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The alloying of metals with foreign elements is a common approach for manipulating catalytic properties of active sites. For palladium-based catalysts, incorporation of light elements receives far less attention than Pd-metal alloys even though incorporated light element are catalytically significant. Due to their small size, light elements (H, B, C, and O) can occupy octahedral sites in Pd to form an interstitial phase, while palladium adjusts its lattice to accommodate the incorporation of larger light elements (S and P) to form distinct phases. The incorporated light element modifies the electronic structure of palladium, influencing the binding energy of substrates and reactive intermediates. Pd hydride and oxide often form in situ during hydrogenation or oxidation reactions, respectively, representing the (more, less) active phase of the catalyst. The reactive interstitial hydrogen dissolved in Pd tends to hydrogenate reactants completely and unselectively. Pd oxide can be the active phase for oxidation reactions, and the incorporated oxygen or oxygen vacancies may participate in the reaction directly. Incorporated light elements change geometric aspects of Pd ensembles, serving the role of site blocking, ensemble isolation, or serve as an additional active site, endowing Pd with bifunctional character. We review the synthetic approaches for incorporating light elements into the palladium lattice. We summarize the catalytic influence of light element incorporation into the palladium lattice with respect to electronic and geometric modification, in situ incorporated hydrogen and oxygen, and discuss the influence of light element incorporation into Pd on specific reactions (i.e., selective hydrogenation, oxidation, electrocatalysis, and C C cross coupling).

The redox properties of ceria make it suitable as a catalyst or support in oxidation reactions. Ceria-supported transition metal nanoparticles or isolated single atoms provide a metal-support interface that reduces the energy cost to remove interfacial oxygen atoms, providing active oxygen species that can participate in Mars van Krevelen oxidation processes. CO oxidation is a key probe reaction to test the reducibility of ceria-supported catalysts and is also practically important in the elimination of CO at relatively low temperatures in various applications. Preferential oxidation of CO (PROX) in excess H2 controls the CO concentration to ultra-low levels to prevent poisoning of hydrogen oxidation electrocatalysts. The reactivity of catalysts in CO oxidation and selectivity towards CO over H2 in PROX is dependent on the type and dispersion of metal species, the structural and chemical properties of CeO2, and the synthetic preparation methods of the catalysts. In this review, we summarize recently published works on catalytic CO oxidation and PROX reactions on ceria-supported metal nanoparticles and single atoms. We summarize the reactivity on different supported metals, and on different CeO2 surfaces with the same metal. We summarize the most likely reaction mechanisms as suggested by density functional theory calculations. The factors contributing to selectivity towards CO oxidation in PROX reactions on various supported metals are also discussed.

The existing literature suggests it is particularly difficult to access the catalytically relevant, and relatively complex, intermetallic γ-brass crystal structure through traditional nanoparticle (NP) synthesis techniques. We introduce a simple and rational approach to access this phase in M-Zn (M = Pd, Cu, Ni) systems as silica-supported single-phase nanocrystals. This hybrid approach involves the initial synthesis of supported M/SiO2 through traditional approaches (dry impregnation and strong electrostatic adsorption) followed by heating to high temperatures in the presence of a stoichiometric amount of metallic Zn in an evacuated closed system for several hours. We demonstrate the generality of this method with three different catalytically important bimetallic systems: Pd-Zn, Ni-Zn and Cu-Zn. Of these three, Pd-Zn is by the far the most popular in terms of catalytic applications and yields the smallest particle size (∼8 nm). We tested the influence of various synthesis parameters on phase purity and particle size distribution in case of the synthesized γ-brass Pd-Zn/SiO2 supported catalysts and provide general guidelines towards optimization of synthesis. Upon transformation of Pd/SiO2 to γ-brass Pd-Zn/SiO2, a precipitous drop in CO adsorption and a 25 kJ/mol increase in the ethylene hydrogenation barrier is observed, indicating the catalytic active sites are significantly modified as a result of alloying. We anticipate these catalysts may find applications in various Pd-catalyzed chemistries.

In this article, we highlight the growing application of intermetallic compounds in heterogeneous catalysis. We clearly discuss intermetallics as distinct from other multi-metallic systems (such as alloys, surface modifiers and dopants). Intermetallics possess a number of attributes over random alloys (i.e., solid solutions) and serve as model catalysts for a number of industrially relevant reactions. We review a variety of methods used for the synthesis of a large number of intermetallic compounds and discuss how standard material characterization techniques can be extended to intermetallics to gain important insight regarding active site morphology, a critical metric in heterogeneous catalyst design. We further summarize the use of intermetallics in understanding changes in reactivity and selectivity due to geometric and electronic effects, with emphasis on determining compositional and structural factors of the active site. We conclude with a brief summary of avenues for future advances in the field and its potential to contribute to environment and economy.

