Charles Mims

• University of Toronto

A nonlinear change in baseline ozone concentrations at northern midlatitudes has been quantified over preceding decades. During the past few years, several studies, using linear trend analyses, report relatively small trends over selected time periods – results inconsistent with the earlier developed picture. We show that reported COVID-19-related...

A simple compartmental model is used to simulate the average (climatic) annual and seasonal distribution of ozone in the Northern Hemisphere midlatitude troposphere. The model (reminiscent of earlier examples) consists of a circular set of segments – 4 marine and 5 continental – which span the globe. Each segment consists of two well-mixed compartm...

A non-linear change in baseline ozone concentrations at northern midlatitudes has been quantified over preceding decades. During the past few years several studies, using linear trend analyses, report relatively small trends over selected time periods – results inconsistent with the earlier developed picture. We show that reported COVID-19 related...

Solar-driven CO2 hydrogenation can provide a renewable source of fuels and reduce greenhouse gas emissions if operated at industrial scales. Herein we investigate the photomethanation (light-driven Sabatier reaction) rates over Ru films sputtered onto silica opal (Ru/SiO2) and inverted silicon opal photonic crystal (Ru/i-Si-o) supports at ambient t...

In article number 1702277, Geoffrey A. Ozin and co‐workers report that the photomethanation of CO2 over highly dispersed nanostructured RuO2 catalysts on 3D silicon photonic crystal supports achieves impressive conversion rates as high as 4.4 mmol gcat⁻¹ h⁻¹ at ambient temperatures under high‐intensity solar simulated irradiation. This performance...

Sunlight-driven catalytic hydrogenation of CO2 is an important reaction that generates useful chemicals and fuels and if operated at industrial scales can decrease greenhouse gas CO2 emissions into the atmosphere. In this work, the photomethanation of CO2 over highly dispersed nanostructured RuO2 catalysts on 3D silicon photonic crystal supports, a...

The field of solar fuels seeks to harness abundant solar energy by driving useful molecular transformations. Of particular interest is the photo-driven conversion of greenhouse gas CO2 into carbon-based fuels and chemical feedstocks, with the ultimate goal of providing a sustainable alternative to traditional fossil-fuels. Highly defected indium ox...

Silicon constitutes 28% of the earth's mass. Its high abundance, lack of toxicity and low cost coupled with its electrical and optical properties, make silicon unique among the semiconductors for converting sunlight into electricity. In the quest for semiconductors that can make chemicals and fuels from sunlight and carbon dioxide, unfortunately th...

Supplementary Figures 1-11 and Supplementary Tables 1-3.

The discovery of homogeneous, solution-based molecular Frustrated Lewis Pairs, denoted FLPs, comprising main group elements that can activate H2 heralded a paradigm shift in chemistry and catalysis. In FLPs, unquenched Lewis base and Lewis acid sites (B•••A) are able to polarize and dissociate H2 heterolytically to form adjacent proton and hydride...

The development of strategies for increasing the lifetime of photoexcited charge carriers in nanostructured metal oxide semiconductors is important for enhancing their photocatalytic activity. Intensive efforts have been made in tailoring the properties of the nanostructured photocatalysts through different ways, mainly including band-structure eng...

Potassium-catalyzed steam gasification experiments of ash-free coal were conducted in a drop-down reactor to study the influence of the catalyst loading, temperature, H2O/H2 ratio, and heating protocol. The higher the catalyst loading, the faster the carbon conversion; however, at an initial K/C ratio of 0.1, a saturation effect (decrease in reacti...

Designing catalytic nanostructures that can thermochemically or photochemically convert gaseous carbon dioxide into carbon based fuels is a significant challenge which requires a keen understanding of the chemistry of reactants, intermediates and products on surfaces. In this context, it has recently been reported that the reverse water gas shift r...

Supplementary

Gaseous CO2 is transformed photochemically and thermochemically in the presence of H2 to CH4 at millimole per hour per gram of catalyst conversion rates, using visible and near-infrared photons. The catalyst used to drive this reaction comprises black silicon nanowire supported ruthenium. These results represent a step towards engineering broadband...

