Density Functional Calculations Research Articles

Heavy Atom Cluster Chains with Strong Spin-Orbit Coupling and Magnetic Cations in Mn[PtBi6I12

In the search for new magnetic topological insulators with strong spin-orbit coupling, by following conceptual considerations that have already proven to be suitable, the bismuth-rich subiodide Mn[PtBi6I12] was discovered. Single crystals were grown from mixtures of the elements and BiI3 using a temperature program developed on the basis of thermal analyses. Single-crystal X-ray diffraction revealed a rhombohedral structure of the cuboctahedral cluster anions [PtBi6I12]2-, which are linked into chains via octahedrally coordinated Mn2+ cations. Partial substitution of Mn2+ by Bi3+ and vacancy formation are responsible for a phase width represented by the general formula (Mn1-3xBi2x)[PtBi6I12]. Density functional theory-based calculations and measurements of the electrical resistance showed that the compound is a semiconductor with a topologically trivial band gap. Nonstoichiometry of chain fragments, corresponding to n- and p-self-doping, strongly increases the conductivity, especially along the chains. The compound is paramagnetic at room temperature. Electron spin resonance spectra indicate an increase in spin correlations and the buildup of internal fields below 30 K.

Cu-induced interface engineering of NiCu/Ni3N heterostructures for enhanced alkaline hydrogen oxidation reaction

Constructing well-defined interfaces in catalysts is a highly effective method to accelerate reactions with multiple intermediates. In this study, we developed a heterostructure catalyst combining fcc NiCu and hcp Ni3N, aiming at achieving superior performance in alkaline hydrogen electrocatalysis. The NiCu/Ni3N not only overcomes the inadequate hydroxyl binding energy performance of NiCu alloys but also solves the problems of insufficient active sites found in most Ni/Ni3N. Experimental results and density functional theoretical calculations reveal that the formation of heterostructure significantly depends on the amount of Cu. This approach effectively prevents the side effects of increased catalyst particle size, typically resulting from the high temperatures and prolonged reaction times required for conventional synthesis of Ni/Ni3N. The interface of this heterostructure induces a distinctive overlapping effect that enhances the adsorption of water and lowers the energy barrier for the rate-determining step. The NiCu/Ni3N catalyst shows an impressive activity of 71.8 mA mg−1 at an overpotential of 50 mV, a 14.7 times efficiency enhancement compared to pure Ni and comparable to that of low-loaded commercial Pt/C. This research highlights the potential of NiCu/Ni3N in advancing catalyst development.

Removal of Cr(VI) from electroplating wastewater by CoNi-LDH@NHCS electrode and its electrocatalytic ammonia production

Excess Cr(VI) and nitrates from industrial processes can pose a serious threat to humans and the environment. In this study, a CoNi-layered double hydroxide@nitrogen doped hollow carbon sphere (CoNi-LDH@NHCS) electrode was prepared and used for Cr(VI) removal by capacitive deionization (CDI) as well as waste CoNi-LDH@NHCS electrodes were used for ammonia production (NO3RR). The CoNi-LDH@NHCS electrode could remove up to 98.66 % of 10 ppm Cr(VI). In the actual electroplating wastewater, the removal of Cr(VI) by CoNi-LDH@NHCS electrode was 73.91 %, which showed good deionization performance. Density-functional theory calculations show that the oxygen atoms in the Cr(VI) anion and the hydrogen atoms on the surface of the electrode form hydrogen bonds and are adsorbed on the surface of the electrode under the effect of polarity, and the OH bonds on the surface of the electrode are elongated or even dehydrogenated and eventually form Cr(III)-OH. We also produced a high ammonia yield of 30.51 mg h−1mgcat−1 by using the CoNi-LDH@NHCS electrode that was discarded after the adsorption cycle as a catalyst for electrocatalytic nitrate reduction. This work enabled the sustainable use of electrode materials in addition to offering an effective technique for removing Cr(VI) from electroplating wastewater.

