Optimal Surface Structure Research Articles

Enhanced Phase Change Heat Transfer with Fused Deposition Modeling (FDM) Printed Pit and Pillar (Pi2) Arrays

Phase change heat transfer, crucial in thermal management systems, can be significantly enhanced through optimized surface structures. This study investigates pool boiling heat transfer enhancement using 3D printed structures with carefully designed pillar and pit geometries. We present a novel approach combining the Dual Rise model with separate liquid–vapor pathways to improve Critical Heat Flux (CHF) and Heat Transfer Coefficients (HTC). Using copper-infused Polylactic Acid (PLA) filaments, we created and sintered structured surfaces featuring pit-assisted nucleation sites, interpillar spacing for vapor escape, and pillar roughness for enhanced liquid supply. Experiments with deionized water and ethanol under atmospheric pressure demonstrated substantial improvements over plain surfaces: water showed an 87% increase in CHF and 39% in maximum HTC, while ethanol exhibited even greater enhancements of 122% in CHF and 61% in HTC. These improvements are attributed to the synergistic effects of optimized surface geometry and separated liquid–vapor pathways, reducing counterflow resistance and improving hydrodynamic stability. A theoretical framework based on the Dual Rise model explains these enhancements, providing insights into coupled capillary action and hemiwicking effects in boiling heat transfer. The study introduces predictive models for CHF and HTC enhancement, offering valuable tools for future design optimization in applications ranging from electronics cooling to power plant thermal management and advanced heat exchangers.

Antimicrobial Activity of Anodic Porous Alumina with Controlled Surface Structures.

The antimicrobial properties of anodic porous alumina (APA) formed by the anodization of Al substrates were evaluated. APA surfaces with needle-like projections fabricated under controlled preparation conditions exhibited high antibacterial activity against Escherichia coli and Staphylococcus aureus. In antibacterial tests using APA with different interpore distances, all APA surfaces showed high antibacterial activity against E. coli, regardless of the interpore distance. In the case of S. aureus, in contrast, the smaller the interpore distance in APA is, the higher the antibacterial activity. These results indicate that different bacterial species require different optimal surface structures for antimicrobial activity. The needle-like projections formed on the surface of APA became finer as the interpore distance decreased; the finer the projections, the more efficiently the soft cell membrane of S. aureus is disrupted and the higher the antibacterial activity. On an APA with an interpore distance of 60 nm, the colony formation rate of S. aureus and E. coli was reduced to less than 1/100,000 compared to that of a nonanodized Al substrate. The fabrication process described in this article is expected to make it possible to impart antimicrobial properties to the surfaces of various Al products.

Droplet asymmetry bouncing on structured surfaces: A simulation based on SPH method

The impact of a liquid droplet onto a macro-structured super-hydrophobic surface, results in an asymmetric spreading-retraction process and a significant decrease in contact time. The process involves large deformation of droplets and evolution of surface morphology, so it is difficult to efficiently simulate using traditional grid-based methods. In this study, a numerical model is established using the mesh-free smoothed particle hydrodynamics (SPH) method to simulate the interaction of liquid droplets with solid surfaces exhibiting complex macro-textures. Leveraging the Lagrange nature of SPH, liquid droplets can be model using free surface boundary condition. The weakly compressible SPH formulation is employed to discretize the governing equations of liquid. Surface tension is captured by introducing an additional negative pressure term, inducing attractive forces among fluid particles. Kernel functions are carefully chosen to mitigate stress instability resulting from droplet spreading and retraction. The model is then applied to simulate the dynamic processes of droplets impact on flat and non-flat super-hydrophobic surfaces. The bouncing dynamics of droplets are investigated under varying conditions, including Weber number, size, and morphology of macro-scale surface structures. Our simulation results for contact time, maximum diameter, and droplet morphology align closely with experimental observations. The contact time of the droplet exhibits a dependency on its size and surface geometry, with a transition towards planar geometry diminishing asymmetric spreading effects. The findings highlight the significance of Weber number and cylinder diameter in determining contact time, providing insights for the design of optimized surface structures for specific droplet impact parameters. In addition, the use of a free-surface condition for modeling proved computationally efficient for 3D simulations. The model effectively reproduces nonlinear behaviors such as droplet spreading, splashing, and bouncing, highlighting the significant advantage of SPH in simulating such problems.

