Effects of Co and Ru Intimacy in Fischer–Tropsch Catalysts Using Hollow Carbon Sphere Supports: Assessment of the Hydrogen Spillover Processes

A CuCo Bimetal Confined Hollow SiC Hybrid Photothermal Nanoreactor for the Integration of Pollutant Mineralization and Solar-Powered Water Evaporation

Growing attention has been paid to the rational treatment of antibiotics-bearing medical wastewater. However, the complexity of polluted wastewater makes the later comprehensive treatment difficult only by the Advanced Oxidation Process technique. Therefore, the coupled water treatment techniques including contaminant mineralization and regeneration of cleanwater become very attractive. A bimetallic functional hollow nanoreactor defined as (Co@SiO2/Cu-X) was successfully constructed by coating a Cu-doped silica layer on the metal-organic framework (ZIF-67) followed by programmed calcination in nitrogen. The nanoreactor was endowed with a hollow configuration composed of mesoporous N-doping C-Silica hybrid shell encapsulated ultrafine Cu and Co metallic species. Such a configuration allows for the efficient diffusion and open reaction space of big contaminant molecules. The catalytic synergy of exposed Co-Cu bimetals and the easy accessibility of electron-rich contaminants by polar N doping sites triggered surface affinity make the optimal Co@SiO2/Cu-6 afford an excellent catalytic norfloxacin mineralization activity (7 min, kabs=0.744 min-1) compared to Cu-free Co@SiO2-6 (kabs=0.493 min-1) and Co-6 (kabs=0.378 min-1) Benefiting from the above unique advantages, Co@SiO2/Cu-6 show excellent removal performance in degrading different pollutants (carbamazepine, oxytetracycline, tetracycline, and bisphenol A) and persistent recycled stability in removing NFX. In addition, by virtue of the excellent photothermal properties, interfacial solar water evaporation application by Co@SiO2/Cu-6 was further explored to reach the regeneration of cleanwater (1.595 kg m-2 h-1, 97.51 %). The integration of pollutant mineralization and solar water evaporation by creating the monolith evaporation by anchoring the Co@SiO2/Cu-6 onto the tailored melamine sponge allows the regeneration of cleanwater (1.6 kg⋅m-2⋅h-1) and synchronous pollutant removal (NFX, 95 %, 60 min), which provides potential possibility the treatment of complicated wastewater.

Synergistic contribution of metal-acid sites in selective hydrodeoxygenation of biomass derivatives over Cu/CoOx catalysts

The efficient hydrodeoxygenation (HDO) of biomass derivatives to yield specific products is a significant yet challenging task. In the present study, a Cu/CoO_x catalyst was synthesized using a facile co-precipitation method, and subsequently used for the HDO of biomass derivatives. Under optimal reaction conditions, the conversion of 5-hydroxymethylfurfural reached 100% with a selectivity of ∼99% to 2,5-diformylfuran. In combination with the experimental results, systematic characterizations revealed that CoO_x, as the acid site, tended to adsorb CO bonds, and the metal sites of Cu⁺ were inclined to adsorb CO bonds and enhance CO bond hydrogenation. Meanwhile, Cu⁰ was the main active site for 2-propanol dehydrogenation. The excellent catalytic performance could be attributed to the synergistic effects of Cu and CoO_x. Further, by optimizing the ratio of Cu to CoO_x, the Cu/CoO_x catalysts exhibited notable performance in HDO of acetophenone, levulinic acid, and furfural, which verified the universality of the catalysts in the HDO of biomass derivatives.

Ruthenium-cobalt single atom alloy for CO photo-hydrogenation to liquid fuels at ambient pressures

Photothermal Fischer-Tropsch synthesis represents a promising strategy for converting carbon monoxide into value-added chemicals. High pressures (2-5 MPa) are typically required for efficient C-C coupling reactions and the production of C₅₊ liquid fuels. Herein, we report a ruthenium-cobalt single atom alloy (Ru₁Co-SAA) catalyst derived from a layered-double-hydroxide nanosheet precursor. Under UV-Vis irradiation (1.80 W cm^-2), Ru₁Co-SAA heats to 200 °C and photo-hydrogenates CO to C₅₊ liquid fuels at ambient pressures (0.1-0.5 MPa). Single atom Ru sites dramatically enhance the dissociative adsorption of CO, whilst promoting C-C coupling reactions and suppressing over-hydrogenation of CH_x* intermediates, resulting in a CO photo-hydrogenation turnover frequency of 0.114 s^-1 with 75.8% C₅₊ selectivity. Owing to the local Ru-Co coordination, highly unsaturated intermediates are generated during C-C coupling reactions, thereby improving the probability of carbon chain growth into C₅₊ liquid fuels. The findings open new vistas towards C₅₊ liquid fuels under sunlight at mild pressures.

