Abstract In this study, we determine the optimal voltage profile for charging a constant phase element (CPE) of order α ∈]0, 1[ that maximizes the ratio of stored to total input energy over a fixed charging interval. Using the frequency-distributed RC network representation of the CPE, the efficiency maximization is reformulated as an isoperimetric variational problem, and solved via the fractional Euler–Lagrange equation. A Mellin transform analysis of the resulting optimality condition identifies the admissible solutions as a one-parameter family of power-law voltage profiles v(t; s0) = V0(t/T)β*, β* = α – s0 > 0. Within the physically relevant class of concave waveforms β* ∈]0, 1[, the optimal charging protocol is the linear ramp, which achieves the maximum energy storage efficiency η* = (4 – 22−α – α)/(2 – α), and produces a power-law current response. Extending to all β* > 0, the efficiency is shown to be monotonically increasing with β*, approaching the supremum α asymptotically as β* → ∞ but never reaching it, establishing α as the theoretical efficiency ceiling for power-law charging of a CPE. This result also provides an energetic interpretation of the CPE order α as the maximum fraction of input energy that can be stored in the capacitive modes of the CPE, over all power-law voltage excitations.
Abstract Singlet fission (SF) holds promise for enhancing photovoltaic efficiency and enabling spin-based quantum technologies. The development of new materials is hindered by the limited understanding of the SF mechanism. One particular challenge lies in the role of the excimer state, which has been proposed as a trap state that deactivates SF. Herein, we demonstrate that a novel pentacene tetraimide (PeTI) undergoes efficient SF via an excimer-like intermediate. Unlike pentacene, the benchmark SF chromophore, PeTI achieves exceptional photostability through peripheral imide functionalization. The formation of an excimer-like intermediate with spectral features characteristic of triplet states was confirmed by transient absorption and sensitization measurements. The decay of the excimer-like state in the visible and near-infrared regions coincided with efficient triplet formation, yielding a triplet quantum yield of 191%. In polystyrene matrices, this excimer-mediated dynamics was suppressed, leading to SF quenching─consistent with solution-phase behavior. Our results showed that PeTI can be used as a novel SF chromophore, and the role of the excimer state in SF needs reconsideration in future material design.
Abstract The small ionic radius of Cs+ results in a low tolerance factor for CsPbI3 perovskite, which intrinsically triggers its spontaneous phase transition from black phase to yellow phase, severely limiting the power conversion efficiency and long-term stability of CsPbI3 perovskite solar cells. Here, we propose an in situ surface reconstruction strategy by introducing formamidinium ions (FA+) onto the CsPbI3 perovskite surface during the spin-coating process. This approach locally increases the tolerance factor in the near-surface region without altering the bulk phase, thereby raising the energy barrier for phase transition and substantially improving phase stability. Furthermore, the incorporation of FA+ boosts the perovskite crystalline quality, reduces defect density, and optimizes interface energy-level alignment. Consequently, the corresponding devices exhibit an improvement in photovoltaic performance alongside significantly enhanced stability under various harsh conditions.
Abstract Nanocrystalline (NC) transition-metal dichalcogenides have received significant attention as earth-abundant electrocatalysts for the hydrogen evolution reaction (HER). MoS2 is the most extensively studied alternative to Pt-group catalysts; however, atomistic insight into its size-dependent catalytic activity remains limited. Here, we investigate HER performance in NC MoS2 with controlled crystallite sizes (6, 11, and 48 nm). The smallest crystallites exhibit markedly enhanced HER activity and higher H2 production compared to larger counterparts, highlighting a strong size–activity relationship. To elucidate the underlying mechanism, we combine electrochemical measurements with in situ and ex situ electron spin resonance (ESR), hyperfine sublevel correlation spectroscopy (HYSCORE), electron–nuclear double resonance (ENDOR), and first-principles calculations. In situ ESR shows that potential-dependent sulfur vacancies in small crystallites actively drive HER. Advanced pulsed ESR techniques (HYSCORE and ENDOR), supported by theoretical modeling, further demonstrate that these sulfur vacancies are preferentially passivated by OH groups rather than hydrogen atoms, forming MoS2-(OH)S adsorbate–defect complexes. These results provide direct spectroscopic evidence linking crystallite size, defect chemistry, and electrocatalytic activity in MoS2. More broadly, this work establishes in situ ESR and advanced magnetic resonance methods as powerful tools for resolving active sites and reaction intermediates in electrochemical energy conversion processes.
