Phase Modulating of Cu–Ni Nanowires Enables Active and Stable Electrocatalysts for the Methanol Oxidation Reaction

The design and development of non-noble metal alternatives with superior performance and promising long-term stability that is comparable or even better than those of noble-metal-based catalysts is a significant challenge. Here, we report the thermal-induced phase engineering of non-noble-metal-based nanowires with superior electrochemical activity and stability for the methanol oxidation reaction (MOR) under alkaline conditions. The optimized Cu–Ni nanowires deliver an unprecedented mass activity of 425 mA mg⁻¹, which is 4.3 times higher than that of the untreated one. Detailed catalytic investigations show that the enhanced performance is due to the large active area, the increased number of active sites (NiOOH), and fast methanol electrooxidation kinetics. In addition, the generated hollow feature in the nanowires provides a unique void space to release the volume expansion, where the activity can be maintained for 5 h without a distinct activity decay. The present work emphasizes the importance of precisely phase modulating of nanomaterials for the design of non-noble metal electrocatalysts towards the MOR, which opens up a new pathway for the design of cost-effective electrocatalysts with promising activity and long-term stability.     

Single Pt–Pd Bimetallic Nanoparticle Electrode: Controllable Fabrication and Unique Electrocatalytic Performance for the Methanol Oxidation Reaction

Understanding the electrocatalytic activity at single nanoparticles/nanoclusters level is extremely important. In this work, a method for the electro-deposition of single Pt–Pd nanoparticles (NPs) is described using a single nanopore electrode as a template. The electro-deposition process was investigated carefully and the results show that the process is controlled by diffusion and electro-crystallization process, simultaneously, and the glass sheath property around the nanopore has a large impact on the formation of single Pt–Pd NPs due to the “edge effect”. The prepared single Pt–Pd NPs exhibit excellent electrocatalytic activity in the methanol oxidation reaction, which can be used to screen electrocatalysts with high efficiency for utility in the energy field.     

Performance of Pt—TiO2 Electrocatalyst for CO Oxidation in the Electrochemical Gas Sensor

It is reported for the first time that the Pt/TiO2 electrocatalyst was successfully used for the electrocatalytic oxidation of CO in the electrochemical gas sensor with a controlled potential mode. The stability of electrocatalytic activity of the Pt-TiO2 electrocatalyst for the CO oxidation is better than that of Pt.     

Oxidation of Methanol on Pt,Pt–Ru,and Pt–Ru–Mo Electrocatalysts Dispersed in Polyaniline: An in situ Infrared Reflectance Spectroscopy Study

The electrochemical oxidation of methanol was investigated on a Pt–Ru–Mo catalyst with an in situ infrared reflectance spectroscopy. The electrocatalysts were prepared by an electrochemical deposition and dispersed in a conducting three-dimensional matrix of polyaniline (PAni). We observed that CO₂ is produced from methanol oxidation at 350 mV vs. RHE on PAni/Pt–Ru–Mo, which is 100 mV less negative than on PAni/Pt–Ru and 200 mV less than on PAni/Pt. The results suggest that Pt–Ru–Mo is less sensitive to CO_ADS poisoning than Pt–Ru and much more sensitive than Pt. Large differences are observed concerning the average wavenumber of _ADS between Pt–Ru–Mo, Pt–Ru, and Pt.     

Hydrogen Evolution on Catalytically Active Electrodeposited Ni–Re Alloy: Electrochemical Impedance Study

Hydrogen evolution reaction on the catalytically active Ni–Re alloy is studied by the method of electrochemical impedance. The alloy was fabricated by the electrodeposition from the ammonium—citrate solutions. The experiments were performed in the 0.1 M sodium hydroxide solution. Based on the analysis of equivalent circuits, it is found that the absorption of hydrogen atoms on the Ni–Re cathode is controlled by diffusion. The parameters of structural elements of equivalent electric circuits are calculated, and the effect of cathodic overpotential on these parameters is analyzed.     

Investigation of the Pt–Ni–Pb/C ternary alloy catalysts for methanol electrooxidation

This research is aimed to increase the activity of anodic catalysts and thus to lower noble metal loading in anodes for methanol electrooxidation. The Pt–Ni–Pb/C catalysts with different molar compositions were prepared. Their performance were tested by using a glassy carbon disk electrode through cyclic voltammetric curves in a solution of 0.5 mol L⁻¹ CH₃OH and 0.5 mol L⁻¹ H₂SO₄. The performances of Pt–Ni–Pb/C catalyst with optimum composition (the molar ratio of Pt/Ni/Pb is 5:4:1) and Pt/C (E-Tek) were also compared. Their particle sizes and structures were determined by means of X-ray diffraction (XRD). The XRD results show, compared with that of Pt/C, the lattice parameter of Pt–Ni–Pb (5:4:1)/C catalyst decreases, its diffraction peaks are shifted slightly to a higher 2θ values. This indicates the formation of an alloy involving the incorporation of Ni and Pb atoms into the fcc structure of Pt. The electrochemical measurement shows the activity of Pt–Ni–Pb/C catalyst with an atomic ratio of 5:4:1 for methanol electrooxidation is the best among all different compositions. The activity of Pt–Ni–Pb (5:4:1)/C catalyst is much higher than that of Pt/C (E-Tek).     

