Metal-free catalytic reduction of 4-nitrophenol to 4-aminophenol by N-doped graphene

The metal-free catalytic reduction of 4-nitrophenol (Nip) to 4-aminophenol (Amp) mediated by N-doped graphene (NG) was reported. Nip could be reduced to Amp completely without any by-product generation. The activity of the NG is comparable with some of the previously reported metallic catalysts. Interestingly, the NG sheet catalyzed reaction follows pseudo-zero-order kinetics, while all the metallic catalysts follow pseudo-first-order kinetics. The in situ FTIR experiment demonstrated that Nip ions will combine with NG via the O atoms of their hydroxyl groups. Theoretical calculations verified this adsorption model, and confirmed that the adsorption of Nip ions is the critical step, leading to the pseudo-zero-order kinetics. Moreover, only the carbon atoms next to the doped N atoms on NG surface can be activated, serving as the active sites. As expected, all four kinds of the doped N atoms are beneficial to the adsorption and activation of Nip, contributing to the catalytic reduction reaction.