts. These high-surface area anodes were synthesized by impregnation with Pt to form the desired methanol electro-oxidation catalysts. The as-prepared catalysts were characterized using XRD, BET surface area, and EDS. High surface areas of 684-778 m 2 /g were achieved for the CeO 2-MC, PrO 2-MC, NdO 2-MC, and SmO 2-MC, which enabled excellent dispersion of the Pt nanoparticles onto their surfaces. The Pt/CeO 2-MC catalyst showed the highest activity for methanol electro-oxidation, which is about 3.5% more than that of the commercial Pt-Ru/C (E-TEK) catalyst. In addition, the prepared catalysts showed significant stability and durability.

Direct methanol fuel cells (DMFCs) are emerging as clean and renewable energy sources for global-scale sustainable energy solutions. However, several limitations of the current standard catalyst (platinum supported carbon black: Pt/C) prevent their commercialization. As an effective co-catalyst, Au@CeO 2 core-shell structures are greatly advantageous for getting over the remaining hurdles of Pt/C in DMFCs. Herein, we report an efficient approach for the fabrication of electrocatalyst for DMFCs consisting of three components (Pt/C, Au@CeO 2 and Pt catalysts) loaded on carbon cloth using spray and electrophoresis deposition methods. The obtained Pt/C-Au@CeO 2-Pt electrocatalyst proved to have high electrochemical surface area (ECSA-77.8 m 2 /g Pt) and high methanol oxidation reaction (MOR) activity (1267 mA/mg Pt), which were 1.7 and 2.3 times greater than those of Pt/C only (45.6 m 2 /g Pt and 560 mA/mg Pt). In addition, the presence of Au@CeO 2 nanoparticles can further enhance the stability of the Pt/C-Au@CeO 2-Pt electrocatalyst toward the MOR activity. The improved MOR performance of the Pt/C-Au@CeO 2-Pt electrocatalyst could be mainly attributed to the production of abundant OH ads promoters, reduction of charge transfer resistance and enhancement of Pt catalytic efficient utilization. It helps to wholly oxidize CO ads intermediate as dominant poisoning species on Pt catalyst, which are often generated during the MOR operation in acidic condition.

In the present work, the WC stability during the preparation of Pt@WC/OMC (Ordered Mesoporous Carbon) electrocatalysts, through a pulse microwave-assisted polyol method, is investigated by the aid of X-ray diffraction and thermogravimetric method. More precisely, OMC self-supported tungsten carbide (WC/OMC) is successfully synthesized by combing the hydrothermal process and a hard template method and its stability is step by step checked during the preparation process of the Pt@WC/OMC electrocatalyst by the pulse microwave-assisted polyol method. It is found that the strong alkaline and acid environment has a relatively small but not serious effect on the stability of WC. It is also found that in absence of Pt precursor, microwave irradiation itself also has a small effect on the stability of WC, while once Pt precursor is introduced into the system, more than half of the initial WC disappears or is oxidized. To avoid this process, Pt@WC/OMC-MM is obtained by mechanically mixing (MM) the as prepared WC/OMC and Pt@C. Moreover, the electrochemical results of methanol oxidation reaction show that the content of WC has an obvious effect on Pt's activity toward MOR, with the best performance in the case of Pt 20 WC 22 /OMC-MM.

In this report, the nickel molybdate (NiMoO 4) nanorods were grown on carbon cloth (CC) with an average length of 3 µm and a diameter of 130 nm. The NiMoO 4 /CC demonstrated a lower onset potential of 0.553 V vs. Hg/HgO at 10 mA/cm 2 for methanol oxidation reaction (MOR). In addition, the electrocatalyst showed notable cyclic stability, where the onset potential attained 0.585 and 0.616 V vs. Hg/HgO at 10 mA/cm 2 during the 250 th and 1000 th cycles, respectively. In the hydrogen evolution reaction (HER), the NiMoO 4 /CC exhibited good performance with an overpotential of − 0.517 V vs. RHE at 10 mA/cm 2 , the Tafel slope of 144 mV/dec, and a turnover frequency of 1.298H 2 /active site. The higher active sites (2.594 × 10 17 cm 2) and high electrochemical surface area (94.63 cm 2) of NiMoO 4 /CC electrocatalyst exhibited stable and efficient MOR and HER performances.

Recently, methanol fuel cell systems have been attracting research activities by improving electrocatalysts to investigate facilitating the methanol oxidation reaction. ZnO and ZnO doped with other metals or metal oxide can be used as an additive in the carbon substrate of an electrocatalyst to improve electro catalytic properties of a platinum electrocatalyst. In this work, a simple low temperature hydrothermal method has been used for synthesis of diff erent morphologies of 1% mol Ni, Cu and Co doped ZnO nanostructures. The prepared nanostructures were used in the carbon substrate of a platinum electrocatalyst on carbon paper. Then platinum was electrodeposited by simple cyclic voltammetry on a modifi ed carbon substrate of the electrocatalyst. Prepared electrodes were investigated for methanol oxidation reaction in a three electrode half-cell system by electrochemical methods like as linear sweep voltammetry. The results revealed that with using Ni doped ZnO in carbon substrate, the current density was increased. While, with using Cu doped ZnO in carbon substrate, a signifi cant reduction in anodic over voltage was observed.

