K+-Doped ZnO/g-C3N4 Heterojunction: Controllable Preparation, Efficient Charge Separation, and Excellent Photocatalytic VOC Degradation Performance

The K+-doped ZnO/g-C3N4 heterojunction had been prepared by an electrostatic attraction self-assemble method. The charge separation efficiency of the K+-doped ZnO/g-C3N4 heterojunction was 17.6 and 2.9 times those of g-C3N4 and KZO. As expected, the K ion-doped ZnO/g-C3N4 heterojunction possessed better photocatalytic isopropanol degradation performance. The highest acetone evolution rate of K+-doped ZnO/g-C3N4 heterojunction was 28.5 ppm·min–1, which was 2.7 times better than that of g-C3N4 and 1.7 times better than that of KZO. The improvement of charge separation efficiency and photocatalytic performance of K+-doped ZnO/g-C3N4 heterojunction is mainly due to the following two points. K+-doped ZnO/g-C3N4 heterojunction with a staggered band structure could effectively improve the carrier separation. The high surface area and mesoporous structure could realize the high efficiency of mass transfer and rapid surface reaction of reactants. These K+-doped ZnO/g-C3N4 heterojunctions with high photocatalytic activities could be widely used in air purification.