Construction of g-C3N4 and FeWO4 Z-scheme photocatalyst: effect of contact ways on the photocatalytic performance

Photocatalysis has been regarded as an attractive strategy for the elimination of contaminants, but its performance is usually limited by the fast recombination of photogenerated electron-holes. A heterojunction photocatalyst could achieve the effective separation of electron-holes. However, the electrons migrate to the less negative band while holes move to the less positive band, leading to a weakened redox ability. Z-scheme photocatalysis is a feasible way to realize the efficient separation of photogenerated electron-holes without sacrificing the reductive ability of electrons and oxidative ability of holes. In this work, a new Z-scheme photocatalyst, composed of g-C3N4 (photocatalyst I), FeWO4 (photocatalyst II) and RGO (electron mediator), was fabricated through a facile hydrothermal and mixing method. The effect of contact ways (the electron mediator firstly combined with photocatalyst I or with photocatalyst II) on the Z-scheme photocatalytic performance was investigated. The photocatalytic removal rate of rhodamine B (RhB) was largely enhanced by the construction of a Z-scheme photocatalyst, compared with the g-C3N4/FeWO4 composite without RGO. The contact ways could affect the photocatalytic ability of a Z-scheme photocatalyst. The enhanced photocatalytic performance was attributed to the Z-scheme induced efficient separation of photogenerated charge carriers. Furthermore, remaining holes (on the VB of FeWO4) or remaining electrons (on the CB of g-C3N4) with powerful oxidation or reduction ability would promote the photocatalytic degradation of RhB.