Plasma- assisted liquid-based growth of g-C3N4/Mn2O3 p-n heterojunction with tunable valence band for photoelectrochemical application

The practical application of graphitic carbon nitride (g-C3N4, CN) is restricted by its low photocatalytic activity and difficult recycling. Herein, we report a CN/Mn2O3 p-n heterojunction grown by a plasma-assisted liquid-based method using a special precursor complex of melamine-cyanuric acid supramolecular on fluorine-doped tin oxide (FTO) substrate. The as-grown CN/Mn2O3/FTO p-n heterojunction exhibits a significantly enhanced photoelectrochemical performance with a photocurrent density of 25 μA/cm2 compared with its powder form (0.9 μA/cm2) formed by common drop coating method，and a tunable valence band (VB) with excellent mechanical strength which is benefit for photocatalytic oxidation reaction and recovery. The formation of CN/Mn2O3/FTO p-n heterojunction can promote the transfer of photoelectrons due to an internal electric field at the interface of p-n junction, leading to the accumulation of electrons and holes in the VB of CN and conduction band (CB) of Mn2O3. The results have shed a light on promoting the practical application of CN, and the developed plasma-assisted liquid-based growth method can be extended to the preparation of other type of functional heterojunctions.