Electrochemical determination of the surface composition of Pd–Pt core–shell nanoparticles

Different amounts of Pt atoms were deposited onto the surface of Pd nanoparticles supported on carbon black by hydroquinone reduction method in anhydrous ethanol. Here, we surveyed electrochemical probing of surface compositions of Pd–Pt surface alloys. They were calculated from hydrogen desorption, carbon monoxide adlayer oxidation, and reduced carbon dioxide oxidation charges. The surface composition of Pt drastically increased up to Pt[0.3]/Pd/C (23.1 at.% of Pt) and then approached that of pure Pt with the moderate rate of increase.     

Modulation of Electrochemical Oscillations by Specific Adsorption of Cl^— during the Electrooxidation of Methanol on Pt Electrode

Potential oscillation during the electrocatalytic oxidation of methanol can be modulated by the specific adsorption of Cl^- on the platinum electrode, which suppresses the electrocatalytic oxidation of methanol, and makes the cross cycle in the cyclic voltammogram become smaller and finally disappear with the increase of Cl^- concentration. The method is also applicable to the electrocatalytic oxidation of other small organic molecules.     

Combinatorial screening of ternary Pt–Ni–Cr catalysts for methanol electro-oxidation

Methanol electro-oxidation activity of ternary Pt–Ni–Cr system was studied by using a combinatorial screening method. A Pt–Ni–Cr thin-film library was prepared by sputtering and quickly characterized by a multichannel multielectrode analyzer. Among the 63 different composition thin-film catalysts, Pt₂₈Ni₃₆Cr₃₆ showed the highest methanol electro-oxidation activity and good stability. This new composition was also studied in its powder form by synthesizing and characterizing Pt₂₈Ni₃₆Cr₃₆/C catalyst. In chronoamperometry testing, the Pt₂₈Ni₃₆Cr₃₆/C catalyst exhibited “decay-free” behavior during 600 s operation by keeping its current density up to 97.1% of its peak current density, while the current densities of Pt/C and Pt₅₀Ru₅₀/C catalysts decreased to 14.0% and 60.3% of their peak current densities, respectively. At 600 s operation, current density of the Pt₂₈Ni₃₆Cr₃₆/C catalyst was 23.8 A g_{noble metal}⁻¹, while that of those of the Pt/C and Pt₅₀Ru₅₀/C catalysts were 2.74 and 18.8 A g_{noble metal}⁻¹, respectively.     

Bimetallic Cage-Based Metal–Organic Frameworks for Electrochemical Hydrogen Evolution Reaction with Enhanced Activity

A cage-based metal–organic framework (Ni-NKU-101) with biphenyl-3,3’,5,5’-tetracarboxylic acid was synthesized via solvothermal method. Ni-NKU-101 contains two types of cages based on trinuclear and octa-nuclear nickel-clusters that are connected with each other by the 4-connected ligands, to form a 3D framework with a new topology. A mixed-metal strategy was used to synthesize isostructural bimetallic MOFs of M_xNi_1-x-NKU-101 (M=Mn, Co, Cu, Zn). The electrocatalytic studies showed that the hydrogen evolution reaction (HER) activity of Cu_xNi_1-x-NKU-101 is much higher than that of other M_xNi_1-x-NKU-101 catalysts in acidic aqueous solution, owing to the synergistic effect of the bimetallic centers. The optimized Cu_0.19Ni_0.81-NKU-101 has an overpotential of 324 mV at 10 mA cm⁻² and a Tafel slope of 131 mV dec⁻¹. The mechanism of HER activity over these bimetallic MOF-based electrocatalysts are discussed in detail.     

Pt–Ni carbon-supported catalysts for methanol oxidation prepared by Ni electroless deposition and its galvanic replacement by Pt

Pt–Ni particles supported on Vulcan XC72R carbon powder have been prepared by a combination of crystalline Ni electroless deposition and its subsequent partial galvanic replacement by Pt upon treatment of the Ni/C precursor by a solution of chloroplatinate ions. The Pt-to-Ni atomic ratio of the prepared catalyst has been confirmed by EDS analysis to be ca. 1.5:1. No shift of Pt XPS peaks has been observed, indicating no significant modification of its electronic properties, whereas the small shift of the corresponding X-ray diffraction (XRD) peaks indicates the formation of a Pt-rich alloy. No Ni XRD peaks have been observed in the XRD pattern, suggesting the existence of very small pockets of Ni in the core of the particles. The surface electrochemistry of electrodes prepared from the catalyst material suggests the existence of a Pt shell. A moderate increase in intrinsic catalytic activity towards methanol oxidation in acid has been observed with respect to a commercial Pt catalyst, but significant mass specific activity has been recorded as a result of Pt preferential confinement to the outer layers of the catalyst nanoparticles.     

