Magnetron Sputtering Deposition Carbon Encapsulated Metal Nanoparticles And Investigation On The Oxygen Reduction Reaction Catalysis And Tribological Properties

Carbon encapsulated metal nanoparticles is a new type of nanocomposite material.It can not only protect the internal metal particles from physical and chemical changes,but also give new properties to the materials,which make it have extensive application prospects in catalysis,energy conversion and storage,biomedicine and friction materials.Therefore,the preparation and application of carbon encapsulated metal nanoparticles has attracted wide attention.In this paper,we fabricate carbon encapsulated metal nanoparticles films by magnetron sputtering,in which the graphite shells grow via in-situ self-assembly process by adjusting deposition temperature.We discuss the ORR catalytic properties and mechanism of carbon encapsulated metal nanoparticles films.We also investigate the friction properties of carbon encapsulated metal nanoparticles films.In order to achieve the controllable synthesis of carbon encapsulated metal nanoparticles and ORR catalytic performance optimization,we firstly adjust the Ar and N₂ gas flow and sputtering current of Cu target.Then,we find it can achieve the controllable synthesis of carbon encapsulated metal nanoparticles by adjusting the deposition temperature.The film deposited at 650?C form a typical few-layer N-doped onion-like graphite encapsulated Cu nanoparticles.However,the higher T of750?C further promotes the thickening of outer onion-like carbon shells.We find the CuCN-650?C catalyst exhibits the optimized ORR electrocatalytic properties,including close half-wave potential and onset potential to commercial Pt/C,coupled with superior stability and higher methanol-tolerance than commercial Pt/C in alkaline electrolytes.Combining the result of X-ray photoelectron spectrum?XPS?with density functional theory?DFT?calculation,the charge transfer from the inner Cu nanoparticles to outer N-doped C shells enhances the adsorption energy of O₂ and enables favorable electronic interactions with adsorbates in the ORR.The improved ORR performance of CuCN-650?C catalyst could be attributed to high content of pyridinic N,the enhanced electrical conductivity and the synergistic effect between the encapsulated Cu nanoparticles and N-doped C shell.The synergistic effect between the encapsulated Cu nanoparticles and high-content pyridinic N is also limited by the thickness of N-doped C shells.Based on the synthesis of N-doped onion-like graphite encapsulated Cu nanoparticles,we fabricate Ag@C,Cu@C and Co@C films by optimizing the sputtering parameters.All films possess the onion-like graphite encapsulated metal nanoparticles structure and exhibit low friction coefficient and great friction properties.According to the Raman spectra,there are graphite tribofilm in wear tracks.The improved friction and wear originated from the incommensurate contact of carbon encapsulated metal nanoparticles and low shear strain of graphite tribofilm.Furthermore,carbon encapsulated metal nanoparticles films also exhibit excellent tribological properties in oil media.