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N-doped carbon (N-C) materials are increasingly popular in different electrochemical and catalytic applications. Due to the structural and stoichiometric diversity of these materials, however, the role of different functional moieties is still controversial. We have synthesized a set of N-C catalysts, with identical morphologies (∼27 nm pore size). By systematically changing the precursors, we have varied the amount and chemical nature of N-functions on the catalyst surface. The CO2 reduction (CO2R) properties of these catalysts were tested in both electrochemical (EC) and thermal catalytic (TC) experiments (i.e., CO2 + H2 reaction). CO was the major CO2R product in all cases, while CH4 appeared as a minor product. Importantly, the CO2R activity changed with the chemical composition, and the activity trend was similar in the EC and TC scenarios. The activity was correlated with the amount of different N-functions, and a correlation was found for the -NO x species. Interestingly, the amount of this species decreased radically during EC CO2R, which was coupled with the performance decrease. The observations were rationalized by the adsorption/desorption properties of the samples, while theoretical insights indicated a similarity between the EC and TC paths.

Different Co contents were used to tune bimetallic Pt–Co nanoparticles with a diameter of 8 nm, resulting in Pt:Co ratios of 3.54, 1.51, and 0.96. These nanoparticles were then applied to the MCF-17 mesoporous silica support. The synthesized materials were characterized with HR-TEM, HAADF-TEM, EDX, XRD, BET, ICP-MS, in situ DRIFTS, and quasi in situ XPS techniques. The catalysts were tested in a thermally induced reverse water–gas shift reaction (CO2:H2 = 1:4) at atmospheric pressure in the 200–700 °C temperature range. All bimetallic Pt–Co particles outperformed the pure Pt benchmark catalyst. The nanoparticles with a Pt:Co ratio of 1.51 exhibited 2.6 times higher activity and increased CO selectivity by 4% at 500 °C. Experiments proved that the electron accumulation and alloying effect on the Pt–Co particles are stronger with higher Co ratios. The production of CO followed the formate reaction pathway on all catalysts due to the face-centered-cubic structure, which is similar to the Pt benchmark. It is concluded that the enhanced properties of Co culminate at a Pt:Co ratio of 1.51 because decreasing the ratio to 0.96 results in lower activity despite having more Co atoms available for the electronic interaction, resulting in the lack of electron-rich Pt sites. [ABSTRACT FROM AUTHOR]

The implementation of supported metal catalysts heavily relies on the synergistic interactions between metal nanoparticles and the material they are dispersed on. It is clear that interfacial perimeter sites have outstanding skills for turning catalytic reactions over, however, high activity and selectivity of the designed interface‐induced metal distortion can also obtain catalysts for the most crucial industrial processes as evidenced in this paper. Herein, the beneficial synergy established between designed Pt nanoparticles and MnO in the course of the reverse water gas shift (RWGS) reaction resulted in a Pt/MnO catalyst having ≈10 times higher activity compared to the reference Pt/SBA‐15 catalyst with >99 % CO selectivity. Under activation, a crystal assembly through the metallic Pt (110) and MnO evolved, where the plane distance differences caused a mismatched‐row structure in softer Pt nanoparticles, which was identified by microscopic and surface‐sensitive spectroscopic characterizations combined with density functional theory simulations. The generated edge dislocations caused the Pt lattice expansion which led to the weakening of the Pt−CO bond. Even though MnO also exhibited an adverse effect on Pt by lowering the number of exposed metal sites, rapid desorption of the linearly adsorbed CO species governed the performance of the Pt/MnO in the RWGS. [ABSTRACT FROM AUTHOR]

Zn- and Mn-doped Cerium-oxide based catalyst textured as a solid solutional as well as interfacial form was compared in CO2 hydrogenation reaction to understand the role of texture as well as dopant type. Ce0.9M0.1O2 (M = Zn, Mn) solid solution was prepared by hydrothermal method and CeO2 supported 10 mol% metal oxide (Metal = Zn, Mn) were prepared by wet impregnation method, where the catalysts were characterized by XRD, N2 adsorption/desorption isotherm, TEM, Raman spectra, HAADF-STEM and H2-TPR. During the CO2 activation reaction, CO was the major product with minor amounts of methane, ethane, methanol and ethanol. In the case of the Zn-doped CeO2 catalyst, the presence of Zn improved catalytic activity in both solid solutional and interfacial form due to the synergetic effect of Zn-Ce-based oxide. However, for MnOx/CeO2 catalysts, the CO2 consumption rate significantly decreased for 10 mol% MnOx/CeO2, Ce0.9Mn0.1O2 and Mn3O4, where the MnOx addition inhibits the reduction of CeO2. In the case of the pure CeO2, DRIFTS spectra show that formate intermediate formed by reaction between activated CO2 and OH transformed into methoxy species through formaldehyde intermediates, which leads to the formation of small amount of methanol and ethanol. [ABSTRACT FROM AUTHOR]

Abstract: The photocatalytic transformation of methane-water mixture over Rh and Au catalysts supported on protonated (H-form) titanate nanotube (TNT) was investigated. The role of the catalyst structure was analyzed using titania reference support. Furthermore the effect of carbon-dioxide addition was also investigated. The catalysts were characterized by high resolution transmission electron microscopy and X-ray photoelectron spectroscopy (XPS). Photocatalytic tests were performed with a mercury-arc UV source illuminating a continuous flow quartz reactor which was attached to a mass spectrometer. The surface of the catalysts was analyzed by diffuse reflectance infrared spectroscopy during the photoreactions. The changes of the catalysts due to photocatalytic usage were investigated by XPS and temperature programmed reduction methods as well. Most of the methane was generally transformed to hydrogen and ethane, and a small amount of methanol was also formed. The carbon dioxide addition enhanced the rate of the photocatalytic transformation of methane on Rh/TNT with increasing the lifetime of the electron-hole pairs. Bigger gold particles with mainly plasmonic character were more active in the reactions due to the photo induced activation of the adsorbed water. Surface carbon deposits were identified on the catalysts after the photoreactions. More oxidized carbon formed on the Au-containing catalysts than on the ones with Rh.Graphical Abstract: [ABSTRACT FROM AUTHOR]