Mn3 O4 /N-Doped Graphite Catalysts from Wastewater for the Degradation of Methylene Blue.

The accelerating research interest in graphene involving the use of Hummers method has generated non-negligible amount of wastewater containing residual graphite as well as Mn2+ . In this paper, we report the first example of using this wastewater as precursor to prepare Mn3 O4 /N-doped graphite (NG) composites through a facile solvothermal process. The mass fraction of Mn3 O4 in the composites was manipulated by adding various amounts of extra Mn2+ . The conversion of Mn2+ to Mn3 O4 nanoparticles and the N atoms doping were achieved by adding hydrazine hydrate and ammonia into the system. The as-obtained Mn3 O4 /NG composites were well characterized by SEM, TEM, EDS, Raman, XPS, TGA, XRD and N2 adsorption-desorption experiments and showed excellent catalytic performances as well as stability in the degradation of a model organic pollutant methylene blue (MB). Theoretical simulation was also carried out to illustrate the structural features of the Mn3 O4 /NG composite. This work presents a novel idea of designing functional materials from waste precursors.