Tuning surface chemistry to reduce the step-like degradation of LiCoO2 at 4.6 V

Elevating the cut-off voltage is an effective route to increase the energy density of LiCoO2 (LCO). However, the highly delithiated LCO faces the issues of poor structural reversibility, O loss, and Co dissolution, etc., especially in the surface region. Herein, the step-like surface degradation (SSD) of pristine LCO (P-LCO) is firstly revealed to be responsible for the rapid capacity decay. To reduce the adverse impact of SSD, a solid electrolyte is coated and annealed to achieve the optimized surface structure chemistry of LCO (SE-LCO), featuring the outermost surface Li3PO4, surface rock-salt layer, and subsurface spinel-like layer. Benefiting from this surface optimization, the SE-LCO not only shows an enhanced but more reversible phase transition to enhance the structure stability, but also promotes the formation of tough cathode electrolyte interface (CEI) to reduce the O loss and Co dissolution issues. As a result, SE-LCO/graphite cell achieves excellent cycle stability with a remarkable capacity retention of 81.2% after 800 cycles in a potential range of 3–4.55 V, which is among the best reported cell performances. This work broadens the cognition for developing more advanced LCO cathodes.

Facile and Green Synthesis of Well-Defined Nanocrystal Oxygen Evolution Catalysts by Rational Crystallization Regulation.

The development of catalysts for an economical and efficient oxygen evolution reaction (OER) is critical for clean and sustainable energy storage and conversion. Nickel-iron-based (NiFe) nanostructures are widely investigated as active OER catalysts and especially shape-controlled nanocrystals exhibit optimized surface structure and electronic properties. However, the structural control from amorphous to well-defined crystals is usually time-consuming and requires multiple stages. Here, a universal two-step precipitation-hydrothermal approach is reported to prepare a series of NiFe-based nanocrystals (e.g., hydroxides, sulfides, and molybdates) from amorphous precipitates. Their morphology and evolution of atomic and electronic structure during this process are studied using conclusive microscopy and spectroscopy techniques. The short-term, additive-free, and low-cost method allows for the control of the crystallinity of the materials and facilitates the generation of nanosheets, nanorods, or nano-octahedra with excellent water oxidation activity. The NiFe-based crystalline catalysts exhibit slightly compromised initial activity but more robust long-term stability than their amorphous counterparts during electrochemical operation. This facile, reliable, and universal synthesis method is promising in strategies for fabricating NiFe-based nanostructures as efficient and economically valuable OER electrocatalysts.

Fluorine-Free Super-Liquid-Repellent Surfaces: Pushing the Limits of PDMS

Methods for fabricating super-liquid-repellent surfaces have typically relied on perfluoroalkyl substances. However, growing concerns about the environmental and health effects of perfluorinated compounds have caused increased interest in fluorine-free alternatives. Polydimethylsiloxane (PDMS) is most promising. In contrast to fluorinated surfaces, PDMS-coated surfaces showed only superhydrophobicity. This raises the question whether the poor liquid repellency is caused by PDMS interacting with the probe liquid or whether it results from inappropriate surface morphology. Here, we demonstrate that a well-designed two-tier structure consisting of silicon dioxide nanoparticles combined with surface-tethered PDMS chains allows super-liquid-repellency toward a range of low surface tension liquids. Drops of water-ethanol solutions with surface tensions as low as 31.0 mN m-1 easily roll and bounce off optimized surface structures. Friction force measurements demonstrate excellent surface homogeneity and easy mobility of drops. Our work shows that fluorine-free super-liquid-repellent surfaces can be achieved using scalable fabrication methods and environmentally friendly surface functionalization.

Impact of surface cooling on the water harvesting efficiency of nanostructured window glass.

Humans face a severe shortage of fresh water due to economic growth, climate change, overpopulation, and overutilization. Atmospheric water harvesting (AWH) is a promising solution where clean water is collected from the air through various approaches, including dropwise condensation. However, designing surfaces that balance rapid condensation with efficient water removal is challenging. To address this issue, inspired by the efficient water collection mechanisms in the skin of cold-blooded tree frogs, we propose an eco-friendly approach to collect fresh water from cooled window glass. We fabricated various planar and TiO2 nanostructured surfaces including surfaces mimicking a lotus leaf and a hybrid surface mimicking a desert beetle and a cactus, with different wettability levels such as superhydrophilic, hydrophilic, hydrophobic, superhydrophobic, and biphilic. Sub-cooling of glass substrates between 5 and 15 °C using a Peltier device significantly enhanced the condensation process for all surfaces, with modest dependency on surface properties. This cooling temperature regime could be achieved by geothermal cooling methods that consume little energy. To improve visibility for window applications, we developed hydrophobic polymer nanofilm-modified glass substrates using a simple spin-coating technique, and achieved comparable water harvesting efficiency to that of nanostructured substrates. Our study provides insight into the optimal surface structures and cooling temperature for window glass AWH systems that could be used with an underground cooling system.

