Preparation Of Hollow Carbon Materials And Study On Their Oxidative Reactivity

In the past decades, porous carbonaceous materials got great development because of their wide application in energy storage and conversion, adsorption, catalysis and others. Among them, hollow carbonaceous materials have attracted widespread concern and research, as their unique core-shell structure, low density and high electric conductivity. What’s more, their physicochemical properties such as alkalinity, conductivity, catalytic activity and oxidative stability could be improved through the material modification (in suit doping of nitrogen). Fuel cells are green, sustainable power generating devices which directly convert chemical energy of fuel and oxidant to electricity and the cathodic oxygen reduction reaction (ORR) is one of the most crucial factors in the performance of fuel cells. Generally, Pt-based catalysts were used as the electrocatalysts for ORR. However, the large-scale application of Pt-based catalysts has been hampered by multiple disadvantages, such as the high cost, vulnerability to methanol and their limited natural reserves. Therefore, exploring new catalysts such as metal-free catalysts (including n-doped carbonaceous materials) as alternatives has attracted enormous interest.Firstly, we used ionic liquid as the carbon source and nitrogen source to prepare n-doped hollow carbonaceous hemispheres (HCHs) as their low melting point, high thermal stability and negligible vapor pressure. The outstanding features of these materials including high nitrogen content (10.9wt.%), thin thickness (-8nm) and high degree of graphitization. The high electronegativity of N in the framework can induce a positive charge density on the adjacent C atom, which can promote oxygen adsorption and subsequently weaken the bonding in O2molecule. Specifically, the prepared HCHs exhibited superior durability and better immunity towards methanol crossover for ORR in alkaline solution than a commercial20wt.%Pt/C catalyst. Therefore, it is expected that they are promising candidates for the next generation of methanol fuel cells. Secondly, considering the sustainable development and the requirement of green chemistry, biomass was used as the carbon source and nitrogen source to prepare n-doped hollow carbonaceous spheres (HCDMSs). The obtained HCDMSs possessed high specific surface areas (770m2g-1), controlled diameter (-450-50nm) and shell thickness (～75-10nm), and interconnected macropores and mesopores. They showed excellent electrocatalytic activity as metal-free catalysts for the oxygen reduction reaction in alkaline media, and good catalytic activity even in acidic solutions, suggesting the products have nice application prospect.In conclusion, we developed an effective and facile approach for the fabrication of functional hollow carbonacous materials, using ionic liquid and biomass as the carbon source. And they served as efficient metal-free catalysts for the oxygen reduction reaction with excellent catalytic activity. Furthermore, this progress provided rich experiences and new ideas for the subsequent researchers in the design of hollow carbonaceous materials.