Interfacial Contact Area Research Articles

Flexible Tuning of Friction on Atomically Thin Graphene.

The tuning of flexible microscale friction is desirable for the reliability of wearable electronic devices, tactile sensors, and flexible gears. Here, the tuning of friction of atomically thin graphene on a flexible polydimethylsiloxane (PDMS) substrate was obtained with the elastic modulus using a 1H,1H,2H,2H-perfluorodecyltrichlorosilane (FDTS) self-assembly monolayers (SAMs)-modified microsphere probe with the diameter of 5 μm at the microscale. The friction can be tuned at a large scale with the difference in the elastic modulus of PDMS and thickness of graphene. The hydrophobic property of the FDTS SAMs-modified probe decreased friction by reducing interfacial adhesion and preventing the effect of capillary interaction; thus, the friction decreased with the increase in the elastic modulus of the PDMS substrate due to decreasing indentation depth and thus the interfacial contact area; and also, the enhanced out-of-plane stiffness effectively decreased the interfacial contact quality with the increase of the thickness of graphene. The flexible tuning of friction on graphene was further verified by the theoretical calculation from the aspects of the friction arising from the normal and lateral deformation around the contacting area. This work is meaningful for promoting the design and reliability of flexible micro-devices.

Optimization of NH2-UiO-66/TiO2/Au composites for enhanced gas-phase CO2 photocatalytic reduction into CH4

Here we report on the optimization of NH2-UiO-66/TiO2/Au (ca. 1.5 wt%) composite photocatalysts applied to gas phase CO2 photocatalytic reduction in presence of water as reducing agent by varying NH2-UiO-66/TiO2 ratio and pH during synthesis. It is shown that 10 wt% NH2-UiO-66/TiO2/Au (at pH=7) composite leads to the best cumulated CH4 production rate of 136 μmol/gcatalyst with 70% electronic selectivity over 5 h of continuous test. This composite exhibits the best compromise between MOF surface area and thus CO2 adsorption sites, visible light photons absorption capacity and a large interface contact area, which ensured preferable metal(Zr)-to-metal(Ti) charge carrier. Au deposition by impregnation/chemical reduction in also required to perform CO2 photoreduction, and may presumably act as electron traps, co-catalyst or surface plasmon resonator.

Interface Manipulation of Composite Solid Polymer Electrolyte with Polydopamine to Construct Durable and Fast Li+ Conduction Pathways

Taking advantage of light weight, flexibility, and flame retardancy, solid polymer electrolytes (SPEs) provide a feasible solution to these safety concerns and to the enhancement of energy density for lithium-ion batteries (LIBs). However, the development of SPEs is still restricted by low ionic conductivity. Herein, we develop a type of SPE filler built by flower-like Co3O4 microspheres as a lithiophilic backbone and polydopamine (PDA) as a multifunctional coating for the engineering of the interphase properties of the polyether-based SPEs. The hierarchical structure of Co3O4 affords large interfacial contact area with SPEs and effectively suppresses the regular crystallinity of poly(ethylene oxide) (PEO) segments. Moreover, the PDA coating layers with diverse surface functionalities serve as a versatile mediator to finely tune ionic distribution and transport behavior via multiple Lewis acid–base interactions. We uncover the interphase characterizations and their synergistic effects to enhance Li+ conductivity and mechanical/electrochemical stability. This study provides intriguing alternatives for developing composite solid polymer electrolytes (CPEs), for which we further demonstrate the potential application of Co3O4@PDA-based CPEs in all-solid-state LIBs.

