Synergistic effect of amorphous ZnO/crystalline N-TiO2 interface for photoreduction of high concentration Cr(VI)

Abstract

Although the synthesis of amorphous/crystalline heterojunction is still difficult due to thermodynamic instability, the introduction of amorphous components not only avoids lattice mismatch but also triggers higher photoelectric activity at the interface, making it particularly attractive. Herein, a novel amorphous ZnO/crystalline N-TiO2 heterojunction (aZn/NT) was firstly synthesized by a simple one-pot synthesis process. Non-specific preparation conditions and inexpensive raw materials [e.g., zinc acetate, bis(ammonium lactate) titanium hydroxide (TALH) and citric acid] are significant indicators of this method. The systematic test shows that the hydrolysis of TALH is independent and precedes the substitution reaction of citric acid to form a composite spherical structure. Different testing methods have shown that the newly formed bonds (Ti-O-N-Zn or Ti-N-O-Zn) between the two components during the hydrothermal process are the basis of the heterostructure association. Moreover, the combination of positively charged surfaces, abundant oxygen vacancy defects, and transport channels accelerates the photoreduction of Cr(VI) on aZn/NT surface. The high catalytic rate [0.022 min−1 for 200 mg L−1 Cr(VI)] and low activity loss rate (∼2.3% within 5 cycles) under optimal conditions indicate that the synthesis of highly active heterogeneous materials can be achieved through a simple path.