There is no doubt that the development of chemical technologies is closely tied to progress in catalysis. Two aspects are crucial here: the search for new, efficient, selective, and stable nanocatalysts tailored to specific reactions and obtaining them in forms best suited for modern catalytic systems, such as structured reactors. Both challenges fit perfectly within the capabilities of cold (non-equilibrium) plasma thin-film deposition technology. The enormous potential of this technology for producing new nanocomposite materials with predetermined molecular structures, nanostructures, and electronic structures that are so crucial for catalytic properties seems unrivaled. This review summarizes recent progress in cold plasma deposition methods, including low-pressure plasma-enhanced chemical vapor deposition (PECVD), atmospheric-pressure plasma deposition (APPD), and plasma-enhanced atomic layer deposition (PEALD), and highlights their usefulness in fabricating thin films on 3D supports as packings for catalytic structured reactors. Advances in plasma deposition of nanocomposite films and the design of their architectures for catalytic activity are also discussed, with particular focus on emerging research involving nanoscale heterojunctions. Furthermore, the most important chemical processes currently being tested using plasma-derived nanocatalysts are presented, providing strong evidence of their practical applicability. Overall, this work demonstrates the significant potential of cold plasma technology for the design and fabrication of innovative nanocatalysts.

Functionalisation of gas diffusion layers via remote plasma deposition: Tailoring surface morphology for enhanced fuel cell performance

Immobilization of lignin nano/microparticles on plasma-modified polymer nanofibers.

Abstract Direct Energy Deposition (DED)-Arc Plasma has emerged as a promising Additive Manufacturing (AM) technology for fabricating high-performance and large-volume metal parts through hybrid AM, where semi-finished conventional products are used as substrates for AM deposition. However, producing multi-material components remains one of the challenges due to the interfacial properties, intermetallic phases, and conditional compatibility of the different alloys to be joined together. The current study investigated the effect of deposition regimes on the substrate-deposition interface properties when combining different substrates (EN AW 7075) and feedstock materials (EN AW 4046) during multi-layer depositions using DED-Arc Plasma. Plasma and mechanical surface treatments were applied to the substrate surface prior to deposition to investigate their effect on the interface properties. The microstructure, second phases, and mechanical properties of the interface were evaluated through optical microscopy (OM), scanning electron microscopy (SEM), electron backscattered diffraction (EBSD), and hardness tests. The structural investigations revealed a well-defined buildup zone (BZ), partially melted zone (PMZ), and heat-affected zone (HAZ). Additionally, interfacial bonding between the buildup and substrate, with no signs of delamination, was observed. The microstructural and mechanical characterisation showed that the localised preheating from plasma treatment resulted in lower porosity percentage, higher penetration, and finer grain structure. However, the larger PMZ and higher grain boundary second phase segregations in the plasma-treated samples caused higher crack propagation and lower hardness. In conclusion, this study provides valuable insights into the effect of pretreatment substrates for hybrid Al-alloys deposition using the DED-Arc Plasma process and unlocks new opportunities for building hybrid structures and repair applications for the process.

Improvement in surface properties of AISI-5160 steel by transition metal (Nb, V) nitride coating through cathodic cage plasma deposition

In this study, polypyrrole/MCM-41 composite was synthesized and characterized via the two different routes of chemical and plasma methods. Glassy carbon electrodes were modified with MCM-41 and its respective composites through drop-casting, followed by drying, to be utilized in the amperometric sensing of glucose. The electrode surface was modified with glucose oxidase via cross-linking. Samples were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction analysis, thermogravimetric analysis and scanning electron microscopy (SEM) techniques. The amperometric determination of glucose was achieved onto modified working electrode at +0.70V vs. Ag/AgCl. The response time of the glucose electrodes was 30 s. In fact, the electrode modified with PPy/MCM-41-plasma exhibited analytical performance comparable to that of PPy/MCM-41-chemical. However, the PPy/MCM-41-chemical composite modified electrode exhibited the superior analytical performance towards glucose compared to the pure MCM-41 and PPy/MCM-41-plasma. The upper limit of the linear working range was 4.1 mM glucose concentration for PPy/MCM-41-chemical. The glucose sensor exhibited an analytical performance, characterized by a low detection limit (LOD) of 381 nM and a high sensitivity of approximately 910.72 µA.mM−1.cm−2. Based on the Lineweaver-Burk plot, the sensor exhibited a KM value of 0.009 mM, indicating a high enzymatic affinity for glucose.

