Au Coatings Research Articles

Facile strategy for uniform gold coating on silver nanowires embedded PDMS for soft electronics

Silver nanowires-embedded polydimethylsiloxane (AgNWs/PDMS) electrodes are promising components for various soft electronics, but face energy mismatch with organic semiconductors. Attempts at galvanic replacement, involving spontaneous gold (Au) formation on the electrodes, often result in non-uniform and particulate Au coatings, compromising device performance and stability. In this study, we introduce a novel approach for achieving a uniform and complete Au coating on AgNWs/PDMS electrodes by adding NaCl to the Au complex solution. This addition slows down the galvanic replacement process and prevents precipitation, enabling a uniform and complete Au coating on the AgNWs surface. Such coating significantly reduces contact resistance (RC), thereby enhancing the electrical characteristics of p-type organic transistors. Furthermore, the development of high-performance, fully soft organic transistors was achieved incorporating an organic semiconductor-elastomer blend. Additionally, reliable, mechanically stable soft glucose sensor was developed, taking advantage of the complete Au coating, which protects against oxidation during the glucose sensing process.

Graphene/polyaniline waterborne composite coatings for metallic bipolar plates

Waterborne composite coatings were formulated for protection of metallic bipolar plates. The challenges lied in two aspects, one was the confliction between high electrical conductivity and good corrosion protection properties; the other was the water dispersibility of the constituent phases. Water-solubility of polyaniline (PANI) were controlled by adding polystyrene sulfonic acid during the polymerization of aniline. Graphene was functionalized by p-aminobenzoic acid and p-phenylenediamine to enhance the compatibility with PANI, while keeping the electrical conductivity of graphene at around 169 S/cm. Upon in-situ polymerization of the functionalized graphene/PANI composites, the electrical conductivity varied significantly from 41 S/cm to 91 S/cm with the surface functionality of graphene. The composite coatings were prepared thereafter with functionalized graphene/PANI/carbon black on the surface of 316 L stainless steel by centrifugal spraying coating. The interfacial contact resistance of the coatings reached 4 mΩ·cm2, comparable to Au coatings, but the corrosion current density was 4.37 μA/cm2 due to the existence of the hydrophilic groups in waterborne coatings, like amino groups and sulfonic acid groups. A post-treatment was carried out to consume some of the amino groups, so that the corrosion current density was decreased to 0.88 μA/cm2.

Sustaining Surface Lithiophilicity of Ultrathin Li-Alloy Coating Layers on Current Collector for Zero-Excess Li-Metal Batteries.

Zero-excess Li-metal batteries (ZE-LMBs) have emerged as the ultimate battery platform, offering an exceptionally high energy density. However, the absence of Li-hosting materials results in uncontrolled dendritic Li deposition on the Cu current collector, leading to chronic loss of Li inventory and severe electrolyte decomposition, limiting its full utilization upon cycling. This study presents the application of ultrathin (≈50nm) coatings comprising six metallic layers (Cu, Ag, Au, Pt, W, and Fe) on Cu substrates in order to provide insights into the design of Li-depositing current collectors for stable ZE-LMB operation. In contrast to non-alloy Cu, W, and Fe coatings, Ag, Au, and Pt coatings can enhance surface lithiophilicity, effectively suppressing Li dendrite growth, thereby improving Li reversibility. Considering the distinct Li-alloying behaviors, particularly solid-solution and/or intermetallic phase formation, Pt-coated Cu current collectors maintain surface lithiophilicity over repeated Li plating/stripping cycles by preserving the original coating layer, thereby attaining better cycling performance of ZE-LMBs. This highlights the importance of selecting suitable Li-alloy metals to sustain surface lithiophilicity throughout cycling to regulate dendrite-less Li plating and improve the electrochemical stability of ZE-LMBs.

