Le regole del gioco: Primo incontro con l'ingegneria strategica

Cu particles decorated carbon composite microspheres (CCMs) with a unique sesame ball structure have been prepared by combining the mass-producible spray drying technique with calcinations. The conventional cuprammonium cellulose complex solution obtained by dissolving cellulose in a cuprammonia solution has been applied as raw materials for the preparation of Cu­(NH₃)₄²⁺/cellulose complex microspheres via a spray drying process. The resulted Cu­(NH₃)₄²⁺/cellulose complex microspheres are then transformed into the Cu particles homogeneously decorated porous carbon spheres <i>in situ</i> by calcinations at 450 or 550 °C. The coordination effect between the Cu­(NH₃)₄²⁺ species and the hydroxyl groups of the cellulose macromolecules has been exploited for directing the dispersion of the Cu particles in the resultant composite CCMs. The antimicrobial effects of the CCMs are evaluated by determining the minimum growth inhibitory concentrations using Staphylococcus aureus and Escherichia coli as representatives, respectively. The CCMs show high efficiency catalytic properties to the conversion of 4-nitrophenol to 4-aminophenol using NaBH₄ as a reductant in a mild condition. The recyclability and stability of the CCM catalysts have also been studied

Nitrogen-Doped Titanate-Anatase Core–Shell Nanobelts with Exposed {101} Anatase Facets and Enhanced Visible Light Photocatalytic Activity

Anatase TiO2 with specifically exposed facets has been extensively studied for maximizing its photocatalytic activity. However, most previous preparation methods involve high-pressure processing and corrosive chemicals. Few works have been conducted on hierarchical composite nanostructures assembled from well-defined TiO2 nanocrystals. Here, we report a facile method for the preparation of nitrogen-doped titanate-anatase core–shell nanobelts. Anatase nanorods with specifically exposed {101} facets were obtained from a simple evaporation-induced, self-assembly (EISA) process and coupled with another semiconductor photocatalyst. The composite material with improved visible-light-harvesting ability, high charge-hole mobility, and low electron–hole recombination exhibited high photocatalytic performance and stability. The results presented here will make significant contributions toward the development of delicate composite photocatalysts for photocatalytic water purification and solar energy utilization

Modulating Charge Carrier Dynamics among Anisotropic Crystal Facets of Cu₂O for Enhanced CO₂ Photoreduction

Photogenerated charge separation is a crucial factor determining the enhancement in the energy efficiency of photocatalysts. In this work, through computational simulations of Cu2O crystals with different facets, edge-truncated cubic Cu2O was confirmed to enable efficient charge separation. To verify the computational predictions, Cu2O photocatalysts with two different morphologies and facet orientations, i.e., cubic and edge-truncated cubic structures, were synthesized and characterized. The photocatalytic activity toward the selective reduction of CO2 to methanol on the edge-truncated cubic Cu2O with anisotropic {100} and {110} facets was found to be nearly 5.5-fold higher than that of cubic Cu2O with only {100} facets. This observed difference is ascribed to the effective separation and migration of photogenerated charge carriers as well as the selective accumulation of electrons and holes on different facets of edge-truncated cubic Cu2O crystals. The effects of work function differences between {110} and {100} facets on the electronic band structure and anisotropic charge separation were also identified. These findings provide important guidelines for the design and synthesis of highly efficient and well-defined photocatalysts for CO2 conversion to fuel

Improved CO₂ Sorption in Freeze-Dried Amine Functionalized Mesoporous Silica Sorbent

This work investigates the structural and CO2 sorption properties of amine-functionalized mesoporous silica prepared by a freeze-drying method. It was found that the freeze-dried samples delivered significantly higher CO2 sorption capacities up to a factor of 18 times as compared to samples prepared by the conventional oven-drying evaporation method. The improved performance of the freeze-drying method was attributed to a higher surface area and access to active amine sites for CO2 sorption. The freeze-dried samples also exhibited good stability at a relatively high sorption temperature (90 °C) and flue gas CO2 partial pressure (15 kPa). The freeze-drying method reached the best CO2 sorption capacity of 4.71 mmol g–1 for samples with 70 wt % amine loading. Higher loading (80 and 90 wt %) led to excess amine not being incorporated into the mesoporous silica structure, thus covering active sites and limiting CO2 diffusion

Nanoconfinement Effects of Yolk–Shell Cu₂O Catalyst for Improved C₂₊ Selectivity and Cu⁺ Stability in Electrocatalytic CO₂ Reduction