Abstract Molecular triplet states are essential for applications in photodynamic therapy, photocatalysis, and energy conversion. However, inefficient intersystem crossing limits their generation. Metal nanoparticles, with their tunable optical responses and rich surface electronic structures, are particularly attractive candidates for enhancing triplet generation. In this work, 1-pyrenecarboxylic acid (PCA) is used as a model molecule to construct Au-PCA, Ag-PCA, Pt-PCA, and Pd-PCA hybrids, enabling the investigation of the universality and metal-dependent effects of nanoparticle-enhanced triplet generation. Transient absorption spectroscopic results show a common kinetic sequence, 1PCA* → PCA– → 3PCA*, for the four metals, which involves interfacial hole transfer, a possible spin flipping, and charge recombination processes. Among the metals, Pt and Pd facilitate charge transfer through high densities of states near the Fermi level, whereas plasmonic Au and Ag further enhance triplet generation via possible plasmonic effects. As a result, the 1O2 quantum yields increase from 13.1% for PCA alone to 42.8%, 36.2%, 27.8%, and 23.8% for Au-PCA, Ag-PCA, Pt-PCA, and Pd-PCA, respectively. Au-PCA and Ag-PCA achieve near-complete inactivation of both Escherichia coli and Staphylococcus aureus. Furthermore, Au-PCA can sensitize RhB to form 3RhB* through solution-phase triplet energy transfer. This work highlights the universality of metal nanoparticles for enhancing triplet generation and reveals key metal-dependent effects that govern their generation and thus performance.
Abstract Separation of Rare Earth Elements (REEs) remains an open challenge for their closely related coordination chemistry and hydration. Neodymium (Nd) and yttrium (Y) form an exemplary pair for this open problem, since Nd is a priority target for recovery from end-of-life magnets while yttrium closely mimics the ionic radius and coordination behavior of heavy rare earth elements, which are common cocontaminants of Nd. Membrane-based separation has been recognized as an efficient and eco-friendly alternative to the conventional solvent extraction procedures. In this context, the development of novel membrane coatings with specific selectivity represents a fundamental challenge that encourages the search for nanostructures equipped with tailored binding sites. In this work, a Density Functional Theory study was conducted to elucidate the adsorption behavior of Y3+ and Nd3+ ions on citrate-functionalized carbon nanotube (CNT-Cit), with the aim of evaluating the potential of this functionalized nanostructure for selective membrane coatings. Adsorption, binding, and deformation energies, in addition to adsorption free energies, were systematically evaluated to quantify the adsorption and stability of metal complexes as a function of the binding topology. The study establishes a structure–energy relationship governing the REEs binding on the citrate-functionalized CNT. The work shows that the adsorption strength and coordination geometry are strongly dependent on the metal ion and functionalization topology. In particular, adsorption at the CNT sidewall site, involving the central carboxylate of citrate, is predicted to be exergonic for Nd and endergonic for Y, whereas adsorption at the CNT tip site was found to be too strong for ion transport. The exergonic and endergonic adsorption of Nd and Y on the citrate functional group at the CNT sidewall suggests that CNT-Cit will be selective for neodymium over yttrium. Although the present study does not directly simulate site-to-site hopping barriers or fluxes in assembled CNT networks, it provides molecular-level guidelines for the design of selective CNT-based networks to be used as membrane coatings for REE recovery.