Dynamic wetting and spreading mechanisms of SAC305 with added Au elements in the laser jet weld ball bonding process

The lead-free solder SAC305 has inferior wetting properties compared to conventional leaded solders, which deteriorates the weld quality. In this study, Au coatings with varying thickness were applied to improve its wettability and the influencing mechanism was investigated. The results indicated that the wetting angle (WA) and spreading area (SA) increased and then decreased with increasing thickness of the Au coating. The minimum value of WA and maximum value of SA were 25.4° and 8.7 mm2, respectively, when Au coating thickness was 50 nm. The analysis of the interfacial microstructure revealed that the generation of AuSn4 in the triple line region would significantly improve the wettability of Sn alloys. However, when the Au coating thickness reach up to 75 nm, the dense intermetallic compound (IMC) (Cu, Ni)6Sn5 was generated and the wettability of Sn alloys was reduced. The effect of the interfacial compounds on wettability depended on the change of energy consumption mechanism during wetting. The main energy consumption mechanism changed from adsorption of elements to a reaction-controlled, which reaction wetting dominated when the Au coating thickness was greater than 50 nm. This study will provide a deep understanding of wetting behavior and a valuable insight for optimizing solder wetting processes.

Surface characteristics of additively manufactured CoCr and Ti6Al4V dental alloys: The effects of carbon and gold thin film coatings, and alkali-heat treatment.

This study investigates the impact of surface modifications on additively manufactured CoCr and Ti6Al4V dental alloys, focusing on surface properties. Thin film carbon (C) and gold (Au) coatings, as well as alkali-heat treatment, were applied to the high- and low-polished specimens. Scanning electron microscopy (SEM) showed that thin film coatings retained the underlying surface topography, while the alkali-heat treatment induced distinct morphological changes. Energy-dispersive x-ray spectroscopy (EDS) analysis revealed that C-coating enriched surfaces with C, and Au-coating introduced detectable amounts of Au. Nevertheless, signs of coating delamination were observed in the high-polished specimens. Alkali-heat treatment led to the formation of a sodium titanate layer on Ti6Al4V surfaces, confirmed by sodium presence and Fourier transform infrared spectroscopy (FTIR) results showing carbonate bands. Surface roughness measurements with atomic force microscopy (AFM) showed that C-coating increased surface roughness in both high- and low-polished alloys. Au-coating slightly increased roughness, except for low-polished Au-coated Ti6Al4V, where a decrease in roughness was observed compared to low-polished bare Ti6Al4V, likely due to surface defects present in the latter resulting from the additive manufacturing process. Alkali-heat treatment led to a pronounced increase in roughness for both alloys, particularly for Ti6Al4V. Both thin film coatings decreased the water contact angles in all specimens in varying magnitudes, indicating an increase in wettability. However, the alkali-heat treatment caused a substantial decrease in contact angles, resulting in a highly hydrophilic state for Ti6Al4V. These findings underscore the substantial impact of surface modifications on additively manufactured dental alloys, potentially influencing their clinical performance. RESEARCH HIGHLIGHTS: Thin film coatings and chemical/heat treatment modify the surface properties of additively manufactured dental alloys. The surfaces of the alloys get rougher and more hydrophilic after alkali-heat treatment. Thin gold coatings exhibit potential adhesion challenges.

Surface Modification of ZnO Nanotubes by Ag and Au Coatings of Variable Thickness: Systematic Analysis of the Factors Leading to UV Light Emission Enhancement.

Surface modification by plasmonic metals is one of the most promising ways to increase the band-to-band excitonic recombination in zinc oxide (ZnO) nanostructures. However, the metal-induced modulation of the UV light emission depends strongly on the production method, making it difficult to recognize the mechanism responsible for charge/energy transfer between the semiconductor and a metal. Therefore, in this study, the ZnO/Ag and Au hybrids were produced by the same, fully controlled experimental approach. ZnO nanotubes (NTs), fabricated by a template-assisted ALD synthesis, were coated by metals of variable mass thickness (1-6.5 nm thick) using the electron beam PVD technique. The deposited Ag and Au metals grew in the form of island films made of metallic nanoparticles (NPs). The size of the NPs and their size distribution decreased, while the spacing between the NPs increased as the mass of the deposited Ag and Au metals decreased. Systematic optical analysis allowed us to unravel a specific role of surface defects in ZnO NTs in the processes occurring at the ZnO/metal interface. The enhancement of the UV emission was observed only in the ZnO/Ag system. The phenomena were tentatively ascribed to the coupling between the defect-related (DL) excitonic recombination in ZnO and the localized surface plasmon resonance (LSPR) at the Ag NPs. However, the enhancement of UV light was observed only for a narrow range of Ag NP dimensions, indicating the great importance of the size and internanoparticle spacing in the plasmonic coupling. Moreover, the enhancement factors were much stronger in ZnO NTs characterized by robust DL-related emission before metal deposition. In contrast to Ag, Au coatings caused quenching of the UV emission from ZnO NTs, which was attributed to the uncoupling between the DL and LSP energies in this system and a possible formation of the ohmic contact between the Au metal and the ZnO.