Hydrogen spillover effects in the Fischer–Tropsch reaction over carbon nanotube supported cobalt catalysts

Support (CNTs) surface defect-induced hydrogen spillover significantly impacted the catalytic activity (turnover frequency, TOF) and methane selectivity evolution in cobalt-based Fischer–Tropsch synthesis.

Vapour phase hydrogenation of cinnamaldehyde using cobalt supported inside and outside hollow carbon spheres

The hydrogenation of cinnamaldehyde is usually performed in the liquid phase in batch mode. In this study, a vapour phase flow system has been used to evaluate the use of cobalt catalysts supported inside and outside hollow carbon spheres (HCSs). The influence of temperature, hydrogen flow rate, and catalyst mass on the hydrogenation reaction was investigated. The catalysts generally showed modest conversion to the required products, hydrocinnamaldehyde, 3-phenyl propanol, cinnamyl alcohol, together with formation of various decomposition products. The data revealed that the Co@HCS showed better conversion and product selectivity compared with the Co/HCS. The catalysts with smaller particle sizes (ca. 6 nm) were more efficient than those with larger particles (30–40 nm). An increase in reaction temperature (200–300 °C) resulted in a lower cinnamaldehyde conversion and a poor product selectivity. TPR studies revealed that the Co@HCSs had a stronger metal-support interaction than the Co/HCSs catalysts. Catalyst recycling studies revealed that only the Co/HCSs could be regenerated (four cycles) and post reaction analysis of the catalysts revealed that this was due to HCS pore blockage and not Co sintering.

H-spilled storage to maximize the catalytic performances of Pd-based bimetals@Ti3C2Tx MXene in selective semihydrogenations

Hydrogen spillover is an important theme for hydrogen storage and H-involving catalytic reactions. This work shows that catalytic reactivity and selectivity can be revealed by differentiating energetic characteristics of the...

Cobalt Catalyst Reduction Thermodynamics in Fischer Tropsch: An Attainable Region Approach

A fundamental understanding of the precise reduction reaction pathway of cobalt-based catalysts is a crucial piece of knowledge in terms of the Fischer–Tropsch Synthesis (FTS) reaction. The use of hydrogen (H2) as the reduction agent results in a two-stage reduction of cobalt tetraoxide (Co3O4) to cobalt oxide (CoO) and then to metallic Co. The objective of the present work is to apply the Thermodynamic Attainable Region (TAR) to cobalt catalyst reduction using H2 so as to gain better insight regarding the thermodynamics of reduction reaction. TAR space diagrams suggest that complete Co3O4 reduction is feasible through two reaction pathways. Thus, the observed AR results suggest that the temperature programmed reduction’s (TPR) first reaction peak may be attributed to direct reduction of Co3O4 → Co and/or reduction to an intermediate compound Co3O4 → CoO. The second peak is a result of the reduction of either of the cobalt oxides to Co (Co3O4 → Co or CoO → Co).

In situ tuning of electronic structure of catalysts using controllable hydrogen spillover for enhanced selectivity

In situ tuning of the electronic structure of active sites is a long-standing challenge. Herein, we propose a strategy by controlling the hydrogen spillover distance to in situ tune the electronic structure. The strategy is demonstrated to be feasible with the assistance of CoO_x/Al₂O₃/Pt catalysts prepared by atomic layer deposition in which CoO_x and Pt nanoparticles are separated by hollow Al₂O₃ nanotubes. The strength of hydrogen spillover from Pt to CoO_x can be precisely tailored by varying the Al₂O₃ thickness. Using CoO_x/Al₂O₃ catalyzed styrene epoxidation as an example, the CoO_x/Al₂O₃/Pt with 7 nm Al₂O₃ layer exhibits greatly enhanced selectivity (from 74.3% to 94.8%) when H₂ is added. The enhanced selectivity is attributed to the introduction of controllable hydrogen spillover, resulting in the reduction of CoO_x during the reaction. Our method is also effective for the epoxidation of styrene derivatives. We anticipate this method is a general strategy for other reactions.

In situ tuning of the electronic structure of active sites is a long-standing challenge. Here, the authors report an approach to tune the electronic structure of cobalt species during the styrene epoxidation reaction by the introduction of controllable hydrogen spillover for enhanced selectivity.

Theoretically predicted surface morphology of FCC cobalt nanoparticles induced by Ru promoter

The addition of Ru promoter has an important role in tuning the stability of the exposed facets of FCC Co NPs, accompanied by the change of surface morphology.

