New Strategy toward a Dual Functional Nanocatalyst at Ambient Conditions: Influence of the Pd-Co Interface in the Catalytic Activity of Pd@Co Core-Shell Nanoparticles

Encapsulation of Pd Single-Atom Sites in Zeolite for Highly Efficient Semihydrogenation of Alkynes

Palladium (Pd)-based single-atom catalysts (SACs) have shown outstanding selectivity for semihydrogenation of alkynes, but most Pd single sites coordinated with highly electronegative atoms (such as N, O, and S) of supports will result in a decrease in the electron density of Pd sites, thereby weakening the adsorption of reactants and reducing catalytic performance. Constructing a rich outer-shell electron environment of Pd single-atom sites by changing the coordination structure offers a novel opportunity to enhance the catalytic efficiency with excellent alkene selectivity. Therefore, in this work, we first propose the in situ preparation of isolated Pd sites encapsulated within Al/Si-rich ZSM-5 structure using the one-pot seed-assisted growth method. Pd1@ZSM-5 features Pd-O-Al/Si bonds, which can boost the domination of d-electron near the Fermi level, thereby promoting the adsorption of substrates on Pd sites and reducing the energy barrier for the semihydrogenation of alkynes. In semihydrogenation of phenylacetylene, Pd1@ZSM-5 catalyst performs the highest turnover frequency (TOF) value of 33582 molC═C/molPd/h with 96% selectivity of styrene among the reported heterogeneous catalysts and nearly 17-fold higher than that of the commercial Lindlar catalyst (1992 molC═C/molPd/h). This remarkable catalytic performance can be retained even after 6 cycles of usage. Particularly, the zeolitic confinement structure of Pd1@ZSM-5 enables precise shape-selective catalysis for alkyne reactants with a size less than 4.3 Å.

High-Performance Styrene Epoxidation with Vacancy-Defect Cobalt Single-Atom Catalysts

Exploring highly active and cost-effective catalysts for styrene epoxidation is of great significance, but it remains challenging to simultaneously achieve excellent conversion and selectivity toward styrene oxide. In this work, the structures and performance of Co, Fe, and Cu single-atom catalysts (SACs) in styrene epoxidation with tert-butyl hydroperoxide (TBHP) are predicted using density functional theory (DFT) calculations. The results reveal that the Co-N structure prefers that of styrene oxide over Fe-N and Cu-N structures. This predicted result is verified via catalytic evaluations, where the Co SACs displayed significantly higher styrene oxide selectivity than Fe and Cu SACs. Moreover, the activity of Co SAC can be further improved by the construction of unsaturated vacancy-defect cobalt single sites. As a result, excellent performance with styrene conversion of 99.9% and styrene oxide selectivity of 71% is achieved after a reaction time of 8 h on the optimal Co SAC.

Fabrication of dual catalytic microcapsules by mesoporous graphitic carbon nitride (mpg-C3N4) nanoparticle–enzyme conjugate stabilized emulsions

Dual catalytic microcapsules (MCs) were fabricated by simultaneous self-assembly and cross-linking of mpg-C₃N₄ nanoparticles (NPs) and lipase conjugates at oil–water interface.

Electronic Integration and Thin Film Aspects of Au-Pd/rGO/TiO2 for Improved Solar Hydrogen Generation

In the present work, we have synthesized noble bimetallic nanoparticles (Au-Pd NPs) on a carbon-based support and integrated with titania to obtain Au-Pd/C/TiO₂ and Au-Pd/rGO/TiO₂ nanocomposites using an ecofriendly hydrothermal method. Here, a 1:1 (w/w) Au-Pd bimetallic composition was dispersed on (a) high-surface-area (3000 m² g^-1) activated carbon (Au-Pd/C), prepared from a locally available plant source (in Assam, India), and (b) reduced graphene oxide (rGO) (Au-Pd/rGO); subsequently, they were integrated with TiO₂. The shift observed in Raman spectroscopy demonstrates the electronic integration of the bimetal with titania. The photocatalytic activity of the above materials for the hydrogen evolution reaction was studied under 1 sun conditions using methanol as a sacrificial agent in a powder form. The photocatalysts were also employed to prepare a thin film by the drop-casting method. Au-Pd/rGO/TiO₂ exhibits 43 times higher hydrogen (H₂) yield in the thin film form (21.50 mmol h^-1 g^-1) compared to the powder form (0.50 mmol h^-1 g^-1). On the other hand, Au-Pd/C/TiO₂ shows 13 times higher hydrogen (H₂) yield in the thin film form (6.42 mmol h^-1 g^-1) compared to the powder form (0.48 mmol h^-1 g^-1). While powder forms of both catalysts show comparable activity, the Au-Pd/rGO/TiO₂ thin film shows 3.4 times higher activity than that of Au-Pd/C/TiO₂. This can be ascribed to (a) an effective separation of photogenerated electron-hole pairs at the interface of Au-Pd/rGO/TiO₂ and (b) the better field effect due to plasmon resonance of the bimetal in the thin film form. The catalytic influence of the carbon-based support is highly pronounced due to synergistic binding interaction of bimetallic nanoparticles. Further, a large amount of hydrogen evolution in the film form with both catalysts (Au-Pd/C/TiO₂ and Au-Pd/rGO/TiO₂) reiterates that charge utilization should be better compared to that in powder catalysts.

Morphology-dependent, green, and selective catalytic styrene oxidation on Co3O4

Defect-less Co₃O₄ nanocube morphology is demonstrated to show high activity for styrene oxidation. Defects do not necessarily enhance the activity.