Phenomenal Insight into Electrochemically Induced Photocatalytic Degradation of Nitrobenzene on Variant Au-Modified TiO2 Nanotubes

TiO2 nanotubes are a prominent type of TiO2-based nanostructure compared to nanorod arrays. A promising way to improve photocatalytic performance is modifying TiO2 nanotubes with metals, either on the surface or inside the tubes. There is a substantial demand for enhancing the conductivity and charge separation of TiO2 nanotubes, with a major focus on gold (Au) modification. Gold (Au) coatings have significantly improved the photocatalytic activity of TiO2 nanotubes, particularly in pollutant oxidation. However, the mechanism underlying the action of Au-modified TiO2 nanotubes in photocatalytic nitrobenzene oxidation under electrochemical induction remains unclear. Therefore, we conducted related experiments to explore the optimal Au concentration under various conditions. Under electric field induction, the maximum removal rate achieved was 54.9%. Lastly, we analyzed the relevant photocatalytic mechanism to elucidate the responses of electrons and holes to a simulated contaminant under a photo-electrochemical field.

Enhancement of the E12g and A1g Raman modes and layer identification of 2H‐WS2 nanosheets with metal coatings

AbstractRaman spectroscopy in transition metal dichalcogenides (TMDCs) helps determine their structural information and layer dependency. Because it is non‐destructive and fast, it is an archetypal spectroscopic technique to investigate the structure and defects in TMDCs. In our earlier study, we used a metal‐dielectric coating to enhance Raman signal of WS2 because the Raman Spectra measured from WS2 coated on the standard Si/SiO2 was significantly lower. This metal‐dielectric coating allowed access to the otherwise unavailable E12g and A1g modes of WS2. In this study, we compare the Raman spectra of WS2 on a Si/SiO2 to that of metal layers (Au [200 nm] and Al [200 nm]). A significant enhancement in the Raman signal of 2‐3L WS2 is observed for both the Au and Al coatings. Although 200 nm Au coating enhances the Raman Signal better than the 10 nm Au coating, it does not resolve the other signature vibrations other than E12g and A1g. Whereas, coating based on Al (200 nm) and Al (10 nm) both enhance the Raman signal of WS2. In the case of Al coating, we report well‐resolved vibrational modes such as the ones below <300 cm−1in a few layered WS2. This enhancement allows us to quantify the number of layers and also investigate the presence of defects. Photoluminescence measurements on 2–3L and 15L WS2 on Al (200 nm) confirm this.

Gold-coated nanoripples produced by UV-Femtosecond lasers for surface enhanced Raman spectroscopy