The solar-to-chemical energy conversion of greenhouse gas CO2 into carbon-based fuels is a very important research challenge, with implications for both climate change and energy security. Herein, the key attributes of hydroxides and oxygen vacancies are experimentally identified in non-stoichiometric indium oxide nanoparticles, In2O3-x(OH)y, that...

Advances towards the vision of the “solar fuels refinery” of the future are portrayed in the cover art, based on article 1400013 by G. A. Ozin and co-workers. In the article, the attributes of hydroxide groups and oxygen vacancies are identified for non-stoichiometric indium oxide photocatalytic nanoparticles in the light-assisted, gas-phase conver...

Supplementary

Steam gasification experiments of ash-free coal with and without potassium carbonate were performed in a newly designed drop-down reactor. The temperature dependency on the carbon conversion and gas production rates was investigated in a range of 600-800 degrees C and 2.5 bar. The gasification rate at 700 degrees C was approximately 20 times faster...

Amber is a polymerized plant resin having remarkable preservation potential in the geological record. Numerous analytical techniques have been applied to the study of amber organic chemistry in order to extract paleobotanical information. However, only exploratory work has been conducted using time-of-flight secondary ion mass spectrometry (ToF-SIM...

Gas phase photomethanation of CO 2 in a hydrogen environment was initially reported using a catalyst composed of dispersed Ru-RuO x on TiO 2. [ 17 ] Enhanced methanation rates were originally attributed to the chemical effects of electron-hole pairs generated from UV-light absorption in the TiO 2 support. However, subsequent studies revealed that p...

The kinetics of K2CO3-catalyzed CO2 gasification of ash-free coal was investigated with a thermogravimetric analyzer and compared to raw coal and uncatalyzed ash-free coal. At 750C, the gasification of ash-free coal dry mixed with 20 wt % K2CO3 was approximately 3 and 60 times faster than the raw coal and ash-free coal without catalyst, respectivel...

The invention provides processes for generating a methane-enriched gas from a gas mixture comprising carbon monoxide and hydrogen such as gas streams generated by gasification of an alkali metal catalyst-loaded carbonaceous feedstock, and a char methanation catalyst useful in such processes.

The low temperature (403–453 K) conversions of CO/hydrogen and CO2/hydrogen mixtures (6 bar total pressure) to methanol over copper catalysts are both assisted by the presence of small amounts of water (mole fraction ∼0.04–0.5%). For CO2/hydrogen reaction mixtures, the water product from both methanol synthesis and reverse water–gas shift serves to...

Co-gasification of biomass, namely switchgrass, with coal and fluid coke were performed to investigate the availability of the gasification catalysts to the mixed feedstock, especially alkali and alkaline earth elements, naturally present on switchgrass. Rates of CO2 gasification of the single and mixed materials were measured at temperatures betwe...

A promotor for lithium batteries: Nanocrystalline cobalt(II,III) oxide supported on graphene enhances the transport kinetics for both oxygen reduction and oxygen evolution in the lithium-oxygen cell. On cycling the lithium-oxygen cell, the effect of the promoter is, however, eventually overwhelmed by side reactions in the cell, such as, the deposit...

Amber comprises polymerized plant resins that have a remarkable capacity for survival in a range of geological environments. Most ambers can be traced to coniferous trees and typically combine a broad array of plant natural products including terpenoids, carboxylic acids, and associated alcohols. Because amber may entomb various organisms at the ti...

Time-of-flight-secondary ion mass spectrometry (TOF-SIMS) is a surface analysis technique that is herein demonstrated to be a viable tool for the detection of enzyme activity on solid substrates. Proof-of-principle experiments are presented that utilize commercial cellulase and laccase enzymes, which are known to modify major polymeric components o...

