Monolayer Thickness Research Articles

Monolayer Ge2Te2P4 as a promising photocatalyst for solar driven water-splitting: a DFT study.

The buckling hexagonal structure of Ge2Te2P4 was studied by first-principles calculations. The newly proposed structure was proven to be stable by analyzing its cohesive energy, phonon dispersion, elastic constants and AIMD results. Poisson's ratio of the Ge2Te2P4 monolayer is in the range 0.16-0.18, and Young's modulus is in the range 40.16-43.74 N m-1. The substituted Te atoms enhance the sp2 orbitals which strengthen the σ-bonds and therefore the thickness of the Ge2Te2P4 monolayer is smaller than that of monolayer GeP3. The Ge2Te2P4 monolayer has an indirect band gap of 1.85 eV, which can be narrowed by strains. The compressive band gaps from -2% to -4% change the electronic structure from the indirect band gap into the direct band gap. Strains can also increase the light absorption rate α(ω) in the visible region, which is 2-3 × 105 cm-1 at equilibrium. The Ge2Te2P4 monolayer has a suitable band gap and an appropriate VBM and CBM position for hydrogen generation. Under strain rate of 4% and higher, the VBM and CBM remain at suitable positions for hydrogen production. Another advantage of the Ge2Te2P4 monolayer is that its charge carrier mobilities are really high. The highest electron mobility is 1301.47 cm2 V-1 s-1, and the highest hole mobility is 28627.24 cm2 V-1 s-1, which are much higher than the mobility in monolayer GeP3. The Ge2Te2P4 monolayer has advantages for photocatalytic applications and it is necessary to perform further study on the material.

Anomalous Second Harmonic Generation from Atomically Thin MnBi2Te4

MnBi2Te4 is a van der Waals topological insulator with intrinsic intralayer ferromagnetic exchange and A-type antiferromagnetic interlayer coupling. Theoretically, it belongs to a class of structurally centrosymmetric crystals whose layered antiferromagnetic order breaks inversion symmetry for even layer numbers, making optical second harmonic generation (SHG) an ideal probe of the coupling between the crystal and magnetic structures. Here, we perform magnetic field and temperature-dependent SHG measurements on MnBi2Te4 flakes ranging from bulk to monolayer thickness. We find that the dominant SHG signal from MnBi2Te4 is unexpectedly unrelated to both magnetic state and layer number. We suggest that surface SHG is the likely source of the observed strong SHG, whose symmetry matches that of the MnBi2Te4-vacuum interface. Our results highlight the importance of considering the surface contribution to inversion symmetry-breaking in van der Waals centrosymmetric magnets.

Effect of naproxen on the model lipid membrane formed on the water-chitosan subphase

Non steroidal anti-inflammatory drugs (NSAIDs) are those of the most common over the counter (OTC) medications widely used by millions of people every day. Unfortunately, despite their popularity those drugs can cause serious side effects in the digestive system (ulcers, bleeding, and pain). These inconveniences are caused by the changes in the structures of the outer phospholipid layers of gastric mucus and mucosa. As a result the H+ ions from the stomach acid can pass easily through these natural protective barriers and damage the epithelial cells which causes ulcers and bleeding. Chitosan as a polysaccharide known for its unique biocompatibility, drug delivery possibilities and wound healing effect has been chosen to examine if it can induce the reduction of undesirable effects of naproxen. This paper focuses on the interactions of the naproxen with a model biological membrane with and without the presence of chitosan. Applying the Langmuir technique coupled with the surface potential measurements and the Brewster angle microscope imaging allowed to characterize successfully examined systems in terms of the monolayer compressibility, thickness, stability, electric properties and morphology. The results proved that the presence of naproxen alters the mechanical and electrical properties of the model membrane depending on its surface pressure. Moreover, the addition of chitosan to the lipid-drug system causes significant changes in the properties of the layer, i.e. a reduction of its compressibility, thickness and morphology modification. Nevertheless, chitosan suppresses some changes induced by naproxen such as alteration of the apparent dipole moment and film stability.