The major products from hydrothermal reactions of tryptophan at 350 and 400 °C in the absence of catalyst were indole and methyl indoles, indicating simultaneous deoxygenation and deamination. In the presence of carbon-supported Ni and NiM catalysts (M = Ru, Cu, Pd, Pt) primary aromatic amines also appeared, via cleavage of the heterocyclic ring of the indoles. Ni and NiCu catalysts have the lowest selectivity for the formation of this family of compounds, while NiRu had the highest selectivity. Catalysts containing noble metals also produced monosubstituted alkylaromatics, due to the deamination of the aromatic amines, with the NiPt catalyst providing the highest molar yield (∼7%). We propose catalytic and non-catalytic hydrothermal reaction pathways for tryptophan based on the observed product distributions. The bimetallic particles were smaller than the pure Ni particles and the surfaces of NiRu and NiPd particles were enriched in Ni, relative to the nominal bulk composition.

The local structures of rhodium complexes derived from the immobilization of Wilkinson’s complex, RhCl(PPh3)3, on SBA-15 silica functionalized with primary–amine, secondary–amine, or diphenylphosphine groups within the mesoporous channels were characterized by a series of techniques including XRD, HR-TEM, multinuclear (13C/29Si/31P) solid-state NMR, 2D 31P{1H} HETCOR NMR, XPS, and Rh K-edge EXAFS. Immobilization of RhCl(PPh3)3 through covalent bond formation with different functional groups grafted to the silica surface lead to variations in the local structure of the Rh center that has important implications for catalysis. The immobilized Rh complexes demonstrated high activity for the addition of alkynes with thiols (hydrothiolation) or sulfonic acids (hydrosulfonation) with excellent regio- and stereoselectivity under mild reaction conditions. This work demonstrates the elucidation of the local structure of the immobilized Rh complexes requires a complimentary multi-technique characterization approach that probes both the metal center itself and surrounding ligands.

The activity and selectivity of activated-carbon-supported Ni, Pt, Ru, and Ni-Ru bimetallic catalysts was examined for hydrothermal denitrogenation of indole. The molar yield of pyrrole ring-opening compounds, without an added hydrogen source, are in the order: Ni

X-ray photoelectron spectra were obtained for a series of M–TiO2 samples in which transition metal ions are directly attached to the surface of anatase TiO2 nanocrystals. The samples were prepared using CrCl3·nH2O, MnCl2·nH2O, FeCl2·nH2O, CoCl2·nH2O, NiCl2·nH2O, and CuCl2·nH2O as metal sources. We observed spontaneous air oxidation of the metal for the Mn–TiO2 and Fe–TiO2 samples as indicated by rapid color changes. X-ray photoelectron spectroscopy (XPS) data confirms the oxidation states of the metals Cr, Co, and Ni are unchanged from the precursor, Mn and Fe are oxidized, and Cu is in a more reduced state. The reduction of Cu likely arises during the XPS experiment – a phenomenon well-documented in the literature; whereas UV–Vis data of the Cu–TiO2 dispersions are consistent with Cu2+.

Silica-supported Pd and PdZn nanoparticles of a similar size were evaluated for neopentane hydrogenolysis/isomerization and propane hydrogenolysis/dehydrogenation. Monometallic Pd showed high neopentane hydrogenolysis selectivity. Addition of small amounts of Zn to Pd lead Pd–Zn scatters in the EXAFS spectrum and an increase in the linear bonded CO by IR. In addition, the neopentane turnover rate decreased by nearly 10 times with little change in the selectivity. Increasing amounts of Zn lead to greater Pd–Zn interactions, higher linear-to-bridging CO ratios by IR and complete loss of neopentane conversion. Pd NPs also had high selectivity for propane hydrogenolysis and thus were poorly selective for propylene. The PdZn bimetallic catalysts, however, were able to preferentially catalyze dehydrogenation, were not active for propane hydrogenolysis, and thus were highly selective for propylene formation. The decrease in hydrogenolysis selectivity was attributed to the isolation of active Pd atoms by inactive metallic Zn, demonstrating that hydrogenolysis requires a particular reactive ensemble whereas propane dehydrogenation does not.