Methanol synthesis from CO2 hydrogenation on supported Cu catalysts is of considerable importance in the chemical and energy industries. Although extensive experimental and theoretical efforts have been carried out in the past decades, the most fundamental questions such as the reaction mechanisms and the key reaction intermediates are still in deb...

An in-situ XPS and voltammetry investigation of the redox properties of LaCr1-xNixO3 (x = 0.4, 1) was carried out by incorporating the materials as one electrode in an electrochemical cell (LaCr1xNixO3|YSZ|Pd:PdO), which was directly mounted on a heated sample stage in an ultra high vacuum (UHV) chamber. Under a 0.7 V cathodic bias, the perovskites...

Isotope exchange with C18O2 followed by depth profiling analysis was used to study surface exchange and bulk diffusion of oxygen in single crystal ((100) surface orientation) yttria-stabilized zirconia (YSZ) in the temperature range 250°C - 350°C. The depth profiles, which were obtained using 18O(ρ,α)15N nuclear reaction analysis (NRA) and secondar...

We have attempted to hydrogenate adsorbed formate species on copper catalysts to probe the importance of this postulated mechanistic step in methanol synthesis. Surface formate coverages up to 0.25 were produced at temperatures between 413 and 453 K on supported (Cu/SiO2) copper and unsupported copper catalysts. The adlayers were produced by variou...

The coverages and surface lifetimes of copper-bound formates on Cu/SiO2 catalysts, and the steady-state rates of reverse water-gas shift and methanol synthesis have been measured simultaneously by mass (MS) and infrared (IR) spectroscopies under a variety of elevated pressure conditions at temperatures between 140 and 160°C. DCOO lifetimes under st...

Here we investigate isotope effects on the catalytic methanol synthesis reaction and the reactivity of copper-bound formate species in CO2–H2 atmospheres on Cu/SiO2 catalysts by simultaneous IR and MS measurements, both steady-state and transient. Studies of isotopic variants (H/D, 12C/13C) reveal that bidentate formate dominates the copper surface...

Biomass gasification has been widely studied over the years to convert wood waste and forestry residues into a combustible synthesis gas (syngas). A bench-scale fixed-bed gasifier with biomass processing capacity of several kilograms per hour was designed and constructed. A standard characterization procedure was also developed. The effect of the o...

As part of an investigation of new cathode materials for intermediate temperature solid oxide fuel cells, we have investigated particular perovskite oxides with ordered A cations which, in turn, localize the oxygen vacancies into layers. The oxygen exchange kinetics of polycrystalline samples of the oxygen-deficient double perovskite PrBaCo2O5+x (P...

At high strontium doping levels, perovskite oxides containing iron have suitable stability and transport properties for use as oxide ion transport membranes. In our studies of these materials, we have investigated the pO2 and temperature dependence of the conductivity and non-stoichiometry of La1−xSrxFe1−yMyO3−δ (M = Cr, Ti) by using electrochemica...

The oxygen exchange kinetics of thin films of the oxygen-deficient double perovskite PrBaCo2O5+delta (PBCO) have been determined by electrical conductivity relaxation (ECR) and by oxygen-isotope exchange and depth profiling (IEDP). Microstructural studies indicate that the PBCO films, prepared by pulsed laser deposition, have excellent single-cryst...

An in situ XPS study of oxidation-reduction processes on three perovskite oxide electrode surfaces was carried out by incorporating the materials in an electrochemical cell mounted on a heated sample stage in an ultrahigh vacuum (UHV) chamber. Electrodes made of powdered LaCr(1-x)Ni(x)O(3-delta) (x = 0.4, 1) showed changes in the XPS features of al...

Surface activation and bulk transport of oxygen in dense samples of La0.2Sr0.8Cr0.2Fe0.8O3−d were studied with Ion Exchange/Depth Profiling (IEDP) techniques. Both high oxygen activity (20% 18O2) and low oxygen activity (CO/C18O2) conditions were studied at 1023 and 1123 K. Mass spectrometry of the gas phase during the isotope infusion allows the r...

