Nanocatalyst materials based on metal nanoparticles (NPs) deposited on mesoporous carbon substrates are widely used in catalysis and energy storage; however, conventional wet-chemical deposition methods based on the reduction of metal salts are not always the best choice when looking for a process ensuring easy scalability and low environmental impact. Moreover, additional surface functionalization steps, such as the addition of nitrogen- or oxygen-containing groups, are more and more explored to increase the activity or the chemical stability of catalysts. In this work, we investigate a new methodology for the fabrication of nickel/carbon nanocatalysts relying on a low-pressure radio frequency plasma treatment of solid (powder) precursors. A mesoporous carbon xerogel is used as support for nickel NPs synthesized through the decomposition of an organometallic nickel precursor in a plasma discharge. Different plasma treatment conditions and chemical environments are applied by varying the plasma power and the gas mixture injected into the plasma chamber (Ar, N2, NH3, and O2). The nucleation kinetics of nickel NPs, their morphology evolution, and chemical state were fully characterized by combining analytical techniques such as in situ optical emission spectroscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Results indicate that the plasma chemistry and conditions strongly influence the organometallic compound decomposition as well as the size and the oxidation state of the homogeneously dispersed nickel NPs. We compare the organometallic precursor degradation efficiency for each plasma by defining a rational “activation power” associated with each plasma chemistry. Moreover, simultaneous carbon substrate functionalization is obtained through plasma treatment, which demonstrates the high versatility of the plasma fabrication for developing green and efficient catalysts and energy materials.

A strategy to reduce critical raw metals in nanocatalysts is to synthesize nanocomposites based on defective or bimetallic nanoparticles deposition on carbon nanomaterials. Conventional solution-based methods suffer from the extensive use of solvents and difficult scalability. In this study, defective Pt-Ni nanoparticles are formed on graphene nanoplatelets thanks to an original approach based on simultaneous or sequential low-temperature oxygen plasma treatments of nickel and platinum acetylacetonates. The two processing conditions produce aggregated Pt-Ni nanoparticles with variable morphologies, size crystallinities, and oxidation states.The materials analytical characterizations show that the sequential treatment promotes small Pt-Ni particle aggregates nucleation, while the simultaneous treatment leads to complex interconnected Pt-Ni-based phases. Such defective nanoparticles are promising for multiple applications in catalysis and energy. K E Y W O R D S graphene, low-pressure plasma treatment, prganometallic, Pt-Ni nanocomposites

Diamond-like carbon (DLC) thin films constitute proven protective coatings due to their outstanding mechanical and tribological properties, combined with a relative chemical inertness and long-term stability. These make them particularly attractive to protect metallic medical implants from corrosion and erosion. However, lack of adhesion between DLC and metallic surfaces is a recurrent problem due to poor interactions with the native oxide layer. An effective strategy to overcome these adhesion issues consists in building interfacial layers. In this context, in this work, the use of a plasma treatment to generate shallow metallic carbide layers was investigated, to promote DLC adhesion directly on the surface of 316L stainless steel (SS).The metallic carbides presence stabilizes and promotes DLC thin film deposition. The highest adhesion was obtained on samples carburized by methane during 20 min with a bias of À700 V. Furthermore, this led to interface amorphization. In conclusion, this study shows that plasma can provide new insights for overcoming the lack of adhesion of DLC thin films on SS metallic surfaces.coating adhesion, depth profile analysis, diamond-like carbon, interface, plasma carburizing | INTRODUCTIONCarbon-based thin films have emerged as potent coatings for a number of applications thanks to the richness and versatility they offer in terms of chemistry and nanostructures. 1,2 In particular, the specific nanostructure of diamond-like carbon (DLC), a metastable form of amorphous carbon characterized by a significant amount of sp 3 bonds, directly confers valuable properties of diamond to the

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