Ag–M (M: Ni, Co, Cu, Fe) bimetal catalysts prepared by galvanic deposition method for CO oxidation

Synergistic antibacterial mechanism of silver-copper bimetallic nanoparticles

The excessive use of antibiotics in clinical settings has resulted in the rapid expansion, evolution, and development of bacterial and microorganism resistance. It causes a significant challenge to the medical community. Therefore, it is important to develop new antibacterial materials that could replace traditional antibiotics. With the advancements in nanotechnology, it has become evident that metallic and metal oxide nanoparticles (MeO NPs) exhibit stronger antibacterial properties than their bulk and micron-sized counterparts. The antibacterial properties of silver nanoparticles (Ag NPs) and copper nanoparticles (Cu NPs) have been extensively studied, including the release of metal ions, oxidative stress responses, damages to cell integrity, and immunostimulatory effects. However, it is crucial to consider the potential cytotoxicity and genotoxicity of Ag NPs and Cu NPs. Numerous experimental studies have demonstrated that bimetallic nanoparticles (BNPs) composed of Ag NPs and Cu NPs exhibit strong antibacterial effects while maintaining low cytotoxicity. Bimetallic nanoparticles offer an effective means to mitigate the genotoxicity associated with individual nanoparticles while considerably enhancing their antibacterial efficacy. In this paper, we presented on various synthesis methods for Ag-Cu NPs, emphasizing their synergistic effects, processes of reactive oxygen species (ROS) generation, photocatalytic properties, antibacterial mechanisms, and the factors influencing their performance. These materials have the potential to enhance efficacy, reduce toxicity, and find broader applications in combating antibiotic resistance while promoting public health.

Effect of reduction pretreatments on PdAg/Al2O3 for HCHO and CO oxidation

PdAg/Al₂O₃ were pretreated by CO and H₂ reduction pretreatments, respectively. The reduced catalysts were tested for HCHO and CO oxidation and characterized by Brunner Emmet Teller (BET), X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and oxygen temperature programmed desorption (O₂-TPD). These results indicate that the pretreatments have effect on PdAg reconstruction, PdAg particle size and active oxygen species, which are responsible for the catalytic performance. Compared with H₂ reduction method, CO reduction is more suitable for PdAg/Al₂O₃ pretreatment. PdAg/Al₂O₃-CO exhibited better catalytic performance.

Influence of cerium doping on Cu-Ni/activated carbon low-temperature CO-SCR denitration catalysts

In this study, to evaluate the effects of two methods for activation of nitric acid, air thermal oxidation and Ce doping were applied to a Cu–Ni/activated carbon (AC) low-temperature CO-SCR denitration catalyst. The Cu–Ni–Ce/AC_0,1 catalyst was prepared using the ultrasonic equal volume impregnation method. The physical and chemical structures of Cu–Ni–Ce/AC_0,1 were studied using scanning electron microscopy, Brunauer–Emmett–Teller analysis, Fourier-transform infrared spectroscopy, X-ray diffractometry, X-ray photoelectron spectroscopy, CO-temperature programmed desorption (TPD) and NO-TPD characterisation techniques. It was found that the denitration efficiency of 6Cu–4Ni–5Ce/AC₁ can reach 99.8% at a denitration temperature of 150 °C, a GHSV of 30 000 h⁻¹ and 5% O₂. Although the specific surface area of the AC activated by nitric acid was slightly lower than that activated by air thermal oxidation, the pore structure of the AC activated by nitric acid was more developed, and the number of acidic oxygen-containing functional groups was significantly increased. Ce metal ions were inserted into the graphite microcrystalline structure of AC, splitting it into smaller graphene fragments, whereby the dispersibility of Cu and Ni was improved. In addition, many reaction units were formed on the catalyst surface, which could adsorb more CO and NO reaction gases. With the increase in Ce doping, the relative proportions of Cu²⁺/Cuⁿ⁺, Ni³⁺/Niⁿ⁺ and surface adsorbed oxygen (Oα) in the Cu–Ni–Ce/AC_0,1 catalyst increased. In addition, after the introduction of Ce into Cu–Ni/AC, the amount of weak and medium acids significantly increased. This may be due to the Ce species or its influence on the Cu/Ni species. Further, the active sites of the acid were more exposed. According to the results of the study, a composite metal oxide CO-SCR denitration mechanism is proposed. Through the oxidation–reduction reaction between the metals, the reaction gas of CO and NO is adsorbed and the incoming O₂ is converted into (Oα), which promotes the conversion of NO into NO₂. The CO-SCR reaction is accelerated, and the rate of low-temperature denitration was increased. Overall, the results of this study will provide theoretical support for the research and development of low-temperature denitration catalysts for sintering flue gas in iron and steel enterprises.