Isotopic labeling and density functional theory (DFT) were used to determine the mechanism for acetylene hydrogenation and oligomerization on well-defined intermetallic nickel–zinc catalysts. The primary benefit of adding zinc to nickel is a reduction in oligomeric species formation which leads to higher ethylene selectivity. The production of ethane is not highly dependent on zinc content; therefore, ethane production is not a good descriptor of ethylene selectivity since acetylene may also be converted to higher molecular weight products. Analysis using DFT and Langmuir–Hinshelwood kinetics shows that the large decrease in the adsorption energy of acetylene on intermetallic NiZn compared to pure Ni is responsible for the observed increase in ethylene selectivity. The adsorption energy of acetylene appears to be a descriptor for carbon–carbon bond formation since a high adsorption energy leads to an increased coverage of C2 species and an increased rate of carbon–carbon bond formation.

We present a thermodynamic study of the chelate effect for a series of P–P, N–N, and P–N bidentate ligands binding to PdCl2(MeCN)2 in acetonitrile (MeCN), using isothermal titration calorimetry (ITC) to measure the solution-phase binding thermodynamics. The chelate effect is considered to be an entropic effect, that is, the enthalpic contributions attributed to binding for comparable monodentate and bidentate ligands are nearly identical, meaning that changes in ΔG are due to favorable changes in ΔS upon displacement of bound solvent molecules. However, our results demonstrate that enhanced enthalpic contributions (i.e. large and exothermic) control the stability of the chelated complexes and generally are accompanied by large entropic penalties. We discuss the contribution of solvent reorganization and its role in enthalpy–entropy compensation for the binding equilibria studied.

Micropatterned poly(dimethylsiloxane) substrates fabricated by soft lithography led to large-scale orientation of myoblasts in culture, thereby controlling the orientation of the myotubes they formed. Fusion occurred on many chemically identical surfaces in which varying structures were arranged in square or hexagonal lattices, but only a subset of patterned surfaces yielded aligned myotubes. Remarkably, on some substrates, large populations of myotubes oriented at a reproducible acute angle to the lattice of patterned features. A simple geometrical model predicts the angle and extent of orientation based on maximizing the contact area between the myoblasts and patterned topographic surfaces. Micropatterned substrates also provided short-range cues that influenced higher-order functions such as the localization of focal adhesions and accumulation of postsynaptic acetylcholine receptors. Our results represent what we believe is a new approach for musculoskeletal tissue engineering, and our model sheds light on mechanisms of myotube alignment in vivo.

The influence of particle size on the poisoning of ethylene hydrogenation by CO was studied over a series of catalysts composed of nearly monodisperse Pt nanoparticles (1.7–7.1 nm) encapsulated in mesoporous silica (SBA-15). The turnover frequency at 403 K in the presence of 0.5 Torr CO was ∼2 × 10−2 s−1 (compared with ∼102 s−1 in the absence of CO). The apparent activation energy in the absence and presence of 0.2 Torr CO was ∼10 and 20 kcal mol−1, respectively. The pressure dependency changes significantly in the presence of CO; reaction orders in hydrogen were 1/2 in the presence of CO at 403 K and noncompetitive with regard to co-adsorption with C2H4. In the absence of CO at similar temperatures, H2 adsorption was primarily irreversible (first-order dependence), and H2 and C2H4 compete for the same sites. Ethylene orders at 403 K were first order in the presence of 0.2 Torr CO and remained unity with increasing CO pressure. At similar reaction conditions in the absence of CO, ethylene had an inhibitory effect (negative reaction order) on the overall hydrogenation reaction. The change in C2H4 and H2 kinetics suggests strong competitive adsorption between C2H4 and CO for the same type of site, whereas H2 apparently adsorbs on distinct surface sites due either to steric hindrance or H2-induced CO desorption. Incorporation of a quasi-equilibrated CO adsorption step into a noncompetitive Langmuir–Hinshelwood mechanism predicts the experimentally observed pressure dependencies and a doubling of the apparent activation energy. Hydrogenation of ethylene in the presence of 1 Torr CO was examined under reaction conditions at 403 K by infrared spectroscopy; the only surface species identified under reaction conditions was linear-bound CO. The hydrogenation of ethylene on clean Pt catalysts was structure-insensitive and remains insensitive in the presence of CO; rates decreased only by a factor of two with increasing particle size.

