Effect of the reduction–preparation method on the surface states and catalytic properties of supported-nickel particles

CO adsorption microcalorimetry was employed in the study of γ-Al2O3-supported Pt, Pt-Sn and Pt-Fe catalysts. The results indicated that the initial differential heat of CO adsorption of the Pt/γ-Al2O3 catalyst was 125 kJ/mol. As CO coverage increased, the differential heat of adsorption decreased. At higher coverages, the differential heat of adsorption decreased significantly. 60% of the differential heat of CO adsorption on the Pt/γ-N2O3 catalyst was higher than 100 kJ/mol. No significant effect on the initial differential heat was found after adding Sn and Fe to the Pt/γ-Al2O3 catalyst. The amount of strong CO adsorption sites decreased, while the portion of CO adsorption sites with differential heat of 60–110 kJ/mol increased after increasing the Sn or Fe content. This indicates that the surface adsorption energy was changed by adding Sn or Fe to Pt/γ-N2O3. The distribution of differential heat of CO adsorption on the Pt-Sn(C)/γ-Al2O3 catalyst was broad and homogeneous. Comparison of the dehydrogenation performance of C4 alkanes with the number of CO adsorption sites with differential heat of 60–110 kJ/mol showed a good correlation. These results indicate that the surface Pt centers with differential heats of 60–110 kJ/mol for CO adsorption possess superior activity for the dehydrogenation of alkanes.

Changes in the selective hydrogenation of citral induced by copper addition to Ru/KL catalysts

Techniques such as adsorption microcalorimetry and the dehydrogenation of alkenes are used to measure the differential heats of adsorption and reactivity of several catalyst surfaces. An adsorption microcalorimeter built specifically to determine adsorption heats is employed. CO was used as the probe molecule in this study and was adsorbed on the following catalysts: Pd/mordenite, Pd–Pt/mordenite, and Pd–Ir/mordenite. The results show that the differential heat of adsorption was between 50 and 150 kJ/mol. The adsorption heat decreases with an increased in CO coverage for all catalysts. The best conversion for alkene studies was seen on the Pd–Ir/mordenite, which was close to 70%.

Adsorption microcalorimetry has been employed to study the interaction of ethylene with the reduced and oxidized Pt-Ag/SiO2catalysts with different Ag contents to elucidate the modified effect of Ag towards the hydrocarbon processing on platinum catalysts. In addition, microcalorimetric adsorption of H2, O2, CO and FTIR of CO adsorption were conducted to investigate the influence of Ag on the surface structure of Pt catalyst. It is found from the microcalorimetric results of H2and O2adsorption that the addition of Ag to Pt/SiO2leads to the enrichment of Ag on the catalyst surface which decreases the size of Pt surface ensembles of Pt-Ag/SiO2catalysts. The microcalorimetry and FTIR of CO adsorption indicates that there still exist sites for linear and bridged CO adsorption on the surface of platinum catalysts simultaneously although Ag was incorporated into Pt/SiO2. The ethylene microcalorimetric results show that the decrease of ensemble size of Pt surface sites suppresses the formation of dissociative species (ethylidyne) upon the chemisorption of C2H4on Pt-Ag/SiO2. The differential heat vs. uptake plots for C2H4adsorption on the oxygen-preadsorbed Pt/SiO2and Pt-Ag/SiO2catalysts suggest that the incorporation of Ag to Pt/SiO2could decrease the ability for the oxidation of C2H4.

Effect of nickel precursor and the copper addition on the surface properties of Ni/KL-supported catalysts for selective hydrogenation of citral

Influence of the nature of support on Ru-supported catalysts for selective hydrogenation of citral

Surface study of graphite-supported Ru–Co and Ru–Ni bimetallic catalysts

Surface sites on carbon-supported Ru, Co and Ni nanoparticles as determined by microcalorimetry of CO adsorption

Interaction of CO probe molecules with Cu(+) in MCM-22 zeolite

Adsorption of CO and NO individually and as a mixture of both on palladium catalysts has been investigated by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The effect of sodium ions has been considered by comparing Pd/SiO2 catalyst, sodium-doped Pd/SiO2, and Pd on natural and synthetic silicoaluminates containing sodium in their bulk structure but differing in the surface area of the support. The presence of sodium induces a different adsorption behavior depending on its location, either at the surface of the catalysts or inside the support structure. As a consequence, different species are formed from the reaction between NO and CO at room temperature and at high temperature. Modification of the metal surface of the various catalysts is observed upon the gas treatments. Palladium is oxidized to a certain extent depending on the type of the catalyst support. Moreover, different chemical states of the adsorbed nitrogen species are found.