Enhanced light extraction by optimizing surface microstructure for AlGaN-based deep ultraviolet light emitting diodes with 265 and 280 nm emission

In order to improve the light extraction for the deep ultraviolet light emitting diodes (DUV-LEDs), the surface microstructure based on a parabola cone array is used and optimized in work. In the optimization of the surface structure, inverse design based on a particle swarm optimization intelligent algorithm is applied to maximize the light extraction. The optimization results show that compared with the traditional planar structure, the optimized surface structure improves the light extraction efficiency by more than 200%. In addition, the influence of the designed surface microstructure on the light propagation is also explored by comparing the light field distribution and the light extraction process with the planar structure DUV-LEDs. It is revealed that the high aspect ratio of an array microstructure can change the light propagation and greatly expand the angle of a light escape cone. This effect can be maximized by the inverse design based on the intelligent algorithm, which has great potential in improving the light extraction of AlGaN-based DUV-LEDs.

Maximizing the Light Extraction Efficiency for AlGaN-Based DUV-LEDs with Two Optimally Designed Surface Structures under the Guidance of PSO

A novel method of utilizing an intelligent algorithm to guide the light extraction surface structure designing process for deep-ultraviolet light emitting diodes (DUV-LEDs) is proposed and investigated. Two kinds of surface structures based on the truncated pyramid array (TPA) and truncated cone array (TCA) are applied, which are expected to suppress the total internal reflection (TIR) effect and increase the light extraction efficiency (LEE). By addressing particle swarm optimization (PSO), the TPA and TCA microstructures constructed on the sapphire layer of the flip-chip DUV-LEDs are optimized. Compared to the conventional structure design method of parameter sweeping, this algorithm has much higher design efficiency and better optical properties. At the DUV wavelength of 280 nm, as a result, significant increases of 221% and 257% on the LEE are realized over the two forms of optimized surface structures. This approach provides another design path for DUV-LED light extraction structures.

Effect of bio-inspired surface texture on the resistance of 3D-printed polycarbonate bonded joints

Surface preparation before adhesive bonding is crucial to improve the resistance and durability of the joint by altering the surface properties of the adherend. The purpose of surface treatment is to clean the surface from contaminants, activate the adherend surface and create an optimal surface structure to promote adhesion mechanisms. In that context, this work aims to investigate the influence of substrate surface texturing on the resistance of adhesive joints. Two bio-inspired surface textures were investigated, Fish scale (FS) and Tree frog (TF). Polycarbonate (PC) specimens with different surface patterns were manufactured using the fused deposition modelling process. Surface morphology, such as pattern dimension (shape and depth), surface roughness (Ra), and wettability, were used to characterise the substrates. The influence of these texture patterns on the shear strength of adhesively bonded joints was evaluated through the standardised block shear test method ASTM D4501-01. Moreover, the shear strength of the structured joints was compared to the results from bonding with polished surfaces (surfaces abraded with 80, 600 and 1000 grit paper), and with as-printed surfaces. The results revealed that the FS and TF surface textures enhanced the shear strength by 242% and 283% compared to the adhesive joints with polished surfaces. It was also shown that the variation in depth of the bio-inspired surface texture has no significant impact on the joint strength. Failure analysis demonstrated that the fracture mode of bonded joints with polished surfaces was the adhesive failure while mixed failure (cohesive and adhesive) characterises the as-printed, TF and FS surfaces. Worthy results are obtained rising the effectiveness of surface texture for the PC's bonded joints. Graphical Abstract [Formula: see text] This is a graphical representation of the abstract.

Optimized Purification Methods for Metallic Contaminant Removal from Directly Recycled Li-Ion Battery Cathodes