Cathodic Cage Plasma Deposition of Ag/Porous Silicon as a Scalable Route To SERS Substrates

This review summarizes the development of cathodic cage plasma nitriding (CCPN) and cathodic cage plasma deposition (CCPD) techniques. CCPN was introduced to eliminate issues in direct current plasma nitriding (DCPN), such as the edge effect, by isolating the sample at a floating potential and using radiative heating. The process was further adapted for CCPD, in which the cage serves as a sputtering target (e.g., Ti, graphite, Mo, Hastelloy) for the deposition of ceramic and metallic films. Combining nitriding pretreatment with CCPD resulted in duplex treatments that establish a hardness gradient and enhance film adhesion. The most recent advance is cathodic cylinder plasma deposition (CCyPD), which employs compacted powder targets (such as MoS2 or metal oxides) for composite film deposition and in situ oxide reduction. The review traces the evolution from process improvement to a versatile platform for surface engineering.

Abstract This work provides a quantitative analysis of what it would take to fully evaporate copper macroparticles embedded in a cathodic arc plasma flow. This analysis is important for the justification of efforts to develop an evaporation scheme based on adding an electron beam. We want to explore if this approach could be an alternative to conventional plasma filtering to obtain macroparticle-free plasma from a cathodic arc plasma source. If successful, cathodic arc plasma deposition could be extended from a popular technology for hard and decorative coatings to much more demanding coatings applications, for example in microelectronics. Here, we study the feasibility and economical implication of evaporating micrometer-sized macroparticles on length and time scales typical for cathodic arc deposition systems. We show by analytical modeling that macroparticles with a radius ⩽1 µ m can be completely evaporated in a plasma of density 10 16 m −3 when using an electron beam of at least 3 keV and a beam electron density of at least 10 14 m −3 . While the theoretical opportunity is shown, we acknowledge the significant practical and economic challenges in the practical implementation of the approach.

Abstract Laser powder bed fusion (L-PBF)-manufactured AlSi10Mg components exhibit localized microstructural inhomogeneities and high surface roughness, rendering them susceptible to corrosion. This study investigates the characteristics of cerium-doped plasma-polymerized hexamethyldisiloxane thin films deposited via atmospheric pressure plasma deposition, with emphasis on the influence of film thickness, governed by the number of deposition cycles (1, 3, and 5) on corrosion protection performance. All films incorporated cerium predominantly as CeO₂ nanoparticles within the polysiloxane matrix, as confirmed by SEM/EDXS and FT-IR analyses. Film thicknesses ranged from ~400 nm to ~1700 nm, increasing nearly linearly with deposition cycles. Electrochemical measurements and a six-week neutral salt spray test demonstrated that a critical film thickness of ~900 nm (3 deposition cycles) is necessary to ensure effective corrosion protection. Thinner film (~400 nm) exhibited incomplete substrate coverage and insufficient protection, attributed to the underlying surface roughness and porosity of the polymer network. Increasing the thickness to ~1700 nm yielded only marginal improvements, indicating the limited protective benefit beyond the optimal thickness. This study highlights the importance of optimizing the deposition parameters to achieve a balance between film performance and material efficiency and demonstrates a scalable approach for improving the corrosion resistance of L-PBF AlSi10Mg components. Graphical abstract

Metal doping hasgarnered attention as a strategy to enhance theoxygen evolution reaction (OER) activity and stability of Ru-oxides.However, the relationship between the surface structure and OER performanceremains poorly understood. In this study, we prepared Ti-doped RuO2(110) thin films using arc plasma deposition and investigatedhow Ti doping affects the near-surface structure and OER propertiesin an acidic environment. Up to 5 at% doped Ti was uniformly incorporatedinto the films without disrupting the 2-fold symmetry of the (110)surface. However, TiO2 segregated near the outermost surfaceat higher doping levels, reducing surface symmetry. Ti doping improvedthe OER activity and Tafel slope across all doping concentrations,whereas the charge-normalized activity showed that the doping effectincluded an increase in the surface area. Furthermore, Ti doping markedlysuppressed the rise in potential and Ru dissolution during constant-currentelectrolysis. In-plane X-ray diffraction and total-reflection X-rayabsorption fine structure analyses revealed that Ti doping inducedanisotropic strain in the RuO2 crystal and altered theelectronic structure of Ru. These findings suggest that Ti dopingsignificantly enhances the activity, stability, and corrosion resistanceof the RuO2(110) surface, driven by synergistic changesin the surface structure, lattice strain, and electronic structureof RuO2.