Abstract We have investigated how Al3+ doping affects the facet-specific performance of SrTiO3 in gas-phase photocatalytic oxidation of acetone, comparing cubic and truncated structures. In situ Diffuse Reflectance Fourier Transform Infrared Spectroscopy (DRIFTS) indicates that Al-doping suppresses facet-specific adsorption of acetone and results in very similar relatively weakly adsorbed states of acetone on both, cubic and truncated structures. Oxidation of adsorbed acetone on both Al3+ doped SrTiO3 structures proceeds via α-cleavage, yielding acetaldehyde and formaldehyde, followed by the formation of surface-bound acetate and formate. The absence of CO2 suggests these species deactivate the surface leading to rapid termination of the oxidation process. Interestingly, the rate at which surface bound products are formed appears higher for the Al3+-doped truncated SrTiO3 than for the cubic morphology─contrary to the undoped analogues showing higher rates for the cubic structure. Time-resolved Photoluminescence (TRPL) analysis shows that Al3+ doping enhances charge carrier lifetimes in both morphologies, compared to undoped SrTiO3 having the same morphologies. Importantly, the Al-doped cubic STO shows shorter carrier lifetimes (τ1 = 86 ± 0.1 ps; τ2 = 709 ± 1 ps) compared to the Al-doped truncated material (τ1 = 116 ± 0.1 ps; τ2 = 1070 ± 1 ps)─which is consistent with the observed faster acetone transformations for the latter. This study shows Al3+ doping of SrTiO3 induces a transition from crystallographically controlled, to defect-dominated surface chemistry upon illumination, prohibiting complete mineralization of acetone, despite a doping induced lengthening of charge carrier lifetimes of cubic and truncated SrTiO3 structures.
Abstract The assembly of molecular photonic wires (MPWs) on DNA scaffolds offers a powerful platform for controlling nanoscale energy transfer. This work demonstrates how the geometric configuration of an excitonic relay, composed of a cyanine (Cy5) dye dimer, regulates energy flow within an MPW. Exploiting linker chemistry, either H-type or J-type aggregates are selectively formed at room temperature. H-type dimers act as energy transfer inhibitors, while J-type dimers function as effective energy relays. In an optimized architecture, J-dimer MPWs outperform equivalent systems using monomeric relays. This performance is significantly amplified upon transitioning the system from solution to solid-state films, where the energy transfer efficiency of J-dimer wires is enhanced by up to 300% relative to monomeric versions. Experimental results also support approximating the dimers as single-point dipoles for Förster resonance energy transfer considerations. These results establish a robust strategy for engineering the optical properties of molecular materials, where nanoscale energy transport is precisely directed by controlling the geometry of excitonic aggregates.
Abstract On-surface chemistry is an effective method for building supra-nanostructures. In this work, we used scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS) to study the reaction between [2,2′/6′,2″-triphenylene]-4,4′,4″-triacetic acid (TPTA) and alkali metal salts on the Au(111) surface. The alkali metal salts electrostatically interact with the TPTA molecules, forming a mixed coadsorption structure. After annealing, the carboxylic deprotonation of TPTA and the decomposition of NaCl occur to form three supra-nanostructures: Na2Cl-TPTA-Na (triangle), NaCl-TPTA-Na (triangle), and TPTA-Na (hexagon). Moreover, scanning tunneling spectroscopy (STS) shows that their lowest unoccupied molecular orbital positions downshift toward the Fermi level (Na2Cl-TPTA-Na 1.94 eV, NaCl-TPTA-Na 1.82 V, and TPTA-Na 1.64 eV). In contrast, KCl and TPTA form multiple K3Cl-TPTA flower-nanostructures. Density functional theory (DFT) calculations and XPS measurements further confirm the deprotonation–decomposition reaction and the formation of supra- and flower-nanostructures. Our work demonstrates a pioneering approach to constructing supra (flower)-nanostructures by alkali metal salts and organic molecules.