Utilization of conventional PXRD apparatus for characterization of thin-films using reconsidered equations for XRR

Conventional powder X-ray diffraction (PXRD) device in Bragg-Brentano configuration was utilized to derive X-ray reflectivity (XRR) measurements of a thin-film without technical specifications provided by the supplier. XRR was reviewed as one of the methods for fast thin-film characterization on behalf of modified equations for quantification of thin-film parameters. We evaluated the feasibility of a conventional PXRD device for an acceptable description of thin-films using the equations for assessment of density, thickness and roughness, modified in manner to address incomplete angular data. We correlated approximations to relative errors. The PXRD-obtained thickness for the sample was 27 nm. The PXRD results were compared with the results obtained using methods that presume some knowledge on the thin-film composition. Ellipsometry considers the thin-film as 61 nm thick metallic-metallic oxide bilayer. Scanning electron microscopy (FESEM) pointed out to homogeneous Ni,Cr-based thin-film sample with a thickness of about 50 nm. Ambiguous FESEM results were corrected with atomic force microscopy (AFM), suggesting a monolayer thickness of 28 nm. Finally, synchrotron XRR allowed the best possible geometry and signal acquisition quality confirming the monolayer with thickness of 27 nm. In conclusion, we find the PXRD setup to be an equally precise method. However, the method shows limitations for complex multilayer thin-film configurations having similar refraction properties. The method can be recommended for thin-film characterization, however, it is not completely self-standing.

Physical Vapor Transport Growth of Antiferromagnetic CrCl3 Flakes Down to Monolayer Thickness.

The van der Waals magnets CrX3 (X=I, Br, and Cl) exhibit highly tunable magnetic properties and are promising candidates for developing novel two-dimensional (2D) spintronic devices such as magnetic tunnel junctions and spin tunneling transistors. Previous studies of the antiferromagnetic CrCl3 have mainly focused on mechanically exfoliated samples. Controlled synthesis of high quality atomically thin flakes is critical for their technological implementation but has not been achieved to date. This work reports the growth of large CrCl3 flakes down to monolayer thickness via the physical vapor transport technique. Both isolated flakes with well-defined facets and long stripe samples with the trilayer portion exceeding 60µm have been obtained. High-resolution transmission electron microscopy studies show that the CrCl3 flakes are single crystalline in the monoclinic structure, consistent with the Raman results. The room temperature stability of the CrCl3 flakes decreases with decreasing thickness. The tunneling magnetoresistance of graphite/CrCl3 /graphite tunnel junctions confirms that few-layer CrCl3 possesses in-plane magnetic anisotropy and Néel temperature of 17K. This study paves the path for developing CrCl3 -based scalable 2D spintronic applications.

Unveiling room temperature upconversion photoluminescence in monolayer WSe2.

Upconversion photoluminescence (UPL) is a phenomenon describing an anti-Stokes process where the emitted photons have higher energy than the absorbed incident photons. Transition metal dichalcogenides (TMDCs) with strong photon-exciton interactions represent a fascinating platform for studying the anti-Stokes UPL process down to the monolayer thickness limit. Herein, we demonstrate room-temperature UPL emission in monolayer WSe2 with broadband near-infrared excitation. The measured excitation power dependence of UPL intensity at various upconversion energy gains unveils two distinguished upconversion mechanisms, including the one-photon involved multiphonon-assisted UPL process and the two-photon absorption (TPA) induced UPL process. In the phonon-assisted UPL regime, the observed exponential decay of UPL intensity with the increased energy gain is attributed to the decreased phonon population. Furthermore, valley polarization properties of UPL emission with circular polarization excitation is investigated. The demonstrated results will advance future photon upconversion applications based on monolayer TMDCs such as night vision, semiconductor laser cooling, and bioimaging.

Influence of3Dprinting process parameters on the tribological properties of acrylic resin

AbstractThis article studied the mechanism of the influence of light‐curing 3D forming parameters of acrylic resin on its tribological and mechanical properties. A three‐factor hybrid orthogonal table was designed, that is, the three key process parameters of printing monolayer thickness (P), heat treatment (H), and ultraviolet curing treatment (U). The priority of three process parameters affecting tribological performance was studied based on Gray Correlation Theory. The results showed that the order of priority was P, U, and H. The tribological and mechanical properties of acrylic resin decreased with the increase of printing monolayer thickness, while the printing efficiency increased with the increase of the printing monolayer thickness. Based on Gray Correlation Theory, the “Wear Resistance Efficiency” (WRE) parameter was defined to comprehensively evaluate the wear resistance and printing efficiency of the samples. When the thickness of the printing monolayer was 30 μm, the comprehensive properties of the material reached the optimal value. The U increased the cross‐linking degree of the acrylic interlayer molecules, and the H reduced the residual stress generated during the printing of the samples. The research results provided data support for the application of 3D printing acrylic resin and its nanocomposites in the field of tribology.

