p-type ZnO for photocatalytic water splitting

Global environmental pollution and energy crisis have been regarded as important issues in recent years, making people aware of the need to develop environmentally friendly energy sources. ZnO photocatalysts play a key role in the development of hydrogen generation from water splitting via a photocatalytic strategy. ZnO generally exhibits n-type conductivity, and the difficulty in preparing p-type for forming stable p–n junctions limits its large-scale application. The doping of related elements into ZnO can introduce new shallow acceptor energy levels to achieve p-type conductivity and also overcome the barrier of the wide bandgap to accomplish higher light absorption efficiency. Meanwhile, the realization of p-type ZnO can facilitate the construction of ZnO-based homojunctions and heterojunctions, which will accelerate the photoinduced charge separation and then enhance the photocatalytic water splitting performance. In this Perspective, we discuss recent advances in the fabrication of p-type ZnO by different dopants and describe the benefits of p-type ZnO compared to n-type ZnO for photocatalytic applications. Finally, we analyze the difficulties and challenges of p-type ZnO employed in photocatalytic water splitting and consider the future advancement of p-type ZnO in an emerging area.