Chemisorption of carbon monoxide on carburized polycrystalline tungsten

Desorption spectra of CO chemisorbed on clean and carburized W at room temperature were measured in the temperature range from 300 to 1900 K and coverage versus exposure plots were constructed. The partial conservation of the β state on carburized W is discussed.     

The adsorption of carbon monoxide on a platinum electrode

The adsorption of CO from 0.5 M H₂SO₄ solution on platinum has been studied using CO labelled with C-14. The adsorption of CO on Pt occurs in the potential range of hydrogen adsorption as well as in the double layer region. In the whole potential range the rate of adsorption follows first order kinetics. From the surface concentrations and charges for oxidation of adsorbed species it follows that the product of chemisorption consists at least of two kinds of species. One of them is the COOH radical probably formed by the reaction of CO with water.     

Hydrogenation of carbon monoxide on platinum metals

Together with methane, methanol is the main product of the hydrogenation of CO in the presence of platinum, palladium, and iridium, applied to Y-Al₂O₃, at atmospheric pressure and temperatures of 473–573 K. Dimethyl ether is also formed on platinum and palladium, while small amounts of ethanol and acetaldehyde are formed on iridium. The hydrogenation of CO in the presence of Rh and Ru leads to the formation of normal C₁-C₅ alcohols and C₂-C₅ aldehydes. Reduction of the energy of the metal-carbon bond in the platinum metals (Pd, Ir, Pt, Rh, Ru) increases their specific catalytic activity with respect to the formation of methane and oxygenated organic compounds, and increases the selectivity for higher alcohols and aldehydes.Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 24, No. 1, pp. 75–81, January–February, 1988.     

Kinetics and mechanism of the early stages of the voltammetric electrooxidation of carbon monoxide preadsorbed on polycrystalline platinum in acid electrolyte

The first stages of the electrooxidation of CO previously adsorbed on polycrystalline Pt in 1 M HClO₄ at 25°C were investigated by means of the triangularly modulated triangular potential sweep technique. Runs were made with a Pt surface covered either partially or completely with adsorbed CO over a wide range of frequency and amplitude of the modulating signal. Reactions between the strongly and the weakly bonded adsorbed oxygen-containing adsorbed species with the linear and the bridge forms of adsorbed CO were followed via the voltammetric measurements. The kinetics of the various possible processes are discussed in terms of previous results on the voltammetric electrooxidation of adsorbed CO and on the early stages of O-electroadsorption on Pt. CO adsorption on Pt produces a change in the apparent electrode capacity which is interpreted in terms of the structure of the inner part of the electrical double layer.     

The electro-oxidation of chemisorbed carbon monoxide on polycrystalline rhodium in acid solution

The electrooxidation of CO adsorbed on Rh in 1 M HClO₄ at room temperature exhibits a complex potentiodynamic E/I profile which depends on the oxygen-containing species present on the electrode. The electrochemical behaviour of the system is explained through the participation of two CO-adsorbed states and the interaction of the latter with electrosorbed oxygen. The electro-oxidation of CO adsorbed on Rh can be correlated with the reaction occurring on Pt.     

Electrodeposition of platinum–nickel alloy nanocomposites on polyaniline-multiwalled carbon nanotubes for carbon monoxide redox

An electrochemical method was developed to deposit platinum (Pt)–nickel (Ni) alloy nanocomposites on polyaniline-multiwalled carbon nanotubes (Pt–Ni/PAN/MWCNTs). The material was characterized by various methods including field emission scanning electron microscope, X-ray diffraction, X-ray photoelectron spectroscopy, and electrochemical techniques. An appreciably improved catalysis toward oxidation of carbon monoxide (CO) was observed at the Pt–Ni/PAN/MWCNTs nanocomposites (real ratio of Pt–Ni of 17:1), which was interpreted by a mechanism based on the bifunctional catalysis. The successful preparation of Pt–Ni/PAN/MWCNTs nanocomposites opens a new path to synthesize the promising catalysts for CO.     

Thermodynamics of carbon monoxide adsorption on polycrystalline titania studied by static adsorption microcalorimetry

The adsorption of CO on polycrystalline TiO2 was investigated by static adsorption microcalorimetry. The initial differential heat of adsorption (qdiff,0) of CO on polycrystalline titania is 40 kJ/mol, and the standard adsorption entropy (Deltas0) is -104 J mol(-1) K(-1). These results are consistent with those derived from temperature-programmed desorption and FTIR results in the literature. The good reproducibility of the isotherms and the stable qdiff indicate that the lattice oxygen and hydroxyl groups on titania surface are basically not reactive to adsorbed CO.     

Effect of mass transfer process on hydrogen adsorption on polycrystalline platinum electrode in sulfuric acid solution

The hydrogen adsorption on polycrystalline platinum electrode experimentally as well as on single crystal Pt(110), Pt(100) and Pt(111) electrode theoretically were studied. The study of forced convection on the electrode surface promotes the HUPD research from static process to a convective mode and provides a new strategy to investigate the hydrogen adsorption in solution.     