Disks of Oxygen Vacancies on the Surface of TiO2 Nanoparticles

Oxide nanopowders are widely used in engineering, and their properties are largely controlled by the defect structure of nanoparticles. Experimental data on the spatial distribution of defects in oxide nanoparticles are unavailable in the literature, and in the work presented, to gain such information, methods of nuclear reactions and deuterium probes were employed. The object of study was oxygen-deficient defects in TiO2 nanoparticles. Nanopowders were synthesized by the sol–gel method and laser evaporation of ceramic targets. To modify the defect structure in nanoparticles, nanopowders were subjected to vacuum annealings. It was established that in TiO2 nanoparticles there form two-dimensional defects consisting of six titanium atoms that occupy the nanoparticle surface and result in a remarkable deviation of the chemical composition from the stoichiometry. The presence of such defects was observed in two cases: in TiO2 nanoparticles alloyed with cobalt, which were synthesized by the sol–gel method, and in nonalloyed TiO2 nanoparticles synthesized by laser evaporation of ceramic target. The concentration of the defects under study can be varied in wide limits via vacuum annealings of nanopowders which can provide formation on the surface of oxide nanoparticles of a solid film of titanium atoms 1–2 monolayers in thickness.

Peptide Self-Assemblies from Unusual α-Sheet Conformations Based on Alternation of d/l Amino Acids.

Peptide self-assembly is a hierarchical process during which secondary structures formed in the initial stages play a critical role in determining the subsequent assembling processes and final structural ordering. Unusual secondary structures hold promise as a source to develop novel supramolecular architectures with unique properties. In this work, we report the design of a new peptide self-assembly strategy based on unusual α-sheet secondary structures. In light of the strong propensity of leucine toward forming helical conformations and its high hydrophobicity, we design two short amphiphilic peptides Ac-LDLLDLK-NH2 and Ac-DLLDLLDK-NH2 with alternating l- and d-form amino acids. Microscopic imaging, neutron scattering, and spectroscopic measurements indicate that the two heterochiral peptides form highly ordered wide nanotubes and helical ribbons with monolayer thickness, in sharp contrast to twisted nanofibrils formed by the homochiral peptide Ac-LLLLK-NH2. Molecular dynamics simulations from monomers to trimers reveal that the two heteropeptides fold into α-sheets instead of β-sheets, which readily pack into tubular architectures in oligomer simulations. Simulated circular dichroism spectra based on α-sheet oligomers validate the proposed α-sheet secondary structures. These results form an important basis for the rational design of higher-order peptide assemblies with novel properties based on unusual α-sheet secondary structures.

Choline amino acid ionic liquids as green corrosion inhibitors of mild steel in acidic medium

The corrosion inhibition performance of three choline amino acid ionic liquids ([Ch][AA]ILs) for mild steel in 1 M HCl solution was evaluated by electrochemical analysis, gravimetric measurement, and surface morphological characterization in the temperature range of 298–328 K in this paper. The results of the polarization experiments show that [Ch][AA]ILs affect the cathode and anode reaction processes, proving that [Ch][AA]ILs are mixed corrosion inhibitors. Choline phenylalanine ionic liquids ([Ch][Phe]) exhibit the highest corrosion prevention efficiency among the three chosen corrosion inhibitors, as proven by SEM/EDS scanning, XPS analysis, and molecular dynamics simulation. The values of standard free energy of adsorption ΔGads range between − 20 kJ·mol-1 and − 40 kJ·mol-1, showing that inhibitor molecule adsorption on the metal surface involves both physical and chemical adsorption. According to the results of XPS research and quantum chemical calculations, the adsorption of corrosion inhibitor molecules on the metal surface is strongly related to the anions. The corrosion inhibitor molecules form a thick monolayer adsorption layer on the metal surface, preventing metal-corrosive media interaction. The molecular dynamics simulation findings reveal that the corrosion inhibitor molecules replace the solvent water or any other ions pre-adsorbed on the metal surface during the adsorption process, protecting the metal from corrosion.

