Fruit wastes to N-containing graphene: chemistry and mechanism

Abstract

It has been found that the presence of nitrogen within the graphene lattice can alter spin density and charge distribution of carbon atoms which influence the electrical and catalytic properties of graphene. In last few years, graphitic precursors and N-containing doping agents were primarily used to prepare N-graphene. However, the potentiality of converting nitrogen rich fruit wastes into N-graphene, without any doping agent has not been reported so far. Although the CVD method is convenient to produce single-layered graphene, it requires very high temperature, inert atmosphere and doping agents whereas, we have used a single precursor to produce very few layers of N-containing graphene in one-step at relatively low temperatures, bypassing multi-precursors and inert atmosphere. Here, three fruit wastes namely, banana peels, papaya seeds and watermelon rinds were pyrolyzed in the temperature range of 250–450 °C in presence of NaOH at normal atmospheric conditions. The results indicated that glucose and amino acids present in the fruit wastes helped in the development of poly-hexagonal array of rings via condensation and polymerization reactions, resulting in the formation of N-graphene, while NaOH was found to prevent the attack of oxygen from the atmospheric air and inhibited the formation of graphene oxide (GO).