The viability of emerging direct recycling techniques for lithium-ion battery materials relies on achieving a high-purity material output. Residual metallic contaminants in recycled cathodes are of particular concern, as they introduce significant variability in cell performance and may cause catastrophic cell failure. Thus, shredded battery materials (i.e., black mass; BM) must undergo a purification process to remove metallic contaminants. In the present work, we demonstrate optimized process conditions for the corrosion of solid impurities to ionic form using tailored alkaline chemistry, without incurring damage to the target cathode material (Li(NixMnyCo1-x-y)O2; NMC). Complete ionization of industrially relevant levels of Al and Cu impurities is achieved under conditions of mildly elevated temperature, ultrasonication, and the use of a chelating agent. Structural (XRD, SEM) and electrochemical (impedance, cycling, dQ/dV) analysis of NMC subject to treatment conditions suggests that purification method does not disrupt the cathode’s bulk physico-electrochemical properties. We have applied this purification technique to a laboratory-simulated BM and demonstrated a restoration of pristine performance. Finally, we report on our efforts to tune post-treatment conditions to ensure optimal surface structure and chemistry for subsequent direct recycling processes. Figure 1

(Invited) Designing Microscale Structures for Enhanced Function of Electrocatalysts for Alkaline Water Electrolysis

Water electrolysis has already been implemented for many decades on an industrial scale. It does, however, remain an active area of research and development for the pursuit of materials that have enhanced electrocatalytic performance and prolonged durability. For example, the accumulation of gas bubbles on the surfaces of electrodes during water electrolysis remains a challenge. Persistent bubbles on the surfaces of electrocatalysts can block electrolyte access to the electrode and reduce the electrochemically active surface area. At current densities that are relevant to industrial applications an extensive portion of the electrode can become covered with bubbles. There are a range of solutions that are being utilized in industrial settings, but also additional solutions being sought to optimize the efficiency of these systems. These solutions include applied shear flows across the surfaces of the electrodes, the implementation of ultrasonic induced cavitation, and an increase in electrolyte temperature. These solutions require further expenditures of energy and decrease the overall energy efficiency of the system. Alternative approaches may yield a lower energy demand for maintaining accessibility of the electrolyte to the electrochemically active surface area. One approach is through the design of electrode surface architectures that can assist with the removal of gas bubbles during water electrolysis. This work includes a review of the progress made in preparing structured electrodes for the alkaline based water electrolysis and specifically for the oxygen evolution reaction. These structures can influence the dynamics that occur at the electrode-electrolyte interface, such as the growth, coalescence, and release of oxygen gas bubbles. Understanding the correlations between the structures on the electrodes and their influence on the function of these materials towards the gas evolution are sought to guide the future development of optimal surface structures that are self-cleaning. Designs of electrode surface architectures are sought that can improve the efficiency of electrodes toward this and other gas evolution reactions.

Investigation of the AgCl Formation Mechanism on the Ag Wire Surface for the Fabrication of a Marine Low-Frequency-Electric-Field-Detection Ag/AgCl Sensor Electrode.

One of the most widely used electric field sensors for low-frequency electric field detection (LFEFD) in seawater uses the Ag/AgCl electrode. The surface structure of the electrode including AgCl layers plays a critical role in the electrode’s electrochemical performance required for the sensor. In this study, the sequential AgCl formation process under the constant current was examined on the Ag wire in an electrode size for actual applications, and an optimal electrode surface structure was suggested for the LFEFD Ag/AgCl sensor. Upon mild anodization (0.2 mA/cm2) in 3.3 M KCl solution that permits us to follow the AgCl formation process manageably, Ag dissolution from the wire surface begins leaving cavities on the surface, with the accompanied growth of initial Ag grains. During this period, AgCl deposits in sizes of about several micrometers to 10 μm with crystal planes also form primarily along scratch lines on the wire surface, but in a partial scale. Then, with further anodization, the assumed thin AgCl deposits start to form, covering a large portion of the wire surface. They grow to become deposits in sizes of about several micrometers to 10 μm with no clear facet planes next to one another and are connected to form the network structure, representing the main developing mode of the AgCl deposits. While they cover all the surface, AgCl deposits also form on the surface of the already formed ones, making multiple AgCl layers. All these deposits develop through the nucleation process with a relatively high surface energy barrier, and their formation rate is solely controlled by the release rate of Ag+ from the wire, thus by the applied current magnitude. The Ag/AgCl electrode with a thick AgCl layer and many holes in the AgCl surface structure like microchannels is considered to work effectively for the LFEFD sensor in terms of both detection sensitivity and service lifetime.