A fully coupled mechano-electrochemical model for all-solid-state Li-ion batteries: An optimal strategy for controlling interfacial contact using internal stress generated by electrode expansion

A fully coupled electrochemical-mechanical model of all-solid-state Li-ion batteries (ASSLBs) considering the interfacial contact loss is established. The influences of current and partial molar volume of cathode/anode on the interfacial contact and performance of the ASSLB are numerically studied. The results show that the range of stress changes within the ASSLB are dependent on the current applied. Lithium (Li) partially inserted into anode cannot return to cathode during discharging, which causes a “residual stress” and then can improves the interface contact. The interfacial contact loss gives rise to an increase in local current density. Cycling with a current density of 0.2 mA cm−2, the local current density across the electrode/electrolyte interface is as high as 0.66 mA cm−2, which increases risks such as dendrite formation. We further show that a large partial molar volume of cathode/anode may directly reduce the capacity retention. Moreover, higher partial molar volume of cathode or lower that of anode reduces the (stack) stress, which can deteriorate the interface contact area. Finally, the cathode materials with lower partial molar volume are recommend to balance capacity and interfacial contact. As for anodes, the moderate partial molar volumes are required for robust ASSLBs with improved performance characteristics.

Renewable pickering emulsion system based on bifunctional materials for highly efficient fuel oil desulfurization without stirring

The mass transfer resistance atliquid (oil)-liquid (extractant)interface seriouslylimits the reaction rate and desulfurization efficiency in extraction-catalytic oxidative desulfurization (ECODS), and the catalyst is difficult to be recycled in the homogeneous system. Herein, we demonstrated a renewable Pickering emulsion system with enlarged interfacial contact area to overcome the mass transfer resistance. The bifunctional materials were designed based on Janus graphene oxide (GO) 2D-sheets, amino-modified SBA-15 (NH2-SBA-15) mesoporous microspheres and H3PW12O40 (HPW), as both catalysts and emulsion stabilizers to establish the catalytic emulsion system. Excellent amphiphilicity was endowed by the anisotropic Janus structure of prepared materials, which could convert the oil/extractant bi-phase into a stable Pickering emulsion. The interfacial contact area was skillfully enlarged in emulsion due to formed micro emulsion droplets and empty channels between the droplets, and the catalyst could be easily recycled by centrifugation. Besides, the unique properties of catalyst including large specific surface area, adequate exposed catalytic active sites and high pore volume could also shorten the reaction path and facilitate the rapid diffusion of reactants and products. This opens the door to the application of Pickering emulsion in ECODS fields based on the design of bifunctional materials.

Controllable Pd@Cu2O Schottky junction interface with improved anti-poisoning effect for efficiently electroreduction of CO2 into syngas

Syngas is an important precursor to numerous value-added products and can be produced by the electrochemical CO2 reduction reaction (ECO2 RR). However, developing high-performance CO2-to-syngas based-Cu2O electrocatalysts remains challenging. Herein, a series of ultrathin two-dimensional (2D) Pd@Cu2O Schottky junction catalysts was designed to afford finely tunable syngas productivity across a wide potential range (–0.37 V to –0.87 V vs RHE) with a Faraday efficiency >80 % through the ECO2 RR. Detailed experiments and Density functional theory (DFT) calculations revealed that the 2D structure provided a high interfacial contact area to promote charge transfer, leading to an improved charge distribution at the Schottky junction interface to accelerate CO2 activation and stable Cu2O. CO2·− readily participated in the subsequent two proton transfer step with neighboring PdH to form CO, and the competitive hydrogen evolution reaction was significantly inhibited. This work provides a new avenue to efficiently convert electrocatalytic CO2 to syngas by regulating the interface configuration.

The generation mechanism of demolding force based on themold‐partinterface contact mode in micro‐injection molding

AbstractDemolding is the key step of micro‐injection molding (μIM), which influences the molding quality of polymer parts to a great extent. The essence of demolding is to overcome interface interactions between the mold cavity surface and the part surface, which is closely related to factors such as the cavity surface topography and process parameters. However, a theoretical model predicting the demolding force of μIM is still lacking, resulting in the difficulty of improving the quality of demolding in μIM. Therefore, a comprehensive demolding force model is proposed to clarify the demolding mechanism of μIM. The model focuses on the adhesion behavior and friction behavior in the special contact mode formed by the replication effect of μIM. The theory proof and computation results indicate that the cavity surface topography determines the contact mode of the mold‐part interface (MPI), which in turn changes the real interface contact area, the composition mode of adhesion stress, and the friction forms, thereby affecting the adhesion and friction force during demolding. In addition, the process parameters can also change the contact mode of MPI as the process parameters have a great effect on the filling capacity and the degree of replication, thereby influencing the demolding process.

