Preparation of manganese oxide-porous carbon nanocomposites by self-activation and their enhanced performance for methylene blue degradation

Manganese oxides and their composites are promising catalysts for the Fenton-like reaction, which generates hydroxyl radical to eliminate the ever-growing organic pollutants in water. Here, a new solution synthesis approach combined with the self-activation carbonization process has been developed to prepare the MnOx-porous carbon nanocomposites (MnOx-C(SiO2)). First, Mn ions are easily incorporated into resorcinol-formaldehyde (RF) resin with the help of polyacrylic acid (PAA) and then transformed into MnOx particles during carbonization. When the Mn-RF sphere is coated in a silica shell in advance, the pyrolysis process can endow the product with a high BET surface area of 962.8 m2 g−1, much larger than that of the counterpart prepared without SiO2 coating (MnOx-C). In the meantime, the SiO2 shell also prevents the in situ formed MnOx particles from getting larger, making them well dispersed in the porous carbon. The size of MnOx particles in MnOx-C(SiO2) is only 5 nm, which shows superior catalytic performance toward methylene blue (MB) degradation via the Fenton process. The MB degradation rate is close to 100% and remains 98.9% after five cycles.