LAUSR

g-C_3N_5 is a new 2D material synthesized only in the last few years which has better absorption ability in visible light range than traditional g-C_3N_4. However, the narrower bandgap restricts its redox ability when used as a photocatalyst. In this work, ferric iron and g-C_3N_5 heterojunctions were prepared through post-calcination (Fe/CN-a) and solvothermal (Fe/CN-b) methods. The photo-Fenton catalytic activity of Fe/CN-a under visible light is remarkably increased by 17.0 times compared to the g-C_3N_5 in degrading methyl orange (an anionic dye), while that of Fe/CN-b increases by 4.8 times in the degradation of methylene blue (a cationic dye). The iron element exists in the form of monodispersed Fe(III) in Fe/CN-a, while it forms α-Fe_2O_3 nanocubes in Fe/CN-b. The Z-scheme heterojunctions, which simultaneously maintain the narrow bandgap, efficient electron–hole separation and strong redox ability, account for the photo-Fenton catalytic activity enhancement. Graphical abstract