Lattice energy transfer from homo-crystalline substitution for enhanced piezo-photocatalytic CO2 conversion

The rapid recombination of carriers and large activation energy of CO2 compromise the efficiency of CO2 photoreduction. Herein, SrTiO3 (STO) with different molar ratios of La3+ and Al3+ double-site homo-crystalline substitution is prepared by a ball-milling molten salt method. The concentration of Ti3+ and excess oxygen vacancies decrease to improve the catalytic activity. Meanwhile, the double sites act as electron transfer platforms for easy electron transfer from the bulk phase to the surface to foster CO2 photoreduction. Not only that, the energy transfer due to doping-induced lattice distortion can potentially enhance the photocatalytic activity. A piezoelectrically polarized electric field is introduced to further expedite charge transport. As a result, the activity of La, Al-STO piezo-photocatalytic CO2 reduction is improved to 39.17 µmol g-1h−1, which is more than seven times better than that of the pure STO. Furthermore, CO2 adsorbs spontaneously on the catalysts because the thermodynamic energy barrier decreases due to the piezoelectric force, which is verified by density-functional theory calculation. This study reveals the great potential of double-site homo-crystalline substitution of STO pertaining to the charge transport kinetics and thermodynamics of the catalytic reaction in the piezo-photocatalytic CO2 process.

Gold/HNTf2-Cocatalyzed Asymmetric Annulation of Diazo-Alkynes: Divergent Construction of Atropisomeric Biaryls and Arylquinones.

Due to the inherent challenges posed by the linear coordination of gold(I) complexes, asymmetric gold-catalyzed processes remain challenging, particularly in the atroposelective synthesis of axially chiral skeletons. Except for extremely few examples of intramolecular annulations, the construction of axial chirality via asymmetric gold-catalyzed intermolecular alkyne transformation is still undeveloped. Herein, a gold/HNTf2-cocatalyzed asymmetric diazo-alkyne annulation is developed, allowing the atroposelective and divergent synthesis of chiral non-C2-symmetric biaryls and arylquinones in generally good to excellent yield (up to 93% yield) and enantioselectivity (up to 99% ee), with broad substrate scope. Notably, this work represents the first gold-catalyzed atroposelective construction in an intermolecular manner. More interestingly, this strategy is successfully extended to the first asymmetric construction of seven-membered-ring atropisomers bearing one carbon-centered chirality in excellent diastereoselectivity and high enantioselectivity (up to 93% ee and 50:1 dr). Remarkably, the utility of this methodology is further illustrated by the successful application of a representative axially chiral ligand in a series of enantioselective reactions. Importantly, the Brønsted acid as a proton-shuttle cocatalyst significantly promotes this asymmetric annulation. Additionally, the origin of enantioselectivity of this annulation and the role of HNTf2 are disclosed by density functional calculations and control experiments.

Encapsulation-induced hypsochromic shift of emission properties from a cationic Ir(III) complex in a hydrogen-bonded organic cage: A theoretical study.

Encapsulation of coordination complexes within the confined spaces of self-assembled hosts is an effective method for creating supramolecular assemblies with distinct chemical and physical properties. Recent studies with calix-resorcin[4]arene hydrogen-bonded hexameric capsules revealed that encapsulated metal complexes exhibit enhanced and blue-shifted photoluminescence compared to their unencapsulated forms. The photophysical change has been hypothetically attributed to encapsulation-induced confinement, which isolates the metal complex from the solvent, suppressing stabilization of the excited state of the guest by solvent reorganization and structural relaxation, and altering the local environment, such as solvent polarity and viscosity, around the guest. In this study, density-functional theory calculations were conducted to explore how encapsulation affects the photophysical properties of a cationic iridium complex within a hydrogen-bonded hexameric capsule. The encapsulation-induced emission shift was analyzed by separating it into three factors: suppression of solvent reorganization, suppression of structural relaxation of the complex, and electronic interactions between the complex and the capsule. The findings indicate that the photoluminescence modulation is driven by the electronic interaction between the host and guest, which affects the energy levels of the molecular orbitals involved in the T1 excited state and the suppression of excited-state structural relaxation of the Ir complex due to the presence of the host. This study advances our understanding of the photophysical dynamics of coordination complexes within the confined spaces of hexameric capsules, providing a valuable approach for tuning the excited state properties of guest molecules.

Engineering the band structure of type-II MoSe2/WSe2 van der Waals heterostructure by electric field and twist angle: A firstprinciples perspective.