Carbon isotope transients (12CO→13CO) at reaction steady state were used to correlate the in situ surface inventories of active carbon species with product selectivity variations in the Fischer–Tropsch synthesis. The measurements were conducted on an unsupported cobalt catalyst at a variety of elevated pressure conditions (syngas pressures from 3 t...

Catalyst composition effects on site activity, active carbon coverage, and methane selectivity in the cobalt-catalyzed Fischer–Tropsch synthesis were examined using 12CO→13CO isotope transients at reaction steady state. All catalysts (18 total) were tested at identical conditions: 221 °C, 6.5 atm of H2/CO/Ne=2/1/1. The intrinsic site activity of un...

Carbon isotope transients at reaction steady state are used to examine the effect of water vapor on the amount and reactivity of the surface carbon intermediates involved in the Fischer–Tropsch synthesis on both a supported and an unsupported cobalt catalyst. Water increases the amount of active surface carbon, present predominantly as monomeric sp...

A novel application of 12CO→13CO isotope transients at elevated reactor pressures was used to measure the intrinsic site reactivity of a variety of cobalt Fischer-Tropsch synthesis catalysts (220°C, 5 atm syngas, H2:CO = 2:1, CO conversion = 12-16%, C5+ selectivity > 70%). We found that the in-situ measured CO-TOF and methane selectivity values wer...

Methane activation at 450–700°C by 14 mol% calcia-stabilized zirconia was studied by the transient reaction of pure methane with the oxidized material. Three distinct sequential reaction regimes are observed. Initially, methane oxidation rates are similar to those in cofed methane–oxygen mixtures. After a small amount of oxygen (amount) is removed...

We have used isotope transients,16O2–18O2, at reaction steady state to investigate the epoxidation of ethylene over unsupported silver powder catalysts. The reactive oxygen inventory at steady state consists of two types: one with a short residence time (15s). The latter (assigned to subsurface oxygen) can comprise as much as 2.5 monolayer-equivale...

Methane (CH3D) is formed directly by abstraction by methyl radicals of adsorbed D on a Ni(111) surface. This reaction occurs at a surface temperature of 120 K and in the presence of open metal binding sites. A direct reaction by unaccommodated methyl radicals is involved, since accommodated methyl radicals on Ni(111) react only above 200 K. Modelin...

The oxidation of propene over mixed metal oxide catalysts based on cation substituted 2:1 bismuth molybdates (Bi2Mo1_xMexO6_y, Me = Ni (x = 0.0, 0.25)) and vanadates Bi2V1_XMexO5.5_y, Me = Mn(x = 0.25), and Mo(x = 0.0, 0.25 and 0.50) has been studied. At atmospheric pressure and temperatures of 350–550°C, the Mo:V containing catalysts are more sele...

We have studied the reactions between submonolayer coverage amounts of methyl iodide and adsorbed hydrogen on Ni(111) using high-resolution electron energy loss spectroscopy (HEELS), temperature-programmed desorption (TPD), Auger electron spectroscopy (AES), and low-energy ion scattering (LEIS). Methane is the only hydrocarbon product during TPD to...

Ternary perovskite oxides LaCr1−xNixO3, (x=0 to 1.0) were evaluated as methane oxidation catalysts over the temperature range 300–500°C and as a function of the partial pressures of oxygen and methane (12–90 kPa). All catalysts are stable in oxygen containing atmospheres, while oxygen starvation causes destructive reduction to Ni metal forx>0.5. Th...

A series of perovskite oxide catalysts with the composition LaCr1−xNixO3(0≤x≤1) has been synthesized by a modification of the Pechini method. The oxides have been characterized by powder X-ray diffraction, elemental analysis and surface area measurements. The LaCr1−xNixO3phases have the orthorhombic GdFeO3(x0.6), in agreement with previous results....