Behavior of a nickel electrode in the presence of carbon monoxide

The electrochemical behavior of a nickel electrode with limited volume (LVE) electrodeposited as a thin layer on gold has been studied. The influence of the gold matrix on the electrochemical Ni electrode behavior has been considered. The electrosorption and oxidation of carbon monoxide on the Ni surface and its influence on hydrogen sorption has also been demonstrated. Received: 21 May 1997 / Accepted: 9 June 1997     

Supplement to the theory of normal pulse voltammetry and its application to the kinetic study of methanol oxidation on a polycrystalline platinum electrode

The theory of normal pulse voltammetry (NPV) for complex multistep multielectron transfer processes on a plane electrode was advanced and applied to the completely irreversible process of methanol oxidation to formic acid in the potential range from 0.3 to 0.8 V versus Ag/AgCl. The kinetic parameters for this process, such as the standard rate constant (k0) and anodic transfer coefficient (alpha) for this irreversible heterogeneous electron transfer process at the electrode/solution interface and apparent diffusion coefficient (D(app)) for the homogeneous charge transfer process within liquid film near the electrode surface, were obtained with NPV theory from analyzing the dependence of current-potential curves upon the sampling times. The results showed that this process is truly a very slow, completely irreversible kinetic process, as k0 is in the order of 10(-9) cm/s for the rate-determining step. The values of k0 and D(app) decreased with the increase of methanol concentration, while alpha was independent of the concentration of methanol and its value was 0.35 +/- 0.05. Theoretical fitting is very consistent with the experimental data.     

Initial stages of copper electrocrystallization on polycrystalline platinum and glassy carbon in the presence of acetonitrile

The kinetics of formation of copper adlayer, three-dimensional nucleation, and the deposit growth on polycrystalline platinum and glassy carbon in the 0.5 M H₂SO₄ + 10 mM CuSO₄ + (0–2) M acetonitrile (AcN) solutions at the cathodic overvoltages is studied using the methods of cyclic voltammetry and potentiostatic current transients on a ring-disc electrode. At [AcN] = 2 M, the process of formation of copper adatoms on platinum is significantly retarded. In the solutions with high contents of AcN, the processes of Cu⁺ ion production, the formation of their complexes with acetonitrile, hydrogen evolution, copper nucleation, and the deposit growth proceed in parallel. The contribution of any process to the overall current depends on the amount of adsorbed AcN at the surface of substrate and copper deposit and on the electrode potential. At [AcN] = 2 M, an increase in the cathodic overvoltage to 0.32 V leads to an abnormal increase in the current of Cu⁺ ion production on platinum, which is caused by insufficiently rapid formation of copper atoms in the reduction of Cu⁺(AcN) _x complexes.     

Stripping voltammetry of carbon monoxide oxidation on stepped platinum single-crystal electrodes in alkaline solution

The electrochemical oxidation of a CO adlayer on Pt[n(111)x(111)] electrodes, with n = 30, 10, and 5, Pt(111), Pt(110) as well as a Pt(553) electrode (with steps of (100) orientation) in alkaline solution (0.1 M NaOH) has been studied using stripping voltammetry. On these electrodes, it is possible to distinguish CO oxidation at four different active oxidation sites on the surface, i.e. sites with (111), (110) and (100) orientation, and kink sites. The least active site for CO oxidation is the (111) terrace site. Steps sites are more active than the (111) terrace sites, the (110) site oxidizing CO at lower potential than the (100) site. The CO oxidation feature with the lowest overpotential (oxidation potential as low as 0.35 V vs. RHE) was ascribed to oxidation of CO at kink sites. The amount of CO oxidized at the active step or kink sites vs. the amount of CO oxidized at the (111) terrace sites depends on the concentration of the active sites and the time given for the terrace-bound CO to reach the active site. By performing CO stripping on the stepped surfaces at different scan rates, the role of CO surface diffusion is probed. The possible role of electronic effects in explaining the unusual activity and dynamics of CO adlayer oxidation in alkaline solution is discussed.     

Study of an Au colloid self-assembled electrode and its application to the determination of carbon monoxide

A novel electrochemical sensor has been developed for the detection of carbon monoxide. The chemically modified electrode, prepared by reaction of cysteine and then an Au colloid of size approximately 15 nm with a platinum microelectrode, has excellent catalytic activity toward carbon monoxide, with an oxidation potential of +600 mV relative to the Ag/AgCl electrode. The CO gas sensor is based on an Au colloid self-assembled modified electrode as working electrode, an Ag/AgCl electrode as reference electrode, a Pt electrode as counter electrode, and a porous film which is in direct contact with the gas-containing atmosphere. The effects on the determination of CO of different internal electrolyte solutions of perchloric acid, hydrochloric acid, sulfuric acid, nitric acid, and phosphate buffer of different concentrations were also studied. The sensor is characterized by a short response time and highly reproducible detection of CO. This sensor can be used in the field of environmental monitoring and control.     

Study of an Au colloid self-assembled electrode and its application to the determination of carbon monoxide

A novel electrochemical sensor has been developed for the detection of carbon monoxide. The chemically modified electrode, prepared by reaction of cysteine and then an Au colloid of size approximately 15 nm with a platinum microelectrode, has excellent catalytic activity toward carbon monoxide, with an oxidation potential of +600 mV relative to the Ag/AgCl electrode. The CO gas sensor is based on an Au colloid self-assembled modified electrode as working electrode, an Ag/AgCl electrode as reference electrode, a Pt electrode as counter electrode, and a porous film which is in direct contact with the gas-containing atmosphere. The effects on the determination of CO of different internal electrolyte solutions of perchloric acid, hydrochloric acid, sulfuric acid, nitric acid, and phosphate buffer of different concentrations were also studied. The sensor is characterized by a short response time and highly reproducible detection of CO. This sensor can be used in the field of environmental monitoring and control.