Tubular acceptor-rich ZnO hierarchical heterostructure as an efficient photocatalyst for organic degradation

The intrinsic acceptor-rich ZnO (A-ZnO) microtubes fabricated by optical vaporization supersaturated precipitation (OVSP) are compatible to microfluidic channel for on-chip photodegradation. Unfortunately, the micron size and weak charge separation ability in bare A-ZnO microtube limit its degradation rate. Design of heterojunction structure is a feasible way to improve the photocatalytic performance by efficient separation of photogenerated carriers. Here we synthesize p-CuO and n-ZnS nanostructures on A-ZnO microtubes, respectively, achieving various hierarchical heterojunctions. The massive Zn-vacancy-related shallow acceptor carries in A-ZnO as well as the similar bandgap and crystal structure of A-ZnO/n-ZnS achieve the highest photodegradation efficiency up to 0.105 min(-1). It is about twice and triple higher than bare A-ZnO microtubes and n-ZnO nanoparticles, respectively. The formed type II heterojunction in A-ZnO/n-ZnS boosts the charge separation superior to other ZnO-based heterojunction. The present work paves a new way to the tubular A-ZnO-based hierarchical heterojunction with n-type wide-bandgap semiconductors for high-performance optoelectronic devices.