Incorporation of two or more types of metallic atoms into carbon matrix is of particular interest in the fabrication of high performance electrode materials. This normally requires complex synthetic routes or intricate post-processing process. Moreover, the composition and morphology of the resultant carbon materials are uncontrollable. Herein, we show the first time that a bimetal ions (Sn 4+ and Fe 3+ ) etching method based on Kirkendall effect can transform boronate polymer assemblies into metallosupramolecular polymer hollow spheres, which can be carbonized into carbon shells comprising FeSn 2 alloy. The carbon shells display evidently improved activity towards oxygen reduction reaction with onset potential 0.94 V and half-wave potential 0.84 V vs. RHE, which are comparable to that of Pt/C. The as formed FeSn 2 alloy in the carbon matrix possesses characteristics of rich in electrons, excellent conductivity and high chemical activity. Our supramolecular approach is simple, and able to control both the composition and morphology of the carbon materials, which may afford a new strategy for the design of higher performance electrochemical catalysts.
In this study, 45 steel was taken as the research object, and a tin-iron alloy layer was prepared on its surface via a thermal diffusion tinning process. Combined with a series of characterization methods, the microstructure and element distribution of the thermal diffusion layer were systematically analyzed. Additionally, through cyclic immersion tests, electrochemical measurements, and outdoor exposure tests in marine atmosphere, the effects of thermal diffusion temperature and tin content in the diffusion agent on the structure and corrosion resistance of the thermal diffusion layer were systematically investigated. The results show that thermal diffusion tinning can form an alloy layer dominated by FeSn2 on the surface of 45 steel. Moreover, the higher the thermal diffusion temperature and the greater the tin content in the diffusion agent, the larger the thickness (up to 15 μm) and the better the compactness of the alloy layer. The corrosion resistance of the tinned steel is significantly better than that of 45 steel, and it is further improved with the increase of thermal diffusion temperature, tin content, and extension of thermal diffusion time. Among them, the tinned steel prepared under the thermal diffusion process of 80%-280°C-4h exhibits a corrosion current density of 4.027 μA · cm -2 , which is only 1/400 of that of 45 steel (12.095 μA · cm -2 ), and demonstrates the latest corrosion initiation and slowest development rate in marine atmospheric exposure. The key factors contributing to the improved corrosion resistance are the stable structure of FeSn 2 intermetallic compounds in the thermal diffusion layer, the physical barrier effect of the dense alloy layer, and the protective rust layer formed during the corrosion process.
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