One-step green synthesis of composition-tunable Pt-Cu alloy nanowire networks with high catalytic activity for 4-nitrophenol reduction

4-Nitrophenol reduction and antibacterial activity of Ag-doped TiO2 photocatalysts

Water contamination by organic pollutants is a serious environmental problem. 4-Nitrophenol (4-NP) is a potentially harmful chemical, which is commonly present in industrial effluents and can severely damage human health. Photocatalytic reduction of hazardous 4-NP by nano-sized materials to produce 4-aminophenol (4-AP), which is a commercially valuable product, is a promising alternative as the process is framed within the circular economy. In this context, Ag-doped TiO2 (AT) catalysts were synthesized by liquid impregnation and reduction techniques, and their structure, morphology, elemental composition, textural, and light absorption properties were evaluated by XRD, Raman spectroscopy, SEM, TEM, EDS, BET, and DRS spectroscopy. AT catalysts exhibited an enhanced photocatalytic reduction of 4-NP into 4-aminophenol (4-AP) in the presence of NaBH4. Among the tested catalysts, AT21 prepared by a simple aqueous reduction method showed the highest activity reaching about 98% 4-NP reduction within 10 min. Antibacterial tests of these catalysts against Bacillus subtilis, Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa revealed that AT21 also exhibited the lowest minimum inhibitory concentration, suggesting that it has the strongest antibacterial activity. These findings suggest that AT21 catalyst with improved catalytic and antibacterial properties can potentially be utilized for the remediation of 4-NP-contaminated water environment.

Atomically dispersed and oxygen deficient CuO clusters as an extremely efficient heterogeneous catalyst

Preparation of high-density and atomically-dispersed clusters is of great importance yet remains a formidable challenge, which precludes rational design of high-performance, ultrasmall heterogeneous catalysts for alleviating the energy and environmental crises. In this study, we demonstrated an appealing non-equilibrium growth model to give sub-2 nm CuO clusters not from the growth of nuclei but from the top-down growth of metastable bulk crystals. These CuO clusters have high density and intriguingly uniform orientation, and are atomically scattered on an inactive ultrathin AlOOH substrate, which has been driven by the lattice matching between the CuO clusters and the utlrathin AlOOH substrate. The catalytic activity of CuO clusters, with the hydrogenation of 4-nitrophenol as a model reaction, proved to be extremely efficient and showed a rate constant of 130.0 s^-1 g^-1, outperforming the commercial Pd/C catalysts and reported state-of-the-art noble-metal catalysts (1.89-117.2 s^-1 g^-1). These clusters have abundant interfacial oxygen vacancies (OVs) whose concentration can be regulated, and the OVs are found to be essential, according to density functional theory (DFT) calculations, in reducing the energy barrier of catalytic reduction and significantly boosting the catalytic reaction. These findings could add to the library of crystals downsized to the atomic level and demonstrate how engineering point defects on the sub-nanometer materials help design high-efficient catalysts.

Hierarchical NiCo2S4/ZnIn2S4 heterostructured prisms: High-efficient photocatalysts for hydrogen production under visible-light

Exploring low-cost co-catalyst to ameliorate the photocatalytic activity of semiconductors sets a clear direction for solving energy crisis and achieving efficient solar-chemical energy conversion. In this work, a unique hierarchical hollow heterojunction was constructed by in-situ growing ZnIn₂S₄ nanosheets on the porous NiCo₂S₄ hollow prisms through a low temperature solvothermal method, in which NiCo₂S₄ with semi-metal property acted as non-noble metal co-catalyst. NiCo₂S₄ co-catalyst was innovatively encapsulated in ZnIn₂S₄, which not only relieved the light shielding effect caused by the large loading amount of co-catalyst, but also supplied abundant active sites for H₂ evolution. The hierarchical hollow heterostructure of NiCo₂S₄/ZnIn₂S₄ provided a highly efficient channel for charge transfer. Combining these advantages, NiCo₂S₄/ZnIn₂S₄ composite demonstrated excellent photocatalytic activity. In the absence of sacrificial agent, the NiCo₂S₄/ZnIn₂S₄ photocatalyst achieved a remarkable improved H₂ yield of 0.77 mmol g^-1h^-1 under visible light irradiation (λ > 400 nm), which is 6.6 times greater than that of ZnIn₂S₄. Besides, NiCo₂S₄ even exhibited better performance on the H₂ evolution improvement of ZnIn₂S₄ than precious metal Pt. This work will offer novel insights into the reasonable design of non-noble metal photocatalysts with respectable activity for water splitting.

Completely green synthesis of rose-shaped Au nanostructures and their catalytic applications

A novel protocol for the one-pot, template/seed-free, and completely green synthesis of rose-shaped Au nanostructures with unique three-dimensional hierarchical structures was developed.

Biomimetic strategies to produce catalytically reactive CuS nanodisks

Copper sulfide materials have diverse applications from cancer therapy to environmental remediation due to their narrow bandgap and easily tuned plasmon. The synthesis of these materials often involves toxic reagents and harsh conditions where biomimetic methods may provide opportunities to produce these structures under sustainable conditions. To explore this capability, simple amino acids were exploited as biological ligands for the ambient synthesis of CuS materials. Using an aqueous-based approach, CuS nanodisks were prepared using acid-containing amino acid molecules that stabilize the materials against bulk aggregation. These structures were fully characterized by UV-vis analysis, transmission electron microscopy, dynamic light scattering, atomic force microscopy, selected area electron diffraction, and X-ray diffraction, which confirmed the formation of CuS. The materials possessed a vibrant plasmon band in the near IR region and demonstrated enhanced photocatalytic reactivity for the advanced oxidation of organic dyes in water. These results demonstrate a room temperature synthetic route to optically important materials, which could have important application in catalysis, optics, nanomedicine, etc.