Femtosecond (fs) lasers have been recognized as a powerful tool for micro/nanofabrication, due to their advantages of high flexibility, high repeatability, and minimal introduction of heat. Many studies have been made to employ fs laser processing in fabrication of nanostructures on substrates for surface-enhanced Raman spectroscopy (SERS). However, there have been few reports of ultraviolet (UV)-fs-laser-induced nanoripples for SERS experiments. In this study, we developed simple, easy-to-prepare, and large-active-area SERS substrates using UV-fs laser irradiation. Nanoripples induced in open air by the UV-fs laser on Silicon (Si) substrates with gold coatings were used as SERS-active substrates. Nanoripple evolution by the UV-fs laser was explored to establish the processing windows for nanoripple formation as functions of laser fluence and hatching distances. Moreover, SERS enhancement factors (EFs) were correlated with the laser induced nanoripple patterns. SERS EFs up to 2.4 × 107 were achieved for Rhodamine 6G (R6G) molecules on the laser-textured Si substrates with Au coatings of 34 nm thick. The average period of nanoripples for the highest SERS EF is 253 nm, fabricated by a laser fluence of 0.48 J/cm2 and a hatching distance of 38 µm. R6G concentration down to 10−9 mol/L was detected on the laser-textured Si substrate. Besides Si substrates, three other materials, stainless steel, glass, and polystyrene, were also investigated for nanoripple formation and SERS measurements. Nanoripple structures were formed on stainless-steel surfaces and the highest SERS EF of 1.5 × 107 was achieved. For glass and polystyrene substrates, no nanoripple structures were found. As a result, the SERS EFs (∼106) of glass and polystyrene are one order of magnitude lower than those of the Si and stainless-steel substrates. The SERS demonstration using these materials further supports the mechanisms of nanoripple formation and provides a foundation to make UV-fs laser processing an effective technique for SERS applications using various materials. Applications for Sudan I, small extracellular vesicles (sEVs), and glucose were explored and demonstrated the capability of the SERS substrates.

Improvement of excitation and collection efficiency simultaneously with integrated Au coatings for chip-scale NV magnetometer

Improvement of excitation and collection efficiency simultaneously with integrated Au coatings for chip-scale NV magnetometer

Carbon Electrode with Sputtered Au Coating for Efficient and Stable Perovskite Solar Cells

Halide perovskite solar cells (PSCs) represent a low-cost and high-efficiency solar technology. However, most of the highly efficient PSCs need a noble electrode, such as Au, through thermal evaporation. It is reported that a sputtered Au electrode on a PSC could damage the organic hole transport layer (HTL) and the perovskite layer. Here, we report a simple, yet effective sputtered gold nanoparticle decorated carbon electrode to fabricate efficient and stable planar PSCs. The sputtered Au layer on the doctor-bladed coated carbon electrode can be directly applied to the perovskite semicells by mechanical stacking. By optimizing the gold thickness, a power conversion efficiency (PCE) of 16.87% was obtained for the composite electrode-based PSC, while the reference device recorded a PCE of 12.38%. The composite electrode-based device demonstrated 96% performance retention after being stored under humid conditions (50-60%) without encapsulation for ∼100 h. This demonstrates a promising pathway toward the commercialization of large-scale manufacturable sputtered electrodes for the PSC solar module.

Theoretical and experimental studies of mirror-bright Au coatings deposited from a novel cyanide-free thiosulphate-based electroplating bath

The study describes the electrodeposition of mirror-bright Au coatings from a cyanide-free thiosulphate-based bath. The optimized composition of the electroplating bath contains chloroauric acid, sodium thiosulphate, cetyltrimethylammonium bromide (CTAB), 1,4-diazabicyclo[2.2.2]octane (DABCO), and nicotinic acid (NA). Quantum chemical calculations are carried out to study the electronic properties of various potential bath additives that can be used for the formulation of Au electroplating bath. Based upon these studies DABCO, and NA are selected as bath additives. The electrochemical impedance spectroscopy (EIS) study shows the electrochemical behaviour of the bath and the correlation of impedance values with the current density used. Deposition of Au is carried out from the formulated bath via pulse galvanostatic method at different current densities (10, 50, 100 and 200 mA/cm2) at a pulse frequency of 100 Hz and 50 % duty cycle. The XRD and EDS studies of the coatings confirm the presence of gold in its elemental form. The SEM studies, used for studying the effect of current density on the coating morphology, confirm that the coatings have a smooth and compact microstructure. The XPS study shows the atomic composition of the Au coatings. The nano-hardness tests show that the coating hardness decreases with an increase in current density. The coating deposited at 10 and 200 mAcm−2 has a hardness of 294 ± 11.3 and 190 ± 7.2 VHN, respectively.