Abstract While organic–inorganic hybrid perovskites are widely recognized for exceptional photovoltaic performance, their inherent spin–orbit coupling and polarizability also render them compelling candidates for ferroelectrics and spintronics. In this work, we establish a structure–property relationship across the homologous series (CxH2x+1NH3)2CsPb2Br7 (x = 1–5) by integrating density functional theory calculations with symmetry analysis, revealing how progressive alkyl chain growth drives correlated evolution of crystal symmetry, electronic structure, ferroelectric polarization, and spin properties. The chemically distinct sublattices in hybrid perovskites naturally form dual structural-functional zones quantitatively distinguished by the packing factor (PF), in which the inorganic framework with its consistently higher PF acts as a transport zone, while the lower PF organic sublattice serves as an active zone whose conformational degrees of freedom modulate the ferroelectric response. With increasing chain length, bulk hybrid perovskites undergo a progressive transition from quasi-two-dimensional (2D) to intrinsically confined 2D electronic behavior accompanied by symmetry restoration, enabling a robust momentum-independent persistent spin texture protected by C2v symmetry. Our results demonstrate that the organic spacer acts as an active functional component rather than a passive barrier, offering a precise chemical handle for molecular engineering of 2D hybrid perovskites with tunable electronic properties.
Abstract Vapor-phase layer-by-layer deposition methods are capable of creating thin films of organic, inorganic, or hybrid organic–inorganic nanostructures. This approach allows the combination of the material properties of inorganic matrices with the molecular properties of organic molecules, such as building structures with optoelectronically active dye molecules. One such attractive class of dyes are the porphyrins. However, being macrocycles, their volatility is generally low, which significantly limits their use in vapor-based processes. We have therefore designed and synthesized variously substituted porphyrin macrocycles with the aim of tuning their sublimation properties, as well as their chemical reactivity, to enable their use in vapor deposition processes. A selection of these compounds has been used in molecular layer deposition (MLD) processes, proving their applicability and verifying that the porphyrin macrocycles retain their functional properties within the film material.
Abstract Understanding and controlling reaction mechanisms are essential for the rational design of synthesis protocols for colloidal nanoparticles. In the case of luminescent nanocrystals and semiconductor quantum dots, understanding the correlation between structural and optical properties further enables their optimization for specific applications. Silver sulfide (Ag2S) nanocrystals are promising bioimaging probes due to their tunable photoluminescence emission in the NIR-I and NIR-II ranges and the absence of toxicity of bulk Ag2S. We developed an efficient microwave-assisted aqueous synthesis method using glutathione (GSH) as both the sulfur source and the capping agent for the production of directly water-soluble nanocrystals with potential for bioimaging applications. The nucleation and growth of these crystals are investigated using synchrotron-based X-ray absorption and X-ray photoelectron spectroscopies, which do not rely on either a minimum particle size or their crystallinity. We reveal the local structure around the silver atoms and the surface properties of the nanocrystals and relate them back to their optical properties, size, and crystallinity. This comprehensive and multiscale study reveals the different growth mechanisms taking place as a function of the Ag/GSH precursor ratio. In particular, a switch from a reaction-controlled growth regime to aggregative growth occurs in the case of a low precursor ratio, leading to an abrupt shift in the emission wavelength.
Abstract We synthesize and characterize the solid-solution series xKNbO3–(1 – x)BaFe0.5Nb0.5O3 (x = 1.0 to 0.0) through solid–state reaction. Rietveld refinement and Raman spectroscopy confirm a composition-driven Bmm2→Pm3¯m structural phase transition that completes at x ≤ 0.3. UV–vis Tauc analysis shows the widest band gap tuning (3.11 to 1.65 eV) reported for any single-phase KNO-based system. Progressive photoluminescence quenching confirms decreased electron–hole recombination as BFN content increases, while impedance spectroscopy indicates a 15-fold rise in dielectric permittivity εr, which broadens the space-charge depletion layer. Under a 250 W visible-light source, the x = 0.3 composition (KBFN3) achieves 98.1% photodecolorization (chromophore depletion) of rhodamine B in 50 min (kobs = 0.102 min–1), ∼99× the rate constant of a H2O2-only control lacking catalyst. This is among the highest rate constants reported for any modified KNbO3 system, and, to our knowledge, the only such report for which the catalytic contribution has been isolated from the H2O2/photolysis background via a quantified no-catalyst control, with at least 88% efficiency maintained over five cycles. This work is presented as a proof-of-concept demonstration under controlled laboratory conditions (fixed dye concentration, catalyst loading, and light source). DFT + U calculations link this performance to Fe 3d/O 2p hybridization, which narrows the gap through a valence-band upshift while keeping the conduction-band edge stable, making O2•- the main proposed reactive species. A Marcus outer-sphere electron-transfer analysis of the DFT + U total energies yields reorganization energies of λ(O2•-) = 0.963 eV and λ(•OHdirect) = 1.844 eV, giving activation barriers of 0.231 and 0.677 eV, respectively, and a kinetic rate ratio of ∼107 in favor of the superoxide pathway that remains robust to ±0.2 eV uncertainty in the Mulliken band-edge positions. Complementary climbing-image NEB calculations identify surface hydrogen migration (forward/reverse barriers of 0.536/0.487 eV) as the principal atomic-scale kinetic bottleneck. These findings indicate that dielectric and trap-mediated charge-separation mechanisms can replace ferroelectric polarization in narrow-gap perovskite photocatalysts.
