High Surface Area Porous Carbon Research Articles

Preparation of porous carbons from petroleum coke by different activation methods

Porous carbons were prepared from Shengli petroleum coke (SPC) and Minxi petroleum coke (MPC) by different activation methods with H 2O, KOH and/or KOH+H 2O as active agents. The porous carbons were characterized by nitrogen adsorption at 77 K. It has been found that activation method and component of petroleum coke, of which different kinds of transitional metals on petroleum coke are crucial for preparing high quality porous carbons. Under the identical experimental conditions, the co-activation with KOH and H 2O as active agents in the same activation process, which has been rarely reported in literature, is the easiest method for the preparation of porous carbons with high surface area. The sequence of active agents in terms of difficulty in the preparation of porous carbons with high surface area is as follows: KOH+H 2O>KOH>H 2O. A drawback of KOH+H 2O activation in the preparation of porous carbon in this work is found to be its low carbon yield in comparison to KOH activation. Compared with the SPC coke, the MPC coke with higher contents of transitional metal and carbon and lower content of nitrogen is more suitable for making high surface area porous carbons, which is believed to be mainly due to the difference in the contents of transitional metals. Porous carbon with surface area around 2500–3000 m 2/g and carbon yield about 25–30% has been obtained from MPC coke by KOH+H 2O activation with less KOH and shorter activation time in comparison to the traditional methods.

In situ anomalous small-angle X-ray scattering and X-ray absorption near-edge structure investigation of catalyst structures and reactions

Synchrotron radiation is applied to the combined anomalous small angle X-ray scattering (ASAXS) and X-ray absorption near-edge structure (XANES) in situ studies of platinum electrocatalysts, whose metal content is highly dispersed in the form of small crystallites on high surface area porous carbon supports. Combined measurements with X-ray energies near the Pt- L 3 X-ray absorption edge have been performed in an electrochemical cell to study in situ the anodic oxidation process in cyclic voltammetry both for the anodic oxidized and reduced state of the platinum. The reduction process was monitored with XANES. From ASAXS, the sizes of the platinum catalyst particles have been found to increase during the oxidation process at about 1.1 V vs. Ag AgCl . From this increase one can infer a shell model with a platinum core and an oxide surface layer with a thickness of about 1 nm for the oxidized particles.