Influence of Reaction Conditions on Methanol Synthesis and WGS Reaction in the Syngas-to-DME Process

A series of CuO-ZnO catalysts (with different Cu/Zn molar ratios) were prepared, and evaluated under the reaction conditions of syngas-to-dimethyl ether (DME) with three sorts of feed gas and different space velocity. The catalysts were characterized by X-ray diffraction (XRD) and temperature-programmed reduction (TPR). The experiment results showed that the reaction conditions of syngas-to-DME process greatly affected the methanol synthesis and WGS reaction. The influence caused by Cu/Zn molar ratio was quite different on the two reactions; increasing of percentage of CO2 in feed gas was unfavorable for catalyst activity, and also inhibited both reactions: enhancement of reaction space velocity heavily influenced the performance of the catalyst, and the benefits were relatively less for methanol synthesis than for the WGS reaction.     

Methanol Tolerant FeTPP—Pt／C Co—catalysts for the Electroreduction of Oxygen

It was found for the first time that iron tetraphenylporphyrin(FeTPP)-Pt/C showed the good activity for the electroreduction of oxygen and methanol tolerant abitity,Their perfor-mances were related to the heat-treatment temperature.     

Phosphorescent Trinuclear Pt–Ir–Pt Complexes: Insights into the Photophysical and Electrochemical Properties and Interaction with Guanine Nucleobase

In this study we have analysed the comparative photophysical and electrochemical properties of two isomeric heterotrinuclear Pt^II–Ir^III–Pt^II complexes 3 and 6 and the four corresponding intermediate isomeric homonuclear cyclometalated iridium(III) complexes 1 , 2 , 4 and 5 . The isomerisation originates from positional differences in the formyl, di-2-picolylamine and Pt–di-2-picolylamine moieties appended to cyclometalated or ancillary ligands. The interaction of 5′-GMP with the trinuclear complexes 3 and 6 shows that platinum centres appended to the cyclometalated ligand in 3 facilitate the binding of two 5′-GMP units per Pt^II centre in preference to a single 5′-GMP unit per Pt^II centre as observed in 6 . The 1:2 and 1:1 Pt^II–5′-GMP binding patterns probably arise from the convenient arrangements of the Pt–di-2-picolylamine units in different planes in complex 3 , which is absent in complex 6 .     

Oxidation of Oxalic Acid in the Ozone–Chloride–Ion Reaction System in an Aqueous Solution

Russian Journal of Physical Chemistry A - It is shown that the rate of oxidation of oxalic acid H2C2O4 during the ozonation of its solutions grows considerably if sodium chloride is added to the...     

Effect of the Conditions of Solution Combustion Synthesis on the Properties of Monolithic Pt–MnOx Catalysts for Deep Oxidation of Hydrocarbons

Kinetics and Catalysis - Catalysts based on manganese oxides, doped with Pt, and supported on ceramic monoliths with a honeycomb structure were produced by impregnation and solution combustion...     

Theoretical Study on the Dark Oxidation Reaction Mechanism of Ethers

1 INTRODUCTION Ethers are a kind of organic compounds that are easily oxidized under the conditions of lacking light and any additional excitement. According to dif- ferent mechanisms, the oxidation reactions could be classified into two types: photooxidation reaction and dark oxidation reaction. The former is the reaction with excited state oxygen molecule (singlet state), while the latter is the reaction with ground state oxygen molecule (triple state) without illuminance or any exciter…     

Metal–Organic Frameworks Based Electrocatalysts for the Oxygen Reduction Reaction

In view of the clean and sustainable energy, metal–organic frameworks (MOFs) based materials, including pristine MOFs, MOF composites, and their derivatives are emerging as unique electrocatalysts for oxygen reduction reaction (ORR). Thanks to their tunable compositions and diverse structures, efficient MOF-based materials provide new opportunities to accelerate the sluggish ORR at the cathode in fuel cells and metal–air batteries. This Minireview first provides some introduction of ORR and MOFs, followed by the classification of MOF-based electrocatalysts towards ORR. Recent breakthroughs in engineering MOF-based ORR electrocatalysts are highlighted with an emphasis on synthesis strategy, component, morphology, structure, electrocatalytic performance, and reaction mechanism. Finally, some current challenges and future perspectives for MOF-based ORR electrocatalysts are also discussed.     

Thermal Oxidation Kinetics of Ni100–xPx Powders

The oxidation of Ni_100–xP_x(7.3 at%<x<25.0 at%) powders in air in the temperature range 350–450°C was determined by kinetics and X-ray diffraction. The isothermal kinetics was modeled using theGinstling–Brounstein equations. The oxidation process was found to be thermally activated with activation energy 127.8 kJ mol^–1 for x=7.3 at% to 157.7 kJ mol^–1 for x=25.0 at%. It was found that the rate constants for x=7.3 at% were approximately 100 times lower than those for x=25.0 at%. This revised version was published online in July 2006 with corrections to the Cover Date.