Pressure-sensitive adhesive thin films with tailored properties via solvent-free plasma deposition of EHA/AA copolymers

Introduction Polymer electrolyte membrane water electrolysis (PEMWE) has attracted attention as a hydrogen production method. Currently, iridium oxide (IrO️2) is used as the anode catalyst for PEMWE due to its high electrical conductivity and oxygen evolution reaction (OER) activity. Previous research demonstrated that the OER activity of IrO2 depends on the surface orientation [1]. Although PEMWE is expected to operate with fluctuating power derived from renewable energy sources, catalyst degradation is generally faster under fluctuating power than under constant power [2]. However, the relationship between surface structure of IrO2 and degradation under potential fluctuating conditions has never been clarified. In this study, we investigated the influence of surface orientation on the electrochemical stability of IrO2 using single crystal thin film model electrodes fabricated by arc plasma deposition (APD) method. Experimental Rutile-type TiO2(110) and (100) single crystals were used as the substrates. Ir was deposited on the substrate at 400 ℃ under 0.5 Pa-O2 partial pressure by the arc-plasma deposition (APD) method. The deposition thickness was approximately 20 nm. Subsequently, the sample was post-annealed at 500℃ for 3 hours in air using a tube furnace.Electrochemical measurements were conducted in N️2-purged 0.1 M HClO️4 at room temperature. Potential cycling loadings were applied with triangular wave potential cycles with lower limit potential (LLP) of 0 or 1.2 V vs. reversible hydrogen electrode (RHE) and constant upper limit potential of 1.8 V, 0-1.8 V or 1.2-1.8 V for 2000 cycles. Electrochemical stability was evaluated based on the changes in current density at 1.65 V for IrO2(110) and 1.6 V for IrO2(100) measured by linear sweep voltammetry (LSV) at predefined cycle numbers. In-plane X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used for structural analysis and surface chemical state analysis, respectively. Results and Discussions In-plane XRD analysis indicated that the IrO2 thin films were deposited with same surface orientation of TiO2 substrates. Fig.1 shows the changes in OER current density normalized by the initial (0 cycle) value for (a) IrO️2(110) and (b) IrO️2(100) electrodes. As for the IrO2(110) for LLP=0 V, the current density decreased with increasing numbers of cycles, reaching 45% of the initial value after 2000 cycles. In contrast, for LLP=1.2 V, the activity gradually increased. On the other hand, for the IrO️2(100), the current density decreased regardless of the LLP, while the decreasing rate for LLP=1.2 V is suppressed compared to that for LLP=0 V.XPS analysis after the potential cycle of 1.2-1.8 V test showed no significant differences in the oxidation state of Ir estimated from the Ir4f band in (c), regardless of surface orientation. However, as for the O1s band (d), the IrO️2(110) surface showed larger band intensity for adsorbed H2O component, compared to the (100) surface. These results suggest that the electrochemical stability of IrO️2 under potential cycle loadings depends on both the surface orientation and the potential cycle ranges, and the difference in stability might stem from variations in the chemical species and chemical bonding states at the topmost surface vicinity. Acknowledgement This research was supported by the Iwatani Naoji Foundation, Iketani Science and Technology Foundation, Tanaka Kikinzoku Memorial Foundation. Reference [1] S. Kwon et al., J. Am. Chem. Soc., 146, 11719 (2024).[2] H. Kojima et al., Int. J. Hydrogen Energy, 48, 4572 (2023). Figure 1