Do we need perfect mixing between fuel and oxidizer to maximize the energy release rate of energetic nanocomposites?

It is well accepted that close assembly between a fuel and an oxidizer can increase the interfacial contact-area and reduce the diffusion distances, which can significantly promote a heterogeneous reaction. However, we recently observed for nanocomposites of Al/PVDF (aluminum/polyvinylidene fluoride), that if we separated some of the PVDF to form a laminated structure, the flame propagation rate is significantly increased compared to the homogenous case. To probe the mechanism behind this, we used functionalized aluminum nanoparticles to create microsized aggregates of Al-rich and PVDF-rich regions to induce the inhomogeneity and also fabricated Al/PVDF laminate structure films to control the inhomogeneity systematically. The result demonstrates that the inhomogeneous mixing between Al and PVDF can significantly increase the flame front corrugation (burning area). This presumably occurs due to variations in the microburn rate (local burn velocity vectors at the flame front on the microscale). The benefit of the enhanced flame area can apparently overcome the effects of the decrease in the contact area, leading to enhanced burning for an inhomogeneously mixed system. Finally, fluorocarbon functionalization of Al particles can further increase the microburn rate.

Estimation of surface free energy at microstructured surface to investigate intermediate wetting state for partial wetting model.

While partial wetting at nano-/microstructured surfaces can be described using the intermediate wetting state between the Cassie-Baxter and Wenzel states, the limitations of the partial wetting model remain unclear. In this study, we performed surface free energy analysis at a microstructured Si-water interface from both theoretical and experimental viewpoints. We experimentally measured the water contact angle on microstructured Si surfaces with square holes and compared the measured values with theoretical predictions. Furthermore, the surface free energy was analyzed using the effective wetting area estimated from the measured contact angle and electrochemical impedance spectroscopy results. We verified the validity of the partial wetting model for fabricated Si surfaces with a hole aperture a less than 230 μm and a hole height h of 12 μm, and for a < 400 μm, h = 40 μm. The model was found to be applicable to microstructured Si surfaces with a/h < 10.

Guest Editorial: Solar Energy Utilization

Guest Editorial: Solar Energy Utilization

2D/2D BiOIO3/g-C3N4 S-scheme hybrid heterojunction with face-to-face interfacial contact for effective photocatalytic H2 production and norfloxacin degradation

A two-dimensional (2D)/2D hybrid heterojunction with face-to-face interfacial assembly is a desirable dimensionality design with significant potential for various photocatalytic applications due to the large interfacial contact area, which facilitates charge migration and separation. Herein, we developed an efficient 2D/2D hybrid heterojunction consisting of BiOIO3 nanoplates (BIO) and g-C3N4 nanosheets (CN) using a simple but effective in situ growth method for photocatalytic aqueous antibiotic degradation and H2 generation. The face-to-face interfacial assembly of the BIO and CN components in the BIO/CN hybrid heterojunction was verified using electron microscopy. Remarkably, the BIO/CN hybrid heterojunction outperformed both the BIO and CN counterparts in terms of norfloxacin degradation and H2 generation under simulated solar light irradiation. Moreover, the photocatalytic performance of the hybrid catalyst remained nearly unchanged throughout five consecutive test runs. The exceptional performance and stability of the hybrid catalyst are attributable to its extended optical absorption range, large interfacial contact area provided by the face-to-face assembly in the 2D/2D hybrid configuration, and enhanced photoexcited charge separation efficiency and redox power of the separated charges, which are supported by an efficient S-scheme charge transfer mechanism. This study illuminates the rational construction of novel 2D/2D S-scheme hybrid heterojunction photocatalysts with practical applications in environmental remediation and sustainable energy generation.