Electrocatalytic conversion of carbon dioxide (CO2) to value-added hydrocarbon products provides an industrially viable approach to utilizing carbon resources and the storage of renewable energy. Monovalent copper (Cu+) has been demonstrated to be indispensable for the formation of C2+ products via C–C coupling. However, the C2+ selectivity and stability of Cu+ at the cathodic potential remain a great challenge. In this work, we investigated the electrochemical properties of three Cu-based catalysts with different structures in the electrocatalytic reduction of the CO2 reaction (eCO2RR). Results showed that a Cu2O catalyst with a yolk–shell microstructure having a distance between the shell internal surface and the core external surface of 25 nm displays the best performance. It exhibits a C2+ Faradaic efficiency of 80.2% and a FEC2+ to FEC1 ratio of ∼8.9. Both in situ ATR-SEIRAS and ex situ XPS characterization results reveal that Cu+ is stable under the experimental conditions, and the coverage of adsorbed carbon monoxide (*CO) on the Cu+ active site is enhanced due to nanoconfinement effects. The increased *CO surface coverage significantly promotes C–C coupling, leading to enhanced C2+ selectivity

Charge Storage Behavior of Carbon Nanoparticles toward Alkali Metal Ions at Fast-Charging Rates

Rechargeable batteries with high-rate capability are needed for vehicle electrification. It is important to understand charge storage behavior in battery electrode materials. We have investigated the charge storage capacity and mechanism of alkali metal ions Li+, Na+, and K+ in graphite and hard carbon (HC) nanoparticles of 50 nm in particle size. The charge storage capacity of the carbon nanoparticles follows the order: Li+ > K+ > Na+ in the potential window between 3.00 and 0.01 V vs the individual metal/metal ion couple. Above the plateau regions (above 0 V vs Na/Na+, 0.25 V vs K/K+, and 0.35 V vs Li/Li+), the storage of the alkali metal ions proceeds via a capacitive mechanism due to charge adsorption on the surface and defective sites, leading to a similar specific storage capacity. In the potential range between 3.0 and 0.01 V vs Li/Li+ and at 1 A/g, graphite and HC nanoparticles deliver Li+ storage capacities of 690 and 564 mAh/g, respectively. The significantly higher Li+ storage capacity of the graphite nanoparticles than the theoretical capacity of commercial graphite (372 mAh/g) is due to the extra Li+ storage via the capacitive mechanism. However, at an extremely high current density (e.g., 100 A/g), the HC nanoparticles store more Li+ (324 mAh/g) than the graphite nanoparticles (262 mAh/g). This study sheds light on alkali metal ion storage behavior in carbon nanoparticles and suggests that electrodes fabricated with carbon nanoparticles hold great promise for developing fast-charging rechargeable batteries

Thermally Reduced Ruthenium Nanoparticles as a Highly Active Heterogeneous Catalyst for Hydrogenation of Monoaromatics

We report here a thermal reduction method for preparing Ru catalysts supported on a carbon substrate. Mesoporous SBA-15 silica, surface-carbon-coated SBA-15, templated mesoporous carbon, activated carbon, and carbon black with different pore structures and compositions were employed as catalyst supports to explore the versatility of the thermal reduction method. Nitrogen adsorption, X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, scanning transmission electron microscopy, thermogravimetric analysis, and X-ray absorption near-edge structure techniques were used to characterize the samples. It was observed that carbon species that could thermally reduce Ru species at high temperatures played a vital role in the reduction process. Ru nanoparticles supported on various carbon-based substrates exhibited good dispersion with an appropriate particle size, high crystallinity, strong resistance against oxidative atmosphere, less leaching, lack of aggregation, and avoidance of pore blocking. As such, these catalysts display a remarkably high catalytic activity and stability in the hydrogenation of benzene and toluene (up to 3−24-fold compared with Ru catalysts prepared by traditional methods). It is believed that the excellent catalytic performance of the thermally reduced Ru nanoparticles is related to the intimate interfacial contact between the Ru nanoparticles and the carbon support

Improving the Visible-Light Photocatalytic Activity of Graphitic Carbon Nitride by Carbon Black Doping

Hydrogen production by water splitting and the removal of aqueous dyes by using a catalyst and solar energy are an ideal future energy source and useful for environmental protection. Graphitic carbon nitride can be used as the photocatalyst with visible light irradiation. However, it typically suffers from the high recombination of carriers and low electrical conductivity. Here, we have developed a facile mix-thermal strategy to prepare carbon black-modified graphitic carbon nitrides, which possess high electrical conductivity, a wide adsorption range of visible light, and a low recombination rate of carriers. With the help of carbon black, highly crystallized graphitic carbon nitrides with built-in triazine and heptazine heterojunctions are obtained. Improved photocatalytic activities have been achieved in carbon black-modified graphitic carbon nitride. The dye removal rate can be three times faster than that of pristine graphitic carbon nitride and the photocatalytic H2 generation is 234 μmol h–1 g–1 under visible light irradiation