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Anchoring Cu sites in a hierarchical single-crystalline ZSM-5 zeolite for enhanced diffusion and benzene oxidation
No full textPhenol is an important intermediate for high-value chemicals. Current phenol production via the three-step cumene process leads to significant energy waste and environmental problems. The conversion of benzene to phenol under mild conditions can be achieved by oxidation with Cu-based zeolites. However, conventional microporous zeolites suffer from severe diffusion limitations, especially when bulky molecules, such as benzene, are involved. In this work, we used a hierarchically macro-meso-microporous ZSM-5 single crystal (Hier-ZSM-5) as a substrate for Cu species (Cu@Hier-ZSM-5). The irregular morphology of the opal-like Hier-ZSM-5 exhibited abundant surface Si-OH groups and provided a platform for stabilizing Cu2+ sites. Meanwhile, hierarchical porosity significantly improved the diffusion ability of bulky molecules. As a result, excellent selective oxidation performance of benzene was obtained with Cu@Hier-ZSM-5, achieving a conversion of 77% and a phenol selectivity of 73%, which were 1.5 times and 2 times higher than those obtained with a catalyst based on microporous ZSM-5, respectively. CuOOH species were identified as an important intermediate in benzene oxidation. This hierarchical zeolite system, with a synergistic effect of site anchoring and molecular diffusion, provides an excellent platform for catalyst design.</p
L’affaire Google LLC et autres contre Russie:le contrôle étatique du contenu des plateformes en ligne confronté à la liberté d’expression
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Electrically reconfigurable heteronuclear dual-atom catalysts
No full textScrutinizing the dynamic reconfiguration mechanism of intermetallic single-atom catalysts reveals the chemical origin of the enhanced electrocatalysis performance.</p
Tuning Spin Polarization of Iron in Oxides to Boost Electrocatalytic Ammonia Production
No full textThe electrocatalytic nitrogen reduction reaction (NRR) for ammonia production has gained attention for its potential to reduce energy consumption and environmental impact. However, effective NRR catalysts currently rely on expensive noble metals, the development of cost-effective transition metal alternatives remains highly challenging. Iron-based catalysts are underexplored because of their inherently low reactivity. In this study, it is found that tailoring spin polarization, specifically the occupation state of electronics on d orbital in iron oxides, can highly boost NRR performance with carefully designed spin polarization. Iron in perovskite SrFeO3 with higher spin polarization shows 79 times increase in ammonia yield compared to iron in Fe2O3. This improvement is accompanied with 9 times increase in charge transfer between iron and *NNH, the rate-determining step of NRR manipulating the spin polarization of transition metals can lead to efficient catalysts for electrochemical NRR, offering valuable insights for enhancing catalyst performance and enabling more sustainable ammonia production.</p
Modulating surface charge and offering hydrogen bonding for copper-based materials toward efficient electrocatalytic CO<sub>2</sub> to ethylene
No full textCuprous oxide (Cu2O) has been regarded as a highly promising category of electrocatalyst for carbon dioxide reduction reaction (CO2RR). Nevertheless, the development of highly efficient Cu-based electrocatalysts for the CO2-to-ethylene conversion as well as the elucidation of the possible catalytic mechanism, remain challenging areas of research. This is due to the fact that the electrocatalytic CO2RR conversion to ethylene (C2H4) is a process comprising numerous steps and a sophisticated electrocatalytic mechanism. The absence of a comprehensive understanding of the reaction process is likely to impose significant limitations on the design of highly efficient Cu-based electrocatalysts. In this work, the nitrogen-doped Cu2O nanocubes modified with dodecylamine have been synthesized via a facile refluxing strategy to efficiently promote the conversion of CO2 to C2H4. The present work focuses on a comprehensive analysis of the underlying mechanisms that underpin the enhanced CO2RR activity of the as-synthesized electrocatalysts. First, the introduction nitrogen atoms into electrocatalysts can efficiently modulate the charge of Cu sites, which favors the adsorption of the *CO intermediate. Additionally, the presence of hydrogen bonding serves to stabilize the *CHO intermediate and weaken the C[dbnd]O bond of the O*CCHO intermediate, thereby facilitating the hydrogenation process to the O*CCHOH intermediate. Last but not least, our electrocatalyst present a significant advantage over both the dodecylamine-modified electrocatalyst and the electrocatalyst that has not undergone N doping and dodecylamine in the dehydroxylation of OH*CHCH2 to *CHCH2 intermediates. This is due to the configuration transformation of the *CHCH2 intermediate, which favors the formation of C2H4. Our work proposes a feasible strategy for modulating charge coupled to offering hydrogen bonding for the design and synthesis of the Cu-based electrocatalysts, with the objective of achieving efficient conversion of CO2 to C2H4.</p
Attractive-Repulsive Challenge in Swarmalators with Time-Dependent Speed
No full textWe examine a network of entities whose internal and external dynamics are intricately coupled, modeled through the concept of “swarmalators” as introduced by O’Keeffe et al. [1]. We investigate how the entities’ natural velocities impact the network’s collective dynamics and path to synchronization. Specifically, we analyze two scenarios: one in which each entity has an individual natural velocity, and another where a group velocity is defined by the average of all velocities. Our findings reveal two distinct forms of phase synchronization—static and rotational—each preceded by a series of states where attractive or repulsive interaction dominates the movement of the entities. This interaction phase, which depends sensitively on initial conditions, allows for selective modulation within the network. By adjusting initial parameters, we can isolate specific entities to experience attractive-repulsive interactions distinct from the group, prior to the onset of full synchronization. This nuanced dependency on initial conditions offers valuable insights into the role of natural velocities in tuning synchronization behavior within coupled dynamic networks.</p
Structural, Morphological, and Antibacterial Attributes of Graphene Oxide Prepared by Hummers’ and Brodie’s Methods
Get PDFGraphite oxidation to graphene oxide (GO) is carried out using methods developed by Brodie (GO-B) and Hummers (GO-H). However, a comparison of the antibacterial properties based on the physicochemical properties has not been performed. Therefore, this paper outlines a comparative analysis of GO-H and GO-B on antibacterial efficacy against Gram-positive and Gram-negative bacterial cultures and biofilms in an aqueous environment and discusses which of the properties of these GO nanomaterials have the most significant impact on the antibacterial activity of these materials. Synthesis of GO with Brodie’s and modified Hummers’ methods was followed by an evaluation of their structural, morphological, and physicochemical properties by Raman, FTIR, UV–vis spectroscopy, and X-ray diffraction (XRD). The GO-B surface appeared more oxidized than that of GO-H, which could be crucial for interactions with bacteria. According to our results, GO-B demonstrated notably superior anti-biofilm efficacy. Despite its higher production cost, GO-B exhibits more excellent capabilities in combating bacterial biofilms than GO-H.</p