Molecular dynamics simulation of interface adhesion characteristics between dust suppressant and coal

In the process of coal mining, storage, and transportation, the escape of coal dust restricts the development of various aspects in China, such as environmental pollution, economic loss, and pneumoconiosis. In the present work, molecular dynamics (MD) simulations were used to study the adhesion of dust suppressants to coal molecules. Firstly, the adhesion property of the interface between dust suppressant and coal was studied by calculating the interaction energy and adhesion work of the interface. The dynamic simulation results show that the adhesion between dust suppressant and coal surface is spontaneous, the non-bond interaction plays a key role in this phenomenon, and the electrostatic interaction energy is the main contribution of non-bond energy. In addition, the distribution of dust suppressants on coal surfaces is also analyzed. These analyses contribute to the development of new adhesion dust suppressant materials to solve the problem of coal dust secondary pollution in mining areas. • Atomistic modeling was used to study the adhesive characteristics of dust suppressant • Non-bonded interaction is the key factor of interfacial bonding. • The choice of interface contact area will result in different adhesion work

Analysis of the effect of cryolite on the reaction and combustion process of the mAl/pCuO thermites

Considerable attention has been attracted to thermites due to their high energy density and adjustable burning rate. Compared with nanothermites, micron thermites feature relatively low reaction efficiency due to little interface contact area between reaction components. It is still very necessary to investigate such thermites in which micron Al (mAl) functions as fuel, on account of their low cost and excellent storage stability. Herein, mAl and porous-sheet CuO (pCuO) function as fuel and oxidant, respectively. Different contents of Na3AlF6 are added for constructing mAl/pCuO/Na3AlF6 composites. Results of thermal analysis show that the addition of Na3AlF6 helps increasing the heat release of this thermite system among the temperature range of 25 °C -1000 °C. The existence of Na3AlF6 also improves the duration of combustion. It turns out that the thermite composites containing 10 wt% Na3AlF6 have the highest constant volume combustion pressure. Due to the reaction inertia of Na3AlF6, the burning rate of mAl/pCuO/Na3AlF6 is lower than the pristine mAl/pCuO. Characterization of the reaction products by mAl/pCuO and mAl/pCuO/Na3AlF6 at 1000 °C further illustrates that Na3AlF6 facilitates the reaction between the thermite components. These results indicate that Na3AlF6 shows great potential for improving the combustion efficiency of micron thermites.

3D hierarchical structure collaborating with 2D/2D interface interaction in BiVO4/ZnCr-LDH heterojunction with superior visible-light photocatalytic removal efficiency for tetracycline hydrochloride

Fabrication of heterojunction with specialized geometry shape could improve the photodegradation efficiency of catalysts more efficiently based on the synergistic effect of components. Herein, the BiVO4/ZnCr-LDH type-II heterojunction was successfully synthesized by the growth of two-dimensional (2D) ZnCr-LDH on 2D BiVO4, forming a unique three-dimensional (3D) hierarchical structure. The 3D hierarchical BiVO4/ZnCr-LDH type-II heterojunction with intimate 2D/2D heterointerfaces enlarges the interfacial contact areas and shortens the transfer distance of carriers simultaneously, which could promote the separation and transfer of photoinduced carriers and prolong the lifetime of carriers. Additionally, the 3D structure could enhance the photon utilization efficiency caused by the multiple reflections of incident light, and provide more active sites to promote the adsorption of pollutants. Therefore, the visible light catalytic performance of the optimal heterostructure for the removal of tetracycline hydrochloride is 3.47 times and 22.43 times higher than that of BiVO4 and ZnCr-LDH, respectively. Superoxide radical (O2−) is confirmed as the primary active species, whereas hole (h+) is the secondary active species in the photodegradation process. This work provides a facile strategy to enhance the visible light catalytic behavior of BiVO4 through the fabrication of 3D hierarchical architecture heterojunction for the removal of organic pollutant.