The oxidation and reforming kinetics of methane by O 2 , CO 2 and H 2 O were studied on a stepped Pt(5 5 7) single crystal from 623 to 1050 K under methane rich conditions. The rate of carbon deposition was followed by ex-situ Auger electron spectroscopy under non-oxidative conditions. The apparent activation energy for methane decomposition was significantly lower than the apparent barriers measured for both total oxidation, CO 2 and H 2 O reforming. Total oxidation of methane to CO 2 and H 2 O followed by combined dry and steam reforming (combined combustion-reforming) led to CO production rates which were higher than direct CO 2 or H 2 O reforming rates. The enhanced rates are most likely due to the ability of adsorbed oxygen to prevent carbon nucleation and/or scavenge carbon enabling the reforming reaction to turnover on a larger fraction of sites. Comparable amounts of carbon were found by Auger electron spectroscopy measurements after both direct dry or steam reforming, while combined oxidation-reforming had considerable less carbon. During direct dry or steam reforming, CO 2 and H 2 O serve only to scavenge adsorbed atomic carbon, while in the presence of oxygen, carbon is removed by both combustion and reforming routes.

The influence of substituent effects and CO poisoning were examined during the hydrogenation/dehydrogenation of cycloalkenes (cyclohexene and 1- and 4-methylcyclohexene) on a Pt(111) single crystal. Reaction rates for both hydrogenation and dehydrogenation decreased when a methyl group was added to the cycloalkene ring. The location of a methyl group relative to the C C double bond was influential in the overall kinetics for both reaction pathways. All cycloalkenes demonstrated “bend-over” Arrhenius behavior, after which rates for hydrogenation and dehydrogenation decreased with increasing temperature (inverse Arrhenius behavior). This is explained in terms of a change in surface coverage of the reactive cycloalkene. The potential importance of hydrogen effects is discussed. Introduction of CO in the Torr pressure range (0.015 Torr) led to a decrease in turnover frequency and increase in apparent activation energy for both the hydrogenation and dehydrogenation of all cycloalkenes. Sum frequency generation (SFG) surface vibrational spectroscopy revealed that upon adsorption, the three cycloalkenes form a surface species with similar molecular structure. SFG results under reaction conditions in the presence of CO demonstrated that the cycloalkene coverage is low on a CO-saturated surface. Substituted cyclohexenes were more sensitive than cyclohexene to the presence of adsorbed CO, with larger increases in the apparent activation energy, especially in the case of dehydrogenation. A qualitative explanation for the changes in activity with temperature and the increase in apparent activation energy for cycloalkene hydrogenation/dehydrogenation in the presence of CO is presented from a thermodynamic and kinetic perspective.

The kinetics of isopropyl alcohol (IPA) dehydrogenation over carbon-supported Pt and three bimetallic Cu Pt catalysts were examined and compared with previous results for carbon-supported Cu. Adsorption of H 2 and CO, dissociative chemisorption of N 2 O, and the titration of adsorbed O atoms by H 2 and CO were used to determine surface compositions and metal dispersion. Monometallic platinum catalysts had a higher specific activity than monometallic Cu catalysts and the bimetallic catalysts; for example, at 448 K and 14 Torr IPA, for an activated carbon heat treated at 1223 K as the support, the turnover frequency (TOF) on the Pt catalyst was 0.11 s −1 , the TOF on the Cu catalyst was 0.020 s −1 , and the TOFs on the three bimetallic catalysts were between 0.006 and 0.043 s −1 . Reaction orders were typically between 0 and 1 2 for IPA and slightly negative for acetone and H 2 . Increasing the Cu loading reduced the number of surface Pt atoms, and the kinetic behavior became similar to that of monometallic copper catalysts. The apparent activation energy for acetone production from IPA on Pt/C was 6.8 kcal mol −1 , compared with 21 kcal mol −1 for the monometallic Cu/C catalysts. Apparent activation energies for the Cu Pt/C catalysts (7–9 kcal mol −1 ) were comparable to those of Pt/C at lower temperatures and decreased further to ∼ 3 kcal mol −1 above 443 K. This decrease is not due to diffusional limitations and can be explained by a decrease in the surface coverage of IPA. A Langmuir–Hinshelwood model invoking cleavage of the alcohol O H bond to form a surface isopropoxide species as the rate-determining step fit the data well and accounted for the shift in the apparent activation energy. Physically meaningful values of enthalpies and entropies of adsorption were obtained from the fitting parameters contained in the L-H rate expression. Additional evidence for adsorbed IPA and acetone was provided by infrared spectra of the catalysts obtained under reaction conditions.