Type-II heterostructures composed of transition-metal dichalcogenides have attracted enormous attention due to their facilitation in efficient electron-hole separation. In this work, we performed density-functional theory calculations to systematically investigate the atomic and electronic structures of MoSe2/WSe2 van der Waals heterostructure. Its six high-symmetry configurations with different interlayer coupling under external electric field and twist angle were addressed. Our results reveal that all the configurations exhibit type-II band alignment and their band gaps can be modulated by the electric field. Notably, the direct to indirect band gap transition only occurs in the configurations with strong interlayer coupling. Moreover, twist-induced symmetry breaking weakens the interlayer interactions, thus leading to reduced interlayer charge transfer. Owing to large interlayer distance and weak interlayer coupling, the band structures of the heterostructure remained unchanged for the twist angles ranging from 13.2° to 46.8°. These findings demonstrate the great potential of the MoSe2/WSe2 heterostructure for applications in optoelectronic and nanoelectronic devices.&#xD.

Synthetically modified mixed phase inverse spinel CuFe2O4 magnetic nanoparticles: Structure, physical, and electrochemical properties for photocatalytic applications

Copper ferrite nanoparticles with crystallite sizes between 21.8 and 27.0 nm are developed by modified co-precipitation (C), two-step hydrothermal (H), and polymer-assisted sol-gel (S) methods. The synthetic conditions caused a structure and morphology variation, resulting in their optoelectrical and electrochemical properties becoming markedly different for specific photocatalytic applications. The nanoparticles are p-type semiconducting with direct optical band-gaps between 2.06 and 2.65 eV and carrier concentrations between 1017 ∼1018 cm−3. Magnetization studies demonstrate that the C-sample exhibits saturation magnetization of 32.44 emu/g nearly double as compared to that of H-sample (16.4 emu/g); however, the latter shows the highest coercivity. Impedance spectroscopy reveals faster electron transfer kinetics across the grain boundaries in the S-sample. The pellets prepared from C- and S- samples have larger dielectric constants and better oxygen ion-led conductivity owing to their larger grain size. Density Functional Theory-based calculation shows that oxygen ion conductivity plays a vital role in hole transport and thus an enhancement in the photocatalytic properties. Photocatalytic activity in the H-sample is superior with a degree of methylene blue dye degradation of 55 % in 2 h and a faster rate kinetics of 0.004 min−1 in the first hour under simulated sunlight.

Construction of Interlayered Single-Atom Active Sites on Bipyridine-Based 2D Conjugated Covalent-Organic Frameworks for Boosting the C2 Products of Electrochemical CO2 Reduction.

The electrochemical carbon dioxide reduction (eCO2RR) shows great potential in the realization of carbon neutrality, which requires a dedicated catalyst design. To develop electrocatalysts that favor C2 products, herein, the synthetic protocol for engineering interlayered single-atom metal active sites on the bipyridine-linked 2D conjugated covalent-organic framework (2D c-COF) has been developed by utilizing the interlayer π-π stacking. The resultant M@BTT-BPy-COF (where M = Cu, Ni, and Fe) provides fully exposed single-atom active sites with a suitable interdistance for catalyzing the key C-C coupling in the eCO2RR process. The Faradaic efficiency of ethanol (FEethanol) exceeds 40% with M@BTT-BPy-COF at -0.8 V vs RHE, outperforming most reported COF-based electrocatalysts. Density functional calculations suggest that the proximal active sites in the pore channel of COFs are the key active sites for promoting the C-C coupling to generate ethanol product. This investigation presents a novel way to engineer single-atom catalytic centers on 2D c-COFs, displaying the great potential of 2D c-COFs in electrocatalysis.

Enabling stable cobalt-free Li-rich cathodes through a one-step dual-modified strategy

Cobalt-free Lithium-rich layered oxides (LRLOs) are promising cathodes for low-cost and high-energy-density Li-ion batteries. However, their remarkable capacity comes with challenges including structural degradation, irreversible oxygen release and sluggish kinetics. Herein, we conduct a one-step dual-modified strategy by yttrium doping and Li3PO4 surface modification. Combining density-functional theory calculations with in-situ X-ray diffraction and in-situ differential electrochemical mass spectrometry, the Y3+ doping and Li3PO4 nano coating modified LRLOs is demonstrated has an excellent structural stability with enhanced Li⁺ diffusion kinetics and stabilized oxygen lattice. Excellent rate performance and thermal stability are achieved: high discharge specific capacity of 221 mAh·g−1 at room temperature (96.5 % at 1 C after 100 cycles) and incredible discharge specific capacity of 210 mAh·g−1 at 55 °C (91.8 % at 2 C after 100 cycles). This work resolves the safety and stability issues and provides a feasible strategy for Co-free LRLOs.