Structural engineering and carbon enrichment in V2CTx MXene: An approach for enhanced supercapacitive charge storage

We report a highly electroactive vanadium carbide MXene in a carbon matrix (V2CTx @C), synthesized with the assistance of metal organic frameworks (MOFs). The morphological changes in the stacked nanosheets of V2CTx MXene resulted in the formation of exfoliated carbon enriched V2CTx nanodiscs which exhibited 3 times increased specific surface area, augmented electronic conductivity, and enhanced electrode/electrolyte interfacial contact area. This altogether led to a high specific capacitance (551 F g−1 at 2 A g−1), remarkable rate performance (317 F g−1 at 10 A g−1), and outstanding cycling stability (88.1% retention after 5000 GCD cycles) of the V2CTx @C electrode. The V2CTx @C || V2CTx @C symmetric cell operates up to 1.2 V, displaying ultrahigh energy/power density (48.6 Wh kg−1 and 552 W kg−1). This work provides a new strategy for structural engineering in MXene based electrode materials for next generation energy storage devices.

Effect of duplex treatment on the long-term stability of the abutment-implant interface by plasma nitriding and TiN coating

The purpose of this study was to evaluate the mechanical properties of abutments subjected to duplex treatment with arc plasma nitriding and physical vapor deposition (PVD) TiN coatings. The surface properties of abutments were analyzed. Then, the screw preload and microgap at the abutment-implant interface were measured. Screw loosening, abutment settlement, and abutment pullout force were tested before and after loading. The fatigue life of implant systems was compared. Finally, abutment surface wear and fatigue fracture surfaces were observed and analyzed. The results showed that duplex-treated abutment increased screw preload, interface contact area, loosening torque, and pullout force. Furthermore, the duplex-treated abutment exhibited good wear resistance and prolonged the fatigue life of implant systems. After cyclic loading, the screw torque loss rate decreased by 15.63 % and the abutment pullout force increased by 3 times. Therefore, duplex-treated abutments could effectively improve the long-term stability of the abutment-implant interface, which may be a suitable method for dental application.

Simulation study of carbon dioxide capture in a novel rotating liquid sheet contactor

The principal objective of this research was to perform a computational fluid dynamics simulation of CO2 capture from a gas stream through aqueous potassium glycinate (K-Gly) and potassium glutaminate (K-Glu) solutions in a rotating liquid sheet (RLS) contactor with inner as well as outer diameters with the size 14 and 18 mm. The obtained model has been solved using COMSOL software. The effects of inlet CO2 concentration, rotational speed, gas flow rate, and solvent concentration on CO2 removal efficiency and removal flux have been investigated. The obtained RLS could have a large interfacial contact area with the gas; they could be designed in such a way that the rotation of the liquid sheet could pump the gas through the empty column at rates equivalent to those observed in the considered packed bed contactors. The device’s centrifugal operation substantially reduced droplet entrainment, and the liquid surface generation control also made the device suitable for solvents that were too viscous to be applied in a packed bed or other similar traditional contactors. The results show that using the K-Gly could increase separation efficiency to more than 95 %. It indicates that increasing the rate of the obtained gas flow from 420 to 700 L/h increases CO2 capture. The model’s validity was further confirmed by the fact that the CO2 predicted mole percentage in the exit gas was within 5.13 % of the experimental values.

Interface Engineering of Conjugated Polymer-Based Composites for Photocatalysis.

Photocatalysis can create a green way to produce clean energy resources, degrade pollutants and achieve carbon neutrality, making the construction of efficient photocatalysts significant in solving environmental issues. Conjugated polymers (CPs) with adjustable band structures have superior light-absorption capacity and flexible morphology that facilitate contact with other components to form advanced heterojunctions. Interface engineering can strengthen the interfacial contact between the components and further enlarge the interfacial contact area, enhance light absorption, accelerate charge transfer and improve the reusability of the composites. In order to throw some new light on heterojunction interface regulation at a molecular level, herein we summarize CP-based composites with improved photocatalytic performance according to the types of interactions (covalent bonding, hydrogen bonding, electrostatic interactions, π-π stacking, and other polar interactions) between the components and introduce the corresponding interface building methods, identifying techniques. Then the roles of interfaces in different photocatalytic applications are discussed. Finally, we sum up the existing problems in interface engineering of CP-based composites and look forward to the possible solutions.

