One step synthesis of Pt–Co/TiO2 catalysts by flame spray pyrolysis for the hydrogenation of 3-nitrostyrene

Liquid-Phase Selective Hydrogenation of Furfural to Furfuryl Alcohol over Ferromagnetic Element (Fe, Co, Ni, Nd)-Promoted Pt Catalysts Supported on Activated Carbon

Ferromagnetic element (x = Fe, Co, Ni, and Nd)-promoted Pt/AC catalysts were prepared by co-impregnation method or physical mixing and tested in the liquid-phase hydrogenation of furfural to furfuryl alcohol (FA) under mild conditions (50 °C and 20 bar H2) using water and methanol as the solvent. Among the various catalysts studied, the 0.15FePt/AC exhibited complete conversion of furfural with an FA selectivity of 74% after only 1 h of reaction time in water. The promotional effect of the bimetallic catalysts became less pronounced when methanol was used as the solvent and a 2-furaldehyde dimethyl acetal solvent product was formed. The superior catalyst performances were correlated with the higher Pt dispersion, the presence of low coordination Pt sites, and the strong Pt–Fe interaction as characterized by X-ray diffraction, H2 temperature-programmed reduction (H2-TPR), N2 physisorption, and infrared spectroscopy of the adsorbed CO (CO-IR). However, to simply use a magnet for catalyst separation, 0.5 wt% Fe was the minimum Fe loading on the Pt/AC. The 0.5FePt/AC still exhibited good magnetic properties after the third consecutive runs.

PtCu alloy cocatalysts for efficient photocatalytic CO2 reduction into CH4 with 100% selectivity

In this paper, PtCu alloys with varying Pt/Cu ratios were deposited onto TiO2 nanocrystals to selectively photoreduce CO2 into CH4.

Effects of TiO2 structure and Co addition as a second metal on Ru-based catalysts supported on TiO2 for selective hydrogenation of furfural to FA

The TiO2 supported Ru-based catalysts were prepared with 1.5 wt% Ru and 0-0.8 wt% Co on various TiO2 (anatase, rutile, P-25, and sol-gel TiO2) and studied in the liquid-phase selective hydrogenation of furfural to furfuryl alcohol (FA) under mild conditions (50 °C and 2 MPa H2). The presence of high anatase crystallographic composition on TiO2 support was favorable for enhancing hydrogenation activity, while the strong interaction between Ru and TiO2 (Ru-TiOx sites) was required for promoting the selectivity to FA. The catalytic performances of bimetallic Ru-Co catalysts were improved with increasing Co loading due to the synergistic effect of Ru-Co alloying system together with the strong interaction between Ru and Co as revealed by XPS, H2-TPR, and TEM-EDX results. The enhancement of reducibility of Co oxides in the bimetallic Ru-Co catalysts led to higher hydrogenation activity with the Ru-0.6Co/TiO2 catalyst exhibited the best performances in FA selective hydrogenation of furfural to FA under the reaction conditions used.

Reversed selectivity of photocatalytic CO2 reduction over metallic Pt and Pt(II) oxide cocatalysts

The chemical state of Pt in cocatalysts has a major influence on the activity and selectivity of the photocatalytic reduction of CO2; however, the underlying mechanism is unclear owing to the co-existence of different Pt chemical states and mutual transformation between them. In this study, PtO/TiO2 catalysts were prepared through photodeposition and Pt/TiO2 was prepared by the photoreduction of PtO/TiO2 to avoid interference arising from co-existing Pt forms and different loading amounts. These catalysts exhibited completely reversed selectivity for CO and CH4 production during CO2 photoreduction: PtO/TiO2 tended to produce CO (100%), whereas Pt/TiO2 favored the production of CH4 (66.6%). By combining experimental analysis and theoretical calculations, the difference in selectivity was ascribed to the different charge transfer/separation and CO/H adsorption properties of PtO/TiO2 and Pt/TiO2. Photoelectric and photoluminescence (PL) analysis showed that Pt was more advantageous to the photogenerated carrier separation compared with PtO, which was conducive to the multi-electron CH4 reduction reaction. Fourier transform-infrared spectroscopy, temperature-programmed desorption/temperature-programmed reduction, and density functional theory calculations indicated that the adsorption of CO and hydrogen on Pt was stronger than that on PtO, which favored the further reduction of CO to CH4. Based on the above results, a mechanism was proposed to explain the reversed selectivity of the photocatalytic reduction of CO2 over Pt/TiO2 and PtO/TiO2.

