Facile synthesis of porous metal-doped ZnO/g-C3N4 composites for highly efficient photocatalysts

Metal (M)-doped ZnO/g-C3N4 composites with a sponge-like porous structure have been synthesized by a facile one-pot pyrolysis method. A representative composite, magnesium (Mg)-doped ZnO/g-C3N4 composite was analyzed to contain a 13.7 at% of ZnO and Mg at a standard condition. ZnO and Mg were uniformly distributed over the composite without the formation of clearly separated phases. Optical properties of the composite revealed the extension of light absorption range and the suppressed carrier recombination. Most notably, the photocatalytic efficiency of the Mg-doped ZnO/g-C3N4 composite overwhelmed those of pure ZnO, pure g-C3N4, ZnO/g-C3N4 composite, and ZnO/g-C3N4 composites doped with other metals. Its photoreaction rate constant was estimated to be even higher than the previous reports. A physical mechanism was proposed to account for the observed enhancement of the photocatalytic activity. The synthetic approach and the demonstrated performance of this work may present new direction towards high-performance photocatalysts using composites of g-C3N4 and ZnO.