(Digital Presentation) Validation of Python-Based Automated Analysis Approach for Processing STEM/EDS Maps of Catalyst Samples in AEMFCs – a Comparative Study

Technological innovations in the field of materials science are often connected to the nanometric scale material evaluation which requires utilizing a combination of advanced characterization techniques. The extensive data acquired from these characterization techniques necessitates meticulous and efficient analysis, which can only be accomplished by automated digital image and data processing techniques. The development of such techniques will aid further advancements in the design of functional materials. In this work, we report a novel automatic analysis approach using data acquired by the Scanning Transmission Electron Microscopy (STEM) and Energy Dispersive Spectroscopy (EDS) to determine the component distribution and microstructure descriptors for an anion exchange membrane fuel cell (AEMFC). The current research aims to validate the automated approach by comparison to a manual image processing method based on ImageJ reported in a previous study [1]. STEM and EDS data for three different Pd/CeOx-based catalyst samples with varying bulk atomic fractions of Ce/Pd were collected and analyzed. The STEM/EDS data was used to investigate how the interfacial contact area and agglomerate size distributions of Pd and Ce can be related to the microstructural-level interactions and processes and potentially affect the electrochemical performance of an anion exchange membrane fuel cell (AEMFC). The comparison highlighted the strengths and limitations of both automated and manual approaches and offered substantial justification to predict how excessive Ce agglomeration can be linked to a reduction in the electrochemical performance of the fuel cell.[1] R. K. Singh et al., “Synthesis of CeOx-Decorated Pd/C Catalysts by Controlled Surface Reactions for Hydrogen Oxidation in Anion Exchange Membrane Fuel Cells,” Adv. Funct. Mater., vol. 30, no. 38, 2020, DOI: 10.1002/adfm.202002087.

Advanced Porous-Transport-Layer Interface Design for PEM Electrolyzers

Proton-exchange-membrane (PEM) water electrolyzers are promising technologies for generating clean hydrogen for use in a variety of sectors. The anode catalyst layer/porous-transport layer (CL/PTL) interface plays a vital role in determining performance of proton-exchange-membrane (PEM) water electrolyzers. This interface impacts ohmic, kinetic, and mass-transport overpotentials experienced by the cell. PTLs with large surface pores cause undesired catalyst layer deformation into pores of the PTL, which exacerbates degradation, and leads to high ohmic and kinetic overpotentials due to insufficient interfacial contact area.1,2 On the other extreme, low surface porosity at the interface leads to accumulation of oxygen gas that inhibit water transfer, resulting in mass-transport overpotentials.3 Thus, ideal PTLs should have hierarchical structure with high bulk porosity and low tortuosity to mitigate mass-transport overpotentials, while low surface porosity is need to enhance interfacial contact area. In this talk, we explore controlling the interfacial pore structure of these layers through a subtractive method, namely, laser ablation. Laser ablation is a facile method for tailoring the interfacial pore structure of PTLs. Heat from the laser melts titanium, granting a unique morphology advantageous to electrolyzer performance. Laser-ablated PTLs provide improved contact with the CL, while maintaining the bulk pore structure elsewhere, thereby facilitating gas removal and water transport. We also examine how laser-modified PTLs can help enable ultra-low catalyst loadings by minimizing interfacial contact resistance with the thinner catalyst layers. Overall, our work reveals that laser ablation is a facile method to enhance PEM electrolyzer performance. Acknowledgements This work was funded under the H2NEW Consortium by the Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office, of the U. S. Department of Energy under contract number DE-AC02-05CH11231. References T. Schuler, R. De Bruycker, T. J. Schmidt, and F. N. Büchi, J. Electrochem. Soc., 166, F270–F281 (2019)T. Schuler, T. J. Schmidt, and F. N. Büchi, J. Electrochem. Soc., 166, F555–F565 (2019).X. Peng et al., Adv. Sci., 8 (2021).