“…Among them, semiconductor-based photocatalysts with mild reaction conditions were most widely used [15][16][17][18][19][20][21][22] . In addition, various styles of self-assembled photocatalyst nanostructures were synthesized, such as one-dimensional nanotubes 23 , two-dimensional layered structure 24,25 , three-dimensional network structure 26 , three-dimensional flower-like structure 27 and etc.MnO 2 has some advantages including low cost, high stability and environmental friendliness. Besieds, its narrow band gap can increase the utilization of visible light, which is very promising as a photocatalyst [28][29][30][31][32] .…”