The Structural Modulation of Amorphous 2D Tungsten Oxide Materials in Magnetron Sputtering

Abstract2D oxide materials have gained tremendous attention in the applications. Herein, a synthesis route of 2D WO3 materials via magnetron sputtering is reported. A deposition between 2D monolayers and thin film structure are accomplished according to the temperature of substrate. And 2D monolayers are only formed on a cooled substrate. Ag doping helps to exfoliate 2D WO3 into freestanding monolayers, in which the thickness of 2D monolayer is only ≈3 nm. The ultralarge size of 2D WO3 shows unique features from the traditional 2D material. Resistive switching device and photocatalysis are discussed as examples of application. There is a clear intermediate resistance state in the device with 2D structure. And the failure of resistive switching device is closely related with the 2D structure of WO3. In the application of photocatalysis, an improved two‐step exfoliation, achieving a stack of WO3 monolayers with a large internal volume, is utilized. The enhancements of photocatalysis are obtained with 2D WO3 after exfoliation.

Sub 0.5 Volt Graphene‐hBN van der Waals Nanoelectromechanical (NEM) Switches

AbstractThe Nanoelectromechanical (NEM) switches are a promising candidate to overcome the physical limitations of the complementary metal‐oxide‐semiconductor (CMOS) switches due to their quasi‐zero leakage behavior, sub‐thermal switching, and suitability to operate in harsh environments. The main obstacles affecting NEM switches are their irreversible switch‐contact stiction, the large switching voltage, and its hysteretic loop. In this study, the irreversible static friction is overcome by employing the weak van der Waals (vdW) bonding of graphene‐hexagonal boron nitride (hBN) contact in the Graphene NEM (GNEM) switches. These vdW switches show sub‐0.5 V switching voltage with an ON/OFF ratio higher than 105 and nearly zero hysteretic window characteristics with a high endurance of over 50 000 switching cycles. These remarkable performances are achieved by exploiting graphene's monolayer thickness, high Young's modulus, cubic mechanical restoring force, and low vdW binding energy characteristics. As chemical vapor deposition graphene and hBN are used in these GNEM switches, it exhibits the prospect for large‐scale graphene NEM system applications. These GNEM switches can be potentially used in ultralow‐power CMOS integrated circuits, hybrid NEM‐CMOS systems, logic devices, NEM resonator mass sensing, and single‐molecule sensors.

The Electrochemical Deposition of Pd and Cucl Films on Graphene

Surface limited redox replacement (SLRR) is an electrochemical technique for depositing metal films monolayers in thickness, typically on other metals. As interest in graphene as a highly conductive, chemically resistant support for metal nanoparticles has risen, some have sought to apply this deposition technique to graphene as an electrochemical alternative to other chemical or vacuum-based deposition techniques. To better understand the nature of the interactions between the metal and graphene, our group has used this technique to deposit Pt on graphene to observe the structure of Pt and its epitaxy with the substrate. We have previously found that Pt prefers to bind to the bridge sites of graphene, preferring to form a simple-cubic-like structure and producing a slight lattice compression. We sought to expand on this study by observing the interactions of Pd with graphene. Pd was deposited on graphene using Cu-mediated SLRR, however, most Cu-mediated SLRR is performed with CuSO4 or Cu(ClO4)2 dissolved in H2SO4 or HClO4. This does not necessarily produce a strong Cu underpotential deposition feature on graphene, so HCl was used as the electrolyte instead. This produced a substantially more pronounced underpotential deposition feature, but cyclic voltammograms in this solution do not appear to agree with typical Cu-S-Cl Pourbaix diagram. This also resulted in two different types of structures, primarily Cu-containing films and primarily Pd-containing nanoparticles. The films were always found in the presence of the particles, but the particles did not always have accompanying films. A structural analysis of the particles determined that they preferred to interface with graphene along the (110) planes of Pd and have a slight elongation along the [001] direction of about 1.6% when oriented such that their columns were visible in the scanning transmission electron microscope. Based on an analysis of their orientation, this alignment and elongation appear to be the result of Pd minimizing its interfacial strain with graphene. A structural and compositional analysis of the films determined them to be CuCl, and they prefer to interface with graphene along their (111) plane, although the reason for this particular orientation is unclear as there is weaker evidence for a correlation between the alignment of the graphene and the films.