Selective Hydrogenation of 3-Nitrostyrene over a Co-promoted Pt Catalyst Supported on P-containing Activated Charcoal

A series of Co-modified Pt catalysts supported on P-containing activated charcoal were studied for the selective hydrogenation of 3-nitrostyrene (NS) to 3-aminostyrene (AS). The addition of Co decreased the rate of hydrogenation but enhanced the selectivity to AS, being 92% at nearly 100% conversion over an optimized catalyst. The high AS selectivity should result from the configuration of NS adsorption on the catalyst, which occurs preferentially with its -NO2 group on the Pt–POx interface layer over the surface of supported Pt particles. The formation of such a Pt–POx area is promoted by the Co additive.

Photocatalytic Liquid-Phase Selective Hydrogenation of 3-Nitrostyrene to 3-vinylaniline of Various Treated-TiO2 Without Use of Reducing Gas

In this work, we investigate the effect of TiO2 properties on the photocatalytic selective hydrogenation of 3-nitrostyrene (3-NS) to 3-vinylaniline (3-VA). The P25-TiO2 photocatalysts were calcined at 600–900 °C using different gases (Air, N2, and H2) and characterized by XRD, N2 physisorption, XPS, UV-Vis, and PL spectroscopy. In the photocatalytic hydrogenation of 3-nitrostyrene in isopropanol, the selectivity of 3-vinylaniline of the treated TiO2 was almost 100%. A linear correlation between the 3-NS consumption rate and PL intensity was observed. Among the catalysts studied, P25-700-air, which possessed the lowest PL intensity, exhibited the highest photocatalytic activity due to the synergistic effect that resulted from its high crystallinity and the optimum amount of anatase/rutile phase content, leading to the reduction of the electron-hole recombination process.

Engineering TiO2 supported Pt sub-nanoclusters via introducing variable valence Co ion in high-temperature flame for CO oxidation

As a typical catalytic reaction model, CO catalytic oxidation has many practical applications in gas purification. TiO2 supported Pt sub-nanoclusters have been prepared by introducing variable valence Co ions into a one step flame spray pyrolysis process. Co2+ was oxidized to Co3+ in the high-temperature flame, and the released electrons were transferred to the surface of Pt and suppressed the aggregation of Pt nanoclusters supported on TiO2. As a result, the average size of Pt nanoclusters reduced from 2.47 nm to 0.72 nm with only 1% Co2+ ion doping. Moreover, due to the presence of Co, surface oxygen species were also affected, and these changes also led to a significant increase in the catalytic activity of CO oxidation. The temperature at 100% conversion was decreased from 120 °C to 70 °C, and the TOF increased by an order of magnitude. In addition, in situ DRIFTS was also used to investigate the cause of the significant increase in activity, and it was shown that adsorbed CO species on Pt could be desorbed more easily because of the electron transfer between Pt and Co species.

Magnetic, recyclable PtyCo1−y/Ti3C2X2 (X = O, F) catalyst: a facile synthesis and enhanced catalytic activity for hydrogen generation from the hydrolysis of ammonia borane

Magnetic recyclable Pt_yCo_1−y/Ti₃C₂X₂ (X = O, F) catalyst exhibits excellent catalytic performance for the hydrolysis of AB at room temperature.

A convenient approach of MIP/Co–TiO2 nanocomposites with highly enhanced photocatalytic activity and selectivity under visible light irradiation

MIP/Co–TiO₂ nanocomposites were synthesized. Their mechanisms of preferable photocatalytic activity and good selectivity for target contaminants were identified and discussed.