Activation and Stabilization of Lipase B from Candida antarctica by Immobilization on Polymer Brushes with Optimized Surface Structure

A reusable support system for the immobilization of lipases is developed using hybrid polymer-inorganic core shell nanoparticles. The biocatalyst core consists of a silica nanoparticle. PMMA is grafted from the nanoparticle as polymer brush via ARGET ATRP (activator regenerated by electron transfer atom transfer radical polymerization), which allows defining the surface properties by chemical synthesis conditions. Lipase B from Candida antarctica is immobilized on the hybrid particles. The activity and stability of the biocatalyst are analyzed by spectroscopic activity analysis. It is shown that the hydrophobic PMMA brushes provide an activating surface for the lipase giving a higher specific activity than the enzyme in solution. Varying the surface structure from disordered to ordered polymer brushes reveals that the reusability of the biocatalyst is more effectively optimized by the surface structure than by the introduction of crosslinking with glutaraldehyde (GDA). The developed immobilization system is highly suitable for biocatalysis in non-native media which is shown by a transesterification assay in isopropyl alcohol and an esterification reaction in n-heptane.

Understanding the Effect of Functionalization on Loading Capacity and Release of Drug from Mesoporous Silica Nanoparticles: A Computationally Driven Study.

MCM-41, a type of mesoporous silica nanoparticle, has garnered widespread interests as a useful carrier for drug delivery wherein the drug gets adsorbed into the pores of the carrier. To understand the adsorption mechanism and release of the drug at the molecular level, in the current study, it was attempted to generate a computational model for the loading of 5-fluorouracil (5-FU), a chemotherapeutic agent into surface-modified MCM-41. The molecular surface models of the mesoporous silica (MCM-41) nanoparticle with different surface substitutions were created. In the first stage, molecular mechanics (MM) simulations were carried out to obtain the optimized surface structures. Subsequently, a 5-FU drug molecule in its different forms was docked on top of different MCM-41 surfaces to understand the adsorption orientation and energetics. To further validate the results, more accurate quantum mechanical (QM) calculations were also carried out, and the energetics between the QM and MM calculations are found to be similar. All the substitutions (−NH2, −CN, −COOH) except the methyl substitution exhibited favorable interactions compared to the unsubstituted MCM-41 surface which was in accordance with the experimental observations. The release rate of 5-FU from MCM-41 and aminopropyl-substituted MCM-41 (MCM-NH2) was studied using molecular dynamics simulations which revealed that the release rate of 5-FU from the MCM-NH2 surface was slower compared to that of plain MCM-41. The detailed surface characteristics and the adsorption energies from the molecular simulations correlating the loading capacity and release are reported in here.

Expanding Biomaterial Surface Topographical Design Space through Natural Surface Reproduction.

Surface topography is a tool to endow biomaterials with bioactive properties. However, the large number of possible designs makes it challenging to find the optimal surface structure to induce a specific cell response. The TopoChip platform is currently the largest collection of topographies with 2176 in silico designed microtopographies. Still, it is exploring only a small part of the design space due to design algorithm limitations and the surface engineering strategy. Inspired by the diversity of natural surfaces, it is assessed as to what extent the topographical design space and consequently the resulting cellular responses can be expanded using natural surfaces. To this end, 26 plant and insect surfaces are replicated in polystyrene and their surface properties are quantified using white light interferometry. Through machine-learning algorithms, it is demonstrated that natural surfaces extend the design space of the TopoChip, which coincides with distinct morphological and focal adhesion profiles in mesenchymal stem cells (MSCs) and Pseudomonas aeruginosa colonization. Furthermore, differentiation experiments reveal the strong potential of the holy lotus to improve osteogenesis in MSCs. In the future, the design algorithms will be trained with the results obtained by natural surface imprint experiments to explore the bioactive properties of novel surface topographies.

Bactericidal efficacy of nanopatterned surface tuned by topography

Due to the exciting physical mechano-bactericidal approach developed in recent years using nanopatterned surfaces with its potential applications in biomedical engineering, now it becomes crucially important to fabricate optimal surface structures so as to achieve the best bactericidal ability. In this paper, the bactericidal efficacy of the cylindrical nanopillar-patterned surface and the sinusoidal nanopillar-patterned surface is presented via minimizing total free energy for a bacterial cell adhered on these two kinds of surfaces. Our theoretical analyses show that the adhesion depth at equilibrium along the nanopillar shafts and the corresponding stretching degree is related to the the nanopillar density and nanopillar radius. The bactericidal efficacy on the nanopillar-patterned surface is determined by the combination of nanopillar density and naopillar radius, which is also supported by the phase diagrams obtained, showing that at large internanopillar spacing and nanopillar radius, the sinusoidal nanopillar-patterned surface is more advantageous in bactericidal efficacy, while in small interspacing and nanopillar radius, the cylindrical nanopillar-patterned surface structure is more powerful. The conclusions obtained in this paper unveil how the mechano-bactericidal effect is achieved by tuning the topography of the nanopatterned surface, a technique helpful to the optimal design and fabrication of bio-mimicking nanotextured surfaces.