Synergistic effect of cobalt, nitrogen-codoped hollow carbon sphere hosts for high performance lithium sulfur batteries

Co, N@CPDA-HCS exhibits better electrochemical performance due to the embedding of cobalt on the special structure as a host for sulfur.

Origin of synergistic effects in bicomponent cobalt oxide-platinum catalysts for selective hydrogenation reaction

The synergistic nature of bicomponent catalysts remains a challenging issue, due to the difficulty in constructing well-defined catalytic systems. Here we study the origin of synergistic effects in CoO_x-Pt catalysts for selective hydrogenation by designing a series of closely contacted CoO_xPt/TiO₂ and spatially separated CoO_x/TiO₂/Pt catalysts by atomic layer deposition (ALD). For CoO_x/TiO₂/Pt, CoO_x and platinum are separated by the walls of titania nanotubes, and the CoO_x-Pt intimacy can be precisely tuned. Like CoO_xPt/TiO₂, the CoO_x/TiO₂/Pt shows higher selectivity to cinnamyl alcohol than monometallic TiO₂/Pt, indicating that the CoO_x-Pt nanoscale intimacy almost has no influence on the selectivity. The enhanced selectivity is ascribed to the increased oxygen vacancy resulting from the promoted hydrogen spillover. Moreover, platinum-oxygen vacancy interfacial sites are identified as the active sites by selectively covering CoO_x or platinum by ALD. Our study provides a guide for the understanding of synergistic nature in bicomponent and bifunctional catalysts.

Supported Co-Re Bimetallic Catalysts with Different Structures as Efficient Catalysts for Hydrogenation of Citral

Bimetallic Co-Re/TiO₂ catalysts were developed for efficient citral hydrogenation. Bimetallic catalysts were prepared by co-impregnation (CI), successive-impregnation (SI), and surface redox method (SR). The arrangement between the Co and Re species on these systems was fully characterized using several techniques (TEM-energy-dispersive X-ray spectroscopy, H₂ temperature-programmed reduction, temperature-programmed desorption, XRD, CO FTIR spectroscopy, model reaction of cyclohexane dehydrogenation), and their catalytic performances were evaluated for the selective hydrogenation of citral towards unsaturated alcohols. The Re and Co species are completely isolated in the CI sample, presenting a very limited Co-Re interaction. In SI samples, the metals coexist in a Janus-type structure with a concentration of Re around Co. Decoration/core-shell structures are observed for SR samples resulting from the redox exchange between the metallic surface of the parent Co/TiO₂ catalyst and the Re⁷⁺ species of the modifier precursor salt. The contact degree between the two metals gradually increases as follows: Isolated structure (CI)<Janus-type structure(SI)<decoration/core-shell structure (SR). The unchanging structure of all SI samples independent of the Re loading leads to similar electron transfer, and the increase in Re content results in agglomeration of Re, thus decreasing the catalytic activity. Density-of-state (DOS) calculations prove that the high valence of Re is a disadvantage for the hydrogenation reaction. For SR samples, the increase of Re loading contributes to the electron transfer from Re to Co that is consistent with a change of structure from decoration to core-shell. The lack of directly accessible Co atoms for SR catalysts with fully coated structure decreases the efficiency of Re reduction. The presence of Co-Re interaction resulting from the close contact between metals plays a dominant role in the hydrogenation of citral. Nevertheless, an excessively high contact degree is unnecessary for citral hydrogenation once Co-Re interaction has formed.

From CO2methanation to ambitious long-chain hydrocarbons: alternative fuels paving the path to sustainability

Comprehensive insight into the thermochemical, photochemical and electrochemical reduction of CO₂to methane and long-chain hydrocarbons as alternative fuels.

Suppression by Pt of CO adsorption and dissociation and methane formation on Fe5C2(100) surfaces

To understand the chemical origin of platinum promotion effects on iron based Fischer–Tropsch synthesis catalysts, the effects of Pt on CO adsorption and dissociation as well as surface carbon hydrogenation on the Fe₅C₂(100) facet with different surface C* contents have been studied using the spin-polarized density functional theory method.

Supported Fe/MnOx catalyst with Ag doping for remarkably enhanced catalytic activity in Fischer–Tropsch synthesis

The role of Ag in the promotion of the FTS performance and the evolutions of structure and phase over the Fe/MnO_x catalyst has been clearly elucidated.

Insight into the structure and morphology of Run clusters on Co(111) and Co(311) surfaces

The adsorption configurations, growth modes and morphology of a Ru promoter under the approximate conditions of cobalt catalyzed Fischer–Tropsch synthesis (FTS) were investigated by density functional theory (DFT) calculations.