Effect of Au Coating on the Electrolytic Migration of Ag Bonding Wires for Electronic Packaging Applications

Ag-based bonding wires were generally accepted as the most promising material to substitute for Au bonding wires, however, the electrolytic migration concern of Ag limited its industrial application in electronic packaging, especially in ultra-fine pitch wire bonding. In the present study, the electrolytic migration behaviors of Au-coated Ag bonding wires and Ag wires were studied through water drop tests. The dendrites’ growth and morphology evolution were investigated by in-situ optical microscope observation and the microstructure of the cathodic and anodic bonding wires were characterized by scanning electron microscope test. It could be seen that when comparing Au-coated Ag bonding wires with Ag wires, the dendrite assembled by a large number of Ag nanoparticles grew much more slowly from cathode to anode. The Ag2O particle layer on the anodic wires was thinner, the dendrite contact time was delayed and the current densities at the dendrite contact time were much smaller when the Au coating layer exist. The above results show that Au coating could act as a barrier to inhibit electrolytic migration, which has contributed to electronic packaging applications of Au-coated Ag bonding wires.

Facile engineering of gold alloying on the constancy of silver with polytetrafluorethylene denture base nanomaterial for antimicrobial investigation

Herein, nanocomposites comprising Ag–Au-alloy-based nanomaterials ensembled on the polytetrafluoroethylene (PTFE) were fabricated using the physical vapor deposition method. The Ag-based nanomaterials (AgNMs) undergo oxidation and dissolution in water; therefore, changes in the shape, optical characteristics, and composition of the nanocomposites were investigated through transmission electron microscopy, ultraviolet-visible spectroscopy, and X-ray photoelectron spectroscopy. PTFE@Ag–Au coatings exhibited high antibiofilm efficacy against E. coli WT F1693 and governed the synergistic effect of antibacterial non-stick PTFE and the Ag–Au alloy. The PTFE@Ag–Au-coated NMs sustained the release of Ag+ ions and inhibited up to 50% bacterial growth after 7 days in relation to the PTFE-coated NMs. The conventional XDLVO and DLVO theories were used to describe bacterial adhesion and understand the anti-adhesion process. Despite concerns associated with the hazardous effect of excessive Ag release on fibroblast cells, the coating methods precisely controlled Ag loading, thereby reducing metallic-implant-related bacterial infections.

Enhancement of Magnetic Surface-Enhanced Raman Scattering Detection by Tailoring Fe3O4@Au Nanorod Shell Thickness and Its Application in the On-site Detection of Antibiotics in Water.

Surface-enhanced Raman scattering (SERS) has become a promising method for the detection of contaminants or biomolecules in aqueous media. The low interference of water, the unique spectral fingerprint, and the development of portable and handheld equipment for in situ measurements underpin its predominance among other spectroscopic techniques. Among the SERS nanoparticle substrates, those composed of plasmonic and magnetic components are prominent examples of versatility and efficiency. These substrates harness the ability to capture the target analyte, concentrate it, and generate unique hotspots for superior enhancement. Here, we have evaluated the use of gold-coated magnetite nanorods as a novel multifunctional magnetic-plasmonic SERS substrate. The nanostructures were synthesized starting from core-satellite structures. A series of variants with different degrees of Au coatings were then prepared by seed-mediated growth of gold, from core-satellite structures to core-shell with partial and complete shells. All of them were tested, using a portable Raman instrument, with the model molecule 4-mercaptobenzoic acid in colloidal suspension and after magnetic separation. Experimental results were compared with the boundary element method to establish the mechanism of Raman enhancement. The results show a quick magnetic separation of the nanoparticles and excellent Raman enhancement for all the nanoparticles both in dispersion and magnetically concentrated with limits of detection up to the nM range (∼50 nM) and a quantitative calibration curve. The nanostructures were then tested for the sensing of the antibiotic ciprofloxacin, highly relevant in preventing antibiotic contaminants in water reservoirs and drug monitoring, showing that ciprofloxacin can be detected using a portable Raman instrument at a concentration as low as 100 nM in a few minutes, which makes it highly relevant in practical point-of-care devices and in situ use.