A study on the interactions between polycarboxylate ether superplasticizer and montmorillonite

The adsorption of polycarboxylate ether (PCE) superplasticizer on the surface of cementitious materials is a prerequisite for its dispersion and water reduction capability. This paper investigated the adsorption isotherms and kinetics of PCE on montmorillonite (MMT) at 278, 288, 298, and 308 K, respectively. Based on the adsorption behaviors, the critical intercalation concentration of PCE was estimated, and the characterizations of surface adsorption and intercalation were examined. Results show that when its concentration is <0.9 mg/mL, PCE is mainly adsorbed on the surface of MMT. The galleries of MMT are intercalated by the side chain of PCE completely at a concentration of 10 mg/mL. The adsorption isotherms and kinetics of PCE on MMT follow the Freundlich isotherm equation and the pseudo-second-order adsorption equation, respectively. The surface adsorption of PCE is not affected by the temperature, but it presents a lower adsorption saturation at a higher temperature. PCE shows a monolayer thickness of 5.63 nm on the surface, but intercalation conforms to multi-layer adsorption.

Interfacial engineering of 1D/2D heterostructured photoanode for efficient photoelectrochemical water splitting

Solar-driven photoelectrochemical (PEC) water splitting for hydrogen generation is regarded as a sustainable strategy to relieve fossil resource issue. However, its PEC conversion efficiency still suffers from the low light absorption and high electron–hole recombination. Herein, we report 1D/2D hierarchical heterostructured photoelectrode constructed by ordered ZnO nanorod array and intimately attached ultra-thin Hematene (thickness of monolayer: 1–2 nm) for effective PEC water oxidation with visible light irradiation. The onset potential of Hematene/ZnO NRs photoanode (0.28 V versus RHE) for PEC water oxidation has an obvious negative shift compared with that of ZnO NRs (0.32 V versus RHE) indicating the enhanced PEC kinetics. Furthermore, reduced charge transport resistance (18.82 KΩ cm−2), a high carrier density of 9.03 × 1018 cm−3 and the resulting significantly enhanced incident photon-to-current efficiency enhancement compared with ZnO NRs photoanode were obtained for Hematene/ZnO NRs photoanode. All these were ascribed to the formation of large built-in electric field which was arising from the charge redistribution at the ZnO and Hematene interface, and the band alignment engineering between the components. In summary, such interfacial engineering may inspire the future development of 1D/2D hierarchical heterostructured photoanodes in the field of PEC water splitting.

Phonon anharmonicity in multi-layered WS2 explored by first-principles and Raman studies

Anharmonicity is an essential property of two-dimensional materials due to its significant impact on lattice dynamics – involving interactions between phonons, thermal expansion of the structure, and interaction with the substrate. The effects manifest in temperature-dependent redshifts of the phonon frequencies and reduced lifetime. In this work, we investigate phonon anharmonicity in supported 1–5 layered WS2 by performing Raman measurements in the temperature range of 80–500 K and explore the results by ab-initio DFT study. An ab-initio model including three-phonon interaction processes and thermal expansion of all geometrical degrees of freedom (in-plane lattice constant, interlayer distance, and monolayer thickness) well describes the experimental temperature trends of the fundamental E2g1 (in-plane) and A1g (out-of-plane) phonon modes, giving a great promise of using simulation to quantitatively analyze phonon propagation and heat transport in multi-layered two-dimensional materials. The models predict a noticeable increase in the temperature-induced slope of A1g vibrations’ frequency with the number of layers – primarily due to the thermal expansion of interlayer distance. Additionally, we study the impact of the substrate on the phonon properties – concerning cumulated effects of induced strain and electron doping. We show that the effect of biaxial strain is the most significant in the E2g1 phonon mode and independent of the number of layers, while the excess charge is more significant in thin films and affects mainly the A1g mode. The presented studies based on a combination of ab-initio and experimental approaches can be extended to quantitatively analyze phonon evolution with structural modification and external stimuli.

Synthesis of Large-Area MXenes with High Yields through Power-Focused Delamination Utilizing Vortex Kinetic Energy.