Catalysis in the 20th century focused primarily on activity, increasing turnover rates to produce more molecules per unit time. High selectivity was of lesser concern because disposal of undesirable byproducts was not costly and raw materials were abundant. This has changed in the 21st century because waste disposal is now expensive and the negative ecological impacts are well-documented. As a result, the present focus and roadmap of catalysis science is to achieve high selectivity in all catalyst-based chemical processes. Our knowledge of the molecular ingredients that influence selectivity is poor compared to our understanding of activity. There are six identifiable features that influence both catalyst activity and selectivity. They are metal surface structure, bonding modifier additives, mobility of metal clusters to restructure as well as the mobility of adsorbates on these clusters, selective site blocking, bifunctionality, and oxide-metal interface sites. Identification of the molecular ingredients of catalyst activity and selectivity provides opportunity for catalyst design, combined catalyst synthesis, characterization and reaction studies. In order to obtain high selectivity towards the ultimate goal of 100% selectivity, synthetic methods that enable molecular control over the size, location, structure of the metallic nanoparticles and catalyst promoters must be developed. We are attempting to do this by fabricating two- and three-dimensional catalysts. Two-dimensional nanoparticle or nanowire array catalysts are fabricated by electron beam lithography (EBL) or size reduction lithography (SRL). Arrays with metal surface areas of about 1 mm 2 or 10 9 nanoparticles are fabricated by EBL. These model catalyst systems enable the study of high-turnover reactions such as ethylene hydrogenation. SRL and a lithographic polymer imprinting technique are used to produce nanowire or nanodot array model catalysts with metallic surface areas up to 1 cm 2 or 10 11 nanoparticles. High surface area (1 m 2 or 10 15 nanoparticles) is produced by a one-step method in which polymer-stabilized monodisperse nanoparticles are synthesized in solution and incorporated into high-surface area mesoporous silica mechanically or through hydrothermal synthesis. Both types of model catalysts are characterized by a variety of physical and chemical techniques and are catalytically active for hydrocarbon conversion test reactions. Our catalyst design approach combines synthesis (fabrication), characterization and reaction studies.

Deuterium isotope exchange was employed to investigate some of the reaction steps for the hydrodechlorination of CF 3 CFHCl and CH 3 CH 2 Cl on supported Pd catalysts. Hydrodechlorination rates for both compounds using D 2 or H 2 were identical. It is concluded that H or D species are not involved in the rate-determining step of the hydrodechlorination reaction. Experiments using a combined H 2 and D 2 feed for hydrodechlorination of CF 3 CFHCl showed that CF 3 CFH 2 was preferentially formed over CF 3 CFHD. This experimental observation can be explained by isotope effects and is consistent with gas phase H 2 in equilibrium with adsorbed H and a reaction step consisting of the combination of surface adsorbed CF 3 CFH species with adsorbed H. Deuterated product distributions of CF 3 CFHCl and CH 3 CH 2 Cl hydrodechlorination experiments with D 2 were analyzed to explore the reaction steps beyond the kinetically relevant steps. The main product of CF 3 CFHCl hydrodechlorination was CF 3 CFHD, showing that the CCl bond is preferentially broken. In the case of CH 3 CH 2 Cl, substantial CH bond breaking accompanies the initial CCl scission. Deuterium exchange experiments with ethane on Pd/C and Pd/ZrO 2 were also investigated and the results indicate that the CH 3 CH 2 Cl product distribution is not caused by re-adsorption and subsequent exchange reaction of ethane.