Wet Chemical Synthesis and Characterization of Au Coatings on Meso- and Macroporous Si for Molecular Analysis by SERS Spectroscopy

Porous silicon (PS) is a promising material for nanostructure fabrication providing a precise control over its size, shape, and spatial distribution. This makes it an excellent candidate for constructing highly sensitive, reproducible, and low-cost platforms for surface enhanced Raman scattering (SERS) spectroscopy. In this work, we connect the PS structural parameters with the morphology of the gold nanostructures fabricated on its surface, placing the emphasis on the SERS response. Two different types of PS are considered here, namely meso- and macro-PS. The former is prepared by Si electrochemical etching, applying three different current densities: 100 mA cm−2, 60 mA cm−2, and 30 mA cm−2, while the technological parameters for the latter are selected to mimic metal nanovoids’ (Me NVs) configuration. The gold-coated PS surfaces are produced via an electroless chemical deposition method for different time periods. By performing comprehensive structural, morphological, and optical characterization, we show the importance of the size and density of the PS pore openings, which govern the Au growth kinetics. The results presented in this work assure a simple yet flexible approach for the fabrication of large-area plasmonic gold nanostructures, which are not only suitable for advanced SERS spectroscopy studies but can also serve for a wider range of plasmonic applications.

Synthesis of Gold Nanoparticles from Gold Coatings Recovered from E-Waste Processors.

This work presents the synthesis of Au nanoparticles from gold coatings recovered from processor pins with minimal waste generation. The process consisted of four main steps: (1) physical recovery of pins, (2) recovery of gold coatings by acid digestion, (3) synthesis of HAuCl4 under mild conditions and, (4) synthesis of Au nanoparticles by the Turkevich method. The small dimensions of Au coatings allowed the synthesis of HAuCl4 with lower amounts of HClconc and HNO3conc than those used with aqua regia. This method has significant advantages, such as lower NO2(g) emission, easy post-treatment and purification, low synthesis cost and high yields. Gold nanoparticles synthesized from HAuCl4 were characterized by transmission electron microscopy (TEM) and UV-Vis spectroscopy. Size distribution analysis showed particles 14.23 nm in length and 12.05 nm in width, while absorption spectra showed a surface plasmon located at 523 nm; these characteristics were very similar to those observed with Au nanoparticles obtained with Aldrich’s reagent. It is suggested that recycling procedures can be improved by taking into account the size and shape of the metals to be recovered, thus introducing a new field of research known as hydronanometallurgy.

Perspectives for Deep Eutectic Solvents and Ionic Liquid Analogues in Metal Electroplating

Here we will specifically describe the opportunities and perspectives offered by non-aqueous so-called deep eutectic solvents (DES) and ionic liquid analogues (ILA) in the materials finishing and metal electroplating industries. We will describe a range of plating and dissolution processes from anti-corrosion coatings to new battery technologies. Details will be presented of the plating and characterisation techniques using some novel in-situ methods. These include electrochemical processing and characterisation as well as a number of cutting-edge surface methodologies including acoustic resonance methods, ESR, EXAFS, atomic force microscopy, neutron scattering techniques and magnetic resonance imaging.We will describe a number of case-studies including electrolytic deposition of nickel, alloys such as Ni/Zn, and galvanic methods associated with Au and Ag coatings for the electronics industry. 1, 2, 3 In all these studies we have focused on a combination of fundamental chemical, electrochemical, structural and spectroscopic studies, maintaining close links with industrial partners through collaboration and scale-up trials.We will include very recent updates and future prospects on the use of ILA's in energy storage vectors such as Al secondary batteries. We will describe the advantages and drawbacks of DES and ILA systems in terms of functionality, sustainability and economic cost.