The critical role of electrochemically activated adsorbates in neutral OER

Developing efficient electrocatalysts for the oxygen evolution reaction (OER) under neutral conditions is important for microbial electrolysis cells (MECs). However, the OER kinetics in neutral electrolytes at present are extremely sluggish, resulting in high overpotentials that greatly limit the energy conversion efficiencies of MECs. Previous studies failed to probe the adsorbates on surface metal sites of catalysts at the atomic scale and elucidate their influence on the catalytic activities, which has impeded the rational design of efficient neutral OER catalysts with optimal surface structures. Here, using in situ transmission electron microscopy (TEM), in situ X-ray photoelectron spectroscopy (XPS) and in situ low-energy ion scattering studies, we have identified, for the first time, that the electrochemically activated adsorbates on surface metal sites play a critical role in boosting the neutral OER activities of Ru-Ir binary oxide (RuxIryO2) catalysts. The adsorbate-activated RuxIryO2 on a glassy carbon electrode achieved a low overpotential of 324 mV at 10 mA cm−2 in neutral electrolyte, with a 36-fold improvement in turnover frequency compared with that of IrO2 benchmark. Upon application in an MEC system, the resulting full cell showed a decreased voltage of 1.8 V, 200 mV lower than the best value reported to date, facilitating efficient synthesis of poly(3-hydroxybutyrate) from bioelectrochemical CO2 reduction. Density functional theory (DFT) studies revealed that the enhanced OER activity of RuxIryO2 catalyst arose from local structural distortion of adjacent adsorbate-covered Ru octahedra at the catalyst surface and the consequently decreased adsorption energies of OER intermediates on Ir active center.

Facile fabrication of functional cellulose paper with high-capacity immobilization of Ag nanoparticles for catalytic applications for tannery wastewater

It has been a research goal to develop macroscopic materials with an optimized surface structure to affix silver nanoparticles which could contaminate water and maximize their practical functions. Cellulose paper is a versatile biomass material valued for its abundance, low cost, biocompatibility, and natural composition. Until now, its potential application in water purification has not been adequately explored. In this study, gallic acid-modified silver nanoparticles (GA@AgNPs) were loaded onto commercial cellulose filter paper using a simple lipoic acid modification process (GA@AgNPs-LA-CP). Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) were used to characterize the GA@AgNPs-LA-CP. The catalytic activity of the GA@AgNPs-LA-CP was evaluated by the reduction reaction of methylene blue (MB), Rhodamine B (RhB), and 4-nitrophenol (4-NP) with sodium borohydride (NaBH4). The GA@AgNPs-LA-CP exhibited excellent catalytic activity toward MB, RhB, and 4-NP, taking advantage of its high specific surface area generated by the cellulose fiber network structure. Interestingly, due to the electrostatic interactions between the cationic dyes and the GA@AgNPs, the as-prepared catalytic composite material serves as a better catalyst for MB and RhB, suggesting dual applications of the composite materials for organic wastewater treatment and the removal of harmful dyes. This implies that the immobilization of AgNPs on cellulose papers is an effective method and can be applied to efficient wastewater treatment applications.Graphical abstract

Strain-Modulated Platinum-Palladium Nanowires for Oxygen Reduction Reaction.

Electrocatalytic activity of alloy nanocatalytsts can be manipulated effectively by tuning their physical properties (ensemble, geometric, and ligand effects) to afford optimal surface structure and compositions for proton exchange membrane fuel cell (PEMFC) application. Herein, highly catalytic platinum-palladium nanowires (PtnPd100-n NWs) with a subtle lattice strain and Boerdijk-Coxeter helix type morphology are synthesized through a surfactant-free, thermal single phase solvent method. X-ray diffraction results show that PtnPd100-n NWs are exposed through the (111) facets and their shrinking or expanding lattice parameters can be modulated by the alloy compositions. Electrochemical results reveal that their high catalytic activity correlates with the lattice shrinking, facets, and bimetallic compositions, showing higher activity when the ratio of Pt and Pd is ∼78:22, which is further supported by DFT results. Compared to the nanoparticle type platinum-palladium alloyed catalysts with similar metal compositions (PtnPd100-n NPs), the PtnPd100-n NWs exhibit significantly improved electrocatalytic activity and stability for the oxygen reduction reaction. These findings open new strategies to design the highly active and stable alloy nanocatalysts with controllable compositions.