For accurate catalyst comparisons and kinetic modeling, data free of mass and heat transfer effects must be acquired over a range of temperature and reactant concentrations using well-characterized heterogeneous catalysts. For semibatch reactors operated at constant pressure, selectivity vs conversion profiles at several temperatures, preferably obtained with catalysts reduced in situ, are required to allow complicated reaction networks to be defined. Vapor-phase isopropyl alcohol (IPA) dehydrogenation over carbon-supported Cu catalysts in a differential fixed-bed reactor was studied and compared to UHP Cu powder and a Cu chromite catalyst. Low dispersions of Cu (ca. 0.02–0.17) were obtained in all these catalysts. Cu dispersed on an activated carbon heat-treated at 1223 K had the highest turnover frequency (0.052 s−1 at 448 K) of all the Cu/C catalysts, more than double that on an industrial Cu chromite catalyst; thus the rate with this 5.0% Cu/C catalyst (6.0 μmol s−1 g−1) was close to that of the chromite catalyst containing 41% Cu (10.6 μmol s−1 g−1). The steady-state selectivity to acetone was 100% for all catalysts except those containing the nitric-acid-treated carbon. In the absence of Cu, the nitric-acid-treated carbon produced propylene under steady-state reaction conditions, and reduction at 573 K decreased activity compared to reduction at 423 K. This dehydration reaction is associated with the presence of oxygen-containing acidic groups on the C surface. The apparent activation energy for acetone formation was typically near 20 kcal mol−1 for all the Cu/C catalysts and the Cu powder, but it was near 12 kcal mol−1 for the Cu chromite catalyst. A DRIFT spectrum under reaction conditions indicated the presence of an isopropoxide species and molecularly adsorbed IPA on the surface. A Langmuir–Hinshelwood mechanism, which assumed removal of the first hydrogen atom as the rate-determining step and incorporated adsorbed IPA, hydrogen, acetone, and a surface isopropoxide species into the site balance, fit the kinetic data well and gave physically meaningful values for the enthalpies and entropies of adsorption.

Reaction steps for the reaction of hydrodechlorination on Pd were investigated by means of isotope-exchange experiments. The reversibility of bond scission for the two C–Cl bonds in CF3CFCl2 was investigated by following 37Cl enrichment in the reactant and products. No enrichment of 37Cl was observed in the reactant CF3CFCl2 but the product CF3CHFCl was enriched. Thus, the scission of the first C–Cl bond is irreversible; once the reactant loses the first chlorine it desorbs only as a product. However, after the first C–Cl bond is broken, the second chlorine may be exchanged with the pool of surface chlorine. Isotope exchange experiments between D2 and HCl during hydrodechlorination of CF3CFCl2 showed that the forward rate and reverse rate for the overall reaction H2+2Cl*=2HCl+2* were nearly 400 times faster than the overall hydrodechlorination reaction rate. Thus, this experiment confirms that this step is in quasi-equilibrium.

The reaction of hydrodechlorination for the chlorofluorocarbons (CFCs) CF 3 –CFCl 2 and CF 3 –CCl 3 was studied over Pd supported on carbon and Pd black catalysts. The rates and selectivity were similar on all samples although Pd black samples had a higher selectivity for the more hydrogenated products. The difference in selectivity and rate for Pd black is attributed to the presence of an impurity on the surface. The reaction orders are about first order in CFC, half-order in H 2 , and inverse first-order in HCl. These results indicate that the irreversible adsorption of CFC is the rate-determining step and that H 2 and HCl are equilibrated with hydrogen and chlorine on the surface. Experiments with D 2 on CF 3 –CFHCl confirm that the adsorption step is irreversible.

Catalyst T RED (K) CO uptakea (μmol g−1) COT/CuT COirr/CuT ‘O’ uptakeb (μmol g−1) Cu0 disp. dc (nm) Total Irreversible 4.96% Cu/AC–HNO3 423 170.0 62.0 0.218 0.079 12.1 0.031 35.5 473 35.4 6.1 0.045 0.008 18.3 0.047 23.5 573 19.6 0.0 0.025 0.0 16.5 0.042 26.0 4.89% Cu/AC–ASIS 423 54.0 0.0 0.070 0.0 0.0 0.0 0.0 473 54.6 0.0 0.071 0.0 8.8 0.023 48.1 573 51.6 0.0 0.067 0.0 16.6 0.043 25.5 5.01% Cu/AC–HTT–H2 423 79.4 5.7 0.101 0.007 54.0 0.137 8.0 473 83.5 5.6 0.106 0.007 58.9 0.149 7.4 573 59.1 0.0 0.075 0.0 67.3 0.171 6.4 0.98% Cu/AC–HTT–H2 473 52.5 1.1 0.340 0.007 11.1 0.144 7.6 573 53.2 0.0 0.345 0.0 8.9 0.115 9.5 0.63% Cu/GF-IE 573 0.0 0.0 0.0 0.0 0.9d 0.018 60.6 Cu powder 573 – – – – 1.8d 2.3 × 10−4 ∼4800 Cu chromite 573 55.0 18.3 0.009 0.003 181.5 0.056 19.6 a Volumetric uptakes at 75 Torr corrected for irreversible uptake on support. b Uptakes at 363 K and 75 Torr N2O determined gravimetrically. c Cu crystallite size based on d = 1.1/(2Oad/CuT). d Determined volumetrically.