The structures of LaCr0.6Ni0.4O3 and LaCr0.6Ni0.4O2.8 have been determined by Rietveld refinement of neutron powder diffraction data. LaCr0.6Ni0.4O3 adopts the orthorhombic GdFeO3 structure with space group Pnma, a = 5.4735(1) Angstrom, b = 7.7568(2) Angstrom, c = 5.5105(1) Angstrom, V = 233.96 Angstrom(3), Z = 4. LaCr0.6Ni0.4O2.8 is rhombohedral,...

A series of perovskite oxide catalysts with the composition LaCr1-xNixO3 (0≤x≤1) has been synthesized by a modification of the Pechini method. The oxides have been characterized by powder X-ray diffraction, elemental analysis and surface area measurements. The LaCr1-xNixO3 phases have the orthorhombic GdFeO3 (x<∼0.6) and the rhombohedral LaAlO3 str...

Reactions of hydrocarbon fragments such as methyl groups on transition metal surfaces play an important role in a number of catalytic processes, including oxidative coupling of methane, methanation of syngas, steam reforming, and partial oxidation of methane to syngas. Although important, knowledge of the fundamental mechanisms and kinetics of thei...

A series of expanded pyrochlore oxides Bi2Sn2−xBixO<7−x/2 (0 ≤ x ≤ 0.86) was synthesized and the influence of their composition on their performance as methane coupling catalysts was examined. A trend to higher selectivity and lower activity accompanies increases in x. However, analysis of the kinetic data by a simple procedure which separates the...

Surface activation of methane and formation of a methyl intermediate is widely accepted as the first step in the reaction mechanism of methane selective oxidation to formaldehyde1,2,3. The fate of the methyl intermediate, particularly whether it is desorbed into the gas phase and the surface involvement in the subsequent steps is as of yet unresolv...

The reaction pathways of ethylene during methane oxidative coupling over (Li)MgO catalysts were investigated by detailed isotopic anal. of all the products from 12C2H4:13CH4:O2 reactant mixts. Ethylene oxidn. has little effect on the concurrent methane conversion, even at comparable mole fractions. By comparison with an extensive computer model of...

Utilizing in-situ FT-IRAS, we have investigated the decomposition kinetics of ethylidyne in the presence of coadsorbates on Ru(001). The results demonstrate that the stabilizing effect of coadsorbed CO and hydrogen is significantly enhanced at elevated pressure, supporting a model wherein an empty neighboring metal site is required before decomposi...

Utilizing time-resolved FT-IRAS we have investigated the thermal stability and decomposition kinetics of formate and ethylidyne under reaction conditions at elevated pressures and temperature, and compare the results with studies on UHV model adsorbates. CO coadsorbed with the intermediate in a hollow site is found in both cases to thermally stabil...

Oxygen pathways for CH4 partial oxidation over a silica-supported molybdena catalyst were investigated using a series of oxygen isotopic exchange experiments and steady state oxygen isotope transients. The initial source of oxygen in the products is masked by rapid and extensive oxygen exchange between the catalyst and the products CO2 and HCHO. Th...

The formation, thermal stability and reactivity of NiO surface films on Ni(100) have been studied in the temperature range of 300 to 900 K. The well known, 2-3 monolayer surface oxide film formed at 300 K undergoes a phase transformation at 525 K, disproportionating into small, crystalline clusters of NiO(100) and large regions of c(2x2)-O on Ni(10...

This patent describes a process for the conversion of light hydrocarbons to higher hydrocarbons and olefins, it comprises: contacting the light hydrocarbons with a catalyst comprising a mixed metal oxide having the pyrochlore structure.

The formation and reactivity of multilayer NiO films, both with and without added potassium, have been investigated by using high-resolution electron energy loss spectroscopy, low-energy electron diffraction, and X-ray photoelectron spectroscopy (XPS). The kinetics of oxygen removal by hydrogen and methane were investigated by using time-resolved X...

The formation and reactivity of multilayer NiO films, both with and without added potassium, have been investigated using high‐resolution electron‐energy‐loss spectroscopy, low‐energy electron diffraction, and x‐ray photoelectron spectroscopy. We have found a strong interaction between K and NiO, as evidenced by the formation of K–O bonds, by a hig...