Abstract We have developed and validated the Solution-Potential-Harmonized Parallel Potential-Synchronized Isolated-Cell (SPH-PPSIC) method as a universal, calibration-free electroanalytical platform. This method achieves absolute fluidic protection of the primary analyte domain by partitioning the system into two entirely separate compartments: an independent sample bulk cell (Cell 1) housing the main working and counter electrodes, and a distinct reference cell (Cell 2). To automate cross-boundary potential synchronization without manual tracking, Cell 2 is filled with an identical sample solution, into which a liquid-junction-equipped isolation holder that contains exclusively a supporting electrolyte matrix is immersed. By evaluating the effective configuration of the system, the dynamic interaction between the bulk solution volume in Cell 2 (approximately 18 mL) and the restricted internal volume of the isolation holder (approximately 0.3 mL) yields an approximately 60-fold volumetric asymmetry. This architecture establishes a substantial electrostatic capacitance asymmetry (CCell2≫ Cholder) that spontaneously and continuously clamps the inner potential of the holder to match that of the sample phase. Under complete solution harmonization, cyclic voltammetry of a reversible ferrocyanide probe plotted against the programmed set potential (Eset) yields millivolt-level agreement with the standard three-electrode method without requiring postmeasurement mathematical corrections (ΔECE = 0). Furthermore, severe dynamic wave compression artifacts unmasked in the ferricyanide system under neutral limits─identified as a localized charge-transfer bottleneck caused by the sluggish oxygen evolution reaction at the counter electrode─were successfully mitigated and optimized via targeted solution-phase (alkalinization) and material-phase (Pt–Ni catalytic composite) kinetic approaches.
Abstract Results of first-principles simulations of aqueous solution layers (with and without reactiveFeaq2+) adsorbed on the protonated (001) and (012) crystal surfaces of hematite (Fe2O3) are presented. PBE+U calculations show that the ground-state magnetic structures of both surfaces remain consistent with the bulk antiferromagnetic ordering and that the stable terminations are O-terminated. With these terminations, the calculated interlayer spacings in the bulk just beneath the surfaces agree with experiment to within 4.9%. AIMD simulations with spin order were performed using both PBE+U and SCAN gradient corrections. Results from the two methods are in semiquantitative agreement. At the hematite/water interfaces, the average OD···OA (donor oxygen to acceptor oxygen) distance for hydrogen bonds and the corresponding OD–H···OA angle are ∼2.8 Å and 158°, respectively, close to values in bulk water. The vibrational power spectrum indicates that interfacial water in our simulations exhibits a mixed liquid-like behavior and features of a more strongly hydrogen-bonded structure. The (001) surface structure is consistent with several CTR models, whereas for the (012) surface, the structure agrees with one of the CTR models but deviates from two others. The calculated distance between the first hydration layer and the outermost surface oxygen, however, is consistently larger than experimental estimates. This reveals significant discrepancies in the X-ray reflectivity measurements, likely due to unmodeled surface defects. For the (001) surface, the first-layer height is 2.59 Å by PBE+U and 2.51 Å by SCAN, compared with an experimental value of 1.9 ± 0.6 Å. For the (012) surface, a single adsorbed water layer at 2.34 Å is found, whereas experimental studies report two absorbed water layers with the first located at ∼1.0 Å and the second between 1.4 Å and 2.6 Å from the surface. AIMD simulations of Fe2+ adsorption reveal distinct site preferences at the two hematite interfaces. On the (001) surface, the adsorbed Fe2+ achieves 6-fold coordination by forming three bonds with surface hydroxyl groups and three with water molecules, whereas on the (012) surface it bonds to only two hydroxyls and four water molecules. Projected density of states (PDOS) analysis shows that the energy gap between Fe2+ states and surface oxygen bands is ∼0.5 eV on the (001) surface but ∼1.5 eV on the (012) surface. The greater delocalization of the HOMO into the (001) surface, together with these PDOS features, suggests that absorption and electron transfer are more favorable on (001) than on (012), consistent with their surface magnetic structures.