A first-principle study on the band structure of GePb alloys

Abstract Single crystal GePb alloys have been considered as potential direct bandgap materials for optoelectronics application. In this work, density-functional theory calculations were performed to investigate the crystalline and electronic structures of the GePb alloys. The lattice constants of the unstrained GePb alloys are found positively deviating from Vegard’s law with a bowing coefficient of 0.587 Å. GePb has a higher Poisson’s ratios than GeSn with a similar alloying concentration. With the increasing Pb concentration x in Ge1−x Pb x , a new alloying energy level brought by Pb appears at the bottom of the conduction band and continuously decreases. The new energy level is constructed to a new valley as compared to the initial Γ valley and the new energy level is acquiring its higher spectra weights with increasing Pb concentration. An indirect-to-direct bandgap transition occurs with a Pb concentration of 3.3%. The effective masses of holes and electrons in the GePb Γ valley are calculated to decrease with the increasing Pb concentration, while the effective masses of the electrons in the L valley only change slightly. The small effective masses of the electrons in the Γ valley are favorable for high-speed GePb device application.

Double-barrier magnetic tunnel junctions with enhanced tunnel magnetoresistance

Tunnel magnetoresistance (TMR) ratio is a key parameter characterizing the performance of a magnetic tunnel junction (MTJ), and a large TMR ratio is essential for the practical application of it. Generally, the traditional solutions to increasing the TMR ratio are to choose different material combinations as the ferromagnetic (FM) leads and nonmagnetic tunnel barrier. In this work, we study an architecture of MTJs of “FM/barrier/FM/barrier/FM” with double barriers, in contrast to the traditional single barrier structure “FM/barrier/FM.” We first analytically show that double barrier MTJ will generally have much higher TMR ratio than the single barrier MTJ and then substantiate it with the well-known example of “Fe/MgO/Fe” MTJ. Based on density functional calculations combined with nonequilibrium Green's function technique for quantum transport study, in the single barrier “Fe/MgO/Fe” MTJ, the TMR ratio is obtained as 122%, while in the double barrier “Fe/MgO/Fe/MgO/Fe” MTJ, it is greatly increased to 802%, suggesting that double barrier design can greatly enhance the TMR and can be taken into consideration in the design of MTJs.

A computational study of AlScN-based ferroelectric tunnel junction

Ferroelectric (FE) AlScN materials have been experimentally explored for memory and neuromorphic computing device applications. Here a computational study is performed to simulate the device characteristics and assess the performance potential of a ferroelectric tunnel junction (FTJ) based on AlScN. We parameterize an efficient k⋅p Hamiltonian from the complex band structure of AlScN from ab initio density-functional theory calculations to enable efficient quantum transport simulations of the FTJ device. Using a metal–FE–graphene structure enhances the barrier height modulation and the tunneling electroresistance (TER) ratio, compared to a metal–FE–semiconductor FTJ device structure. The barrier height modulation between ON and OFF states can reach ∼ 0.7eV with a FE polarization of 25 μC/cm2. Reducing the AlScN tunnel layer thickness is important for increasing the device ON current and reducing the read latency. The results indicate the importance of contact designs and FE layer thickness in the design of AlScN-based FTJ devices, and highlight the potential of AlScN FTJ for future memory device technology applications.

Facile construction of multifunctional Cu2O@ZnIn2S4 heterojunction with accelerated charge transfer for efficient photocatalytic treatment of tetracycline (TC) under visible light irradiation, DFT calculations

The extensive applicability and remarkable stability of nano-semiconductor photocatalysts are of paramount importance for advancing the field of efficient water treatment. This study presents, Cu2O@ZnIn2S4 photocatalytic materials with type II heterostructure were prepared by indium zinc sulfide capping technology to degrade tetracycline. Characterization results indicated that the degradation rate of tetracycline hydrochloride (TC) could achieve 99.2 % under simulated aqueous environmental conditions, maintaining a degradation rate exceeding 85 % after five cyclic stability tests. Concurrently, the constructed type-II heterojunction effectively enhanced the transient photo responsiveness of the catalyst, facilitating the rapid transfer of photogenerated electrons. Furthermore, the structural configuration of the parceled ZnIn2S4 lamellae acted as a photon trap, minimizing the reflection of incident light and augmenting light utilization efficiency. The inherent electric field of the heterojunction significantly facilitated the degradation of TC, while the nanosheet architecture and surface porosity of the catalyst contributed to enhanced mass transfer capabilities, as corroborated by density-functional theory calculations and band gap analysis. This study utilized Cu2O@ZnIn2S4 as an efficient photocatalyst for water treatment, thereby offering a viable approach for practical applications of the catalyst.

