The quest for efficient and durable catalysts using abundant resources has garnered significant interest in the field of bifunctional oxygen electrocatalysis. In this work, the electrocatalytic performances of CoC 8 N 8 bilayers with and without O/S axial coordination toward oxygen reduction and oxygen evolution have been systematically investigated via density functional theory calculations. Our results demonstrate the stacking manner influences the catalytic performance. Furthermore, the presence of axial coordination modulates the oxygen bifunctional electrocatalysis. According to the thermodynamic analysis, the CoC 8 N 8 bilayer with O axial coordination delivers the outstanding performances toward oxygen reduction and oxygen evolution, as reflected by the small overpotentials of 0.37 and −0.36 V, being superior than the benchmark materials of Pt and IrO 2 , respectively. Conversely, the introduction of S axial coordination degrades the thermodynamic activity of oxygen electrocatalysis. This work opens a new path for designing the efficient electrocatalysts via modification of coordination environment.
Despite the intense interest in 2D magnetic second‐order topological insulators (SOTIs) over the past 5 years, realistic 3D magnetic SOTI materials remain extremely limited. Based on first‐principles calculations, we demonstrate that bulk ferromagnetic CuF 6 Sr 2 is an intrinsic three‐dimensional magnetic second‐order topological insulator. Notably, only the spin‐up channel hosts a nontrivial bulk band gap, whereas the spin‐down channel remains topologically trivial. Specifically, only the spin‐up channel in CuF 6 Sr 2 carries a quantized fractional topological charge ( Q (2) = e /4), whereas the spin‐down channel is topologically trivial ( Q (2) = 0), highlighting a spin‐selective fractional topological response. According to the higher‐order bulk–boundary correspondence, we further confirm that, in the absence of SOC, CuF 6 Sr 2 hosts topologically protected, ultra‐clean hinge states in the spin‐up channel, which are clearly distinguishable from the bulk bands. Remarkably, unlike previously reported nonmagnetic SOTI materials, the hinge states in CuF 6 Sr 2 are spin‐polarized, providing a magnetic platform for exploring spin‐dependent higher‐order topological phenomena and their potential relevance to topological spintronics.
The [3 6 ](1,2,3,4,5,6)cyclophane ([3 6 ]superphane) is characterized by a conformational phenomenon associated with the possibility of inversion of six trimethylene blades connecting two opposite benzene rings. Detailed characterization of the transition pathway from the most energetically stable C 6h form, having all blades bent in the counterclockwise direction ( 0 ), to its equivalent form with all blades bent in the clockwise direction ( 0′ ) is studied by Ab Initio Molecular Dynamics (AIMD) and Quantum Mechanical (QM) methods. This transition requires four intermediate local minima and five transition states with very similar relative energies in the range 10.2–10.9 kcal/mol (in excellent agreement with the experimental energy barrier of 10.9 kcal/mol) and proceeds via sequential correlated inversions of side blades. Previously unknown structures of the [3 6 ]superphane are also found. Notably, among them, there is yet another transition state, TS3′ , which can be considered as an alternative to TS3 being halfway along the 0 ⇌ 0′ transition pathway. AIMD simulations confirm the transition path realized by sequential blade inversions and support the possibility of TS3′ occurrence in the process. Qualitative energy differences between individual stationary points are explained by a model that introduces different types of interactions depending on the mutual arrangements of adjacent lateral superphane blades.
With increasing atmospheric CO 2 , photocatalytic CO 2 reduction has emerged as a promising strategy to mitigate climate change. CuBi 2 O 4 , a semiconductor with a bandgap of 1.75 eV, shows broad visible absorption, making it a suitable candidate for photocatalytic applications. We used CuBi 2 O 4 as the photocatalyst and combined in situ Raman spectroscopy with density functional theory (DFT) calculations to investigate CO 2 reduction. Over 12 intermediates were assigned, and five new Raman bands of intermediates were identified. The Raman spectra showed a fast production rate, with downstream intermediates forming early and upstream species accumulating later. The intermediates O*CCO and O*CCHO arose from distinct pathways, confirming multiple C2 processes. DFT results revealed two active sites, O–Cu and O–Bi, both promoting C–C coupling. Significant amounts of CO (11.4 μmol g −1 h −1 ), H 2 (2.36 μmol g −1 h −1 ), CH 4 (0.85 μmol g −1 h −1 ), and a large fraction of C2+ products (C 2 H 4 /CH 4 ∼42%) were produced; hydrocarbons were promptly produced, and CO and H 2 were gradually produced and reached maximal amounts at later stages. DFT calculations show that CO 2 was converted to *CO via O*COH, and *CO, with high free energy, can easily desorb to form gas‐phase CO. This explains the high yield of CO product.
Molecular dynamics simulations are used to investigate the equilibrium solubility and solution structure of paracetamol (or acetaminophen) in water, ethanol, acetone, diethylamine, dimethylformamide, dimethyl sulfoxide, toluene, and cyclohexane. A rigorous thermodynamic framework relates the solution‐phase concentration‐dependent number density and solvation free energy to the pure crystalline excess Gibbs free energy, predicting solubility across four orders of magnitude. Results for ethanol agree with experimental data and reference simulations. The infinite dilution approximation is established as a rapid diagnostic tool and strategic method for staging simulations, especially for sparingly soluble systems where standard simulations are inherently supersaturated. In diethylamine, the model under‐predicted solubility by two orders of magnitude. Structural analysis reveals that underestimating solvent‐solute hydrogen bonding leads to unphysical aggregation, illustrating the critical distinction between experimental and model equilibrium. This work highlights phase equilibria expressions as essential diagnostics for the future parameterization of force fields for complex, multifunctional molecules.