Abstract Controlling the size of materials has long been a pursuit of the materials science community because it is required to meet specific requirements of functional devices and potential applications. However, reducing the size of two-dimensional (2D) moiré structures is constrained by experimental challenges, particularly in stabilizing nanoscale 2D moiré structures. Herein, we report a universal strategy to realize stabilized edgeless finite-size moiré superlattice, even down to the zero-dimensional regime, within continuous 2D van der Waals heterostructures, via the combination of conventional restacking techniques and scanning tunneling microscope nanolithography. We demonstrate the ability to generate finite-size twisted-double-bilayer-graphene and magic-angle twisted-bilayer-graphene moiré superlattices with custom-designed sizes and sites in (bilayer graphene)-monolayer WSe2-(bilayer graphene) and (monolayer graphene)-monolayer WSe2-(monolayer graphene) sandwich heterostructures, respectively. Our result indicates that the structural reconstruction and the flat band-derived peaks are robust in the finite-size moiré superlattice, even when its size is smaller than a single moiré spot. The method reported here can be generalized in other 2D heterostructures, which will help us to realize a wide variety of high-quality stabilized finite-size moiré superlattices without introducing rough edges.
Abstract Methane migration in cold seep systems involves complex pore-scale dynamics, where gas flow interacts with hydrate formation and gas channel morphology changes. However, the nanoscale coupling mechanisms among methane nanobubbles, methane hydrate, and transport pathways under flowing conditions remain poorly understood. This study investigated how methane seepage flow modulated the evolution of nanobubbles, gas transport channels, and hydrate cages using molecular dynamics simulations. While increasing pressure under static conditions promoted nanobubble growth and gas channel constriction in a manner consistent with classical nucleation theory, the methane flow fundamentally altered this behavior. Beyond a critical acceleration threshold, hydrate formation shifted from thermodynamics-dominated to dynamics-controlled. At high-speed flow, nanobubble populations stabilized despite marked declines under weaker flow, while the bubble size became independent of pressure. Simultaneously, hydrate cage formation was enhanced, while gas channels remained open, a dual outcome attributed to selective surface-saturated cage growth and flow stabilization. Results also revealed a self-stabilization mechanism at high-speed gas flow that suppressed hydrate cage count fluctuations and enabled kinetic energy to dominate both the mass transport and net hydrate formation. These findings established acceleration-driven dynamic control as a fundamental process that reconfigured hydrate growth while preserving essential gas transport channels under cold seep temperature–pressure conditions.