Depth-Resolved Profile of the Interfacial Ferromagnetism in CaMnO3/CaRuO3 Superlattices.

Emergent magnetic phenomena at interfaces represent a frontier in materials science, pivotal for advancing technologies in spintronics and magnetic storage. In this Letter, we utilize a suite of advanced X-ray spectroscopic and scattering techniques to investigate emergent interfacial ferromagnetism in oxide superlattices composed of antiferromagnetic CaMnO3 and paramagnetic CaRuO3. Our findings demonstrate that ferromagnetism exhibits an asymmetric profile and may extend beyond the interfacial layer into multiple unit cells of CaMnO3. Complementary density functional calculations reveal that the interfacial ferromagnetism is driven by the double exchange mechanism, facilitated by charge transfer from Ru to Mn ions. Additionally, defect chemistry, particularly the presence of oxygen vacancies, can play a crucial role in modifying the magnetic moments at the interface, possibly leading to the observed asymmetry between the top and bottom CaMnO3 interfacial magnetic layers. Our findings underscore the potential of manipulating interfacial ferromagnetism through point defect engineering.

Interface-Engineering-Induced C-C Coupling for C2H4 Photosynthesis from Atmospheric-Concentration CO2 Reduction.

Producing ethylene (C2H4) from carbon dioxide (CO2) photoreduction under mild conditions is primarily restricted by the difficulty of C-C coupling. Herein, we designed highly active metal atom clusters anchored on semiconductor nanosheet, which established heteroatom sites on the interface to steer C-C coupling, realizing air-concentration CO2 photoreduction into C2H4 in pure water for the first time. As an example, the Pd nanoclusters loaded on ZnO nanosheets are prepared, demonstrated by the X-ray photoelectron spectroscopy and high-angle annular dark-field image. In situ Fourier transform infrared spectroscopy confirms the C-C coupling step over the Pd-ZnO nanosheets, while quasi in situ X-ray photoelectron spectroscopy illustrates the active sites of Pd and Zn atoms on the Pd-ZnO nanosheets during CO2 photoreduction. Density functional theoretical calculations unveil the transition state energy barrier of C-C coupling of CO* and COH* intermediates are only 0.998 eV, hinting the easy C-C coupling to produce C2 fuels. Therefore, the Pd-ZnO nanosheets first realize C2H4 photosynthesis by atmospheric-concentration CO2 reduction with the formation rate of 1.03 μmol g-1 h-1, while the ZnO nanosheets only acquired the carbon monoxide product.

Interface‐Engineering‐Induced C–C Coupling for C2H4 Photosynthesis from Atmospheric‐Concentration CO2 Reduction

Producing ethylene (C2H4) from carbon dioxide (CO2) photoreduction under mild conditions is primarily restricted by the difficulty of C−C coupling. Herein, we designed highly active metal atom clusters anchored on semiconductor nanosheet, which established heteroatom sites on the interface to steer C−C coupling, realizing air‐concentration CO2 photoreduction into C2H4 in pure water for the first time. As an example, the Pd nanoclusters loaded on ZnO nanosheets are prepared, demonstrated by the X‐ray photoelectron spectroscopy and high‐angle annular dark‐field image. In situ Fourier transform infrared spectroscopy confirms the C−C coupling step over the Pd‐ZnO nanosheets, while quasi in situ X‐ray photoelectron spectroscopy illustrates the active sites of Pd and Zn atoms on the Pd‐ZnO nanosheets during CO2 photoreduction. Density functional theoretical calculations unveil the transition state energy barrier of C–C coupling of CO* and COH* intermediates are only 0.998 eV, hinting the easy C–C coupling to produce C2 fuels. Therefore, the Pd‐ZnO nanosheets first realize C2H4 photosynthesis by atmospheric‐concentration CO2 reduction with the formation rate of 1.03 μmol g−1 h−1, while the ZnO nanosheets only acquired the carbon monoxide product.

