A newly-constructed double p-n heterojunction based on g-C3N4@NiO/Ni@MIL-101 ternary composite with enhanced photocatalytic performance for wastewater purification

In this study, a double p-n heterojunction based on g-C3N4@NiO/Ni@MIL-101 ternary composite was successfully prepared by a feasible method. Results suggested that the rational growth of NiO and MIL-101 on the surface of g-C3N4 can improve the absorption capacity for visible light. Importantly, the formation of double p-n heterojunction can effectively inhibit the recombination of photogenerated electrons and holes. Due to the significant Fermi level differences among NiO, MIL-101 and g-C3N4, the internal electric fields were established on the interface after constructing the composite, consequently reducing the electrical resistance and accelerating the transfer of photoinduced charge carriers. As expected, the g-C3N4@NiO/Ni@MIL-101 ternary composite with good stability had excellent photocatalytic performance in the degradation of emerging pollutants, and the removal efficiency of ibuprofen was as high as 95.6%. The center dot O-2(-), center dot OH and O-1(2) were the major active species in the reaction system. Furthermore, developed photocatalytic oxidation system can also achieve the rapid inactivation of bacteria. Based on the synergistic effects of energy band position and double internal electric fields, the separation and transfer of photogenerated charge carriers followed a traditional type-II route. In short, current work not only constructed a promising photocatalyst, but also shared an effective strategy for boosting the photocatalytic activity.