ZnS/ZnO heterojunction as photoelectrode: Type II band alignment towards enhanced photoelectrochemical performance

Heterojunction structures are attracting lots of attention for enhancing the electron injection across the interface. The ZnS/ZnO one-dimensional heterojunction film was firstly prepared via a chemical sulfidization following hydrothermal reaction. The heterostructure was characterized as ZnS(blende)/ZnO(wurtzite) shell–core nanorods via XRD, SEM and TEM. A type II band alignment structure of ZnS/ZnO composite was synthesized via a temperate condition proved by PLS and XPS. The values for valence band offset (VBO) and conduction band offset (CBO) were calculated to be 0.96 eV and 1.25 eV, respectively. The special electron structure in the heterojunction helped reduce the energy barrier height at the interface and enhance the separation of photo-generated carriers. Thus, the photoelectrochemical performance was highly improved, and a photocurrent density of 380 μA/cm2 at 0.9 V (vs. Ag/AgCl) was obtained.