Abstract To extend the study of vanadium disulfide (VS2) nanostructures beyond the system size and simulation time limits of ab initio methods, we introduce a new ReaxFF parameter set: ReaxFF VS2-2025. The ReaxFF VS2-2025 potential was parametrized against extensive quantum mechanical and experimental data, and it can accurately capture the energetic and physicochemical properties of two-dimensional (2D) VS2. Using this force field in molecular dynamics (MD) simulations, uniaxial tensile tests on 2H-VS2 yield Young’s moduli of 122.5 ± 0.1 GPa in the zigzag direction and 108.0 ± 0.2 GPa in the armchair direction, revealing an anisotropic elastic response. Defect formation energy calculations indicate that single sulfur vacancies are the most energetically favorable defect across the entire range of the allowed chemical potential for V and S, and single vanadium vacancies are more favorable than sulfur divacancies in sulfur-rich conditions, all consistent with density functional theory results. The melting simulations yield a melting temperature of 920 ± 50 K for monolayer 2H-VS2. Notably, during the melting process, VS2 shows a transient amorphous structure that has a drop in potential energy. This amorphous structure even shows a lower potential energy than that of the 2D VS2 in a follow-up relaxation at 0 K. These MD simulations confirm that the 2D 2H-VS2 is indeed metastable, explaining why synthesizing layered VS2 is experimentally difficult. Overall, this study offers insights into the structural and physicochemical behavior of VS2, providing a foundation for the rational design of VS2-based materials for catalytic, electronic, and electrochemical applications.
Abstract The manipulation of crystal facets and oxygen vacancies provides an effective strategy for tuning the magnetic properties of functional perovskite oxides. However, the synergistic relationship between facet evolution, oxygen vacancy concentration, and magnetic behavior remains insufficiently understood. Herein, a polyvinylpyrrolidone (PVP)-assisted hydrothermal strategy was developed to regulate the crystal facets of orthorhombic YFeO3 through controlled growth processes. The effects of mineralizer species (KOH and NaOH) and PVP content on facet evolution, oxygen vacancy concentration, and magnetic properties were systematically investigated. XRD results demonstrate that hydrothermal regulation effectively modifies the texture coefficients of specific crystal facets while maintaining the orthorhombic perovskite structure. KOH induces stronger anisotropic growth than NaOH, while PVP promotes the formation of well-defined polyhedral crystals by regulating facet growth. XPS analysis reveals that facet regulation is accompanied by variations in surface oxygen vacancy concentration. The optimized YFeO3 crystals exhibit tailored magnetic properties, with a maximum remanent magnetization of 0.81 emu·g–1, arising from the cooperative modulation of facet-dependent structural evolution and oxygen vacancies on spin canting and magnetic anisotropy. This work provides insights into facet–defect engineering for designing magnetic perovskite oxides.
Abstract Covalent organic frameworks (COFs) have emerged as promising photocatalysts for hydrogen evolution due to their tunable electronic structures and extended π-conjugation. However, a quantitative understanding of how excited-state dynamics and interfacial charge-transfer processes govern photocatalytic efficiency remains limited. In this work, we develop an integrated theoretical framework that links light absorption, exciton dynamics, and interfacial charge-transfer kinetics in substituted COFs, with direct relevance to experimentally measured hydrogen evolution rates. This framework explicitly treats photocatalysis as a sequence of coupled processes culminating in catalytically relevant charge-transfer events. Using a combination of real-time excited-state simulations and Projection Operator Diabatization (POD), we systematically investigate how chemical substitution modulates exciton delocalization, initial electronic coherence, and electronic couplings at the COF–sacrificial donor and COF–Pt cocatalyst interfaces. We show that halogen substitution induces distinct charge-carrier redistribution and separation behaviors, which translate into measurable differences in interfacial electronic couplings. By incorporating these couplings, energetic alignments, and reorganization energies into the Marcus–Hush formalism, we compute hole- and electron-transfer rates that reproduce the experimentally observed trends in hydrogen evolution efficiencies in a semiquantitative manner, without empirical fitting. Extending this analysis to hypothetical functionalizations (−Br, −CN, −NO2, and −COOH) reveals that photocatalytic performance is governed by the emergence of energetically downhill, strongly coupled interfacial states rather than by static descriptors such as molecular dipole moment or binding energy alone. These findings establish charge-transfer rates as a mechanistically grounded descriptor of catalytic activity, demonstrating how subtle modifications in framework chemistry control excited-state dynamics and interfacial charge extraction in a unified manner. More broadly, the methodology established here provides a predictive, physical-chemistry-driven framework for the rational design and screening of efficient light-driven hydrogen evolution catalysts.