Oxidation of uncatalyzed and Ca-catalyzed soot was investigated in terms of the overall reaction rate as well as the CO and CO2 evolution rates. Temperature-programmed desorption was also studied to provide a better understanding of the carbon oxidation process. Both CO and CO2 are primary products during carbon oxidation but are generated via diff...

A new series of bismuth tin pyrochlore oxides have been synthesized by precipitation from aqueous potassium hydroxide and calcination at 400°C. The low temperature synthesis method leads to the formation of compounds with compositions Bi2(Sn2-xBix)O7-x/2 (0.05<x<0.86) in which bismuth is present on both the A and B sites of the pyrochlore structure...

The presence of almost any inorganic constituent will produce a measurable increase in the rates of gasification of solid carbons. Figure 1 on the next page illustrates most of the elements for which there is evidence of a catalytic effect when added to carbons as a single component. The impact of this catalysis is widespread. It is desired in such...

Isotope tracing of alkene readsorption has been used to examine reversibility in the growth of higher hydrocarbons in the Fischer-Tropsch synthesis. Some reversibility is indicated, but the degree is insufficient to change previous conclusions from isotope transient studies; namely that the surface concentrations of the growing hydrocarbon oligomer...

Isotope tracer experiments prove the role of methyl in the oxidative coupling of methane and disprove a recently proposed mechanism involving methylene. The ethane product from oxidative coupling of CH4/CD4 mixtures over a Li/MgO catalyst consists of C2H6, C2D6 and CH3CD3 thus proving that ethane is formed by combination of methyl intermediates. Th...

The effect of Cu overlayers on the chemistry of ketene on Ru(001) was studied by high-resolution electron energy loss spectroscopy (HREELS), temperature-programmed desorption (TPD), and Auger electron spectroscopy (AES). Adding Cu in submonolayer amounts shifts the selectivity of the ketene hydrogenation channel from η 2 (C, O) CH 3CHO to η 2 (C, O...

The active surface carbon in the Fischer-Tropsch synthesis over a cobalt catalyst spends most of its time on the surface as an intermediate which is common to both methanol and hydrocarbon products. This intermediate is distinct from COads but contains the original C-O bond.

Ketene (CHâCO) adsorption and reaction on Ru(001) were studied by high-resolution electron energy loss spectroscopy (HREELS), static secondary ion mass spectrometry (SSIMS), and temperature programmed desorption (TPD). Only Hâ, CO, and COâ are observed in TPD. At 105 K, low ketene exposures dissociate to CO and methylene and adsorb molecularly as a...

Ketene (CH/sub 2/CO) adsorption and reaction on Ru(001) were studied by high-resolution electron energy loss spectroscopy (HREELS), static secondary ion mass spectrometry (SSIMS), and temperature programmed desorption (TPD). Only H/sub 2/, CO, and CO/sub 2/ are observed in TPD. At 105 K, low ketene exposures dissociate to CO and methylene and adsor...

The chemistry of ketene (CH/sub 2/CO) on Ru(001) was studied by static secondary ion mass spectrometry (SSIMS) and temperature programmed desorption (TPD). Ketene adsorption at 105 K is both molecular and dissociative and leads to H/sub 2/, CO, and CO/sub 2/, but no hydrocarbons, in TPD. Between 200 and 250 K, molecular ketene is hydrogenated to ad...

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We have been able to quantitatively unify the relative reaction rates for alkali (Li through Cs) salt-catalyzed carbon gasification by H2O, D2O, and CO2. The key to unification is the measurement of catalyst dispersion by a surface alkylation technique in conjunction with the relative rate measurements. After accounting for changes in the catalyst...

The reactions of ketene on clean and hydrogen predosed Pt(111) have been studied using temperature programmed desorption (TPD) and secondary ion mass spectrometry (SIMS). Various evidence suggests that ketene is adsorbed molecularly at 100 K. At low exposure, the only desorption products observed in TPD are H2 and CO, with carbon remaining on the s...