In the process of denitrification, the reaction between NO and CO (NO + CO → N₂ + CO₂) occurs. There will be a redox reaction between copper, nickel and cerium (Cu²⁺ + Ce³⁺ → Cu⁺ + Ce⁴⁺, Ni³⁺ + Ce³⁺ → Ni²⁺ + Ce⁴⁺).

Ultrafast Laser Manufacture of Stable, Efficient Ultrafine Noble Metal Catalysts Mediated with MOF Derived High Density Defective Metal Oxides

Supported metal nanoparticles (MNPs) undergo severe aggregation, especially when the interaction between MNPs and their supports are limited and weak where their performance deteriorates dramatically. This becomes more severe when catalysts are operated under high temperature. Here, it is reported that MNPs including Pt, Au, Rh, and Ru, with sub-2 nm size can be stabilized on densely packed defective CeO₂ nanoparticles with sub-5 nm size via strong coupling by direct laser conversion of corresponding metal ions encapsulated cerous metal-organic frameworks (Ce-MOFs). Ce-MOF serves as an ideal dispersion precursor to uniformly encapsulate noble metal ions in their orderly arranged pores. Ultrafast laser vaporization and cooling forms uniform, ultrasmall, well-mixed, and exceptionally dense nanoparticles of metal and metal oxide concurrently. The laser-induced ultrafast reaction (within tens of nanoseconds) facilitates the precipitation of CeO₂ nanoparticles with abundant surficial defects. Due to the well-mixed ultrasmall Pt and CeO₂ components with strong coupling, this catalyst exhibits exceptionally high stability and activity both at low and high temperatures (170-1100 °C) for CO oxidation in long-term operation, significantly exceeding catalysts prepared by traditional methods. The scalable feature of laser and huge MOF family make it a versatile method for the production of MNP-based nanocomposites in wide applications.

Synthesis of Supported Bimetal Catalysts using Galvanic Deposition Method

Supported bimetallic catalysts have been studied because of their enhanced catalytic properties due to metal-metal interactions compared with monometallic catalysts. We focused on galvanic deposition (GD) as a bimetallization method, which achieves well-defined metal-metal interfaces by exchanging heterogeneous metals with different ionisation tendencies. We have developed Ni@Ag/SiO₂ catalysts for CO oxidation, Co@Ru/Al₂ O₃ catalysts for automotive three-way reactions and Pd-Co/Al₂ O₃ catalysts for methane combustion by using the GD method. In all cases, the catalysts prepared by the GD method showed higher catalytic activity than the corresponding monometallic and bimetallic catalysts prepared by the conventional co-impregnation method. The GD method provides contact between noble and base metals to improve the electronic state, surface structure and reducibility of noble metals.

Methane combustion over Pd/CoAl2O4/Al2O3 catalysts prepared by galvanic deposition

Pd/CoAl₂O₄/Al₂O₃ methane combustion catalysts were synthesized using a galvanic deposition (GD) method (PdCoAl-GD).

Enhanced activity for methane combustion over a Pd/Co/Al2O3 catalyst prepared by a galvanic deposition method

A Pd/Co/Al₂O₃ catalyst prepared by a galvanic deposition method exhibited notable catalytic activity for methane combustion, due to the higher reducibility of PdO nanoparticles on CoO_x.