PEFC is attracting attention as the next generation of energy due to its high efficiency and low environmental impact during power generation. The current cathode catalyst, Pt-supported carbon, has durability problems such as dissolution [1], aggregation, and sintering [2,3] of Pt nanoparticles in acidic solutions. We have studied group 4 and 5 metal oxide electrocatalysts, particularly Ti- and Zr-based oxides as alternatives to Pt-based catalysts [4]. However, these materials have serious problems with electrical conductivity due to their n-type semiconductor properties. We need to overcome this limitation to create excellent oxide-based catalyst supports and ORR catalysts. In this study, noble metal nanoparticles were deposited on the surface of Ti-based oxides and their effects on semiconductor properties were investigated. A glassy carbon (GC) plate was used as the substrate. The substrate was mirror-polished and then plasma-treated in a vacuum. A 10 nm-thick TiO 2 thin film was deposited on the GC plate by atomic layer deposition (ALD) using water vapor as the oxidant and tetrakis (dimethyl amido)titanium(Ⅳ) (TDMAT) as the precursor at 180 o C. After that, noble metal nanoparticles (NPs) were deposited onto the TiO 2 thin film by arc plasma deposition (APD) using gold and platinum targets at room temperature. The number of plasma pulse shots, n, was varied as n= 1，3，5，7，10, 15 and 25. During the process, the discharge voltage and the discharge condenser capacity were set to 100 V and 1800 µF, respectively. Electrochemical measurements were performed in 0.5 mol dm −3 H 2 SO 4 at 30±0.5 o C using a conventional three-electrode cell. A reversible hydrogen electrode (RHE) and a glassy carbon rod were used as a reference and a counter electrode, respectively. Impedance measurements were performed at an AC frequency of 1 kHz with a potential range from −0.2 V to 1.2 V, starting from the high potential under N 2 . The flat band potential ( E fb ) was determined from Mott-Schottky plots. Cyclic voltammetry was conducted at a scan rate of 50 mV s −1 from 0.05 V to 1.2 V vs. RHE under N 2 . Slow scan voltammetry (SSV) was performed at a scan rate of 5 mV s −1 from 0.05 V to 1.2 V vs. RHE under O 2 and N 2 . The ORR current ( i ORR ) was determined by calculating the difference between the current under O 2 and N 2 . In addition, ORR onset potential ( E ORR )was determined as the potential at which i ORR reached -0.1 µA cm −2 . Figure 1 shows cyclic voltammograms (CVs) in a 0.5 M H 2 SO 4 solution with a saturated N 2 atmosphere for TiO 2 (ALD)/GC and GC plate. Unlike GC plate, TiO 2 (ALD)/GC exhibited no significant current until the potential reached E fb , demonstrating a characteristic property of n-type semiconductors. Figure 2 shows the E fb determined from Mott-Schottky plots in Au/TiO 2 (ALD)/GC and Pt/TiO 2 (ALD)/GC as a function of the number of plasma pulse shots using Au and Pt targets. The E fb of both catalysts were shifted to higher potentials compered to that of TiO 2 /GC, suggesting the formation of interface levels by surface modulation of TiO 2 with Au and Pt NPs. Figure 3 shows the hydrogen desorption charge Q H (triangles) and the ratio of charge for oxide formation relative to hydrogen desorption charge Q Ox / Q H (circles) as functions of the number of plasma pulse shots using the Pt target. Both Q H and Q Ox / Q H are obtained from CVs for electrodes subjected to different numbers of Pt shots. Q H increased dramatically from the fifth shot, which can be attributed to the increase in hydrogen adsorption and desorption peaks in CVs. This result suggests electron transfer from the TiO 2 thin film to the Helmholtz layer via interface levels with a tunneling effect. On the other hand, Q Ox / Q H increased from 10th shot, with CVs resembling that of bulk Pt. This indicates that voltage was directly applied to the Helmholtz layer. With increasing the surface level, the TiO 2 band structure transitioned from band-edge pinning to Fermi-level pinning. Base on these results, the modulation of n-type semiconductor properties of TiO 2 by Pt NPs deposition can be classified into three different types of electron transition behavior, as determined from CVs (I-III). Reference [1] S. Mitsushima et al., Erectrochimica Acta ., 54, (2008) 455−460. [2] J. Schröder et al., ACS Catal ., 12 , (2022) 2077−2085. [3] T. Hansen et al., Acc Chem. Res ., 46 , (2013) 1720−1730. [4] A. Ishihara et al., Curr. Opin. Electrochem ., 21 , (2020) 234−241. Figure 1

