| The systematic research was undertaken to explore the carbon-silica based mesoporous composite film from the aspects of organic-inorganic composite film, the in situ reduction of metal nanoparticles on the mesoporous film, the modification of nitrogen element existent in the mesoporous film, respectively, with the focus on preparing the mesoporous composite film characteristic of high electrical conductivity and excellent protective performance.The mesoporous carbon-silica composite film was fabricated by spin-coating method using low-molecular soluble phenolic resins as carbon precursor, tetraethyl orthosilicate (TEOS) as silica precursor, copolymer F127 as the structure directing agent. The controllable synthesis of mesoporous composite film with varying organic-inorganic compositions was realized via changing the addition of carbon source in the sol-gel. XRD, BET and TEM results showed that, the as-prepared carbon-silica mesoporous composite film, with the carbon content ranging from 0 to 100%, all possessed highly ordered mesoporous structure. FE-SEM revealed that the film is arranged in the form of 1-D spiral-shaped channels, and controllable in the thickness. Elementary distribution results showed that, the elementary distribution site of carbon was completely coincident with that of silica, and the film was uniform and dense. The tests in 0.5 M H2SO4 corrosion measuring system displayed that, compared with mere stainless steel, composite film exhibited excellent protective performance, with corrosion potential increased by 250-1000 mV and corrosion current decreased by 1-3 orders of magnitude. C-50%60% composite film showed the optimal protective performance, and the corresponding potentiostatic polarization process was extremely stable in the anodic working potential of simulated fuel cells, with the current density stabilized at only 1.2μA/cm-2.In order to increase the electrical conductivity of the film, one-step method was employed to introduce Ni2+. In such a way, the metal Ni nanoparticles were successfully in situ reduced on the mesoporous film. It was found that, the highly ordered mesoporous structure was well preserved for the composite film, wherein, metal Ni nanoparticles were homogenously encapsulated in the skeleton of mesoporous film, significantly increasing the electrical conductivity of the composite film and catalyzing partial carbon atoms in the film architecture to graphitize. Tests results in corrosion system showed that such a composite film exhibited a lower corrosion current. In addition, in the potentilstatic polarization process, the film was stable and exhibited a low current density. The AC impedance results showed a smaller semi-arc-shaped radius and a lower Wo-T coefficient, suggesting a excellent electrical conductivity and protective performance.Potentiostatic depositing method was further utilized to deposite a polyaniline conductive layer on the carbon-silica mesoporous composite film, the N element modification on the mesoporous composite film was realized via low-temparature thermal treatment. It was found from the experiment that, polyanline was grown on the surface of carbon-silica film based on the growing principle of in the sequence of first spot-shaped growth vertical to the substrate, secondly 1-D lateral growth, and lastly 2-D spatial accumulating thickening. The optimal deposition conditions were: deposition potential of 0.90 V, deposition time of 250 s. Furthermore, experimental data also showed that, polyaniline was existent in the form of N-containing functional groups, and composite film possessed relatively higher surface free energy, evidenced by a contact angle of slightly more than 90. electrochemical testing results also revealed that, this composite film exhibited a smaller semi-arc-shaped radius and a lower Wo-T coefficient, indicating an excellent electrical conductivity and protective performance.
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