The authors have examined hydrocarbon chain growth in the Fischer-Tropsch reaction by following both the rate and position of incorporation of /sup 13/C into the hydrocarbon products after an abrupt switch from /sup 12/CO to /sup 13/CO in the reactant gas. On two catalysts (cobalt supported on silica and precipitated iron combined with various prom...

The authors have performed a kinetics and isotope tracer study of the mechanism of CHâ formation from a potassium catalyzed carbon during gasification in atmospheres containing HâO, Hâ, COâ, and CO Temperatures from 925 to 1025 K and pressures up to 8 atm were studied. The authors found that although potassium salts catalyze the formation of CHâ, t...

Processes occurring during dosing of ketene on a heated Pt(111) surface were investigated using high-resolution electron energy loss spectroscopy and temperature-programmed desorption. During dosing at 400 K, CO and H2 are evolved and ethylidyne accumulates on the surface. In contrast, at 350 K a CxHy species, not ethylidyne, is formed and some CO...

The interaction of KOH with oxidized edge graphite and glassy carbon surfaces was studied with Auger electron spectroscopy (AES), ultraviolet photoemission spectroscopy (UPS), and X-ray photoelectron spectroscopy (XPS). These results are compared to those from pure KOH deposited on the oxygen free basal and edge surfaces of graphite. Submonolayer c...

The authors have examined the Fischer-Tropsch reaction by following both the rate and position of incorporation of **1**3C into C//4 hydrocarbons after exchanging **1**3CO for **1**2CO in the reactant gas. Such isotopic transients under reaction steady state provide a valuable tool for the in situ study of catalytic reactions. By examining both the...

Potassium catalysts active toward gasification of carbon by H//2O and CO//2 can be generated by addition of KOH to carbon. This study characterized the controlled addition of KOH to the edge surface of graphite and the surface of a glassy carbon using AES, XPS and UPS. Submonolayer concentrations of potassium-oxygen surface species are formed from...

Controlled atmosphere electron microscopy has been used to study the catalytic influence of potassium salts on the graphite-oxygen and graphite-steam reactions. This investigation showed strong interaction of potassium species with the graphite substrate in both reactant atmospheres. Potassium salt particles in contact with the edges of the graphit...

We have examined the interaction of H 2 O vapor with three structurally different carbon surfaces. The edge and basal surface of crystalline graphite as well as a ‘‘paracrystalline’’ glassy carbon were characterized with LEED, UPS, and AES. Structural characterization by LEED showed the typical ‘‘ring’’ pattern for the basal surface; the edge surfa...

We report the first observation of an ordered LEED pattern from the edge or prism surface of graphite. The surface structure was developed after in-situ gasification and is not equivalent to that resulting from any termination of the low index crystal planes of graphite. The pattern is indexed c(2 × ) relative to termination parallel to {101̄0} and...

The interaction of in-situ evaporated KOH with the basal plane of highly oriented pyrolytic graphite was investigated using UPS, AES and LEED from 30 to 600°C and multilayer to submonolayer coverage. The monolayer is more thermally stable than the multilayer. He II UPS results in the monolayer regime show emission from the potassium 3p level and th...

Zur Untersuchung des Mechanismus der Katalyse der Vergasungsreaktion von Kohle mit Wasser (C+H20 -+ CO + H2) durch Kalium werden Kohlenstoffproben (Spherocarb von Analabs, Inc.) in Lösung mit K2CO3 imprägniert, danach bei 700°C einer H2O/H2O-Strömung bis zur Konstanz der Reaktionsgeschwindigkeit (15 min) ausgesetzt, unter Argon abgekühlt und anschl...

The authors have previously demonstrated the existence of surface salt complexes on alkali-catalysed carbon surfaces under gasification conditions (770–1000 K). Chemical characterization of these complexes coupled with kinetic measurements provide insight into their role in catalytic gasification.