Evaluating the delamination process in the synthesis of MXenes (2D transition metal carbides and nitrides) is critical for their development and applications. However, the preparation of large defect‐free MXene flakes with high yields is challenging. Here, a power‐focused delamination (PFD) strategy is demonstrated that can enhance both the delamination efficiency and yield of large Ti3C2T x MXene nanosheets through repetitive precipitation and vortex shaking processes. Following this protocol, a colloidal concentration of 20.4 mg mL–1 of the Ti3C2T x MXene can be achieved after five PFD cycles, and the yield of the basal‐plane‐defect‐free Ti3C2T x nanosheets reaches 61.2%, which is 6.4‐fold higher than that obtained using the sonication–exfoliation method. Both nanometer‐thin devices and self‐supporting films exhibit excellent electrical conductivities (≈25 000 and 8260 S cm‐1 for a 1.8 nm thick monolayer and 11 µm thick film, respectively). Hydrodynamic simulations reveal that the PFD method can efficiently concentrate the shear stress on the surface of the unexfoliated material, leading to the exfoliation of the nanosheets. The PFD‐synthesized large MXene nanosheets exhibit superior electrical conductivities and electromagnetic shielding (shielding effectiveness per unit volume: 35 419 dB cm2 g–1). Therefore, the PFD strategy provides an efficient route for the preparation of high‐performance single‐layer MXene nanosheets with large areas and high yields.

Layer-engineered atomic-scale spalling of 2D van der Waals crystals

<h2>Summary</h2> Transition-metal dichalcogenides (TMDCs), whose physical properties can be modified by the number of layers within the atomic thickness range, are emerging as an essential active interlayer for nanoelectronic devices based on van der Waals (vdW) heterostructures. Here, we show the atomic spalling of vdW crystals that achieves large-area TMDCs with a controlled number of layers. Unlike 3D covalent network solids, the TMDCs are layered crystals featuring strong in-plane covalent bonding and weak out-of-plane vdW interaction, which allow the crack propagation depth to be reduced to the atomic scale. By adjusting the residual stress of the stressor film, we controlled the crack propagation depth at a scale corresponding to the monolayer thickness of the TMDCs. Consequently, mono-, bi-, and trilayer TMDCs were selectively separated from the vdW crystals. The presented results show huge potential for the manufacture of layer-engineered, high-quality vdW materials, which can be developed into functional optoelectronic devices.

Effect of different valent ions (Na+, Ca2+ & Y3+) on structural and morphological features of protein (BSA) thin films adsorbed on hydrophobic silicon (H-Si) surface

Structure and morphology of bovine serum albumin (BSA) films adsorbed on hydrophobic silicon (H-Si) surface from BSA solution in presence of different cationic ions (Na+, Ca2+ and Y3+) are studied. Electron density profile as obtained from X-ray reflectivity analysis shows that ≈ 55 Å thick monolayer of pure BSA is adsorbed on H-Si surface, while atomic force microscopy image displays its globular morphology. A bilayer of globular BSA molecules of average thickness ≈ 85 Å is formed on the H-Si surface at 1–10 mM of Na+ and Ca2+ ions. However, Y3+ ions favor the immobilization of a tri-layer of BSA on H-Si surface except for 5 mM, at which a tetralayer is formed due to the effect of re-entrant condensation of BSA solution. Elemental mapping analysis as obtained from scanning electron microscopy confirms that the attachment of Y3+ ions is higher in comparison with Na+ and Ca2+ ions due to maximum charge density of hydrated Y3+ ions. The contact angle results display intermediate hydrophobicity for Na+ ions, whereas minimum and maximum hydrophobicity for Ca2+ and Y3+ ions interacted protein films, respectively. It is found that the adsorption of BSA is relatively higher in presence of all ions on hydrophobic surface than hydrophilic. All the adsorbed BSA films are found mostly stable with time.

Carbon nanotubes decorated with Pt as a viable electrocatalyst system using electrochemical atomic layer deposition

Surface limited redox replacement (SLRR) is an electrochemical deposition method designed to deposit metal thin films, typically onto other metals, that are mere monolayers in thickness, where such low dimensions allows catalyst-support interactions to affect catalyst efficiency. Here we explore the growth of Pt, using iterative Cu-mediated SLRR cycles, directly onto carbon nanotubes (CNTs) which are potentially good candidates as electrocatalyst supports due to their electrical conductivity and chemical resistance. Scanning electron microscope images showed that Pt grew as nanoparticles, and hydrogen underpotential deposition from cyclic voltammetry showed that the active surface area approached an asymptotic value around eight iterations. Catalytic activity, measured using the oxygen reduction reaction, reached a maximum at ten iterations. Both are shown to be influenced by the growth mode, but electrochemical modeling indicates that the trend in activity is also due to a change in activation energy, possibly due to changes in Pt electronic structure due to interactions with the CNTs. Durability cycling showed a greater than 85% retention of surface area for the first 10,000 cycles of accelerated stress testing but decayed steadily to about 50% after 30,000 cycles. This performance may be related to the phenomenon that limits surface area growth.