Triggering lattice oxygen in in-situ evolved CoOOH for industrial-scale water oxidation

Oxygen evolution reaction (OER) is a kinetic bottleneck in water electrolysis. Activating lattice oxygen oxidation mechanism (LOM) can break the limitation of the theoretical overpotential of the traditional adsorbate evolution mechanism (AEM) and improve the intrinsic activity. Here, we introduced Ag single atoms and Se vacancies in CoSe2 (Ag-CoSe2), and found that Ag single atoms and Se vacancies could activate lattice oxygen in CoOOH electrochemically in-situ derived from CoSe2, triggering the LOM. The catalyst exhibits a low overpotential of 167 mV@10 mA cm−2 and a high mass activity of 732.925 A g−1@250 mV. More importantly, the Ag-CoSe2||Pt/C pair requires only 1.68 V to deliver 500 mA cm−2 in an anion-exchange membrane electrolyzer (30 wt% KOH, 60℃) and maintains virtually no degradation for up to 1500 h. Advanced spectroscopic analyses and density-functional theory calculations demonstrate that the synergy between Ag single atoms and Se vacancies results in an upward shift in the O 2p band and strengthens the covalency of metal-oxygen bonds. This effect activates the lattice oxygen oxidation mechanism and reduces the adsorption energy barrier. Additionally, the shortened Co-Se bond and the decreased formation energy of Se vacancies contribute to enhanced structural and catalytic stability in CoSe₂.

Metalized Borylene in Boron-Gold Carbonyl Complexes: Infrared Spectra and Theoretical Calculations.

Borylenes (:B-R), built on a single B-R bond between boron and another nonmetallic atom or group,are a heated subject of special interest due to their intriguing transition-metal-mimicking reactivity, but the relative lack of understanding for the electronic structure and chemical bonding of transition metal borides leads to lingering neglect of metalized borylenes (:B-M) based on covalent B-M bonding. Here we use infrared photodissociation spectroscopy in combination with density functional calculations to study the geometric structure and chemical bonding of boron-gold carbonyl complex cations. The structure and bonding analyses demonstrated that the BAu(CO)3+ and BAu2(CO)4+ complexes can be described as bis-carbonyl-trapped borylene adducts. While the metal-rich BAu3(CO)4+ complex represents an unusual multicenter-bond-stabilized borylene cation with excellent σ-acidity and π-backbonding capability for CO activation, featuring Cs symmetry with a quasi-T-shaped BAu3+ core. It is manifested that BAu3+ presents greater amphoteric reactivity and improved stability compared to BAu1,2+ due to the presence of the three-center-two-electron Au-B-Au bond. This study discloses a conceptually new platform for accessing reactive metalized borylenes by exploiting the boron-mediated multicenter-bond stabilization strategy and using more bench-stable and ubiquitous metal carbonyl fragments as starting materials, thus providing a broader opportunity for the design of novel chemical structures and catalysts.

Catalytic Synergy between Pd Nanoclusters and Ligand-Functionalized Layered Silicates for Improved Formic Acid Dehydrogenation.

The synthesis and stabilization of Pd nanoclusters on a support, as well as simultaneously achieving optimal catalytic activity, remain challenging tasks. Functionalizing the support surface with specific ligands offers a promising solution, but it often requires carefully balancing trade-offs between the reaction yield and catalyst stability. Here, we used two different ligands (propylamine and propylthiol) to functionalize the layered silicate's interlayer surface for Pd nanocluster synthesis and stabilization. For dehydrogenating formic acid, Pd nanoclusters on aminopropyl groups achieved a catalytic activity ∼27-fold higher than that of thiopropyl groups at 70 °C. Our density functional calculations compared the adsorption energetics and bonding characteristics of single Pd atoms and Pd13 nanoclusters on amino- and thio-functionalized silicate surfaces. Pd-N bonds were predicted to be weaker with minimal covalency, while Pd-S bonds exhibit greater covalency due to higher 4d-3p hybridization, resulting in better stability. However, Pd13 clusters undergo severe structural deformation on thiol-functionalized surfaces, resulting in a smaller overall surface area and diminished catalytic stability.