Carbon materials based on poly(phenylene oxide): Preparation, characterization and application in electrochemical devices

A series of novel carbon materials has been synthesized from poly(2,6- dimethyl-1,4-phenylene oxide) (PPO). These carbons with very high BET surface area, exceeding 4000 m2/g, have been characterized thoroughly and are proven to be excellent based material for electrochemical devices. The preparation of such carbon is divided into three major steps: thermal oxidation of PPO, pyrolysis and carbonization of the oxidized PPO in an inert atmosphere, and activation of the carbon with steam or metal hydroxide.; Oxidation in air at elevated temperatures (ca. 230°C) successfully crosslinks the polymer, which improves the carbon yield from 25 wt% to ∼50 wt% The identification and preliminary kinetics of functional groups formed during oxidation was thoroughly investigated. MDSC indicated an increase of glass transition temperature (T_g) of the PPO during the thermal oxidation, which is a result of crosslinking.; Contrary to a simple chain scission degradation of PPO during pyrolysis, the carbonization of oxidized polymer was identified as a two-stage process: pre-stage at <400°C and a main decomposition at 400°–600°C. Pyrolysis mass spectrometry (Py-MS) revealed that CO₂, CO and H ₂O are released during the pre-stage decomposition while the maximum m/z of the evolved fragments is substantially reduced compared those evolved form the untreated PPO.; The KOH activated PPO microporous carbon display a very narrow pore size distribution with an average diameter of ∼2 nm. The pore structure of non-activated and activated carbons was characterized by SAXS, WAXD, nitrogen adsorption and AFM. The KOH activated PPO carbon has a fractal surface as revealed by SAXS. A new equation, which describes the SAXS curves in full range, has been proposed with excellent fitting results. A new concept of measurement of order (MO) was introduced to facilitate the WAXD characterization of activated carbons. BET surface area, microporosity and pore diameters are obtained from nitrogen adsorption measurement, which agrees with the results from Fourier transform analysis of AFM data. The surface groups introduced during activation were characterized by TPD.; The PPO carbon materials have been successfully incorporated into, or as components, of: carbon paper, double layer capacitor and carbon supported platinum catalyst for fuel cell.