Spectroscopic characterization of Co3O4 catalyst doped with CeO2 and PdO for methane catalytic combustion

Effects on structure by spectroscopic investigations, valence state and morphology properties of FeCo-containing SnO2 catalysts for glycerol valorization to cyclic acetals

The effects on the structure, valence state and morphological properties of FeCo-containing SnO2 nanostructured solids were investigated. The physicochemical features were tuned by distinct synthesis routes e.g., sol-gel, coprecipitation and nanocasting, to apply them as catalysts in the glycerol valorization to cyclic acetals. Based on Mössbauer and XPS spectroscopy results, all nanosized FeCoSn solids have Fe-based phases, which contain Co and Sn included in the structure, and well-dispersed Fe3+ and Fe2+ surface active sites. Raman, FTIR and EPR spectroscopies measurements of the spent solids demonstrated structural stability for the sol-gel based solid, which is indeed responsible for the highest catalytic performance, among the nanocasted and coprecipitated counterparts. Morphological and elemental analyses illustrated distinct morphologies and composition on solid surface, depending on the synthesis route. The Fe/Co and Fe/Sn surface ratios are closely related to the catalytic performance. The improved glycerol conversion and selectivities of the solid obtained by sol-gel method was ascribed to the leaching resistance and the Sn action as a structural promoter.

Toluene catalytic oxidation over gold catalysts supported on cerium-based high-entropy oxides

A series of cerium-based high-entropy oxide catalysts (the ratio of CeO2 and HEO is 1:1) was prepared by a solid-state reaction method, which exploit their unique structural and performance advantages. The Ce-HEO-T samples can achieve 100% toluene conversion rate above 328°C when they were used as catalysts directly. Subsequently, the Ce-HEO-500 exhibited the lowest temperature for toluene oxidation was used as a support to deposit different amounts of Au for a further performance improvement. Among all of prepared samples, Au/Ce-HEO-500 with a moderate content of Au (0.5 wt%) exhibited the lowest temperature for complete combustion of toluene (260°C), which decreased nearly 70°C compared with Ce-HEO-500 support. Moreover, it also showed excellent stability for 60 h with 98% toluene conversion rate. Most importantly, under the condition of 5 vol.% H2O vapour, the toluene conversion rate remained unchanged and even increased slightly compared with that in dry air, exhibiting excellent water resistance. Combined with the characterizations of XRD, SEM, TEM, BET, Raman, H2-TPR and XPS, it was found that the high dispersion of active Au NPs, the special high-entropy structure and the synergistic effect between Au and Ce, Co, Cu are the key factors when improving the catalytic performance in the Au/Ce-HEO-500 catalyst.

Neodymium (Nd) based oxide perovskite nanostructures for photocatalytic and photoelectrochemical water splitting functions

Neodymium (Nd) based perovskite (Nd_1-xCo_xFeO₃) nanostructures were processed to address the rising energy and environment crisis through offering solutions by photocatalytic and photoelectrochemical (PEC) water splitting reactions. The impact of cobalt (Co) ions on the physicochemical properties of Nd-perovskites were studied using X-ray diffraction (XRD), Raman and electron microscopic instruments. The interaction of metal ions was studied in depth via X-ray photoelectron spectroscopy (XPS). Absorption and photoluminescence signals inferred the optical band gap to be lowered and defect states to increase upon Co substitution. Improved photocatalytic efficacy in Nd_1-xCo_xFeO₃ was evaluated by comparative studies using NdFeO₃. Secondly, the enhanced conductivities in Nd_1-xCo_xFeO₃ studied via Nyquist plot was found to be advantageous in photoelectrode fabrication for PEC functions. Time-dependent photocurrent density results affirmed the stability in processed devices. Co ions were also inferred to boost the separation of charge carriers effectively. The improved performance in Nd_1-xCo_xFeO₃ nanostructures were well justified to the successful incorporation of Co ions that sway the Nd-O, Co-O and Co-Fe-O bondings and boost the photon absorption and electronic conductivity to facilitate the observed performance.

Sonically modified hierarchical FAU-type zeolites as active catalysts for the production of furan from furfural

In this study, the sonochemical-assisted desilication method was applied as a special and innovative way of preparing hierarchical zeolites. The physicochemical properties of the hierarchical zeolites prepared using the sonochemical route were compared with those prepared using the conventional desilication method. Commercial zeolite with FAU-type structure was desilicated with a sodium and tetrabutylammonium hydroxide aqueous solution (NaOH/TBAOH) for 30 min. The ultrasound treatment process was performed using a QSonica Q700 sonicator (Church Hill Rd, Newtown, CT, USA) equipped with a ½″ diameter horn. The average power of sonication was 60 W, and the frequency was 20 kHz. During the sonication procedure, the alkaline solution with the catalyst precursor and sonicator probe were placed in an ice bath to keep them at room temperature. The prepared catalyst samples were examined by ICP-OES, XRD, SEM, NMR, and nitrogen sorption techniques. The acidic properties of the prepared hierarchical zeolite samples were assessed by means of IR spectroscopy with ammonia and carbon monoxide sorption as probe molecules. All catalysts were studied in the decarbonylation of furfural into furan. Independently of the application of ultrasonic irradiation, desilication of zeolites with an NaOH/TBAOH mixture extracts comparable amounts of silicon, resulting in comparable crystallinity and acidity. On the other hand, the samples prepared in the presence of ultrasounds revealed higher both mesoporosity and enhanced catalytic properties in the reaction of decarbonylation of furfural into furan in comparison with their counterparts prepared using the conventional method.

Strong metal–support interactions in Pd/Co3O4 catalyst in wet methane combustion: in situ X-ray absorption study

CoOx inhibits Pd oxidation in CH₄ combustion in the wet feed.

Non-Noble Metal Oxide Catalysts for Methane Catalytic Combustion: Sonochemical Synthesis and Characterisation

The aim of this study was to obtain nanocrystalline mixed metal-oxide–ZrO₂ catalysts via a sonochemically-induced preparation method. The effect of a stabiliser’s addition on the catalyst parameters was investigated by several characterisation methods including X-ray Diffraction (XRD), nitrogen adsorption, X-ray fluorescence (XRF), scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectrometer (EDS), transmission electron microscopy (TEM) and µRaman. The sonochemical preparation method allowed us to manufacture the catalysts with uniformly dispersed metal-oxide nanoparticles at the support surface. The catalytic activity was tested in a methane combustion reaction. The activity of the catalysts prepared by the sonochemical method was higher than that of the reference catalysts prepared by the incipient wetness method without ultrasonic irradiation. The cobalt and chromium mixed zirconia catalysts revealed their high activities, which are comparable with those presented in the literature.