Reactive Spray Deposition Technology As an Alternative Method for Precious Metals Deposition on Sintered Titanium Porous Transport Layers for Application in Advanced Proton Exchange Membrane Water Electrolyzers

The metal layer deposition technologies have been revolutionized throughout the years. One of the most common forms of thin metal film deposition techniques is Physical Vapor Deposition (PVD). Within the category of PVD, there are many modifications based on the source of deposition. Among all PVD variations, the Electron Beam Physical Vapor Deposition (EB-PVD) has the advantages of higher deposition rates, the ability to deposit a wide range of high purity metals for high purity films, and the creation of continuous film layers. [1,3]. EB-PVD is better known as a thermal vaporization technique. Thermal Vaporization focuses on a source, in this case an Electron Beam (EB), which bombards the desired source material with electrons. The electron beam increases the temperature of the porous metal source until it reaches its vapor phase. The metal vapor is then condensed onto the surface of the substrate holder perpendicular to the source material. While EB-PVD is known for its advantages of higher material utilization efficiency, higher deposition rates, and better step coverage [1], it lacks in its ability to penetrate into the volume of Porous Transport Layer (PTL) or coat surfaces that are not perpendicular to the source. This is important as the PTL is in contact with a corrosive environment, which causes metal corrosion and degradation of the PTL at the surfaces that are not protected by the coating.A key aspect plaguing the thin film deposition techniques is the ability to penetrate deep into the volume of a PTL and provide full coating of the porous material, including surfaces not perpendicular to the source. In an attempt to find a solution to this challenging task, we explored the capability of the Reactive Spray Deposition Technology (RSDT) to deposit precious metal nanoclusters directly onto all surfaces in the volume of the sintered titanium material [2]. The studied metal coating of interest is Gold (Au). In this work, we have deposited Au coatings of various thicknesses onto the Ti-PTLs by using both EB-PVD and RSDT techniques. The Au thin film deposits are characterized by scanning electron microscopy (SEM), digital optical microscopy, inductively coupled plasma (ICP), and focused ion beam scanning electron microscopy (FIB-SEM) [2]. The optimal deposition parameters for thin and continuous Au films with precisely controlled thicknesses have been identified. In addition, the depth of penetration of the deposits in the volume of the PTL as a function of the deposition parameters have been studied in detail, and the results will be reported at the ECS 242 meeting.

A Path to Significant Reduction of the Interfacial Contact Resistance of Sintered Titanium Porous Transport Layers in Advanced Proton Exchange Membrane Water Electrolyzers

Proton exchange membrane water electrolyzers (PEMWEs) are a leading industry solution to large scale production of green hydrogen, and as a form of energy storage [5]. The PEMWEs have the advantages of having greater energy efficiency, higher product purity, and are environmentally friendly. Within the construction of a PEMWE stack, there are many catalysts coated membranes (CCMs) sandwiched between anode porous transport layers (PTLs) and cathode Gas Diffusion Layers. The PTL is constructed of sintered titanium powder or fibers. The Ti-PTL is on the anode side of a PEMWE cell where the water diffuses towards the CCM. The anode half-cell reaction or oxygen evolution reaction (OER) occurs on this side of the cell. This is important as the PTL is in contact with the bipolar plate (BPP) and the anode catalyst layer [9].A key aspect plaguing the PEMWEs is the highly oxidative and corrosive environment that is typically observed on the anode side. This significantly affects the interfacial contact resistance (ICR) of the components as the corrosion can cause the ohmic resistance of the PTL to increase. In order to combat the corrosion in the PTLs, in this work we use two thin film deposition methods, Physical Vapor Deposition (PVD) and Vacuum Sputtering, to deposit protective metal layers on top of the state-of-the-art Ti PTLs [2]. The explored metal coatings of interest are Platinum (Pt) and Gold (Au) [9]. For the purposes of these experiments, Au and Pt coatings with various thicknesses are deposited on Ti-PTLs by using either PVD or vacuum spattering method. As deposited thin films are characterized by scanning electron microscopy (SEM), digital optical microscopy, and inductively coupled plasma (ICP) analysis. Also, the in-plane conductivity and the ICR of all samples of interest are measured before and after the electrochemical tests by using the 4-probe method and in-house build setup for ICR measurements. The optimal deposition parameters for fabrication of thin, continuous and smooth Pt and Au protective coatings that result in minimum ICR and improved in-plane conductivity of the PTLs of interest are identified, and the results will be reported at the ECS 241 meeting.