Introduction The reliance on platinum group metal materials in polymer electrolyte membrane (PEM) water electrolysis remains a significant barrier to its large-scale commercialization1. In particular, the reduction of iridium (Ir) catalysts at the anode and platinum (Pt) coatings on the porous transport layer (PTL) is crucial for decreasing the overall system cost. Addressing these challenges is essential for enabling cost-effective and scalable hydrogen production through PEM water electrolysis. Our research group has developed a catalyst-integrated porous transport layer (Ir-PTL) by modifying the surface of Ti-PTL to increase its surface area, followed by the coating of iridium2,3,4. In this electrode design, iridium serves two functions: as a catalyst for the oxygen evolution reaction (OER) and as a conductive coating on PTL. This approach offers the potential to eliminate the need for Pt coating on the PTL. In this presentation, we evaluate how the structural characteristics of the PTL affect the electrochemical performance of the Ir-PTL. Experimental Titanium sheets, serving as both catalyst supports and PTLs, were prepared using Ti fiber sheets or Ti powder sheets, as shown in Fig. 1. The Ti fiber sheet consisted of Ti microfibers with a diameter of approximately 20 μm, and samples with porosities of 70%, 60%, and 50% were used. The Ti powder sheet was composed of Ti powders sintered with diameters of approximately 10-20 μm and had a porosity of 40%.Chemical etching with NaOH solution was performed to increase the surface area of the titanium PTL. First, titanium sheets were etched in an aqueous 1 M NaOH solution at 60 °C for 1 h. After that, the etched titanium sheets were washed under ultrasonication in 0.01M HNO3 solution for 30 min and then washed in deionized water at room temperature for 10 min. Heat treatment was then performed at 400 °C in 5% H2-N2 gas for 30 min. The Ir-PTL was prepared by depositing the Ir catalyst onto the NaOH-etched titanium sheets at room temperature via arc plasma deposition (APD-S, Advanced RIKO, Inc., Yokohama, Japan). The Iridium catalyst loading was fixed at 0.172 mg cm-2. The PTEs deposited with the Ir catalysts were applied as anodes. MEAs were prepared by hot-pressing the PTLs with the cathode catalyst-coated electrolyte membranes (Nafion 212, Chemours, USA). Results and discussion When PTLs with relatively high porosity were used, the I-V performance was lower. In contrast, employing PTLs with lower porosity improved the I-V characteristics. The Ti powder PTL, which had the lowest porosity of 40%, exhibited the best performance. The differences in I-V characteristics between PTLs were particularly pronounced in the high current density region. While the activation overpotentials were nearly identical for all PTLs, both mass transport and ohmic overpotentials tended to increase with increasing porosity. This increase in overpotential is believed to result from hindered water supply to the catalyst and electrolyte membrane due to intense oxygen gas formation at high current densities, leading to reactant depletion and a decrease in membrane hydration. References The International Renewable Energy Agency, Green Hydrogen Cost Reduction (2020).M. Yasutake, D. Kawachino, Z. Noda, J. Matsuda, S. M. Lyth, K. Ito, A. Hayashi, and K. Sasaki, J. Electrochem. Soc., 167, 124523 (2020).M. Yasutake, Z. Noda, J. Matsuda, S. M. Lyth, M. Nishihara, K. Ito, A. Hayashi, and K. Sasaki, Int. J. Hydrogen Energy, 49, 169 (2024).M. Yasutake, Z. Noda, J. Matsuda, S. M. Lyth, M. Nishihara, K. Ito, A. Hayashi, and K. Sasaki, J. Electrochem. Soc., 170, 124507 (2023). Acknowledgments This study was supported by the Iwatani Naoji Foundation. The authors gratefully acknowledge the financial support. Figure 1

Boron carbide (B4C) is an attractive inertial confinement fusion ablator material. The fabrication of B4C ablators by magnetron sputtering requires process optimization. To increase process flexibility, here we explore high-power impulse magnetron sputter (HiPIMS) deposition of B4C in pure Ar and mixed Ar-Ne plasmas. The results show that higher plasma discharge currents can be reached with a mixed Ar-Ne plasma in the entire working pressure range studied ( 5 to 50 mTorr). At 45 mTorr with 10% of Ne in the Ar-Ne mix, high peak target current densities of ~1 A cm−2 were demonstrated. Films deposited with such a mixed Ar-Ne plasma with a full-face erosion magnetron source on substrates biased at −25 V exhibited higher density and improved mechanical properties, albeit with higher compressive residual stresses compared to the case of HiPIMS deposition in a pure Ar plasma. This work demonstrates additional process flexibility of the HiPIMS discharge mode for the deposition of B4C coatings.

Fabrication of high-porosity ITO ceramics for emerging reactive plasma deposition technique

Plasma deposition of hybrid nanocomposite coatings from aerosol containing TiO2 and AgNO3

Abstract This study investigates the structural and mechanical properties of TiCrFeCoNi high-entropy alloy coatings synthesized using pulsed magnetron sputtering (PMS) and cathodic arc plasma deposition (Arc-PVD) on 304L stainless steel, molybdenum, Armco iron, and Si(100) substrates. PMS coatings exhibited uniform amorphous structures across all conditions, with thicknesses of 580–610 nm and hardness up to 9.39 GPa. Arc-PVD coatings, with thicknesses from ~ 600 nm to > 4 µm depending on current and time, ranged from amorphous to polycrystalline; cyclic deposition promoted crystallization, forming FCC, B2, and Laves phases. Arc-PVD coatings achieved a maximum hardness of 10.40 GPa and reduced Young’s modulus ( E r ) of 203.96 GPa, while PMS coatings showed superior wear resistance at low modulation frequencies ( H / E r = 0.08; H 3 / E r 2 = 0.05 GPa). Wear resistance correlated with H / E r and H 3 / E r 2 ratios, and structural features were strongly dependent on deposition parameters and substrate type. These findings clarify the link between process conditions, substrate effects, and performance, enabling tailored HEA coatings for advanced industrial applications.

Characterization and optimization of an atmospheric plasma deposition system for in-line glass fibers treatment