Direct methanol fuel cells (DMFCs) are emerging as clean and renewable energy sources for global-scale sustainable energy solutions. However, several limitations of the current standard catalyst (platinum supported carbon black: Pt/C) prevent their commercialization. As an effective co-catalyst, Au@CeO 2 core-shell structures are greatly advantageous for getting over the remaining hurdles of Pt/C in DMFCs. Herein, we report an efficient approach for the fabrication of electrocatalyst for DMFCs consisting of three components (Pt/C, Au@CeO 2 and Pt catalysts) loaded on carbon cloth using spray and electrophoresis deposition methods. The obtained Pt/C-Au@CeO 2-Pt electrocatalyst proved to have high electrochemical surface area (ECSA-77.8 m 2 /g Pt) and high methanol oxidation reaction (MOR) activity (1267 mA/mg Pt), which were 1.7 and 2.3 times greater than those of Pt/C only (45.6 m 2 /g Pt and 560 mA/mg Pt). In addition, the presence of Au@CeO 2 nanoparticles can further enhance the stability of the Pt/C-Au@CeO 2-Pt electrocatalyst toward the MOR activity. The improved MOR performance of the Pt/C-Au@CeO 2-Pt electrocatalyst could be mainly attributed to the production of abundant OH ads promoters, reduction of charge transfer resistance and enhancement of Pt catalytic efficient utilization. It helps to wholly oxidize CO ads intermediate as dominant poisoning species on Pt catalyst, which are often generated during the MOR operation in acidic condition.

A key enabling step in leveraging the properties of nanoparticles (NPs) is to explore new, simple, controllable, and scalable nanotechnologies for their syntheses. Among 'wet' methods, cathodic corrosion has been used to synthesize catalytic aggre-gates with some control over their size and preferential faceting. Here, we report on a modification of the cathodic corrosion method for producing a range of non-aggregated nanocrystals (Pt, Pd, Au, Ag, Cu, Rh, Ir, Ni) and nanoalloys (Pt50Au50, Pd50Au50, AgxAu100-x) with potential for scaling up the production rate. The method employs polyvinylpyrrolidone (PVP) as a stabilizer in an electrolyte solution containing non-reducible cations (Na+, Ca2+), and cathodic corrosion of the corresponding wires took place in the electrolyte under ultrasonication. The ultrasonication not only promotes particle-PVP interactions (enhancing NP dispersion and diluting locally high NP concentration), but also increases the production rate by a factor...

Due to its large surface area, high electrical conductivity as well as mechanical and thermal stability, pristine graphene has the potential to be an excellent support for metal nanoparticles (NPs), but the scarce amount of intrinsic chemical groups/defects in its structure that could act as anchoring sites for the NPs hinders this type of use. Here, a simple strategy based on the stabilization of pristine graphene in aqueous dispersion with the assistance of a low amount of flavin mononucleotide (FMN) is shown to yield a material that combines high electrical conductivity and abundance of extrinsic anchoring sites, so that pristine graphene-metal (Pd and Pt) NP hybrids with good dispersion and metal loading can be obtained from FMN-stabilized graphene. The activity of these hybrids towards the methanol oxidation reaction (MOR) both in acidic and alkaline media is studied by cyclic voltammetry (CV) and their stability investigated by chronoamperometry. The pristine graphene-Pt NP hybrid prepared by this simple, eco-friendly protocol is demonstrated to outperform most previously reported pristine graphene-and reduced graphene oxide-metal NP hybrids as electrocatalyst for the MOR, both in terms of catalytic activity and stability, avoiding at the same time the use of harsh chemicals or complex synthetic routes.

Recent reports about the promising and tunable electrocatalytic activity and stability of nanoalloys have stimulated an intense research activity toward the design and synthesis of homogeneously alloyed novel bimetallic nanoelectrocatalysts. We herein present a simple one-pot facile wet-chemical approach for the deposition of high-quality bimetallic palladium-silver (PdAg) homogeneous nanoalloy crystals on reduced graphene (Gr) oxide sheets. Morphological, structural, and chemical characterizations of the so-crafted nanohybrids establish a homogeneous distribution of 1:1 PdAg nanoalloy crystals supported over reduced graphene oxide (PdAg-Gr). The PdAg-Gr nanohybrids exhibit outstanding electrocatalytic, catalytic, and electroanalytical performances. The PdAg-Gr samples were found to exhibit exceptional durability when subjected to repeated potential cycles or long-term electrolysis. In the CVs recorded for fuel cell reactions, viz. methanol oxidation reaction and oxygen reduction re...

Tailoring the morphology and composition of Pt-based nanostructures is crucial to design high-performance electrocatalysts for direct methanol fuel cells. In this work, we propose a facile strategy to fabricate one-dimensional PtM (M = Co, Ni) mesoporous nanotubes (PtM MNTs), in which F127 and Te nanowires facilitate the formation of mesoporous exteriors and cannular interiors, respectively. Owing to the structural advantages of bimetallic mesoporous nanotube architectonics, the PtM MNTs exhibit superior electrochemical performance for the oxygen reduction reaction and methanol oxidation reaction. The proposed dual-template strategy is highly promising for designing active Pt-based mesoporous nanotubes with desired composition toward various electrocatalytic fields.

Mesoporous TiO 2 was prepared, inside "Taurasi" grape skins. The peel impregnation was followed by magnetic resonance imaging, to monitor the transport process in the natural template and the interaction of the solute with the templating structure. Moreover, the prepared mesoporous structure was used to support ultra-small platinum nanoparticles (USNPs), allowing high dispersion and maximizing active metals utilization. USNPs characterization was performed by means of high-resolution analytical transmission electron microscopy, CO-Diffuse Reflectance Infrared Fourier Transform spectroscopy, and X-ray photoelectron spectroscopy. Low Pt loaded TiO 2 was then tested in methanol oxidation reactions, showing an excellent behavior: negligible onset potentials (0.06 V) and very high If/Ib ratio (3.85). The results obtained in this work evidence the outstanding performances of the synthesized nano-electrocatalysts.