Mesophase carbon materials doped with S Javier Narciso and Enrique V. Ramos-Fernandez Department of Inorganic Chemistry, Institute of Materials of the University of Alicante (IUMA) At present there is increasing interest in developing carbon materials doped with certain elements such as N and S for different applications, especially in electrocatalysis, generally for use as electrodes in the ORR, in the case of N has been widely studied. To date, in the case of Nitrogen, post-synthetic treatments have been carried out such as the use of NH3, or cocarbonization with melanin. However, to date the most efficient and simple method is the carbonization of MOFs (ZIF8, ZIF-67), where it has been possible to obtain coals with a content of up to 21 at.% [1] . However, MOFs with S are not very common, and therefore this synthesis method is not valid. So the usual thing is the use of post-synthetic treatments with compounds that have S in activated carbons, which are not very efficient as we have already commented. The present investigation shows a new very simple synthetic route that is the cocarbonization of mesophase pitches with S. Similar to the vulcanization of rubber. In this case up to temperatures of 600 ºC. The reason for choosing this Carbon precursor is because it gives very ordered carbons, and therefore good electrical conductors, which makes it ideal for this application. The reactions that take place are different in the first place they are the same as in vulcanization reactions with the double bonds to form C-S-C and join chains, so the average molecular weight increases, the viscosity and carbonization yield increase. Subsequent rearrangement reactions generate thiophenic, Ph-S-S-Ph, and sulfonic groups, as shown in the figure 1. The other important aspect is that the addition of S does not modify the microstructure of the carbon phase, since the presence of sulfur is normally associated with a loss of anistropy and even with the fact that the material is totally isotropic, therefore the transport properties of this carbon material decrease by up to an order of magnitude. In our case, the material continues to be completely anisotropic (see Figure 2), although with a 20% decrease in the fluid domains compared to the original, which in principle affects very little. In conclusion, we can say that we have developed a C material doped with S in a controlled manner, ideal for use as an ORR electrode. References 1. Villalgordo-Hernández, D.; Grau-Atienza, A.; García-Marín, A.A.; Ramos-Fernández, E.V.; Narciso, J. Manufacture of Carbon Materials with High Nitrogen Content. Materials 2022, 15, 2415. https://doi.org/10.3390/ma15072415
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