Introduction The authors reported that PtPb and PtBi intermetallic compounds exhibited high and stable activity for MeOH and EtOH in alkaline aqueous solutions on the basis of examinations of various Pt-based intermetallic compounds.1) The results revealed that the PtPb intermetallic compound exhibited the highest oxidation activity for MeOH and EtOH, and the PtBi intermetallic compound had the highest durability among the Pt-based intermetallic compounds examined in the study. The electrocatalytic activity strongly depended on the type of second element in the Pt-based intermetallic compounds. In addition, authors and coworkers have reported that the electrocatalytic activity of the oxygen reduction reaction (ORR) can be related to the d-band center of Pt in Pt materials and Pt-based NPs. In short, a so-called volcano-type correlation between the ORR activity and the d-band center was maintained for a series of catalysts prepared in this research (Fig. 1).2, 3) To continue this discussion, the volcano-type correlation between the electrocatalytic activity and the d-band center of Pt in catalysts should be investigated in electrochemical reactions other than the ORR. In this study, the electrochemical oxidation of MeOH and EtOH on Pt-based alloy catalysts in alkaline aqueous solution is the targeted reaction for investigations of the volcano-type correlation. To systematically change the values of the d-band center, the type and elemental ratio of the secondary element in the Pt-based NPs were controlled by the conditions used to synthesize the NPs. Experimental To examine the relationship between the electronic state of platinum (Pt) in Pt-based nanoparticle (NP) catalysts and their catalytic activities in the electrochemical oxidation of methanol (MeOH) and ethanol (EtOH) in alkaline aqueous solutions, Pt-based NP catalysts were synthesized (Table 1), their electrocatalytic activities were evaluated by rotating electrode techniques, and the electronic state of Pt in Pt-based catalyst surfaces was analyzed via X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS). Finally, plots of the electrocatalytic activity vs. electronic state of the Pt atoms on the catalyst surface were obtained.4) Results and discussion XPS and XAS measurements were used to evaluate the electronic state of the electrode catalyst. In addition, to confirm the change in the electronic state of Pt in the Pt-based NPs, the adsorption of CO onto the catalyst surfaces was investigated, and the relationship between the oxidation potential of the adsorbed CO and the catalytic activity was confirmed. The relationship between the electronic state of Pt in the catalyst and the catalytic activity shows a volcano-shaped trend (Fig. 2), indicating that there is a suitable electronic state that maximizes the catalytic activity. Among the samples examined in this study, PtPb1.1 showed the highest activity, which is thought to be due to its optimal electronic and atomic configuration. Strictly speaking, the XPS and XAS measurement results used in this study do not reflect the electronic state of the catalyst outermost surface. In this regard, we believe that measurement methods that can obtain information only from the surface should be applied to samples to obtain surface information. A careful look at the plots of the results reveals that there is another small peak in the volcano-shaped plot. The reason for this small peak is currently under investigation. We will investigate the reason for this in the future, as it is believed to provide important information regarding the reaction mechanism and catalytic activity. In order to clarify the relationship between the structural factor of the catalyst and its catalytic activity in the analysis, the electronic state of surface atoms must be determined using a single crystal with a regulated structure. It is also necessary to investigate the structure in more detail in conjunction with other measurements, and this is currently under consideration. References (1) F. Matsumoto, Electrochemistry 2012, 80, 132–138.(2) F. Ando, T. Gunji, T. Tanabe, I. Fukano, H.D. Abruña, J. Wu, T. Ohsaka, F. Matsumoto, ACS Catalysis 2021, 11, 9317–9332.(3) F. Ando, T. Tanabe, T. Gunji, S. Kaneko, T. Takeda, T. Ohsaka, F. Matsumoto, ACS Applied Nano Materials 2018, 1, 2844–2850.(4) F. Matsumura, M. Fukunishi, F. Matsumoto, ACS Omega, 2025, 10, 10060-10070. Figure 1

Surface study of rhodium nanoparticles supported on alumina

Determination of the surface states of metallic clusters supported on alumina using microcalorimetry of CO adsorption

To date, microcalorimetry of CO adsorption onto supported metal catalysts was mainly used to study the effects induced by the nature and the particle size of supported metallic clusters, the conditions of pretreatment and the support materials on the surface properties of the supported metallic particles. The present chapter focuses on the employ of adsorption microcalorimetry for studying the interaction of carbon monoxide with platinum-based catalyst aimed to be used in proton exchange membrane fuel cells (PEMFCs ) applications.

Effect of the functional groups of carbon on the surface and catalytic properties of Ru/C catalysts for hydrogenolysis of glycerol